Monday, February 16, 2009

Epigenetics != Lamarckism

So my dude noticed on /. this article entitled Acquired Characteristics May Be Inheritable. He pointed this And since I think slashdot articles are worth just about nothing, I looked at its source article. Which is entitled A Comeback for Lamarckian Evolution?.

These articles makes me head hurt. Because... Lamarck was pretty soundly spanked. And even with my limited wiki-education, I can tell the difference between epigenetics and Lamarckism.

(Edit: Evolving Thoughts has this excellent post about Lamarckism if, like me, you could use a refresher that's not wikimedia.)

So I went to look at the original paper, care of my University's subscription to the Journal of Neuroscience. It looked at a strain of mice which had been genetically engineered to have messed up long-term potentiation mechanisms (which are important for learning). It exposed some of these mice to an enriched environment for two weeks, one with toys and cardboard and tubes and such, and as expected these mice got better at long-term potentiation for about three months after exposure. What I like to call "happy mice" are better at learning, which we've known for a while.

So what's the huge Lamarckian finding in the study?

When these "happy mice" became mothers, their babies were also marginally better at long-term potentiation than they otherwise would have been, despite being raised in typical impoverished mice conditions. This finding seems fairly well-controlled, so we can be pretty sure that it's an effect that's specifically caused by the moms' exposure to an enriched environment.

Why is this finding not Lamarckian?

By the second generation, this "happy mom" effect was almost completely diminished. The improvement in long-term potentiation wasn't a truly heritable effect, but instead a very temporary one. It's not Lamarckian to say that the embryonic environment affects development. Environment.... affects.... development. It is true. However, it is still the rule that strictly phenotypic changes to an individual organism due to interaction with the environment are not the means by which diversity arises. This finding does NOTHING to change that.

This is where I'd normally start bitching about science journalism, but it turns out that the researchers themselves included the "Lamarckian" bit. A little bit of sensationalist -ahem- framing that seems to have gotten out of hand.

Dudes... no. No, no no... no. Just no. There's nothing wrong with Darwinian evolution, plus a heapin' helpin' of epigenetics. You don't have to keep beating Lamarck's dead horse.

5 comments:

  1. "Natural Selection is a beguiling counterfeiter of deliberate purpose." -Richard Dawkins-

    This junky psuedo-science keeps coming up because evolution by natural selection is so damned counter-intuitive.

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  2. Butbutbut... it's NOT counter-intuitive, unless you are profoundly ignorant of *everything* or your head's been filled with crap. Organisms (genes) breed... not all of them can or do survive... so the ones that DO survive to breed are propagated, and the ones that don't... aren't. Let this happen over a billion or two years (starting from simple chemical precursors to life) and TA-DA!

    I mean, common ancestry seems pretty obvious to me. Go to a zoo, look at the apes. Have a pet for a couple years. And then really look at human behavior. It has a couple more layers on it, sure, but we're basically shit machines that fuck, like every other animal on this planet.

    /rant :)

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  4. Kamaka is actually right. The generality of evo by natural selection on heritable variation is intuitive enough, but the application of the highly general concept to specific cases can be quite beguiling, and yes, counterintuitive. Isn't it more intuitive to imagine that organisms have developed highly relevant mutations to specific environmental stresses precisely because there is some meaningful communication between heritable factors and environmental factors? For complex structures to evolve, even the ability to process a different kind of sugar, MANY spontaneous mutations are necessary, the likelihood of even one relevant, fortuitous mutation being low, the likelihood of many being exceedingly improbable, even over long stretches of time. In fact, natural selection should favor a system that provides the hereditary material with some clue about how to generate novelty, and this may be just what has happened. An exceedingly large amount of experimental evidence points to this fact... soft inheritance is undeniable, though as of yet its role in evolution is uncertain. In any case, don't be so quick to dismiss.

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  5. "In fact, natural selection should favor a system that provides the hereditary material with some clue about how to generate novelty, and this may be just what has happened. An exceedingly large amount of experimental evidence points to this fact..."

    I know I'm coming back to a very old post, but... I'd like to see some of that "exceedingly large amount of experimental evidence" for Lamarckism. :P How would that work, praytell?

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