Further thoughts on convergent evolution

In my last post I talked about the phenomenon of convergent evolution (CE) in a rather speculative and tongue in cheek short essay.

In my admittedly biased opinion, I think that this is one of the most interesting and yes, mysterious aspects of out current understanding of evolution. Briefly, CE explains the many similarities between distantly related organisms. The classical example is the common general morphology between let’s say sharks, porpoises and the extinct ichthyosaurs, the idea is that this close morphology develops because it is one of the optimal solutions to the problem of locomotion in a liquid environment.

Keep in mind though, that morphology is but one aspect of a phenotype, namely the ultimate expression of the genetic instructions of an organism. Phenotypes are not limited to morphology though; anything that is controlled by genes, like metabolism and other aspects of physiology are also phenotypes, and therefore convergence can also be present in these aspects as well (I go over genotypes / phenotypes in a little more detain here and here).

In addition to convergent evolution’s explanatory power in terms of known biology, a rather interesting application of convergent evolution thinking is the (at this moment sheer) speculation on possible alternate forms of life, here on Earth or elsewhere.

One of the most visible scientists that explores convergent evolution is Simon Conway Morris of Cambridge University. He is a paleontologist who happens to be one of the heroes of the late Stephen Jay Gould’s book Wonderful Life (oh, how I miss your writing, Steve, you pompous guy!).

Ironically, Conway Morris fundamentally disagrees with Gould’s thesis. For a few years now, Conway Morris has had his sights on CE; in 2003 he published Life’s Solution: Inevitable Humans in a Lonely Universe, an interesting but dense, thick book, full of CE examples. I intend to re-read it as soon as I can so I can share my thoughts with you, however, a more tractable book is a series of essays compiled by Conway Morris based on a 2004 Templeton Foundation Symposium on “Purpose in Evolution”.

***To my non-theist friends: Please stop your heads from spinning, I have not gone to the dark (or is it bright?) side. My thoughts, hopes and doubts on theism have not changed***

(:-)

The book that includes the proceedings of that meeting is The Deep Structure of Biology: Is Convergence Sufficiently Ubiquitous to Give a Directional Signal? (2008) Templeton Foundation Press (friends, see my note “***” above).

The currently accepted “core” of evolution implies a lack of directionality, masterfully articulated by Gould. He famously compared the history of life on Earth with a video tape (archaic technology, look it up). Essentially, life is seen as the result of many upon many contingent (aleatory) events, irrepetible in principle. So irrepetible that if you rewind the tape (another archaic reference) and replay it, it would be very unlikely, if not impossible for the same outcome to take place.

In other words, if we could go back and replay the history of life here, nothing like humans is likely to appear again, and the same is true for everything else. Sure, life would be here, but a very different type of life. And intelligent life? Well, so far we are the only example we know of intelligent, technological life; many thinkers believe that our type of intelligence is not absolutely required for survival, and they are of course, absolutely right! Just look at our biodiversity.

Truth be told, The idea expressed by Gould makes sense to me; just think about your own existence for example. Millions of sperm swam frantically to reach an egg; of those millions, only one “won” and here you are! But let’s not stop there, think about the multiple events that had to happen for your parents to meet, and your grandparents, and so on…

I am sure that you have seen enough time travel in movies and SF shows to know what I am talking about. Any apparently small change in any of the events in the past would have drastic consequences to our present reality. That is one of the reasons why I would not like time travel to exist, even though I have no way of knowing if this has ever happened.

One of the alternate ideas to life as an intrinsically contingent phenomenon, as far as CE is concerned, championed by Conway Morris, is that evolution may follow certain patterns, certain constraints, in other words, limited ways of doing things. This is not to say that we humans as we exactly are today are inevitable, just something very much like us is bound to appear sooner or later (again, Life’s Solution is much more detailed, we’ll talk about it hopefully soon).

The Deep Structure of Biology includes 12 essays with an ostensibly unifying theme, CE. Some essays are certainly better than others and the last two are unapologetically (see what I did there?) theologically inclined. I am planning to write a review of each individual chapter, time permitting. In the meantime, here are the chapters:

1. Chance and Necessity in Evolution – Richard E. Lenski
2. Convergent Evolution: A Periodic Table of Life? – George McGhee
3. Life’s Evolutionary History: Is It Determinate or Indeterminate? – Karl J. Niklas
4. Evolution and Convergence: Some Wider Considerations – Simon Conway Morris
5. Aspects of Plant Intelligence: Convergence and Evolution – Anthony Trewavas
6. Convergent Evolution, Serendipity, and Intelligence for the Simple Minded – Nigel R. Franks
7. Canny Corvids and Political Primates: A Case for Convergent Evolution in Intelligence – Nicola S. Clayton and Nathan J. Emery
8. Social and Cultural Evolution in the Ocean: Convergences and Contrasts with Terrestrial Systems – Hal Whitehead
9. The Illusion of Purpose in Evolution: A Human Evolutionary Perspective – Robert A. Foley
10. Purpose in a Darwinian World
P – Michael Ruse
11. Plumbing the Depths: A Recovery of Natural Law and Natural Wisdom in the Context of Debates about Evolutionary Purpose
– Celia Deane-Drummond
12. Purpose in Nature: On the Possibility of a Theology of Evolution
P – John F. Haught

This compilation is certainly biased, but it is interesting nonetheless. One thing is for sure, CE deserves to be examined more closely. Talk to you soon!

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Credit: http://bio-ditrl.sunsite.ualberta.ca

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4 Comments

  1. “I am sure that you have seen enough time travel in movies and SF shows to know what I am talking about. Any apparently small change in any of the events in the past would have drastic consequences to our present reality. ”

    Did you see the Futurama episode when they all went back in time to 1940s US, and the Professor says something like, “Remember not to do anything that will change history. Unless that’s what you were supposed to do all along, then by all means do it”? (By the way, I’ve been reading your blog for a couple weeks now–someone referred me to your post on Tyson, Sagan, and Einstein–and I’m really enjoying it.)

    1. Yes, I have seen the episode. I love Futurama! Thank you for your kind words about the blog and I am happy that you like it. I like getting feedback from readers!

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