Evolution

A few summary comments about evolution:

  • Evolution occurs because the genetic code allows for variations and is not error-free. Thus, one panda sometime in history had -- by chance -- a slightly enlarged radial sesamoid and there was an evolutionary advantage to that, in that this panda (and its offspring) survived and reproduced more successfully.

  • For every random evolutionary advantage, exaptation, or adaptation, there are many failures. Remember the Opabinia -- it seems like five eyes (the better to see you with) and a elephant-like trunk/mouth (the better to eat you with) might be advantageous traits. But, for some reason, this species was not successful, and died out. The process of evolution by definition must have at least as many failures as successes: for every random mutation that creates an enlarged radial sesamoid there must also be a random mutation that creates a smaller radial sesamoid. Those lesser sesamoid pandas were evolutionary disadvantaged and did not successful propagate their genes.

  • Remember that Lamarck suggested that if giraffes stretched their necks to get food then giraffe children would be born with long necks. I said that the causality was wrong, but not that the conclusion was wrong. It may be that giraffes with longer necks are better equipped to get more food, see predators come from farther away, etc. In this case -- unlike the wing -- 5% of a long neck, 10% of a long neck may have been evolutionarily advantageous. In this case, giraffes with longer necks might have been more successful in reproducing their random mutation. Thus, over time, children of giraffes would indeed be born with longer and longer necks, as long as it remained an evolutionary advantage. Thus, Lamarck's steps were correct -- that giraffe children would be born with longer necks -- but his causality was incorrect.

    One might therefore ask why giraffes' necks aren't longer than they are? It may be that having necks that are really long is an evolutionary disadvantage -- easier prey when drinking, for example.

    Photo by DET

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