Are the 5 digits of all land vertebrates an accidental number?

Question

All land verterbrates except some frogs have 5 fingers on hands and feet.

The first vertebrate lizards came out of the water and had 7 fingers ( -370mn yrs), and then 6 fingers, and after 30 million years, all their descendents had 5 fingers on both limbs.

someone told me "5 is much more of an accidental number", so if all land vertebrates had 7, then 6 fingers, why did that get selected to 5?

Related (if not duplicate): Why don't mammals have more than 4 limbs? and Why do some bad traits evolve, and good ones don't? — Remi.b, Oct 02 '17 at 17:07
There are more exceptions than frogs. It depends a bit upon what you call a finger, but typically snakes don't have fingers, ungulates don't have fingers, cats have 4 toes at each hind paw, .... — Remi.b, Oct 02 '17 at 17:10
Note also that the first vertebrate coming out of the water was not a lizard (not a squamata). — Remi.b, Oct 02 '17 at 17:13
By the question why did that get selected to 5 there is a potential false assumption that make it clear that your question is a duplicate of Why do some bad traits evolve, and good ones don't?. I'm voting to close as duplicate. Please have a look at this post and if you think it did not answer your answer, please clearly explain why. — Remi.b, Oct 02 '17 at 17:14
The general question is a duplicate. Articles here, here, and here emphasize the contingent nature of the five-finger tetrapod. — iayork, Oct 02 '17 at 17:16

Are the 5 digits of all land vertebrates an accidental number?

0 Answers0