29 October, 2009

Ouch. I Just Got Bopped on the Head by Bad Science Programming

I watched a Nova episode before the evening's writing.  It's about a family who has a passel of children who walk on all fours.  The show babbled about reverse evolution.  A lot.

Shoot me now.  Here's why (h/t):
Nobody thinks that the Hobbit is “reverse evolution,” because such a thing doesn’t exist.  While some interpretations conclude that Flo has an australopithecine-like wrist, that doesn’t mean that it’s identical to an australopithecine, or even that the wrist is identical to an australopthecine’s wrist.  What it means is that, in a statistical analysis, the capitate groups more closely with australopithecines than with modern humans.  The Hobbit’s trapezoid also groups more closely with those from chimps and gorillas than it does with humans, but again, this doesn’t mean that it was identical.

Furthermore, not only are there no cases of “wholesale reversions” in primate evolution, but I’ve never heard of such a thing happening in any lineage at all!  Sure, there are atavisms, or reversions back to a “primitive” trait, but those result in a descendent with an ancestor-like trait, not a perfect duplicate of the ancestor.

“Reverse evolution” doesn’t happen.  Once an animal evolves, it can’t un-evolve.  It can loose traits, or re-evolve a basal trait, but a human isn’t going to “reverse evolve” into an australopithecine, and a bird isn’t going to “reverse evolve” into a dinosaur.  That bird may re-evolve teeth, but that wouldn’t make it a dinosaur.  The analysis of the wrist may lead us to the conclusion that the ancestor of the Hobbits left Africa before our modern wrists had evolved.  It may even lead us to the conclusion that the Hobbits left Africa with a modern wrist and then evovled a wrist that looks more primitive, but even that’s a stretch.  What it doesn’t lead us to conclude is that the ancestor of the Hobbits left Africa and then reverse evolved back into Australopithecines.
Can we please stop the reverse evolution babble now?  KTHXBAI.

Let us also stop this talk about "the gene" for bipedal walking.  It's not likely to be a gene, for fuck's sake.  We're talking a host of genes, a gaggle of genes, a veritable crowd of genes, that give us the ability to walk on two feet:
Again, unfortunately, the atavism angle is emphasized. This is good copy, but we should be skeptical of this. It is possible, but that does not imply it is probable. It seems that the 17p mutation is a loss of function which has had wide pleiotropic effects. I am skeptical that the ancestral gene shifted from null function to a new function. As Carl Zimmer pointed out bipedalism is a complex and exceptional trait which resulted in the retrofitting of a host of other aspects of our morphology and physiology. Though it might not have emerged in a classic gradualistic fashion, it seems unlikely to have been the result of a single positive mutation around which modifier genes evolved over hundreds of generations.
Oh, and there's this, too. Which kind of says exactly what I was thinking the whole time I suffered through this tripe.  Look, if even a two-bit armchair biologist like me can figure out  within five minutes that a buncha relatives walking on all fours = pathology, not reverse evolution and/or mutant bipedal gene, then you should've figured it out too, Nova.

Nova.  I like you.  You're a nice show, and you do some really great things, but you really butchered this one.  I hope we don't have to have this talk again.

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