If certain genes turn off (or on) to effect some of these changes, isn't it reasonable to assume that there would be the occasional "throwback" that exhibited the properties of an earlier version?
Are they inferring that a creature's habits cause it to "evolve" to meet the preferred environment (whales lost their legs because they swam and legs were a hindrance) instead of having the changes occur, which would require the creature to either adapt or perish (whales lost their legs and had to become full-time swimmers because they couldn't get around on land)?
This evolution stuff gets so confusing sometimes - it seems that it can follow either the nature or nurture path and all findings are good because they give more credence to evolution even (or perhaps especially) if they seem to contradict the theory.
Depending on the mechanism of the gene regulation, it's possible. This is why humans are sometimes born with little tails.
Are they inferring that a creature's habits cause it to "evolve" to meet the preferred environment (whales lost their legs because they swam and legs were a hindrance) instead of having the changes occur, which would require the creature to either adapt or perish (whales lost their legs and had to become full-time swimmers because they couldn't get around on land)?
No, it is never accurate to say that a change occurred because the creature needed it. Evolution is not prescient. If a necessary beneficial mutation does not occur, the species simply goes extinct. The same mutation that caused these legs not to develop could happen in a land-dwelling whale ancestor as well. The difference is the land-dwelling ancestor can't manage without hind legs and would die, while the ocean-dwelling whale does better without its legs. By the time this change occurred, whales were already obligate marine creatures, with vestigial legs whose only utility is possibly as claspers (similar to sharks' claspers) for aid in mating. If the complete absence of hind legs is more beneficial, eventually that phenotype is likely to become the prominent phenotype.
It's more a question of, if you don't use your legs, does it matter if if you have a birth defect that causes them not to grow.
There are birth defects in humans where their limbs don't develop that's similar to what happened to the thalidomide babies in the '50's. If we were aquatic, we wouldn't need legs. And it would allow us to swim faster and easier, so it would likely be passed on to our offspring. No one would want to mate with the slowskys.
Yup. There have been "throwbacks".
Just look for the guy ordering the duck with mango salsa.
I think the argument is that some creatures accidentally lost their hind legs and that this proved to be advantageous, but it was not necessary for this to happen, because creatures like the ancestors of the wahles, like walruses, survived qiite nicely. However, Darwinism always had had some teleology built into it, a least the explanations of it, because it is always a backward look. It has the same logical problems as historicism.
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