[__ Science __ ] Does Evolution Go Backward? A Look at Blind Cave Fish

[AIG.com]

“Regressive evolution” refers to the loss of complex features and functions. Now are blind cave fish an example of this supposed “regressive evolution”?

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[Milk-Drops]

“Regressive evolution” refers to the loss of complex features and functions. Now are blind cave fish an example of this supposed “regressive evolution”?

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No, it's just Evolution. Evolution is the decent with modification and natural selection. Don't need eyes and they end up being an energy drain? Those without or reduced functionality have an advantage.

 

[Barbarian]

“Regressive evolution” refers to the loss of complex features and functions. Now are blind cave fish an example of this supposed “regressive evolution”?

There's no "regressive" evolution. Eyes don't disappear and slowly reverse their evolutionary past. Instead they atrophy and form vestigial structures of tissues that may be useless, or possibly adapted to other purposes. This is how the pineal gland evolved. At the boundary between therapsid (mammal-like) reptiles and cynodont mammals, there was the loss of the "third eye" and the formation of a somewhat different organ, one that functioned as a different sort of regulator.

Turns out, that bit of evolutionary development was a signal for the evolution of warm-blooded mammals:

What our ancestors’ third eye reveals about the evolution of mammals to warm blood

Mammals’ ancestors had a third eye and the fossil record of its disappearance tells us the story of the evolution of one of our most important features: warm blood.

theconversation.com

We need that gland today, but not for distinguishing light from darkness; it regulates circadian rhythms and the production of melatonin.

"Even if these new cave fish have lost the ability to develop eyes, it’s not evidence for evolution. After all, they’re losing something—which is the exact opposite of evolution!"

Wrong. Evolution is a change in allele frequency in a population. So losing a function (and in this case, gaining another one) is evolution. But merely losing a function is also evolution. AIG remains stuck in an old confusion about evolution. It's not about "progress", even if we often do see fitness increase in an evolving population. It's about change. And simplification can often increase fitness; we lost cervical ribs and a functional tail, among other things.