Thinking that my days are limited made me want to make sure that the things I have to contribute to understanding the major features of the evolutionary tree of life are passed on to the next generation. I think this blogsite has enough information to do the job if it is studied by a well-trained biologist.
THE BODY CAVITY
Others apparently have found the 2/17/15 post on the body cavity of interest since over half of the pageviews each month are to that post. I suspect it is assigned reading in some classes on several continents because of the clustered nature of the country sources of the views. The post was included almost as an afterthought to supplement coverage of evolutionary discussion of body systems.
Its major interest to me was the minor bit about formation of openings where layers of bare ectoderm and entoderm cells meet. That can help one understand the new location of the mouth of deuterostomes when the connecting link, the pognophorans, emerged upside down (compared to protostome ancestors) as they re-entered coastal waters following extinction events. The resulting inversion of systems of deuterostomes, as compared to protostomes, was discussed in the post dated June 28, 2013. This process enabled fusion of ganglia to a compact brain close to sensory inputs of a head in an anterior position enabling short and speedy neural connections as the owner probed the environment. Perhaps this phenomenon is best illustrated by birds and their ability to fly through a sea of tree branches.
THE DEEP SEA
Structure of the ocean and its physical state under great pressure needs to be understood to see how the pogonophorans can survive the many generations virtually unchanged in the deep sea while their wandering descendants evolve to produce the deuterostomes in shallow water. Several old and some recent posts address this issue. The common ancestry of all deuterostomes with a close relative of the earliest annelids explains why nucleic acids produce odd results in some erroneous molecular phylogenies. The results are only odd because they complicate phylogenies calculated with invalid assumptions of uniform rates of genetic changes in evolution.
THE POGONOPHORA
These tubeworms represent survivors of an evolutionary bottleneck, the deep-sea, where they developed a new type of embryonic development (or cleavage), lost blood pigments other than hemoglobin, and lost the ability to make chitin in the stem group leading to vertebrates.
The blood vascular system was needed to store and transmit oxygen to the portion of the worm embedded in anaerobic sediments. A functional digestive system was reduced to near disappearance and it reformed in a way that did not penetrate the brain in descendants moving to shallow sea areas.
REGRESSIVE EVOLUTION
It is counter-intuitive to give importance to regressive evolution when we think about the grand scheme of evolution going from the first small cells to the diversity of size and complexity of the world of life today. Simple to complex, or progressive evolution, is the explanation our intuition provides.
So the loss of a functional digestive system seems counter intuitive and hard to accept as a way forward to the vertebrate gut from the "degenerate" pogonophoran reduction or loss. Paleontologists found the simple to complex markings on certain cephalopod shells actually went from complex to simple as the fossil record was better developed in their collections.
In regressive evolution, the regressing feature may be targeted for loss indirectly by the better survival of organisms that no longer need the feature; any mutations causing less nutrients to go to such a feature leave the organism more for better reproduction. The speed of regressive evolution can be much faster than progressive evolution. Both can be happening at the same time.
The largest animals are a remarkable example of regressive evolution in the whale's adaptation to aquatic life. All that process of evolution through four-legged ancestors to some with remnants of leg bones no longer used is one example of loss or regressive evolution while other adaptations are evolving.
The annelid worms provided an important feature in our evolution by the segmentation or metamerism producing a series of duplicated structures that could produce different structures in different parts of the body. The phenomenon is graphically illustrated by the appendages of the crayfish in the protostome line of animals.
MOLECULAR SIMILARITIES
We share many molecular features with other organisms. Nucleic acids and biochemistry of energy production are even shared across kingdom boundaries. More specialized biochemical functions often are shared by coelomate protostomes and deuterostomes having closely related compounds although simpler molecular versions may also be found in more ancient protostomes.
Neurosecretions, biochemistry of vision, and biochemistry of metameric processes have similarities that help make the pogonophoran link of deuterostomes to protostomes much more obvious than is generally recognized.
DO NOT FORGET
Pogonophorans are the only animals with structural features demonstrating the transition from annelid to deuterostomes. They explain the importance of their deep-sea life in the regressive evolution leading to a new type of embryology in the deuterostomes, their survival during extinction events, their extremely low metabolic rate enabling long life and slow evolution in the impoverished environment of the deep sea.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan February 12, 2019 (Happy 128th birthday, Dad)
Showing posts with label Pogonophora. Show all posts
Showing posts with label Pogonophora. Show all posts
Tuesday, February 12, 2019
Friday, July 27, 2018
STEPS TO A REMARKABLE EVOLUTIONARY DISCOVERY
Discovery of the extreme age of the likely longest-lived animals on this planet was a slow process over many years. It involved the combination of many discoveries by others that has not yet been comprehended by my peers, many of whom are much smarter than I am. That the animals, the Pogonophora, are also closest living relatives of the link where the change from one major branch of the animal kingdom, the protostomes, gave rise to the other major branch of the animal kingdom, the deuterostomes, becomes understandable and obvious when all the facts are considered.
Getting ready for the discovery.
My early dreams as a biologist were to focus on some obscure invertebrate, that no one was interested in, so I could be the world's expert on an organism. I didn't intentionally pursue that goal in graduate school, although I realized that many important discoveries had been made by people who were not looking for their discovery.
My master's degree research was about colony growth rates of a protozoan and its lipid cytochemistry as related to culture pH. For that, Dr. Richard Fennel was my advisor at Michigan State University.
I began doctoral research at The University of Tasmania with the aid of a U.S. Fulbright Scholarship to Australia in 1956. A planned study of river pollution as indicated by invertebrates of the Derwent River was abandoned as impractical. The chair of the zoology department there, Dr. Vernon V. Hickman, suggested a poorly known isopod crustacean living in pools on top of Mount Wellington as a good object of study. It was. Dr, Eric Guiler became my mentor for the isopod study while I was at the University of Tasmania.
Dr. T. W. Porter became the chair of my doctoral committe at Michigan State University. On my return, the committee thought I should enlarge on the comparative studies of the Tasmanian isopod with a somewhat ecologically equivalent Michigan isopod. Both lived in temporary ponds approximately the same distance from the equator.
The isopod study provided background for understanding principles related to adaptive changes, early embryological development and extremes of life cycle length associated with anatomy, physiology, and environment. I had no premonition that I would find it was preparation for recognizing important elements of the life cycle extremes, anatomical, and embryological adaptations of an organism with such evolutionary importance as the Pogonophora. At the time I, like most biologists, had not even heard of the Pogonophora.
Developing an interest in Pogonophora.
The interest came gradually as I taught invertebrate zoology and found out about the new minor group of worms, the Pogonophora, having no mouth and no agreement on how they took in nutrients. The experts asserted that they were minor, degenerate, dead end, tube-dwellers of no evolutionary importance. I found them interesting for having so many rings on their tubes, a possible indication of greater than usual age. Most species were found at great depth, embedded in the ocean bottom.
Western Michigan University was the host of the C. C. Adam's collection of books and journal papers collected by the early ecologist. The C. C. Adams Center published a series of ecology papers and used the publication in exchange for other publications. One was Sarsia, a Scandinavian publication I might never have otherwise encountered. M. Webb had several research reports in the 1960's; in 1964, two of special significance were published. The first, described a rarely recovered rear portion of the worm with annelid like segmentation and setae. The second, described a clear section of tube around the worm where it had broken through and secreted fresh tube. It was similar to the upper portion of the same tube and indicated the tube was stationary in the sediment.
Webb's above findings sent me back to studies of marine sediments that show abyssal sediments accumulate very slowly, The probable near vertical orientation of tubes and stable positioning, their length, and widespread distribution in the abyssal oceans where sediment accumulation rates are often extremely slow supported a conclusion that the worms reached great age. Cold temperatures and low food supply seemed to support the idea of very slow growth when I put a question mark at the end of the title in a short paper, "Pogonophora: the oldest living animals?" published in 1968.
Studies suggesting verification of extreme age of pogonophorans.
Multiple studies found various indications of probable slow metabolism in the deep sea. One of the most dramatic was the very low rate of bacterial metabolism indicated by the excellent condition of food after eight months in the submarine "Alvin" before its recovery related by Jannasch et al. in 1971.
A recent post about ocean circulation showing the thousands of year needed for polar water to reach the surface indicates very slow respiratory rates in the deep sea. It is more dramatic when you see many locations have high numbers of brittle stars in the photos illustrating Heezen and Hollister's 1971 book, The Face of the Deep.
Questions about nutrition of pogonophorans make the absorption of nutrients from pore water in the sediments a likely answer since Southward and Southward (1982) have shown that they can absorb nutrients from water where the concentration is as low as that found in deep sea sediments.
Studies suggesting the pogonophorans are the missing link.
I am embarrassed that I was so slow to see the pogonophorans as the link between protostomes and deuterostomes. I was quite content with the posterior segmented body section discovered by Webb and the possession of chitin as reason for their polychaete ancestry. The report of Gans and Northcutt in 1983 that developmental features of pogonohorans put them among the deuterostomes was unbelievable. My distress was short-lived when I thought it was impossible unless they were an intermediate form; all the answers seemed to pop into my head- how that would explain the inversion, the changed embryology, and the hemichordate resemblance.
There are many more features of advanced protostomes and deuterostomes made understandable by common ancestry instead of convergent evolutionary origin, The different evolution rates possible are also well illustrated by understanding the pogonophoran's evolutionary position. My isopod study, teaching a broad range of biology courses, and having to write a new section on pogonophora, provided needed background for discovery of the important evolutionary role for the supposed evolutionary dead-end, the Pogonophora.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan July 27, 2018
Getting ready for the discovery.
My early dreams as a biologist were to focus on some obscure invertebrate, that no one was interested in, so I could be the world's expert on an organism. I didn't intentionally pursue that goal in graduate school, although I realized that many important discoveries had been made by people who were not looking for their discovery.
My master's degree research was about colony growth rates of a protozoan and its lipid cytochemistry as related to culture pH. For that, Dr. Richard Fennel was my advisor at Michigan State University.
I began doctoral research at The University of Tasmania with the aid of a U.S. Fulbright Scholarship to Australia in 1956. A planned study of river pollution as indicated by invertebrates of the Derwent River was abandoned as impractical. The chair of the zoology department there, Dr. Vernon V. Hickman, suggested a poorly known isopod crustacean living in pools on top of Mount Wellington as a good object of study. It was. Dr, Eric Guiler became my mentor for the isopod study while I was at the University of Tasmania.
Dr. T. W. Porter became the chair of my doctoral committe at Michigan State University. On my return, the committee thought I should enlarge on the comparative studies of the Tasmanian isopod with a somewhat ecologically equivalent Michigan isopod. Both lived in temporary ponds approximately the same distance from the equator.
The isopod study provided background for understanding principles related to adaptive changes, early embryological development and extremes of life cycle length associated with anatomy, physiology, and environment. I had no premonition that I would find it was preparation for recognizing important elements of the life cycle extremes, anatomical, and embryological adaptations of an organism with such evolutionary importance as the Pogonophora. At the time I, like most biologists, had not even heard of the Pogonophora.
Developing an interest in Pogonophora.
The interest came gradually as I taught invertebrate zoology and found out about the new minor group of worms, the Pogonophora, having no mouth and no agreement on how they took in nutrients. The experts asserted that they were minor, degenerate, dead end, tube-dwellers of no evolutionary importance. I found them interesting for having so many rings on their tubes, a possible indication of greater than usual age. Most species were found at great depth, embedded in the ocean bottom.
Western Michigan University was the host of the C. C. Adam's collection of books and journal papers collected by the early ecologist. The C. C. Adams Center published a series of ecology papers and used the publication in exchange for other publications. One was Sarsia, a Scandinavian publication I might never have otherwise encountered. M. Webb had several research reports in the 1960's; in 1964, two of special significance were published. The first, described a rarely recovered rear portion of the worm with annelid like segmentation and setae. The second, described a clear section of tube around the worm where it had broken through and secreted fresh tube. It was similar to the upper portion of the same tube and indicated the tube was stationary in the sediment.
Webb's above findings sent me back to studies of marine sediments that show abyssal sediments accumulate very slowly, The probable near vertical orientation of tubes and stable positioning, their length, and widespread distribution in the abyssal oceans where sediment accumulation rates are often extremely slow supported a conclusion that the worms reached great age. Cold temperatures and low food supply seemed to support the idea of very slow growth when I put a question mark at the end of the title in a short paper, "Pogonophora: the oldest living animals?" published in 1968.
Studies suggesting verification of extreme age of pogonophorans.
Multiple studies found various indications of probable slow metabolism in the deep sea. One of the most dramatic was the very low rate of bacterial metabolism indicated by the excellent condition of food after eight months in the submarine "Alvin" before its recovery related by Jannasch et al. in 1971.
A recent post about ocean circulation showing the thousands of year needed for polar water to reach the surface indicates very slow respiratory rates in the deep sea. It is more dramatic when you see many locations have high numbers of brittle stars in the photos illustrating Heezen and Hollister's 1971 book, The Face of the Deep.
Questions about nutrition of pogonophorans make the absorption of nutrients from pore water in the sediments a likely answer since Southward and Southward (1982) have shown that they can absorb nutrients from water where the concentration is as low as that found in deep sea sediments.
Studies suggesting the pogonophorans are the missing link.
I am embarrassed that I was so slow to see the pogonophorans as the link between protostomes and deuterostomes. I was quite content with the posterior segmented body section discovered by Webb and the possession of chitin as reason for their polychaete ancestry. The report of Gans and Northcutt in 1983 that developmental features of pogonohorans put them among the deuterostomes was unbelievable. My distress was short-lived when I thought it was impossible unless they were an intermediate form; all the answers seemed to pop into my head- how that would explain the inversion, the changed embryology, and the hemichordate resemblance.
There are many more features of advanced protostomes and deuterostomes made understandable by common ancestry instead of convergent evolutionary origin, The different evolution rates possible are also well illustrated by understanding the pogonophoran's evolutionary position. My isopod study, teaching a broad range of biology courses, and having to write a new section on pogonophora, provided needed background for discovery of the important evolutionary role for the supposed evolutionary dead-end, the Pogonophora.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan July 27, 2018
Monday, July 16, 2018
THE MAJOR EVOLUTIONARY TRANSITION
Annelid worms are ancestral to all of the advanced major phyla. Arthropods and mollusks retained annelid features as one major grouping of advanced phyla. Chordates and echinoderms are the other major grouping. The two groups share some common feature as a result of their annelid ancestries.
There are eight posts in this blog-site from 6/17/13 to 6/30/13 that are a more extended description of the basis for accepting the annelid theory of chordate origin. The annelid theory eliminates the need to (1) assume a second early origin of segmentation and/or metamerism from acoelomate protostomes, (2) explain numerous bits of molecular similarity between coelomate protostomes and deuterostomes, (3) and, with the incorporation of information about the pogonophoran bottleneck connection provided in this blog, provides a logical rationale for the embryological differences as well as the mechanism of inversion of systems in the transition of protostomes to deuterostomes.
THE ANNELID PHASE
The pogonophora are fairly well established as close relatives of some marine polychaete annelids. The fossil record provide very little evidence of events, but some annelid descendants clearly existed during the pre-Cambrian.
Step one. Tube-dwelling worms such as Sabella, started the rotation as they reoriented their posterior to a position in the sediments and left their plumose tentacles up in the water.
Step two. Those becoming pogonophorans had multiple changes selected by the rigor of life at constantly increasing depths as they struggled to survive asteroid bombardments in the pre-Cambrian. In particular, low metabolic rates due to abyssal pressure and temperature, tubes extending deep into the sediments for absorption of fossil nutrients, as well as retention of a blood vascular system to transfer oxygen from the water to the embedded end of the worm deep in the sediments, and loss a many non-essential features. The thinning of the eggshell enabled dropping the spiral development of annelids and the ability of eggs to develop even if some cells were lost. Loss of obvious segmentation left only a remnant of segments at the posterior to anchor the worm in its tube.
Part of step two was the reduction of the digestive system, particularly the mouth and esophagus. This allowed the later fusion of the ganglia of the head into a brain blocking the mouth formation on the old ventral side.
Step three. As asteroid caused extinctions in the surface areas of the oceans eased, progeny of the abyssal worms survived as they moved into shallow water and benefited by mouths developing where gut remnants touched epidermis on the old dorsal side. As they extending from their tube they now would use their relocated mouth to feed on particulate matter in their vicinity.
Step four. As they increased their activities they were doing it with the old dorsal side now the new ventral side. SO THE WORMS DID NOT ROLL OVER, THEY DID A BACK-FLIP as they made their transition from annelid to pre-Chordate organisms during the pre-Cambrian.
Referring to the February 27, 2015 post on "Evolution: the body cavity" may help you understand the bit about relocation of the mouth above. The March 2, 2015 post on "Abandoned theories and Libbie Hyman" has a brief discussion of the annelid theory and an associated figure.
THE IMPORTANCE OF THE REGRESSIVE POGONOPHORAN STEP
The loss of features as pogonophorans adapted to life in the deep sea were essential factors enabling the climb to the branch of the animal kingdom known as the deuterostomes, with the vertebrates members dominating life on earth. It enabled rearrangement of the head with fusion of ganglia into a brain and mouth formation on the former dorsal surface, simplified embryology of radial cleavage and delayed determination of first cells of the embryo. The loss of ability to form chitin in deuterostomes meant other structural materials became more important. Hemoglobin is the only blood pigment surviving in deuterostomes although a diversity of blood pigments are found in annelids prior to the pogonophorans.
OTHER PHYLA
There are other major and minor animal groups that are side shoots at many positions along the groups of the tree of life leading to as well as following the significant deuterostome branch. They continued, some becoming extinct, others diversifying into forms still present. One major group of arthropods, the trilobites, dominated paleozoic seas before becoming extinct. The sponges of today no longer include the group giving rise to early protostomes.
The above figure shows the central sequence of protostomes leading to annelids from which all above them trace their ancestry and have coelomate body cavities. The sequence follows a time sequence of origin of groups having living representatives (except for the hypothetical protonemerteans). The pogonophorans provide a transition from coelomate protostomes to the vertebrate line that clarifies the transition without the mystery of many unknown ancestral groups coming from flatworms.
Many invertebrate groups such as ctenophorans, chaetognathans, lophophorates, echinoderms, sipunculids, extinct groups, and many others are not represented in the diagram.
Joseph Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan July 16, 2018
There are eight posts in this blog-site from 6/17/13 to 6/30/13 that are a more extended description of the basis for accepting the annelid theory of chordate origin. The annelid theory eliminates the need to (1) assume a second early origin of segmentation and/or metamerism from acoelomate protostomes, (2) explain numerous bits of molecular similarity between coelomate protostomes and deuterostomes, (3) and, with the incorporation of information about the pogonophoran bottleneck connection provided in this blog, provides a logical rationale for the embryological differences as well as the mechanism of inversion of systems in the transition of protostomes to deuterostomes.
THE ANNELID PHASE
The pogonophora are fairly well established as close relatives of some marine polychaete annelids. The fossil record provide very little evidence of events, but some annelid descendants clearly existed during the pre-Cambrian.
Step one. Tube-dwelling worms such as Sabella, started the rotation as they reoriented their posterior to a position in the sediments and left their plumose tentacles up in the water.
Step two. Those becoming pogonophorans had multiple changes selected by the rigor of life at constantly increasing depths as they struggled to survive asteroid bombardments in the pre-Cambrian. In particular, low metabolic rates due to abyssal pressure and temperature, tubes extending deep into the sediments for absorption of fossil nutrients, as well as retention of a blood vascular system to transfer oxygen from the water to the embedded end of the worm deep in the sediments, and loss a many non-essential features. The thinning of the eggshell enabled dropping the spiral development of annelids and the ability of eggs to develop even if some cells were lost. Loss of obvious segmentation left only a remnant of segments at the posterior to anchor the worm in its tube.
Part of step two was the reduction of the digestive system, particularly the mouth and esophagus. This allowed the later fusion of the ganglia of the head into a brain blocking the mouth formation on the old ventral side.
Step three. As asteroid caused extinctions in the surface areas of the oceans eased, progeny of the abyssal worms survived as they moved into shallow water and benefited by mouths developing where gut remnants touched epidermis on the old dorsal side. As they extending from their tube they now would use their relocated mouth to feed on particulate matter in their vicinity.
Step four. As they increased their activities they were doing it with the old dorsal side now the new ventral side. SO THE WORMS DID NOT ROLL OVER, THEY DID A BACK-FLIP as they made their transition from annelid to pre-Chordate organisms during the pre-Cambrian.
Referring to the February 27, 2015 post on "Evolution: the body cavity" may help you understand the bit about relocation of the mouth above. The March 2, 2015 post on "Abandoned theories and Libbie Hyman" has a brief discussion of the annelid theory and an associated figure.
THE IMPORTANCE OF THE REGRESSIVE POGONOPHORAN STEP
The loss of features as pogonophorans adapted to life in the deep sea were essential factors enabling the climb to the branch of the animal kingdom known as the deuterostomes, with the vertebrates members dominating life on earth. It enabled rearrangement of the head with fusion of ganglia into a brain and mouth formation on the former dorsal surface, simplified embryology of radial cleavage and delayed determination of first cells of the embryo. The loss of ability to form chitin in deuterostomes meant other structural materials became more important. Hemoglobin is the only blood pigment surviving in deuterostomes although a diversity of blood pigments are found in annelids prior to the pogonophorans.
OTHER PHYLA
There are other major and minor animal groups that are side shoots at many positions along the groups of the tree of life leading to as well as following the significant deuterostome branch. They continued, some becoming extinct, others diversifying into forms still present. One major group of arthropods, the trilobites, dominated paleozoic seas before becoming extinct. The sponges of today no longer include the group giving rise to early protostomes.
The above figure shows the central sequence of protostomes leading to annelids from which all above them trace their ancestry and have coelomate body cavities. The sequence follows a time sequence of origin of groups having living representatives (except for the hypothetical protonemerteans). The pogonophorans provide a transition from coelomate protostomes to the vertebrate line that clarifies the transition without the mystery of many unknown ancestral groups coming from flatworms.
Many invertebrate groups such as ctenophorans, chaetognathans, lophophorates, echinoderms, sipunculids, extinct groups, and many others are not represented in the diagram.
Joseph Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan July 16, 2018
Tuesday, March 6, 2018
WMU MEDICAL SCHOOL RESEARCH
Grant for Medical School Research
Medical
research at the Dr. Homer Stryker Medical School of Western Michigan University
and at its two collaborating teaching hospitals of Borgess Health and Bronson
Healthcare will benefit from a two million dollar bequest given by Martha
Parfet's estate. She is a granddaughter
of the founder of the Upjohn Company, Dr. W. E. Upjohn. Kalamazoo has benefited greatly by the
generosity of numerous relatives and friends of both of the doctor’s families.
Clinical
research will benefit from the bequest, as well as basic research using tissue
culture and cells and animals that share functions in ways more accessible than in human subjects. Such non-clinical
studies can speed, reduce cost, and sometimes simplify the discovery of things
beneficial in modern medicine.
BACTERIA share many biochemical features of
all more advanced organisms. In
particular, they contributed greatly to understanding DNA related details. Their beneficial roles as well as the
diseases some caused will encourage continued searches for new antibiotics when
resistance to old ones develop.
The bacteria
of today and ourselves share some of our biochemical processes as a result of
our common ancestry over two billion years in the past. As organisms share more recent common
ancestry with us, they are expected to share more features with us although they
may lose some and gain others unique to themselves and their descendants.
The figure
above is just to suggest what happens many times during the ancestral history
of organisms. There is no precision to
it, but the internal lines show continuity in one or both branches (multiple
branches may also occur at the same time) and it may take very many
generations that may include the beginning or end of new or old features. The short blue line on the right branch could be repeated in many times and places for numerous other extinct groups from the past.
INVERTEBRATE animals range from protozoans and
simple sponges to complex ones, some of which, especially the giant squid,
reach large size. Invertebrates began leaving an
abundant fossil record of great diversity about 500 million years ago.
VERTEBRATE animals of today share a common
ancestry with echinoderms, perhaps lophophorate animals, and a few degenerate
annelid-like worms that gave rise to early pre-vertebrate chordates that
diverged from the other advanced invertebrates (annelids, mollusks, and arthropods)
near the beginning of the Cambrian. The
following figure is intended to represent an educated guess of some of the
ancestral tree major relationships.
The tree of life is to graphically show the central role of the annelids leading to the two main branches of coelomate animals (protostomes left, deuterostomes right with the pogonophorans linking them to the other line) with the vertebrates upper right and the arthropods, upper left. Plants in green are are lower left, and nematodes are on the blue and red left middle main branch.
Why are organisms important in
medical research?
1. Shared system features of physiology,
structure, and biochemistry are likely to be most similar when the distances
(or perhaps generations) from one group to another along the branches of the ancestral
tree of life are shortest (or fewer).
2. Some organisms have feature
comparable in some ways to ours, but in a more accessible or larger form. For example, the transmission of nerve
impulses was made understandable by studying the giant nerve fibers of
squids. Fruit-fly larvae have giant
chromosomes that led to some genetic discoveries.
3. Basic toxicity studies of proposed
drugs can be on simple organisms after or in place of initial tissue culture or
other studies. Such tests may be much less
costly in time and/or money.
Where should medical research start?
1. Most likely it will start as you work with a senior medical researcher using you as an assistant performing work for
which you are trained.
2. A first step that should become a
habit is studying the research literature in the library, on-line, in
appropriate journals, and attending meetings of your research group. Especially, attending related research being
reported at local, state, or national conferences. Often, verbal presentations of research
include clues of value to apply in your research.
How is evolution
important in medical research?
It may not always be important to you if you are a
specialist is some aspect of a research project. If you are planning research it may help you
select organisms for non-human aspects of research such as in the first list
above. Keep abreast of new developments,
even the most unlikely organisms may teach us things of value.
Although
animals greatly separated from us on the tree of life may share some identical
features with us, they are expected to have greater differences than ones that
are more recently separated. The
pogonophorans clue us in on where differences in biology are more likely to be
greater in some instances and less in others.
The
pogonophorans are a bottleneck where they branch off from the annelids, losing
the spiral cleavage of the three big invertebrate groups - the annelids,
mollusks, and arthropods – as well as loss of much of the gastrointestinal
system and skeletal functions. In spite
of the latter, cartilage of the squid seems indistinguishable from vertebrate
cartilage with casual microscopic examination.
Many
biochemical features survived the pogonophoran link bottleneck. Hemoglobin is the blood pigment of
vertebrates as well as some invertebrates across the pogonophoran divide. Aspects of delivery of pituitary hormones in
our endocrine system show remarkable similarities in mammals and
arthropods. Peculiar intercalated disks
of our heart muscle are also seen in some mollusks.
If you find
commonalities of another organism and humans, don’t use the just stated facts
as reason to change your experimental animals.
But consider the discussion as an aide to picking new ones if
evidence warrants it. Selective evidence
was used to put nematode worms in a major cluster with arthropods when most
evidence indicated otherwise. The post -
- and the post
on May 31, 2013 indicate otherwise, Ecdysozoa is not a valid related group. Both posts provide references supporting that
statement. I write this with hope
that it may be of some benefit to the researchers the grant will fund in the university
from which, twenty-two years ago, I retired.
Thursday, December 14, 2017
EVOLUTION: The Eureka Moment
The
“eureka!” moment, when I saw the Pogonophora as the significant link of the two
main divisions of higher animals, can be credited to the stimulation of reading
Gans and Northcutt, 1983.
Gans, Carl, and R. Glenn Northcutt. 1983.
Neural crest and the origin of vertebrates: a new head. Science,
220:268-274.
They placed
the pogonophorans in line with the vertebrates based on development. I was sure the evidence was overwhelming that
pogonophorans were close to, or one of, the annelids. But I also realized most scientists are
honorable and truthful in their work and deserve to be taken seriously. But how could Gans & Northcutt be right when the
overwhelming evidence indicated pogonophorans were close to annelids and other
protostomes? Somehow, in an instant, I
realized it could be true if pogonophorans were a connecting link. A deluge of such evidence came to mind. And, as I followed new, as well as some older,
molecular and other evidence the connection became well supported.
Engemann, Joseph
G. 1968.
Pogonophora: the oldest living animals?
Pap. Mich.
Engemann, J.
G. 1983.
Coelomate animals are monophyletic.
American Zoologist,
23(4):1008. Abstract # 753. The
Pogonophora have characteristics of both protostomes and deuterostomes and
provide support for the annelid theory of origin of deuterostomes.
Understanding the extreme
age of individual pogonophorans, suggested in the 1968 report above, was a result
of preparing a new section on pogonophorans for the 1968 edition of Hegner and
Engemann’s Invertebrate Zoology
text. It was reprinted in chapter 14 of the
1981 edition (Engemann and Hegner) which discussed the evidence making it very
likely deep-sea animals typically have very extended lives and low respiratory
rates. My 1983 abstract noted above was
reported shortly after Gans and Northcutt triggered my conclusion with their
evidence.
A full
report of the paper was submitted to Nature.
The reviewers did not reject the paper but the editor decided not to
publish it because it was not of wide enough interest. I had given it a title suggesting pogonophorans
were the protostome-deuterostome link.
He was not moved by my suggestion that a catchier title would have been
“my ancestors were worms”.
Of course,
there is a whole sequence of organisms from protozoans through sponges,
jellyfish, flatworms, fish, amphibians, reptiles, insectivores, primates and
closer relatives in our direct lineage.
But we don’t have direct ancestry through either nematodes, mollusks,
arthropods, echinoderms, or many other groups. If people squirm to think some ape-like primate was in our evolutionary ancestry, how much more appropriate to squirm for a worm.
What about extreme longevity of pogonophorans?
It helps explain their slow evolutioary rate, and thus, their close molecular relationship to diverse groups of animals.
What is so important about abyssal life of pogonophorans?
The slow pace of life at great depths, due to great pressure, low food and oxygen input to the depths, paucity of life, probable absorption of fossil nutrients from sediments, and isolation from many surface extinction factors makes them living "fossil" ancestors. [Note: really old people may live to see great, great, great grand-children]
What has pressure to do with it?
It has not been demonstrated but it is obvious that reduced diffusion based metabolism is probably the missing factor in reduced community respiration noted at great depths. I await someone making observations of reduced Brownian movement and/or diffusion of dyes at great depths. It may be a factor in extended submersion time for deep-diving whales. Water is ever so slightly compressed at great pressures- it may be the cause.
Could circulatory systems increase activity and decease longevity at great depths?
Perhaps. But whales presumably shut down some less essential portions of theirs.
What about the great difference in early embryology of the groups alleged to be connected by the pogonoporans?
That has been discussed in other posts. Also, observation of isopod development in Tasmania and Michigan gives some clues to different rates of development associated with ecological factors. Abyssal life put a species survival premium on shifting from protostome to deuterostome development.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan December 14, 2017
Friday, October 20, 2017
EVOLUTION: MAINSTREAM IDEAS
UPDATING MAINSTREAM IDEAS
About a half-century ago I was confused by the distinction between Darwinism and Neo-Darwinism. The "Neo" prefix had been added to designate the discoveries of Darwin enhanced by understanding of hereditary or genetic principles clarifying the principles of natural selection. Such proliferation of terms helps the specialists introducing them but brings confusion to the generalists.
Discovery of details of pogonophoran biology provides near certainty that the abandoned annelid theory of chordate ancestry was actually correct when modified as done in numerous posts on this evolutioninsights blog. The separation of the chordate line from protostomes via the polychaete - pogonophora - hemichordate - chephalochordaate sequence has sufficient evidence to justify abandoning the old idea that the deuterostome departure from protostomes was near the flatworm level.
Updating the annelid theory
First, the original abandonment of the annelid theory on embryological grounds was dismissed by the drastic differences between protostome and deuterostome development. This blog (June 24, 2013 etc.) is the only source showing a plausible reason for the change via the pogonophorans.
Second, the current popular distortion of animal phyla relationships is based on faulty research described in this site's blog of May 31, 2013. The post on Evolution: Molecular Clocks on November 25, 2014 contains numerous citations to research showing the great variations possible in studies based on molecular clocks.
Third, the input from ecological and structural studies shows the simplicity of inversion of systems to deuterostome chordates from protostome annelids via tube-dwelling polychaetes noted in Evolution of systems inversion posted June 28, 2013. Several other June 2013 posts should also be viewed.
Fourth, the post on EVOLUTION AND THE OLDEST ANIMAL, June 13, 2014, should be a great help understanding the unique evolutionary position of the pogonophorans and their position as a very important connecting link between the two major lines of higher animals.
Updating the Tree of Life
The June 30 2013 and subsequent posts to August 3, 2013 have information about the linking of mainstream invertebrate groups as well as arthropods and mollusks. There are many important subgroups of sponges, cnidarians, and flatworms in the mainstream. Interesting sideshoots include ctenophores, rotifers, nematodes. The protonemerteans are a hypothetical descendent of flatworms preceding the polychaete annelids; they represent the most uncertain guess for continuity in the protozoan to people ancestral tree. Arthropods and mollusks probably have separate origins from polychaete annelids.
Branches from uncertain places in the tree of life include lophophrates such as bryozoans and brachiopods, and echinoderms; they may be near the pogonophorans in origin. Chaetognathan origins are uncertain, as are the origins of a number of unsegmented worms.
Joseph Engemann, Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan October 20, 2017
About a half-century ago I was confused by the distinction between Darwinism and Neo-Darwinism. The "Neo" prefix had been added to designate the discoveries of Darwin enhanced by understanding of hereditary or genetic principles clarifying the principles of natural selection. Such proliferation of terms helps the specialists introducing them but brings confusion to the generalists.
Discovery of details of pogonophoran biology provides near certainty that the abandoned annelid theory of chordate ancestry was actually correct when modified as done in numerous posts on this evolutioninsights blog. The separation of the chordate line from protostomes via the polychaete - pogonophora - hemichordate - chephalochordaate sequence has sufficient evidence to justify abandoning the old idea that the deuterostome departure from protostomes was near the flatworm level.
Updating the annelid theory
First, the original abandonment of the annelid theory on embryological grounds was dismissed by the drastic differences between protostome and deuterostome development. This blog (June 24, 2013 etc.) is the only source showing a plausible reason for the change via the pogonophorans.
Second, the current popular distortion of animal phyla relationships is based on faulty research described in this site's blog of May 31, 2013. The post on Evolution: Molecular Clocks on November 25, 2014 contains numerous citations to research showing the great variations possible in studies based on molecular clocks.
Third, the input from ecological and structural studies shows the simplicity of inversion of systems to deuterostome chordates from protostome annelids via tube-dwelling polychaetes noted in Evolution of systems inversion posted June 28, 2013. Several other June 2013 posts should also be viewed.
Fourth, the post on EVOLUTION AND THE OLDEST ANIMAL, June 13, 2014, should be a great help understanding the unique evolutionary position of the pogonophorans and their position as a very important connecting link between the two major lines of higher animals.
Updating the Tree of Life
The June 30 2013 and subsequent posts to August 3, 2013 have information about the linking of mainstream invertebrate groups as well as arthropods and mollusks. There are many important subgroups of sponges, cnidarians, and flatworms in the mainstream. Interesting sideshoots include ctenophores, rotifers, nematodes. The protonemerteans are a hypothetical descendent of flatworms preceding the polychaete annelids; they represent the most uncertain guess for continuity in the protozoan to people ancestral tree. Arthropods and mollusks probably have separate origins from polychaete annelids.
Branches from uncertain places in the tree of life include lophophrates such as bryozoans and brachiopods, and echinoderms; they may be near the pogonophorans in origin. Chaetognathan origins are uncertain, as are the origins of a number of unsegmented worms.
Joseph Engemann, Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan October 20, 2017
Thursday, January 12, 2017
DISCOVERY
TYPES OF DISCOVERY
Serendipity
Many discoveries are due to chance or an unexpected observation. Such discoveries are more likely to occur if the observer is alert to the environment. How many people noticed a zone of no bacterial growth adjacent to a mold colony before Sir Alexander Fleming did, but did not pause to consider the cause? Fleming's discovery of penicillin's inhibition of bacteria provided the model for discovery of many additional antibiotics.
Planned
The search for additional antibiotics was a logical expansion of the serendipitous discovery of penicillin. Targeted research is common in the research and development units of many companies. Universities used to be primarily focused on basic research that might, or might not, have commercial application. Now, research faculty have one eye on the potential valuable uses that might sway granting agencies to provide greater monetary support.
Unrecognized
Recognition of value of research can escape others, especially when it is novel and/or goes counter to accepted thinking of leaders in the subject area. The significance of Mendel's studies of inheritance in peas was not given much recognition until thirty some years later when it complemented the understanding of chromosomes in genetics.
I think it may be thirty years after I die before zoologists and evolutionary biologists will become aware of how (1) extreme age is a characteristic of abyssal organisms, (2) the stable deep-sea environment provided a refuge for survival during celestial bombardment by asteroids etc. during the early history of life on earth, (3) one such surviving group was the Pogonophora which (4) show the embryological and morphological connection of protostome ancestors to deuterostomes such as vertebrates, and (5) illustrate the error of ancestral trees that ignore the effects of generation time in calculating branching patterns.
The five points mentioned have been discussed in earlier posts of this blog and may be enough to help some curious scientist of the future to set the record straight. Much of the information can be found in a hypothetical discussion of invertebrates in the final chapter of the 1981 3rd edition of Engemann and Hegner's Invertebrate Zoology published by Macmillen Publishing Company. Points 4 and 5 were arrived at shortly after I realized the theory proposed in the final chapter represented reality.
At eighty-eight I do not expect to be here for nearly as long as the twenty years I have been retired. And low energy and memory lapses are more frequent. I think I have included the basics of what is important in my work in this blog. So now I may go to some unpublished work of mine of less consequence to the accurate understanding of evolution. In fact, I had started one on eyelines and coevolution when it disappeared with a wrong keystroke. I have typed this with greater care and have to get my computer's word-processing and photo programs fixed so I can work more efficiently. If you have read this far, thank you.
Joseph Engemann, Emeritus Professor of Biology, Western Michigan University, Kalamazoo. January 12, 2017
Serendipity
Many discoveries are due to chance or an unexpected observation. Such discoveries are more likely to occur if the observer is alert to the environment. How many people noticed a zone of no bacterial growth adjacent to a mold colony before Sir Alexander Fleming did, but did not pause to consider the cause? Fleming's discovery of penicillin's inhibition of bacteria provided the model for discovery of many additional antibiotics.
Planned
The search for additional antibiotics was a logical expansion of the serendipitous discovery of penicillin. Targeted research is common in the research and development units of many companies. Universities used to be primarily focused on basic research that might, or might not, have commercial application. Now, research faculty have one eye on the potential valuable uses that might sway granting agencies to provide greater monetary support.
Unrecognized
Recognition of value of research can escape others, especially when it is novel and/or goes counter to accepted thinking of leaders in the subject area. The significance of Mendel's studies of inheritance in peas was not given much recognition until thirty some years later when it complemented the understanding of chromosomes in genetics.
I think it may be thirty years after I die before zoologists and evolutionary biologists will become aware of how (1) extreme age is a characteristic of abyssal organisms, (2) the stable deep-sea environment provided a refuge for survival during celestial bombardment by asteroids etc. during the early history of life on earth, (3) one such surviving group was the Pogonophora which (4) show the embryological and morphological connection of protostome ancestors to deuterostomes such as vertebrates, and (5) illustrate the error of ancestral trees that ignore the effects of generation time in calculating branching patterns.
The five points mentioned have been discussed in earlier posts of this blog and may be enough to help some curious scientist of the future to set the record straight. Much of the information can be found in a hypothetical discussion of invertebrates in the final chapter of the 1981 3rd edition of Engemann and Hegner's Invertebrate Zoology published by Macmillen Publishing Company. Points 4 and 5 were arrived at shortly after I realized the theory proposed in the final chapter represented reality.
At eighty-eight I do not expect to be here for nearly as long as the twenty years I have been retired. And low energy and memory lapses are more frequent. I think I have included the basics of what is important in my work in this blog. So now I may go to some unpublished work of mine of less consequence to the accurate understanding of evolution. In fact, I had started one on eyelines and coevolution when it disappeared with a wrong keystroke. I have typed this with greater care and have to get my computer's word-processing and photo programs fixed so I can work more efficiently. If you have read this far, thank you.
Joseph Engemann, Emeritus Professor of Biology, Western Michigan University, Kalamazoo. January 12, 2017
Saturday, July 23, 2016
MY PATH TO THE PRESENT
The Present
The three years of this blog presents a mix of evolution and other topics that may lack focus for those wanting the story of evolution, or God, or creativity, or science. My life, in retrospect, seems to bring me to a blend of those topics in a cohesive view not easily clarified for others.I have not tried to clarify things as much as I should have. In the rush (can one who works at snail or turtle's speed rush?) to get the essential new points presented before they got buried with me, I neglected making all the needed connections and clarifications,
I recently abandoned work on a blog post about the importance of the end products of protein metabolism (primarily ammonia, uric acid, and urea) in the evolutionary transition of animals from aquatic to terrestrial habitats. The uric acid method of storing many toxic ammonia molecules in less soluble, and therefore less toxic molecules, made possible the shelled eggs of vertebrates, and less need for water for elimination of those wastes by birds and insects, Mammals emphasized the conversion of ammonia to urea as a less toxic alternative. But the evolutionary story of these facts are well covered in many basic biology texts.
Many other important facts of evolutionary significance are also well covered in basic texts. But, unfortunately, extreme age of abyssal organisms due to their greatly slowed metabolism, the close relationship of all advanced animals via annelid ancestors, and related facts are missing. Those missing facts are explained in earlier posts during the three years of this blog.
How I Found Those Facts
Finding new facts of evolution
The reasons had nothing to do with sheer brilliance. It might seem like serendipity, since very little of it was planned by me. Things that I now see as part of the reason I see and understand seem to parallel things of the spiritual realm identified in both Old Testament and New Testament words as seeing but not seeing or hearing but not hearing among those not believing.
When Jesus said no one knows the Father except the Son
and those to whom the Son has revealed Him, it may explain why many fail to see
God as the Creator and evolution as part of God’s work of creation. So how does one as unworthy as myself manage
to see those things?
Perhaps it began with my youthful amazement at the
extent of creation when looking at the night sky and reflecting on the near
infinite distance and numbers of the stars as described by astronomers of the
time.
ROUTE TO THE DISCOVERIES
My post retirement reflections show a
number of events in my life that make serendipity an unlikely explanation for my
blundering into an evolutionary understanding others have not yet been able to
see, especially the role of pogonophorans explaining puzzles of molecular
biology and chordate origin.
1. It started early with a family that valued education and many other
important values. I was born into it and
in childhood had my physical activity periodically impeded by bouts of asthma; consequently,
at times all I could do was think. My
verbal skills were not up to explaining my reasoning to my older brother who
insisted that you didn’t know it if you couldn’t say it. Years later I realized my right-brain
thinking did not yet readily transfer to the left-brain for verbalization. But the sibling conflict helped make me look
for alternative explanations with very productive results in later analysis of
science research of both myself and others.
Score that as a benefit of having had asthma.
2.
At the same time my skin, especially on my hands was very scaly with
what was variously diagnosed as eczema, ichthyosis, and eventually
psoriasis. Concerns about my medical
state made me exclude careers in medicine and the ministry from consideration,
question whether I had a right to marry and bring children into the world, and
a partial withdrawal from developing my social life.
Such concerns receded during high school
and were mostly gone by the time I was drafted following college
graduation. Two years in close
association with army friends made me realize I was reasonably normal
(eccentricities seem to be part of being normal).
3. I
loved science and nature but only moved into biology as a sophomore in college
when a biology course, to meet part of the liberal arts requirements and was taught
by a very inspirational teacher, lured me in to biology. I minored in English and got a Bachelor of
Arts degree with a major in Biology. I
would have needed more of other sciences to get a Bachelor of Science with a
Biology major. Invertebrate zoology was
one of my favorite biology courses.
Biology was largely a mix of interesting disconnected facts to be
memorized until a class in genetics and a class in evolution finally helped me
to see the sense and connections in the diversity of life. Once that step is made, ecology, physiology,
and other specialties in biology also made sense. Perhaps others reach the same result via many
roads.
After the army I spent a little over a
year in tool and die work that made me consider engineering. But when I checked into the engineering
program at Michigan State I found that I would get no credit from my biology
degree toward a Bachelor’s of engineering.
So I went to the Zoology Department and expressed possible interest. A week later they called and offered me a
part-time instructorship, replacing someone with one on a grant that had resigned,
beginning immediately in the spring term.
It was essentially a graduate assistantship, but with the perk of a
faculty parking sticker for my car.
Two years later I was finishing my
Master’s degree after a thesis research project studying protozoan
cytochemistry. I applied for a Fulbright
award for studying in Australia because I thought there would be less competition
than for one in England. I didn’t speak
any other languages than English, that limited my ability to apply
elsewhere. I did not foresee that
Tasmania would be an entry into studies leading to my evolutionary findings.
About seven years later I finished my
doctoral thesis after three years teaching full-time at Western Michigan
University. Then, at a summer, 1963,
biological conference I contacted the Macmillan Publishing Company
representative about possibly revising their Invertebrate Zoology authored by
the deceased Robert Hegner. I had used
it as a student 15 years earlier, but was using one of the more recent books,
none of which were as student friendly as Hegner’s book. At a subsequent meeting, after he talked to
Dr. Stiles (author of their best-selling college zoology text), Zoology Chair
at Michigan State University and a fan of mine, he quickly arranged a contract
to revise their book. I would have been
very unlikely to be writing this blog without the experience of adding the new
group, the Pogonophora, to the text revision for Macmillan.
4.
After 23 years teaching invertebrate zoology, marine biology,
introductory zoology and numerous other courses at WMU I read the 1983 paper by
Gans and Nortcutt that gave me the cognitive dissonance experience yielding the
eureka moment of seeing the connecting link role of the Pogonophora. It is impossible for me to define all the
inputs giving rise to the moment.
5.
In the 1960’s I had developed the idea of extreme age among abyssal
Pogonophora. In 1983 their extreme
longevity and intermediate blend of features made me aware of their
evolutionary role.
6.
Failure to get acceptance of manuscripts over the years may have been
due to my poor writing. I prefer to
think it was due to reviewers having inadequate background, as well as their
accepting flawed research that had been published, had more to do with the
rejections.
The above recitation of factors shaping
the somewhat random direction of my life leading to my unique view of evolution
may have other meaning. It may be that
diverse life experience can be the grist for creative thinking. Moreover, many failures, not listed,
including inventions, grant and publication rejections, and other events that
might have absorbed my attention with otherwise narrowly focused activity
inhibiting global thinking. An example
is shown in the two posts about a Puttmeter.
I think it would have been a successful product if I had been willing to
put the effort into developing and marketing it. Proper packaging, marketing and advertising
has made commercial success of many other simple things.
ROUTE TO THIS BLOG
The accumulation of the eclectic research
and writing projects were originally began to be viewed late in my career as
something so disconnected that it might fit collectively into a volume called
“Animal Evolution: A Serial Symposium”.
As time went on, I thought there were only a few things of great
importance. They were primarily the two
things my peers did not recognize or accept – extreme age of abyssal
pogonophorans and their role as a major evolutionary link. I seemed to be the only one that knew
that. Two other views I share with
others so it is not so dependent on my proclaiming them are the role of God as
both creator of evolution and the reason the creation/evolution debate is meaningless.
Other of my evolutionary insights that
simplify understanding of animal diversity and function are of value but not
critically so. Fortunately, some of
those older posts about them are among those still attracting numerous viewers.
For about 20 years, extending from before
retirement in 1996 until I was diagnosed with MDS in 2007, I played with
various approaches to an evolution book.
My concern then was that I better pick up the pace of writing if I was
serious about doing it. I thought I had
about six months to two years to complete it.
So not realizing it was a mild version of MDS, I finally finished a
first draft of Evolution Insights in
2009. In early 2010 I completed the last
revision and realized after minimal efforts to find a publisher that the market
for book manuscripts from someone like me was practically non-existent.
The publicity to attract a publisher might
come from a successful blog or website.
Setting up a website turned out to be beyond my capabilities. But somehow I found Google’s Blogger program
and was able to start this blogspot.com blog even though the things that would
make it a more professional project still escape me.
DIVINE INTERVENTION
I think that God is more active in our
lives than we realize. I now see that
the early childhood difficulties were a blessing in disguise, enabling me to
develop as I did. God is usually like
the tiny breeze encountered by the Old Testament writer. But he is constantly with us if we accept
him. The first suspicion I had that it
was truer than we think was when I started reading random selections from the
Bible and found they very frequently gave me insights on current problems or
concerns.
I doubt that I would have started blogging
if I had not developed MDS. But between
writing the manuscript it is based on, and starting the blog, a more direct
event moved me to finally find Google’s Blogger and blogspot blogs. I had been trying to educate myself on blogs
by using publications designed for that purpose Perhaps
the distraction of a series of health issues and the reduced energy often
associated with increased age made the infrequent forays into self-help books
such that each attempt seemed to start from square one.
That was the situation in early 2013 when
a more pronounced reoccurrence of blood flow from my urinary system made me
stop and reflect. In my mind I was
telling Jesus that I had a life I was happy with and was ready any time God
wanted to take me. If I recovered I
would take it as a sign that I should renew my efforts to develop a blog. After that talk the bleeding stopped and has
not repeated in that location. Within
about a month of the event evolutioninsights.blogspot.com/ was an accomplished
fact.
Other people can do what I have been
trying to do. I feel so strongly that God
has made the numerous events occur in my life so that I do not deserve credit
of any of my evolution observations that turn out to be of value. I should pass them on freely to others. And if any profit is derived from my writing
that, rather than the biblical tithe of 10% to charity, 90% or some other substantial
sum should be given. It is the basis for
my encouraging readers who want to use my writing in not for profit ways to do
so, hopefully with a credit to the source.
Joseph G. Engemann Kalamazoo, Michigan July 23, 2016
Monday, May 16, 2016
THE TREE OF LIFE
REVISED TREE OF LIFE
The revised tree of life described in the previous post lacked any illustration to aide understanding. The transfer of files to a new computer, operating system and associated software (Windows Vista to Windows 10) has delayed production of something suitable. I was eventually able to find Paint embedded in 10. But my attempt to modify the diagram below with color to clarify the protostome and deuterostome groupings left an illustration dangling somewhere in a jpg file that I have not been able to migrate to this blog.
The protostomes began with platyhelminthes, the flatworms ancestral to other protostomes, and eventually deuterostomes via annelids. The anthropocentric view showing primates upper right as the ultimate chordates is only for illustration of our lineage. Every living group could have an illustration showing their group at the peak. Some hint of this is shown with wasps and flies being groups of insects at the upper left. And at the far left the cephalopods are perhaps the ultimate mollusks.
The boldface names in the above diagram represent groups in the direct ancestral line to primates. All animals with a eucoelomate body cavity are included in the annelids and those above them in he diagram. Phylum names are in all capital letters. Polychaetes are probably the ancestral annelids for other annelids (oligochaetes and their descendants the leeches), mollusks, and arthropods, as well as the pogonophorans. Echinoderms and lophophorates were probably each derived from ancestors intermediate between polychaetes and hemichordates; echinoderms perhaps being farther along the line to chordates in their origin.
The various other groups are not all fairly treated in showing how advanced they are in an evolutionary sense. Their position is generally more an estimate of the antiquity of their origin.
OLDER VERSIONS OF THE TREE OF LIFE
A. Prior to the erroneous Lophotrochozoa and Ecdysozoa proposals the "Tree of Life" would have looked much like the version presented above with the following evident.
1. a separate origin of the deutrostomes from much earlier connecting the Hemichordates via unknown intermediates to the platyhelminthes.
2. a consequence is the assumption of a separate origin of coelom and blood vascular system of deuterostomes and advanced protostomes.
3. inexplicable cellular, histological, and moleular similarities in advanced protostomes and deuterostomes.
B. The Lophotrochoza error may some value as an assessment of lophophorate invertebrates but is not much use as showing relationships to vertebrates and some other phyla.
C. The Ecdysozoa error is made worthless by trying to make nematodes an important part of the evolutionary history of other some other phyla. Nematodes, as partially indicated in the diagram above, are probably part of an aschelminth group derived from turbellarian flatworms miniaturized by selection for adaptation for life in the interstices of marine, then freshwater and terrestrial sediments. The extreme specialization of nematodes did not provide a good base for selection of new groups. The superficial resemblance of their outer covering with the exoskeleton of arthropods is misleading. Surprisingly or fortunately, they did not make reptiles part of the group for shedding their skin. The post of May 31, 2013 should make it evident why the molecular data they used as a basis for Ecdysozoa is worthless.
D. Other versions of the "tree of life" based on symmetry and other features such as segmentation are not in vogue today, although the data used for them may have application in limited portions of "the tree of life". The antiquity of brachiopods and bryozoans as well as considerable differences in the lophophores would seem to argue for separate origins, perhaps from somewhere along the polychaete to pogonophora line.
E. The ancient annelid theory (over 100 years old) can be tweaked by insertion of the pogonophora to explain several things as shown elsewhere in the blog and indicated by the above diagram.
1. How the pogonophora turned an annelid arrangement of systems in to the chordate pattern.
2. How the anterior nervous system could fuse into a brain without an esophagus penetrating it.
3. How the drastic embryological changes of spiral to radial cleavage were simply made.
4. How molecular homologies of chordates and advanced protostomes came about.
Joseph G. Engemann Emeritus Professor of Biological Science, Western Michigan University, Kalamazoo, Michigan May 16, 2016
Disclaimer: All errors, mistakes, and omissions are my own and not the responsibility of Michigan State University, The University of Tasmania, nor Western Michigan University, nor the U. S. Fulbright Agency; although their assistance was valuable enabling me to make them. jge
The revised tree of life described in the previous post lacked any illustration to aide understanding. The transfer of files to a new computer, operating system and associated software (Windows Vista to Windows 10) has delayed production of something suitable. I was eventually able to find Paint embedded in 10. But my attempt to modify the diagram below with color to clarify the protostome and deuterostome groupings left an illustration dangling somewhere in a jpg file that I have not been able to migrate to this blog.
The protostomes began with platyhelminthes, the flatworms ancestral to other protostomes, and eventually deuterostomes via annelids. The anthropocentric view showing primates upper right as the ultimate chordates is only for illustration of our lineage. Every living group could have an illustration showing their group at the peak. Some hint of this is shown with wasps and flies being groups of insects at the upper left. And at the far left the cephalopods are perhaps the ultimate mollusks.
The boldface names in the above diagram represent groups in the direct ancestral line to primates. All animals with a eucoelomate body cavity are included in the annelids and those above them in he diagram. Phylum names are in all capital letters. Polychaetes are probably the ancestral annelids for other annelids (oligochaetes and their descendants the leeches), mollusks, and arthropods, as well as the pogonophorans. Echinoderms and lophophorates were probably each derived from ancestors intermediate between polychaetes and hemichordates; echinoderms perhaps being farther along the line to chordates in their origin.
The various other groups are not all fairly treated in showing how advanced they are in an evolutionary sense. Their position is generally more an estimate of the antiquity of their origin.
OLDER VERSIONS OF THE TREE OF LIFE
A. Prior to the erroneous Lophotrochozoa and Ecdysozoa proposals the "Tree of Life" would have looked much like the version presented above with the following evident.
1. a separate origin of the deutrostomes from much earlier connecting the Hemichordates via unknown intermediates to the platyhelminthes.
2. a consequence is the assumption of a separate origin of coelom and blood vascular system of deuterostomes and advanced protostomes.
3. inexplicable cellular, histological, and moleular similarities in advanced protostomes and deuterostomes.
B. The Lophotrochoza error may some value as an assessment of lophophorate invertebrates but is not much use as showing relationships to vertebrates and some other phyla.
C. The Ecdysozoa error is made worthless by trying to make nematodes an important part of the evolutionary history of other some other phyla. Nematodes, as partially indicated in the diagram above, are probably part of an aschelminth group derived from turbellarian flatworms miniaturized by selection for adaptation for life in the interstices of marine, then freshwater and terrestrial sediments. The extreme specialization of nematodes did not provide a good base for selection of new groups. The superficial resemblance of their outer covering with the exoskeleton of arthropods is misleading. Surprisingly or fortunately, they did not make reptiles part of the group for shedding their skin. The post of May 31, 2013 should make it evident why the molecular data they used as a basis for Ecdysozoa is worthless.
D. Other versions of the "tree of life" based on symmetry and other features such as segmentation are not in vogue today, although the data used for them may have application in limited portions of "the tree of life". The antiquity of brachiopods and bryozoans as well as considerable differences in the lophophores would seem to argue for separate origins, perhaps from somewhere along the polychaete to pogonophora line.
E. The ancient annelid theory (over 100 years old) can be tweaked by insertion of the pogonophora to explain several things as shown elsewhere in the blog and indicated by the above diagram.
1. How the pogonophora turned an annelid arrangement of systems in to the chordate pattern.
2. How the anterior nervous system could fuse into a brain without an esophagus penetrating it.
3. How the drastic embryological changes of spiral to radial cleavage were simply made.
4. How molecular homologies of chordates and advanced protostomes came about.
Joseph G. Engemann Emeritus Professor of Biological Science, Western Michigan University, Kalamazoo, Michigan May 16, 2016
Disclaimer: All errors, mistakes, and omissions are my own and not the responsibility of Michigan State University, The University of Tasmania, nor Western Michigan University, nor the U. S. Fulbright Agency; although their assistance was valuable enabling me to make them. jge
Sunday, May 1, 2016
REORGANIZING THE TREE OF LIFE
THE MAJOR STEP NEEDED
Third, factors responsible for the slow rate have accumulated but have not been linked with the remarkable longevity I have shown must exist, beginning with the evidence the pogonophorans present (Posted on October 24, 2015) discussed in the post of Jun 9, 2014 and illustrated in the post of June 13, 2014.
The tree of life, revised
The major line of animal evolution, known as deuterostomes and including chordates, hemichordates, and echinoderms, needs to be recognized as having its origin in the early annelid worms via a group of polychaetes now called pogonophorans. This recognizes the longer evolutionary history of protostomes. It also sets aside changes made by the proposals of Lophotrochozoa and Ecdysozoa as significant groups of animals; the post of May 31, 2013 explains why they should be dismissed.
[Engemann's] Modification of the
Annelid Theory of Chordate Origin
If
you have read the recent posts of this blog, starting with SCIENCE PREJUDICE on
March 17, 2016, you will understand why I didn’t say “The Creator’s Use of
Annelids to Make Humans”. My data driven
conclusions leading to understanding of the evolutionary sequence of events involved
do not discredit God by presenting it as a scientifically credible theory. That is especially true because the multiple
lines of evidence were unlikely to have been discovered by my
feeble efforts. I say the same thing
about Darwin’s work on developing the Theory of Natural Selection underpinning
our understanding of evolution. I hope I
will not withdraw recognition of the Creator’s role as Darwin may have done. Maybe I should just say “Modified Annelid
Theory of Chordate Origin”.
The lines of evidence
First, the observation of inverted systems, noted
for annelids as compared to chordates, was responsible
for the original proposal of annelid origin over a century ago.
Second, observations that evolution can occur
in developmental stages independent of adult features. This has been known for a long
time without perception of its significance.
Third, evolutionary rates at the abyssal depths
of the ocean can be so slow it makes molecular clocks
for determining evolutionary rates in different branches of the tree of life almost meaningless.
Some evidence of it being known in 1915 exists*,
but who would realize the importance of nothing happening?
Fourth, conditions in the abyssal depths
were the driving force for natural selection to bring about the deuterostome embryological
features from the original protostome annelid embryological features.
Fifth, the Pogonophora, unknown at the time of
the original annelid theory, embed the major evidence of intermediate linking features.
Where
is the evidence?
First,
the inversion is illustrated in the post of March 2, 2015. The concept was discussed in the June 28,
2013 post.
Second,
this fact of some independent evolution of embryonic features is generally accepted since the “Biogenetic Law” was
discredited. I was impressed by the
existence of an egg appendage (post of June 5, 2014) not found on more
primitive isopods (post of June 6, 2014) illustrating the concept.
Third, factors responsible for the slow rate have accumulated but have not been linked with the remarkable longevity I have shown must exist, beginning with the evidence the pogonophorans present (Posted on October 24, 2015) discussed in the post of Jun 9, 2014 and illustrated in the post of June 13, 2014.
Fourth, a number of research
reports have demonstrated the slowing of metabolic rates with depth in the
ocean. Some references are given in the
post of June 22, 2013. When data is
limited some have assumed the ages of organisms fell at the lower end of the
predicted range of error. Isopod egg features noted in other posts apply to understanding the cleavage change (protostome to deuterostome type via pogonophorans) due to reduced egg membrane constriction as a possible selective force.
Fifth, the pogonophorans show a
number of features intermediate between annelids and chordates noted in some of
the posts referenced above and in the post of October 24, 2015. Their importance is made clearer by their
critical role in life surviving extinction events as discussed in my post on
May 11, 2013.
The tree of life, revised
A simple correction for the tree of life is to leave the entire
protostome line intact (from the version before the Lophotrochozoa/Ecdysozoa
errors) and graft the deuterostome (or chordate) line on to the
Pogonophora/Polychaeta basal group of the Annelida. Echinoderms and
perhaps some lophophorates may have ancestry among other pogonophorans than
those leading to the chordate line.
*Brooks, William Keith. 1915. The Foundations of Biology. Columbia Univ. Press, New York. 339 pp.
He comments on - the unchanging nature of Lingula (page 219), and p. 217
“the diversity of the Lower Cambrian fauna and of its intimate relation to the
fauna on the bottom of the modern ocean”.
Joseph G. Engemann Kalamazoo, Michigan May 1, 2016
Sunday, May 17, 2015
ABYSSAL OCEAN ENVIRONMENT AND EXTREME AGE
THE WORLD'S OLDEST ANIMAL
In my post of June 13, 2014 I noted some evidence that pogonophorans can easily live to be over 10,000 years old. A brief discussion of factors leading to extreme longevity in the deep sea was presented earlier in a post on June 22, 2013. The importance of the pogonophorans as an over-looked link connecting chordates to annelid ancestors makes it important to understand deep-sea conditions better in order to understand the reality of that relationship.
OXYGEN, SALINITY, TEMPERATURE AND DEPTH OF THE OCEANS
My first clue to understanding the problem preceded my understanding of the pogonophorans. When teaching a marine biology class in my early years at Western Michigan University I was examining one of the fifty volumes of Challenger Reports of deep-sea research done in the 1870's. A map or graphs included distribution of oxygen, salinity and temperature by depth and latitude.
An oxygen minimum zone, with little or no oxygen, was centered at about 500 meters depth in temperate, sub-tropical, and tropical latitudes. In contrast to eutrophic fresh-water lakes where the oxygen rich zone is seldom more than ten meters thick, the oceanic counterpart may be over 100 meters thick. Oxygen was most abundant at the surface, but, after a brief, rapid increase below the oxygen minimum zone, gradually increased with depth below 1000 meters until, at the bottom a few miles lower, oxygen concentration was almost comparable to surface concentrations.
Temperature decreases with depth, salinity increases with depth. The change is most rapid near the surface and very gradual with increasing depth.
THE MAIN CIRCULATION FACTOR
Density of ocean water increases with depth until about 2000 meters depth due to greater salinity and lower temperature. So away from the polar regions bottom water is slowly rising with replacement from cold, salty, oxygen-rich water sinking along the bottom from polar regions at a relatively slow rate because of entrapment in the Arctic Ocean by shallower sea bottoms near most of its fringe.
The replacement of the sea-water beneath the oxygen-minimum zone takes over 10,000 years. The rate can vary according to overall ocean levels and depth of sills where Arctic Ocean water spills over to sink and eventually reach topical latitudes.
THE CONSEQUENCE OF SLOW REPLACEMENT
Oxygen would be depleted and the deep ocean would be an anoxic wasteland if animals lived at the same rate they do in shallower waters. Photosynthetic production of oxygen is limited to the first 100 meters or so of the ocean. Enrichment from the atmosphere is the only other significant source of oxygen in the ocean and is limited to the surface and circulation by mostly wave induced surface currents. The warmer surface and rain combine to lower density of water and make wave induced circulation ineffective below the thermocline (the zone of rapid drop in temperature).
AN ASIDE ABOUT HURRICANE SEVERITY
The thickness and depth of the thermocline can vary within the 50 to 300 meter depths of ocean water. Presumably a very intense hurricane induced wave episode could mix the ocean to a greater depth and compress the thermocline. That could perhaps store excess heat for a few years and reduce surface water temperatures so they have less heat energy to produce another mammoth hurricane for a few years. So the complications of predicting global warming rates is increased.
OTHER FACTORS
The ocean is generally more productive, with nutrients and organisms abundant, in shallow regions fringing continents, and in areas of up-welling currents which bring colder nutrient rich water to the surface. Sedimentation rates are generally very slow beyond the continental shelves. Most of the open ocean can be thought of as biological desert, but some very small organisms may be more abundant than others that are better known. More recent research indicates the small organisms may be more important than generally is known.
THAT OLDEST ANIMAL AGAIN
As long as its descendants stay in abyssal waters they will remain to help remind us of the stage that survived extinction episodes and enabled those moving to shallow water to adapt again to shorter lives and greater variety that includes the chordates. The previous post has a figure that shows one of the annelid-like features of the pogonophora and their similarity to near chordate relatives, the hemichordates.
Molecular clocks fail to place pogonophorans in the correct position in the "tree of life". The problem is addressed in the February 2, 2015 post; a better guess at the correct position is in the post
http://evolutioninsights.blogspot.com/2014/12/our-evolutionary-lineage.html
and why the molecular clock estimates of phylogeny of phyla is wrong in the post
http://evolutioninsights.blogspot.com/2013/05/science-screw-up-no-1.html
Inspiration for understanding evolutionary aspect of the embryological differences between protostomes and deuterostomes was presented in six posts from June 22, 2013 to June 30, 2013.
A MAJOR POINT OF THIS POST
The long residence time of bottom water of the ocean would make it anoxic if animals lived at the same rate we see occurring in shallow water. The alternative explanation would be extremely low populations and/or biomass in the abyss. Life is less abundant, but not nearly enough to account for the difference. The stability of conditions made it an ideal refugium to allow survival of forms that could later repopulate surface waters after an extinction event bad enough to cause the demise of over 90 percent of living species.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University May 17, 2015
In my post of June 13, 2014 I noted some evidence that pogonophorans can easily live to be over 10,000 years old. A brief discussion of factors leading to extreme longevity in the deep sea was presented earlier in a post on June 22, 2013. The importance of the pogonophorans as an over-looked link connecting chordates to annelid ancestors makes it important to understand deep-sea conditions better in order to understand the reality of that relationship.
OXYGEN, SALINITY, TEMPERATURE AND DEPTH OF THE OCEANS
My first clue to understanding the problem preceded my understanding of the pogonophorans. When teaching a marine biology class in my early years at Western Michigan University I was examining one of the fifty volumes of Challenger Reports of deep-sea research done in the 1870's. A map or graphs included distribution of oxygen, salinity and temperature by depth and latitude.
An oxygen minimum zone, with little or no oxygen, was centered at about 500 meters depth in temperate, sub-tropical, and tropical latitudes. In contrast to eutrophic fresh-water lakes where the oxygen rich zone is seldom more than ten meters thick, the oceanic counterpart may be over 100 meters thick. Oxygen was most abundant at the surface, but, after a brief, rapid increase below the oxygen minimum zone, gradually increased with depth below 1000 meters until, at the bottom a few miles lower, oxygen concentration was almost comparable to surface concentrations.
Temperature decreases with depth, salinity increases with depth. The change is most rapid near the surface and very gradual with increasing depth.
THE MAIN CIRCULATION FACTOR
Density of ocean water increases with depth until about 2000 meters depth due to greater salinity and lower temperature. So away from the polar regions bottom water is slowly rising with replacement from cold, salty, oxygen-rich water sinking along the bottom from polar regions at a relatively slow rate because of entrapment in the Arctic Ocean by shallower sea bottoms near most of its fringe.
The replacement of the sea-water beneath the oxygen-minimum zone takes over 10,000 years. The rate can vary according to overall ocean levels and depth of sills where Arctic Ocean water spills over to sink and eventually reach topical latitudes.
THE CONSEQUENCE OF SLOW REPLACEMENT
Oxygen would be depleted and the deep ocean would be an anoxic wasteland if animals lived at the same rate they do in shallower waters. Photosynthetic production of oxygen is limited to the first 100 meters or so of the ocean. Enrichment from the atmosphere is the only other significant source of oxygen in the ocean and is limited to the surface and circulation by mostly wave induced surface currents. The warmer surface and rain combine to lower density of water and make wave induced circulation ineffective below the thermocline (the zone of rapid drop in temperature).
AN ASIDE ABOUT HURRICANE SEVERITY
The thickness and depth of the thermocline can vary within the 50 to 300 meter depths of ocean water. Presumably a very intense hurricane induced wave episode could mix the ocean to a greater depth and compress the thermocline. That could perhaps store excess heat for a few years and reduce surface water temperatures so they have less heat energy to produce another mammoth hurricane for a few years. So the complications of predicting global warming rates is increased.
OTHER FACTORS
The ocean is generally more productive, with nutrients and organisms abundant, in shallow regions fringing continents, and in areas of up-welling currents which bring colder nutrient rich water to the surface. Sedimentation rates are generally very slow beyond the continental shelves. Most of the open ocean can be thought of as biological desert, but some very small organisms may be more abundant than others that are better known. More recent research indicates the small organisms may be more important than generally is known.
THAT OLDEST ANIMAL AGAIN
As long as its descendants stay in abyssal waters they will remain to help remind us of the stage that survived extinction episodes and enabled those moving to shallow water to adapt again to shorter lives and greater variety that includes the chordates. The previous post has a figure that shows one of the annelid-like features of the pogonophora and their similarity to near chordate relatives, the hemichordates.
Molecular clocks fail to place pogonophorans in the correct position in the "tree of life". The problem is addressed in the February 2, 2015 post; a better guess at the correct position is in the post
http://evolutioninsights.blogspot.com/2014/12/our-evolutionary-lineage.html
and why the molecular clock estimates of phylogeny of phyla is wrong in the post
http://evolutioninsights.blogspot.com/2013/05/science-screw-up-no-1.html
Inspiration for understanding evolutionary aspect of the embryological differences between protostomes and deuterostomes was presented in six posts from June 22, 2013 to June 30, 2013.
A MAJOR POINT OF THIS POST
The long residence time of bottom water of the ocean would make it anoxic if animals lived at the same rate we see occurring in shallow water. The alternative explanation would be extremely low populations and/or biomass in the abyss. Life is less abundant, but not nearly enough to account for the difference. The stability of conditions made it an ideal refugium to allow survival of forms that could later repopulate surface waters after an extinction event bad enough to cause the demise of over 90 percent of living species.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University May 17, 2015
Monday, May 4, 2015
EVOLUTION: ANNELIDS TO CHORDATES, THE MIDDLE STEP
THE MIDDLE STEP
The pogonophora to hemichordate transition is the most difficult step to see because pogonophorans are most easily seen as specialized polychaete annelids; and hemichordates are generally accepted as being in the chordate line. So the big step from the first (the protostome part of the lineage) to the last (the deuterostome part of the lineage) faces the greatest difficulty in seeing for those not familiar with what I have tried to show in earlier posts about this topic.
An obstacle is the residue left from past objections when the annelid theory was thought to be discredited by embryological and molecular evidence. Why those objections are irrelevant has been treated in earlier posts.
SOME GRAPHIC EVIDENCE OF THE MIDDLE STEP
A, B, and C illustrate the progression of stages from early larva to adult anterior of the hemichordate, Saccoglossus.
D, E, and G illustrate the progression of comparable stages of the pogonophoran, Siboglinum.
F illustrates the segmented posterior portion of an adult Siboglinum, and G- its anterior.
H illustrates the anterior of a giant pogonophoran from a thermal vent community. (A, B, and C, after Hyman and others; D, E, F, and G, adapted fromEngemann and Hegner after Webb; H, from a specimen in the U. S. National Museum.) [Fig. 12-5 in my unpublished 2010 manuscript, Evolution Insights.]
F, above, illustrates the posterior segmentation not reported until done so by Webb [Webb, M. 1964. The posterior extremity of Siboglinum fiordicum (Pogonophora). Sarsia, 15:33-36]. Possibly the segmented end of some species lost this region, or an intermediate species did before becoming hemichordates.
G and H show some of the variability of the anteriors of pogonophorans that resemble the anterior of C, a hemichordate.
A and D are not as precisely alike as one might like. But this was near the evolutionary step where the early embryology was changing drastically from protostome to deuterostome embryology.
REFERENCES to many of the research articles influential in helping me see the protostome-deuterostome connection, especially the molecular evidence showing the error of current studies were posted in
http://evolutioninsights.blogspot.com/2014/11/evolution-molecular-clocks.html
which you can get to by using the Blog Archive at the right and clicking on the 2014 November arrows. Or send the address above to a friend you think might find it interesting. Most of the references are annotated with my comments to myself or quotations from the article.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University May 4, 2015
The pogonophora to hemichordate transition is the most difficult step to see because pogonophorans are most easily seen as specialized polychaete annelids; and hemichordates are generally accepted as being in the chordate line. So the big step from the first (the protostome part of the lineage) to the last (the deuterostome part of the lineage) faces the greatest difficulty in seeing for those not familiar with what I have tried to show in earlier posts about this topic.
An obstacle is the residue left from past objections when the annelid theory was thought to be discredited by embryological and molecular evidence. Why those objections are irrelevant has been treated in earlier posts.
SOME GRAPHIC EVIDENCE OF THE MIDDLE STEP
A, B, and C illustrate the progression of stages from early larva to adult anterior of the hemichordate, Saccoglossus.
D, E, and G illustrate the progression of comparable stages of the pogonophoran, Siboglinum.
F illustrates the segmented posterior portion of an adult Siboglinum, and G- its anterior.
H illustrates the anterior of a giant pogonophoran from a thermal vent community. (A, B, and C, after Hyman and others; D, E, F, and G, adapted fromEngemann and Hegner after Webb; H, from a specimen in the U. S. National Museum.) [Fig. 12-5 in my unpublished 2010 manuscript, Evolution Insights.]
F, above, illustrates the posterior segmentation not reported until done so by Webb [Webb, M. 1964. The posterior extremity of Siboglinum fiordicum (Pogonophora). Sarsia, 15:33-36]. Possibly the segmented end of some species lost this region, or an intermediate species did before becoming hemichordates.
G and H show some of the variability of the anteriors of pogonophorans that resemble the anterior of C, a hemichordate.
A and D are not as precisely alike as one might like. But this was near the evolutionary step where the early embryology was changing drastically from protostome to deuterostome embryology.
REFERENCES to many of the research articles influential in helping me see the protostome-deuterostome connection, especially the molecular evidence showing the error of current studies were posted in
http://evolutioninsights.blogspot.com/2014/11/evolution-molecular-clocks.html
which you can get to by using the Blog Archive at the right and clicking on the 2014 November arrows. Or send the address above to a friend you think might find it interesting. Most of the references are annotated with my comments to myself or quotations from the article.
Joseph G. Engemann Emeritus Professor of Biology, Western Michigan University May 4, 2015
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