Mammals, like humans and apes, have five digits on their fore and hind limbs. Modern horses have one. How might you reconstruct the ancestral state of mammal toe number?

Question

Cruella

Biology

31 October, 08:04

Mammals, like humans and apes, have five digits on their fore and hind limbs. Modern horses have one. How might you reconstruct the ancestral state of mammal toe number?

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Answers (1)

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Kylie Allen · Answer 1

Answer and Explanation;

Investigate the number of toes for other mammals and use parsimony to deduce the ancestral state.

Investigate the number of toes for an out group that is closely related to mammals, for example reptiles or amphibians.

-Primates have five fingers on their hand and five toes on their feet. Most species have fingernails instead of claws and they have touch-sensitive pads on each of their digits. The hands and feet of all primates, except for humans, are designed for grasping. Humans have hands designed for grasping, but not feet! Humans have opposable thumbs.

-The earliest horses had three or four functional toes. But over millions of years of evolution, many horses lost their side toes and developed a single hoof. Only horses with single-toed hooves survive today, but the remains of tiny vestigial toes can still be found on the bones above their hoofs.