Saturday, August 1, 2015



The study of evolution encompasses all of biology.  So we face a problem in understanding evolution much as the ant faces in understanding the tree it is climbing.  It can climb all over it.  But much is hidden in the ground and under the bark.  Even the living part of the tree is mostly hidden by the dead outer layer of bark.  If all the tissues and functions that make up the tree were known, it would still be a monumental task to understand how it worked and how it was affected by its environment.


The fossil record, comparative anatomy, comparative embryology, comparative physiology, and nucleic acid analysis have been the major entries to understanding evolution used by past and present researchers.

1 - The fossil record has left a partially connected chain of organisms leading to the present living world.  It has not left an unambiguous source due to- gaps in fossil bearing sediments - soft bodied forms rarely leaving fossils - and our inability to always determine if a line of fossils was gaining or losing a feature.  Ancestral forms may appear in strata with later descendants as shown by an example in  [ ].

2 - Comparative anatomy and related microscopical studies, especially embryology, did the heavy lifting in bringing evolution studies toward maturity.  It still is a major source of new understanding; for an unusual example connecting anatomy and psychology see [ ].  Many studies need a combination of factors other than anatomy considered, an example is shown in how the extreme longevity of pogonophorans was determined [ ] and [].  The anatomical similarity of pogonophorans and hemichordates is illustrated in [ ].

The sponge-cnidarian transition was first hinted at by a fossil comparison [ see ] supported by a hypothetical argument based on spicules in both sponges and some cnidarian nematocysts [ and illustrated in ].

The cnidarian-flatworm transition is further discussed in [ ] and illustrated in [ ].

3 - Comparative physiology provides many insights regarding relationships.  An example is noted in a comment about vitamin C in the previous post [ ].  The same post mentions the anatomical evolutionary connection of our appendix with the cecum of herbivores, noting that function lacking structures are often rapidly lost by lacking selection for their retention; the appendix may have value from the lymphatic tissue it contains as well as for possible retention of gut organisms for re-inoculation of a gut purged of them by diarrhea.

4 - Comparative biochemistry studies, especially DNA and RNA studies, are still the gold standard of determining close evolutionary relationships.  It is far less useful in determining relationships of phyla because rates of change can vary among the chromosomes as well as differing in different organisms.  This has been discussed in many posts, especially [ ]


Systematics indirectly confirms the reality of evolution.  When Linnaeus classified plants and animals he is thought to have assumed the different forms were created separately by special creation.  Consequently, the groups named were clustered in a hierarchy based primarily on anatomy.  When groups are determined by scientists using an evolutionary hypothesis, they approximate the relationships in the classification designed by Linnaeus.


No one knows the mind of God.  Lacking direct revelation of the creation of diversity that is not clouded by inspired story, parable, and limitations of knowledge among inspired writers, we are left with only science to give us a clear look at the details of how God did it.  Even the best intentions of christian writers can go astray as noted in [ ].  My recent post [ ] might be helpful in providing greater understanding of other arguments.  The tools of science are adequate to prove the existence of evolution, but not the existence of God; they are inadequate to prove God does not exist.


The complexity of the interrelationships of biological sub-disciplines is most fully appreciated in the study of evolution and ecology.  Genetics is also an excellent organizing principle making sense of the diversity of life and evolutionary processes.  One or more of the first three entry points are often missing or insufficiently well known in the education of today's biological scientists.  For those well versed in genetics and molecular biology, just realizing the limitations of those areas are cause for not rejecting the older scheme of phylum relationships, prior to the invalid acceptance of Ecdysozoa and Lophotrochozoa as natural groups.  The post of 2013/05 listed at the end of 4 above tells why.

Joseph G. Engemann    Kalamazoo, Michigan    August 1, 2015

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