Evolution is a result, not a cause

Bernard, This New York Times article, Meet Luca, the Ancestor of All Living Things, exemplifies what I see as wrong-way thinking about evolution, thinking that directly or indirectly attributes purpose and foresight to evolution. Below are examples of what it says as opposed to what I believe it should say. Added text looks like this, deleted text. The article says: A surprisingly specific genetic portrait of the ancestor of all living things has been generated by scientists…

  • I maintain it should say: A surprisingly specific genetic portrait of a proposed ancestor of all living things has been generated by scientists…
  • Comment: Is it absolutely certain that change and natural selection didn’t winnow down more complex microbes, filtering out unused genetic material, resulting in what looks like an ancestor but is actually a residue?

Wayne,

I saw that interesting report too. The researchers applied powerful tools to uncover what genes might have been those of the now long extinct Last Common Ancestor of all living things, LUCA. All knowledgeable scientists, and me too, agree with you that evolution has no purpose or goal to achieve. The fancy way to say this is that it is not teleological. The sources of modification to any creature’s genome are random, and their direction is random. Some of these changes produce changes to the reproductive fitness of that organism in its particular environment, leading to the increase of the fraction of the population with those particular changes. But natural selection is not the only mechanism that leads to changes in a population’s genome. Research in recent decades has shown that random drift in a population the result of genomic changes that are either neutral with respect to natural selection or not exposed to natural selection are important sources of genomic and species change.

Yes. I agree that they should not have been so specific as to imply or say that they had identified the LUCA. As that organism was ancestral to bacteria and archaea, it likely was a similarly small organism, and they may have decided that they had found sufficient possible genes to lead to an actual living creature. But they couldn’t know for sure that they had found at least a minimal set, and they would not have found genes such a creature might have had that have not survived in modern living organisms.

As for whether organisms can evolve to become simpler, the answer is yes. Parasites, often lose many organs necessary for free living organisms. Things like tape worms were once more complex critters than they are now. Or think of that blind cave fish. There is a problem, however, of evolutionary space. There is a kind of least complex possible organism, we may suppose, although we don’t know what it is or was. We’d suppose that the earliest forms of life, just barely different from not being life, we’d guess must have been close to, if not at, this boundary. Around that boundary, there is much more space for a random drift to more complexity. Once organisms have gotten far enough from that lower bound then they might change to be more complex or less complex.

I’d say, however, that since the researchers in the article are talking about an early single celled organism, pond scum of some sort, it might have evolved from some more ancient but now unknown organism, but it seems most likely that it did not. The researchers were impressed, however, to find that the ancient common genes they identified appeared to be those useful to an extremophile, similar to organisms they find living in hot sulfurous springs, or in those smokers, chimneys spewing hot mineral water deep in the sea. Not much like they’d imagine if early life began in some warm shallow pool.

This arises in linguistics, too. (As always, not knowing much won’t stop me now.) Evidently, older languages tend to be more complicated. Following the history of English backwards the scholars find more cases, declensions, irregulars, and so on. The vocabulary might be smaller, but the words, syntax, and grammar may be more complex. Scholars even do the same type of search to find common ancestors, as we say that French, Spanish, Italian, and so on have Latin as a common ancestor. And then back and back to Indo-European, probably spoken by some nomadic horse people who lived near the Black and Caspian seas.

Do you think this applies to programming languages?

Or in Biblical scholarship. All scholars acknowledge that the original manuscripts from the authors’ hands have not survived. All we have are copies of copies, and each copy comes with the possibility of any of many errors. They wish to reconstruct that original first version. They trace errors through manuscripts to find the earliest example of any particular error. In this way, they construct a family tree. Finally comparing the earliest versions and considering any differences between them, the scholars propose the LUCA. Those who assert that the Bible is the inerrant, inspired word of God mean that the LUCA, unknown to us, is the version that was directly inspired. All the copies are but approximations.

Scholars do the same to Shakespeare early editions, apparently written down from memory by actors or perhaps copied from stage versions.

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Filed under Biology, Evolution, Natural Science

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