The scientific consensus is that snakes evolved from lizards – and that they had hindlimbs for millions of years during the transition. But the reason snakes have long been considered a separate kind of reptiles is because of other features they have which lizards do not. This raises the question, h…

Good responses already provided here. Lizards as a group seem to be predisposed to head down the path of limb reduction if not full limblessness. Not all of course, but certain clades such as the skinks. If you’ve ever watched one of the skink species that has limbs make an escape, they look like t…

I’m not a reductionist sort of person - I believe that what happens in the form of non-human life is a product of both chance and selection. Amphibian groups have lost legs, partly because they have that genetic ‘aspect’ to them, and for some reason it persisted. Snakes, a group that arose a long ti…

In mammals, an obligate aquatic lifestyle seems to be necessary for radical limb reduction.

True. Selective pressure I assume. But they will never evolve into fish. That’s all I mean!

[image] mamestraconfigurata: But they will never evolve into fish. That’s all I mean! I think given the right selective pressure over enough time they could. Correct me if I’m wrong, but go far back enough along the evolutionary chain and there were no mammals at all. You might not get back t…

We all are fish anyway, but it’s unlikely to get same mutations, just because mutations are so unpredictable, it’s a small chance to get the same thing twice, and fish evolved from organisms that had a certain set of signs, now when mammals evolve, they go from different point, e.g. we have cranium,…

Not sure the term is still used, but in evolutionary biology there is (was) the term “canalization” which suggests that there are some pathways that an organism is unable to take evolutionarily due to genetic constraints. Basically, once you start down a given path morphologically there are limits …

Adjusting the question a bit so that it reads “How many times have squamates lost limbs?” the answer is at least 25 (including the snake lineage). I’m reading a paper about loss of genes that control limb development in snakes. It turns out that some of the genes that facilitate limb development al…

Looks like this paper is as much as we knew back in 2017. “… the picture that is emerging from these studies is that early truncation of snake hind limb development was caused by deletions in the ZPS [gene]”. “In an elegant test of the functional consequences of the python ZRS deletions in vivo, K…

[image] jnstuart: “canalization” which suggests that there are some pathways that an organism is unable to take evolutionarily due to genetic constraints. That may still hold true, but in this case it’s not the pathway that matters, just the end state. To use a physics analogy, there may be m…

How many times will lizards become "snakes"?

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How many times will lizards become "snakes"?

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