Responding to Turtles: Shells evolved for digging, not protection?, turtle-knowledgeable reader Paul D. Cook kindly writes to say:
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I’m not an expert on turtles. My degrees are in fields of engineering that are unrelated to this subject.
But we have had turtles as pets for over 20 years. (Cute & affectionate critters. And while not as smart as a cat or dog, God has still packed more into their pea sized brain, than one would expect.)
As soon as I read the article, I wondered about some obvious datapoint that might seem to be outliers for this idea.
What about turtles such as the snapping turtles, which have far less protection on their undersides than on their backs. And of course, there are the freshwater softshell turtle varieties, which don’t even have a hard shell. As I understand it, both of these varieties are more likely to burrow into the mud/sand/dirt, then the many varieties with fuller, or harder shells.
If the initial functional advantage for the shell, were to aid in burrowing it is odd that this snapper and softshell are among those having a less full, or less hard shell. If the shell was enough of a functional advantage to drive its development, why was it not enough to keep it?
Snappers and softshell turtles also have a reputation for being prone to bite, and are therefore not suggested as pets for novices. It is only my personal observation, but it does seem like there is an inverse correlation between the degree of protection offered by the shell and the variety’s propensity to bite. But this would make sense. A turtle having shell which well protects it, can retreat to the safety of that shell. While one lacking that protection, would need to rely on biting.
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Darwinism imposes a thought pattern on those who study evolution. Evolution is supposed to be random but nonetheless, it is “for” things, “creates” things, “designs” things.
So researchers snap (so to speak) at any instance of something highly functional that can be imagined to have somehow just happened. Throwing another hypothesis at the history is the goal; taking stock of the implication of the whole is a threatening idea.
The good news is that many more hypotheses are likely possible, which means that in the next two decades there will be many more papers..
See also: Not a Big Bang of turtles TOO? As well as birds and mammals
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