Wednesday, November 8, 2017

JESUS

 Jesus has been closer to me than I realized all of my life.  Unfortunately, I have not given him the recognition he deserves; and as I will be ninety late next year, if I make it, I don’t have a lot of time to make up for my omissions.  I have begun a few posts in the last few years that were almost introductory to a last post.  I have less premonition of such an event now, but the possibility of mental decline increasing made it seem like a good idea to write this now.  I may enlarge on topics in future posts, but I can’t be sure of that.

Who is Jesus?

Jesus is the second identity in the one Trinitarian God who took the human nature to help bring salvation to all people that accept him.  Having become truly human he gives us reason to believe that God really understands our problems.  He sacrificed his life for us to fulfill the will of the Father (at the same time being one with Him) to wipe away our sins that seem to us an impediment to entering heaven.  God’s love is all encompassing, and God’s Holy Spirit is always urging us to improve our love for God and all humanity.

Jesus was born of the virgin, Mary.  His life as the Son of God, a human, as well as his eternal life with the Father and the Holy Spirit, is more than I can explain; but I think it is reasonable when you consider that God is an infinitely powerful, eternal being that precedes the universe and time, both of which are parts of his creation.

Jesus, the Jew.

Born into the chosen people, Jesus was trained in the scriptures and followed the Jewish law and traditions under the guidance of his family in preparation for his brief earthly role as the Messiah predicted by Isaiah and other prophets.

He castigated teachers in the temple who interpreted the law so strictly for the people but, did not act the way they taught.  Jesus summed up the law of the Old Testament as the guiding principle in the New Testament, as love of God and neighbor.

Jesus and science.

It appears that Jesus does not try to teach us principles of science.  Instead he accepts the understanding of the culture of the time and uses it to teach things he is concerned about. 
In the previous post, I mentioned the nematode worm that is wound up on a stick to extract it from the skin of an infected person.  Jesus mentions it as a symbol of the way he would die on a cross (John 3:13-15) and references it later (John 8:28 and 12:32-33); the bronze serpent had been held up by Moses (in Numbers 21:6-9) as instructed by God.  In the telling of the story the worm became a seraph serpent depicted in bronze wound around the stick, converted to the symbolic crucifix, used by Christians as a reminder of Jesus’ death and love for us.  And it is converted to a symbol of the medical professions as the caduceus, usually showing the serpent wound around a winged staff; the medical version may be showing a connection to the method of extracting the nematode, or possibly gods of Greek mythology.  [Credit for my knowing the possible connection of the parasite being the fiery serpent of the bible goes to an unknown colleague of Dr. E. B. Steen, my colleague at WMU, who told me about him nearly sixty years ago.]

The three days before the resurrection of Jesus were prefigured by Jonah’s three days in a big fish.  Whether it was literal truth, but mistaking a whale for a big fish, or myth or legend of the Paul Bunyan sort, it provided a teaching moment linking old and new in the Bible.

Science and Religion

There are numerous bits with accuracy in understanding of science common to biblical days as presented in scripture.  Variation in germination and growth of plant seed dependent on soil and determining yield, predicting weather based on clouds on the horizon, the relative permanence of a dwelling built on rock as opposed to sandy soil, as well as understanding of human behavior, are among examples enriching the teachings of Jesus recorded by his disciple’s followers as well as some apostles.

The findings of science are all tentative, i.e., capable of being falsified by new data.  Of course, laws are not expected to yield to new interpretations, whereas hypotheses change, hopefully with declining frequency as new data is obtained and interpreted.  When it comes to spiritual things, science in incapable of making valid observations to either prove or disprove spiritual matters.

The findings of religion do not appear to have clarity of method in all cases.  Because the three dominant monotheistic views differ to increasing degree as we leave discussion of God and some basic principles, we will probably never reach complete unity even though we should strive for it.  But it is difficult for those believing all scripture should be interpreted literally to believe-- the scientific view of age of the universe, or fossils; the fiction incorporated in some bible stories and parables that were used to teach moral principles; the exaggeration common to speech and scriptures during biblical times.

Can we add separation of science and religion to separation of church and state as a desirable principle?  Maybe separation of science and state too?

My personal relationship with God

It has been a journey, many others have taken it, and it is open to you.  I have no doubt that  God has been with me all my life, even when I did not cooperate.  The same is true for you, just have patience.  In the meantime, I suggest a short daily reading of scripture.  Give God a chance.  

The apostle, John, had a close relationship with Jesus, and cared for Mary after the Crucifixion.  So John had opportunity for learning about Jesus' childhood from Mary and directly observing Jesus during his ministry.  So those constructing his gospel were able to faithfully give a clearer picture of what Jesus taught.  In John 13:34-35 we learn of the new law, "love one another".  We get a clearer picture of the Holy Trinity in John 5:19-30 and 5:14-17.  The equality of men and women is perhaps best shown in John's Gospel.

My love of the gospel according to John may be attributed to the fact it was the first one we studied the first year I joined as the only graduate student, along with some faculty and townspeople, in a study group led by Dr. Joseph Druse, an English Professor at Michigan State University.

Joseph Engemann      Kalamazoo, Michigan    November 8, 2017 




Monday, October 30, 2017

EVOLUTION: NEMATODE WORMS

Nematode worms are typically long, round, unsegmented, gradually tapered at both ends.

"Nematodes have many species with relatively little difference in body form.  Many are parasitic and it is thought that most species of vertebrates may have one or more parasitic nematode species unique to them.  Nematodes parasitize many other groups of animals and plants.  Many live in the intestines of animals.  One free-living nematode species lives in organic rich soil but can also live as a parasite in humans. Rotting organic matter in soil is not so different from the intestinal contents of some animals.  Both are rich in bacteria that the nematodes can feed upon.  Adapting to the rich soil made them somewhat "pre-adapted" to life as an intestinal parasite. This adaptation included an ability to live in environments with oxygen so limited many other animals could not survive." (from my unpublished 2010 manscript)

The similarity of structure of different species disappears when the mouth end, and often the anal end, are examined microscopically.  Three jaws are present in some.  The pharanyx may have a muscular bulb that probably helps ingestion of food without losing pressure, the body contents act as a hydrostatic skeleton.  The cuticular covering of the body is molted or shed typically several times in early development.  During the process of development portions of the chromosomal material can be ejected from the chromosomes; this is perhaps a result of selection for the small size of ancestors living among the sand grains of soils. In one species the ejection of chromatin occurs in all cells except the stem cell until the 32 cell stage.  Body cells of many achelminths other than nematodes also seem to have the loss of ability to regenerate that is thought to be a result of the reduced chromosomal material in body cell nuclei (or nuclei when tissues are syncytial).  Near constant number of nuclei or cells of the species are present in the tissues of many aschelminths.

I was reviewing some of Libbie Hyman's work on Aschelminthes (not accepted as a valid cluster by many zoologists), but unfortunately she did not have the benefit of knowing about gnathostomulids (first described in 1956) which were later.  Gnathostomulids seem to be descendents of the simple early flatworms that are not flat, but are adapted to living in sediments that are often anoxic.  Reidel, 1969, suggests the gnathostomulids can be placed in either the Platyhelminthes or the Aschelminthes.  The gastrotrichs may be the connecting link to rotifers.  Nematodes may have been the termination of a line orginating early in the cluster of achelminth groups; but they have a complete lack of cilia, a fact that makes them unlikely to have given rise to any other groups since arthropods also lack cilia but are so clearly derived from annelids that do have cilia.  Thus the lack of cilia in nematodes and arthropods is an analagous, not homologous, trait.

The reason I referred to Hyman was to find out about the adhesive glands or pedal glands, commonly paired on most ashelminths' posteriors, but absent in the gnathostomulids.  The glands are very small and difficult to see, especially in nematodes.  I did not see them in some nematodes I had watched in water on a microscope slide at low magnification, but those nematodes were clearly adhering by their tail as the writhed around.  One researcher (Chitwood) divided nematodes into two groups depending on whether they had phasmids at their posterior.  The mouth area and anal areas of nematodes show great variation in microcopic details not conducive to casual observation.

Such fine details can be a great help in identifying species and often show revealing variation suitable for showing evolutionary relationships.  The October 20, 2017, issue of Science has a research report detailing such a fact with feather-like hairs on water-strider feet.  In the case of water-striders, the details are limited to very close relatives.  In arthropods, similar microscopic comparisons can be made of structures limited to closely related species of the same genus and sometimes of different orders.

When the very small and the very large features match, relationship seems more likely.  To determine evolutionary relationships, neither can be ignored.  Over-dependence on one may lead to error and demonstrate why the novice or student may see things the specialist or teacher does not see, a relationship affecting creativity as noted by Tinbergen.

Among the larger features distinctive for nematodes, that show them as a terminal group in an evolutionary sense, are the muscle cells of the body of the intestinal parasite, Ascaris.  All are longitudinal and each passes a muscle cell process to the nerve enervating the muscle.  Other lines of evidence that the Ecdysozoa are an invalid group are indicated by some of the references appended.

Ascaris can grow to a foot long during it time in the intestine.  It has a simple life cycle with transmission of eggs, typically ingested with fecal contaminated food, hatching in the intestine and larve going through tissue and blood to the lungs where they break out and get coughed up, swallowed, and then comlete their life in the intestine.  Another nematode parasite of humans is thought to be the fiery serpent mentioned by Moses.  It has a big name, Dracunculus medinensis, and is known as the guinea worm.  The adult female can be as much as a meter long and live in the subcutaneous tissue under the skin.  The larvae are discharged through a hole in the skin and, if ingested by an aquatic microcrustacean named Cyclops, complete their larval development and, if Cyclops is ingested by a human, eventually reach their location under the skin.

The great variations in size, number of host species needed to complete life cycles, and adaption to a single or limited number of final hosts of most vertebrates, as well as many invertebrates, seems to indicate an ancient origin for nematodes.

Joseph G. Engemann    Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan   October 30, 2017

REFERENCES (comments added)

Aguinaldo, Anna Marie A., James M. Turbeville, Lawrence S. Linford, Maria C. Rivera, James R. Garey, Rudolf A. Raff, and James A. Lake.  1997.  Evidence for a clade of nematodes, arthropods and other moulting animals.  Nature, 387:489-493. Unfortunately, textbooks have picked up their grouping of nematodes with arthropods and some other molting animals in a group they named Ecdysozoa; based on 18s ribosomal DNA sequences, it is inadequate to support such a group.  They even say “It was unexpected to find nematodes contained within the Ecdysozoa because in previous molecular studies they diverged deep in the protostome tree, even before the deuterostome-protostome bifurcation.”   -page 491 has discussion of unequal rates found in other nematode studies (documented and ignored) and their search for and choice of slowly evolving representatives [almost guaranteed to put an outgroup in where it doesn’t belong]


Fraser, Hunter B., Aaron E. Hirsh, Lars M. Steinmetz, Curt Sharfe, and Marcus W. Feldman.  2002.  Evolutionary rate in the protein interaction network.  Science, 296:750-752.  (26 Apr 2002)  “We show that the connectivity of well-conserved proteins in the network is negatively correlated with their rate of evolution.”  “interacting proteins evolve at similar rates.” - used “putatively orthologous sequences between Saccharomyces cerevisiae and the nematode Caenorhabditis elegans.” 

Halanych, Kenneth M.  1996.  Testing hypotheses of chaetognath origins: long branches revealed by 18S ribosomal DNA.  Syst. Biol., 45(223-246.   Well-done study but long branches and small sample size make result of relationships beyond the nematode-chaetognath affinity somewhat dubious.

Halanych, Kenneth M., John D. Bacheller, Anna Marie A. Aguinaldo, Stephanie M. Liva, David M. Hillis, and James A. Lake.  1995.  Evidence from 18S ribosomal DNA that the lophophorates are protostome animals.  Science, 267:1641-1643.  “we propose the node-based name (16)[K. de Queiroz and J. Gauthier, Syst. Zool. 39, 307 (1990)] Lophotrochozoa, which is defined as the last common ancestor of the three traditional lophorate taxa, the mollusks, and the annelids, and all of the descendants of that common ancestor.”  Note 10 includes the following statement “Regions that could not be readily aligned were excluded from the analyses.”  Their proposal is ridiculous when all data are considered.

Halanych, Kenneth M., and Yale Passamaneck.  2001.  A brief review of metazoan phylogeny and future prospects in Hox-research.  Amer. Zool., 41:629-639.  maintain Hox gene research supports the earlier ridiculous proposals of ecdysozoans and lophotrochozoans.  Has numerous references.

Hobert, Oliver, and Gary Ruvkun.  1998.  A common theme for LIM homeobox gene function across phylogeny?  Biol. Bull., 195:377-380.  neurogenesis regulatory genes and transcription factors are very similar in vertebrates, insects, and nematodes

Hobmayer, Bert, Fabian Rentzsch, Kerstin Kuhn, Christoph M. Happel, Christoph Cramer von Laue, Petra Snyder, Ute Rothbackerm, & Thomas W. Holstein.  2000.  WNT signaling molecules act in axis formation in the diploblastic metazoan HydraNature, 407:186-189.  the WNT signaling pathway had been found in nematodes, insects and vertebrates.

Kappen, Claudia.  2000.  Analysis of a complete homeobox gene repertoire: implications for the evolution of diversity.  Proc. Natl. Acad. Sci. USA, 97:4481-4486.  used the nematode, C. elegans

Sarnat, Harvey B.  1984.  Muscle histochemistry of the planarian Dugesia tigrina (Turbellaria: Tricladida): implications in the evolution of muscle.  Trans. Am. Microsc. Soc., 103(3):284-294.  Says striated muscle is in every metazoan phylum except Porifera and adult Platyhelminthes. (oblique striations in nematodes – Rosenbuth 1965, 67  Wright 62) 


Van Auken, Kimberly, Daniel C. Weaver, Lois G. Edgar, and William B. Wood.  2000.  Caenorhabditis elegans embryonic axial patterning requires two recently discovered posterior-group Hox genes.  Proc. Natl. Acad. Sci. USA, 97:4499-4503.  “essential embryonic patterning in C. elegans requires only Hox genes of the anterior and posterior paralog groups, raising interesting questions about evolution of the medial-group genes.” Three Hox genes in the nematode



Sunday, October 29, 2017

LUTHER THEN AND NOW

Today's paper

A Washington Post article by Jonathan Kay, “Nobody Listened to Luther at first. That’s why he succeeded”, published in the Kalamazoo Gazette October 29, 2017, deserves reading to see an example of how momentous ideas develop.  Some similar circumstances surrounded Darwin’s ideas about natural selection.

Non-conformists may face problems

Today such factors as rapid communication and professional networks can, Kay writes, “make us more cautious, since we know that any new idea can expose us to instant censure from complete strangers in other parts of the world………. – This phenomenon goes by different names – group think, political correctness, herd mentality.  But in every form, it serves the interest of the orthodox and frustrates the heretic.” 

I sometimes feel like I am a group of one in terms of my findings.  I don’t expect to be in a group with Luther or Darwin, but I am not aware of much acceptance of what I thought were my best ideas about evolution.  I do appreciate the fact that my post about the coelom has received so many views.
An early post of mine-  http://evolutioninsights.blogspot.com/2014/02/creativity-brainstorming.html  has had zero page views. The post makes suggestions for solitary brainstorming that can substitute to some degree for the benefits of group brainstorming.

Nematodes

I have begun a draft of a post on nematodes.  It is hoped to be helpful in understanding the antiquity of their origin, far before the time the erroneous Ecdysozoa implies.  I was reviewing some of Libbie Hyman’s invertebrate volumes and will leave most related comments to the forthcoming post.  But the last two paragraphs of the post http://evolutioninsights.blogspot.com/2015/03/abandoned-theories-and-libbie-hyman.html  said some of the things I might have repeated.


Christian Unity

Today, about the 500th anniversary of the event most associate with Luther’s long campaign, there is a mood that seems to have developed in recent years, of Protestants recognizing that Catholics have gotten past such blemishes as selling indulgences and killing heretics, and of Catholics thinking that Protestants have selectively departed from teachings of Jesus.  There is recognition of a common bond for many on both sides of the former divide; and if it has not been there before, that all humans are created by, and loved by, God.

Joseph Engemann      Kalamazoo, Michigan   October 29, 2017

Monday, October 23, 2017

The Economy

The blog post, “History Repeating”, that I posted in April of 2016 was copied from a journal entry I wrote in 2009.  It seems like history is still repeating in the economy, the political world, and perhaps other ways.  It seems like it is worth reading for those in the USA. 

If you want to read it you can get there by clicking the arrowhead before 2006, then April, then History Repeating.  I think you can also get there by clicking

https://www.evolutioninsights.blogspot.com/2016/04/history-repeating.html

Don’t let it depress you too much – repeating can be better than destroying.  It might be better to call it a cycle, or a day, year, or generation.  It can even make you happy when it is children or grandchildren.

If you apply natural selection theory to economic or political theory it might result in beneficial change.  It doesn't need to be as destructive as revolutionary change that people see in what Marx accomplished.  Gradual change is most likely to be both beneficial and successful.


Joe Engemann     Kalamazoo, Michigan    10/23/17

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

Saturday, September 30, 2017

EVOLUTION: OFFBEAT IDEAS

Evolution: Offbeat Observations

Georg Lichtenberg said “It is impossible to carry the torch of truth through a crowd without singeing someone’s beard”, according to James Geary (2005, The World in a Phrase, Bloombury Publishing, New York, 229 pp.).  It somewhat comforts me as I write about the multiple errors earnest and intelligent researchers of evolution have made, errors I am trying to replace with a more accurate depiction of the tree of life.

One, of the two worst research reports establishing a faulty superphylum, Ecdysozoa, had a lady as the primary author; it made me realize the sexist nature of the aphorism quoted above.  I also do not know if the gentleman first author of the publication setting up the other faulty superphylum, Lophotrochozoa, had a beard to be singed.

The most influential zoologist of the last hundred years could well be Libbie Hyman.  See http://evolutioninsights.blogspot.com/2015/03/abandoned-theories-and-libbie-hyman.html  She deserves the respect given her, mistakes in her work are minimal, and I also do not want to detract from other work by the two authors whose work is criticized in http://evolutioninsights.blogspot.com/2013/05/science-screw-up-no-1.html , after all, “to err is human”.  I guess that proves I am human too.

When offbeat becomes main-stream evolution

Three of the last four blog posts have had bits about the abyssal ocean.  There are several facts about the abyss that can help us understand major consequences for evolution shaping life today in unappreciated but interconnected ways.

One, the stability of the abyssal region offered refuge from numerous early extinction events.

The extreme pressure, lack of light for photosynthesis, low input of surface debris reaching the abyss, near-freezing temperature, and sparse populations were ecological factors leading to the long-life, low reproductive rates, and emphasis on survival adaptations characteristic of K-selected life styles.  They contrast to r-selected life styles of organisms where abundant food and high predation lead to short lives, high reproductive rates, rapid growth, and perhaps higher evolutionary rates of most organisms in lighted, warmer surface habitats.

Two, the abyssal affects on embryology and metabolic rates

The low reproductive potential in the deep sea put such a high priority on survival that it selected for delayed specification of embryonic fate of cells so loss of a cell from an early embryo would not prevent normal development.  This led the transition from protostomes to deuterostomes that have the ability to have an early embryo divide and produce two individuals instead of dying like a protostome embryo would.  Pogonophorans are at the junction where this happened and they have a mix of protostome and deuterostome features.

As I have noted elsewhere, the extreme pressure is probably a factor slowing metabolic rates and extending life-spans in the abyss.  Several studies have shown respiration is slowed greatly beyond what colder temperatures alone would depress rates.  One of the most enlightening clues was that a brown bag lunch contained a sandwich and an apple, that sank to the ocean bottom many months before they were retrieved with the sunken research vessel, Alvin, and were both in fresh condition.  Similar food in cold seawater decayed within a few days.

The ocean layer and circulation patterns described in a recent blog show that oxygen levels below the oxygen minimum layer would be impossible to exist if respiratory rates at abyssal pressures were anywhere near rates normal in shallow water below the photic zone.

Three, it’s a bit complicated

but the things above help show the role of the pogonophorans as an intermediate that also accounts for some features of our development and structure that were first accounted for by the annelid theory of chordate origin, an abandoned theory that is correct when adjusted for the role of the pogonophorans.




Joseph Engemann    Emeritus Professor of Biology, Western Michigan University, Kalamazoo, Michigan    September 30, 2017

Tuesday, September 26, 2017

pre-Cambrian survival

I never knew  -  ‘till Kalamazoo

What did I not know until Kalamazoo?  There is a tremendous amount that I didn’t know, and still don’t.  But that is probably true for most of us.  What I am talking about is some of the events related to how we evolved over the past two billion years to become the dominant species on earth.  Our knowledge of evolution is riddled with gaps and errors, even though the general story of evolution by natural selection is probably close to the truth.  The last section tells of three important ways marine species may have been able to survive the intense extended period of pre-Cambrian asteroid bombardment.

Many that believe in God reject evolution because the sequence of chance and random events are not acceptable as work of a creator conforming to their concept of God.  Many scientists, especially biologists, have found it difficult to accept God as the creator because acceptance is not compatible with their concept of the chance and randomness involved in evolution.  Both may struggle with the chaos, disasters, evil, and other bad things they see in the world and want to blame God, or see it as evidence of God’s non-existence.

Stop for a moment, and think about something in your life that seemed bad, but in retrospect you see that it helped make you who you are.  There are numerous such occasions in the evolution of life that may have been essential for evolution to take its peculiar course over the last billion years it took to produce Homo sapiens.  If that doesn’t inspire you, read on, find out how important extinction events were in the course of evolution leading to us.

THE FIRST TEN BILLION YEARS

The “Big Bang” begs a question like the one asking “is there is a noise if a tree falls in the wilderness and there is no one there to hear it?”  Astrophysicists have an answer for the projected rapid expansion from the first relative speck to the slowing expansion, formation of elementary particles, elements, and the first generation of stars.  Condensation of materials into later generations of stars (after the extinction of some early ones) was responsible for the formation of heavier elements completing the materials needed for the evolution of life on planets with favorable conditions around stars like our sun.

We don’t need to know the details of the formation of our solar system.  It was probably similar to a billion other places of the expanding universe.  Whether the protoplanetary disks around the stars formed by condensation of more diffuse matter, or from emissions or explosions from the newly formed stars, sufficient matter ended up forming planets spinning and orbiting the sun.  Some planets had sufficient gravity to retain gases in their atmosphere and retain space debris striking them.  Planets tend to collect most of the debris as well as larger objects in their orbits.  The larger objects sometimes were captured in orbit as moons or impacted the planets with varying results.  The sun, with its massive gravity, probably collected many objects, even planets, that lost speed due to some collisions and fell into the sun.

Our moon does not have seas and atmosphere like the earth, so erosion has not obscured the craters produced by impacting meteors, comets, and asteroids.  In fact, the moon may have provided some protection to us from some that would otherwise have hit the earth.  Craters are much more numerous on the far side of the moon than they are on the lava fields of the near side.

Some worry more than necessary about the danger of an asteroid causing our extinction as part of a phenomenon much like he events terminating the dinosaurs.  It is remotely possible, but the solar systems planetary arrangement suggests that a much more stable system exists than the state several billion years ago.

Where would we be without asteroids?
 The irregular structure of some asteroids and craters or “pock marks” shows they had been stuck many times.  The presence of many moons and smaller satellites around the four largest planets, all beyond Mars, suggest that some were captured as moons and perhaps the collision with potential moons and or planets may have provided the fragments (asteroids) of the asteroid belt orbiting in space between the orbits of Mars and Jupiter.

Some of those fragments provided extinction-type events in decreasing frequency as they were swept up by earth, the moon, adjacent planets and their moons.  In the beginning impacting asteroids contributed mass to the earth.  They probably sped up some of the potential chemical evolution steps in the pre-biotic earth.  Perhaps their craters filled with water to make many experiments in addition to the intertidal pools where the chemical steps leading to organic life may have started. 

How life survived asteroids

The late pre-Cambrian is thought to have experienced a long period of more intense asteroid impacts.  The abyssal sea was so great a portion of the earth’s surface layer, and the cold polar seawater flowing toward the equatorial region had high density due to temperature and salinity that allowed it to gradually replace bottom water.  The process continued taking thousands of years to have bottom water reach the surface, just as happens today.  Animals able to adapt to the abyss had such an extensive area to inhabit it enabled some to survive even the worst asteroid hits.

A second method was the selection of cysts and other survival mechanisms used as overwintering, drought resistant, and dispersal stages that can emerge from somewhat suspended animation when conditions improve.  Such stages were already being selected by the rigors of surviving dry periods in freshwater temporary ponds as well as in saltwater pools along ocean shores.  Gemmules of sponges and statoblasts of bryozoans are cystlike asexual reproductive bodies, common among freshwater species but missing in marine species, suggesting such survival mechanisms are now less valuable for marine species in their more stable environment.


A third method is direct uptake of nutrients dissolved in seawater.  The mortality of marine species may well have boosted the dissolved organic matter content of seawater following an asteroid extinction event.  It may be an important method in today’s oceans for the survival of larval stages during dispersal, especially in species providing little yolk for nutrient reserves for the larvae.  Stephens, Grover C., and Robert A. Schinske  (1961, Limnology and Oceanography, 6:175-181.)  found that in ten phyla tested only arthropods did not take up amino acids from very dilute solutions in seawater.  Manahan and Crisp (1982, American Zoologist, 22:635-646) found dissolved amino acids could be taken up by bivalves from egg to adult stages.

The pogonophora benefitted by their living in the abyss, a relatively protected location of such great extent that remnants of the population might survive.  They also benefitted from the third method of direct uptake of dissolved nutrients in sediment water.  The "degenerate" appearance of the pogonophorans is part of an evolutionary step backward that laid the groundwork for the advance of animals to today's vertebrates.

Joseph G. Engemann   Kalamazoo, Michigan    September 26, 2017