

The Wrists of Birds Reveal Evolution Undoing Itself - dnetesn
http://www.smithsonianmag.com/science-nature/wrists-birds-reveal-evolution-undoing-itself-180953964/?

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gumby
I don't really see why this should be especially remarkable or subject to some
"law" (especially one framed back when evolution was still being
characterized). It's not like evolution has a "direction" \-- humans are not
"more evolved" than chimps. It's simply that each generation the genes that
provide the most "fitness" for the environment that an individual finds itself
increase the probability that said individual will reproduce. The same
individual in different environment (say a bird in a flood) may be less fit
than another.

Given that, even if a gene stops expressing itself most of the time, that
doesn't mean it vanishes (it may, as their may be no selection to keep it); it
may stochastically express from time to time and give some advantage in a new
environment. Hell, most macro phenomena are the result of _several_ gene
expressions; a gene isn't just a single use subroutine.

What a dumb article about an interesting aspect of birds.

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colin_mccabe
Darwin remarked on the tendency of organisms to re-express ancestral forms.
Sorry, I don't have a citation, but I do remember some commentary about this
by Stephen Jay Gould. It should be pretty clear to anyone following embryology
that a lot of really ancient genes are still present in modern animals,
waiting to be re-awakened when the time is right.

It is possible that some evolutionary paths are unlikely to be trod more than
once by the same organism, but it hardly seems worthy of being called a "law."
Around the turn of the 20th century there was a lot of confusion and people
still proposing non-Darwinian explanations of biology, so I'd be suspicious
that this was just another example of that.

