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