Do monkeys have 2 sets of teeth when born as humans do?

Assuming that they do, where can the two sets of teeth be traced back to? (also assuming that we accept Darwins' theory about the evolution of man.)

Do monkeys have 2 sets of teeth when born as humans do?
Yes, the condition of having two sets of teeth (the so-called 'milk teeth', and the full adult set) is a common characteristic of all mammals.





It's called diphyodonty (which means 'having two sets of teeth'), and it can be traced back to the earliest mammals and the synapsid reptiles that came before them.





Diphyodonty isn't a case where one set of teeth became two, it's actually a reduction from the continuous replacement of teeth in most reptiles, down to only two sets in mammals.





The reason has to do with the development of heterodonty, which is different shaped teeth in different parts of the mouth for different jobs. We have incisors for gripping and pinching food, canines for stabbing, and molars for grinding and processing. Most reptiles (i.e. crocodiles) have lots of very similar teeth - usually pointy - that don't have much differentiation in their function.





The development of heterodonty in mammals provided the means via which different mammals could quickly become specialized to eat specific foods. Some were insectivores, some specialized in gnawing open seeds, some got big canines and meat-slicing molars to become highly efficient carnivores.





However, with heterodonty, the reptilian system of continual tooth replacement doesn't work well. Mammals need all of their teeth working together properly all the time - the cusps and crowns need to occlude in exactly the right way to make an efficient food processing system. If teeth are falling out and growing in at different times, each at different stages of development, then there's too many holes in the processing system, and the parts don't work together properly.





By reducing the replacement to a single exchange, it becomes more efficient. It means that if a mammal ever gets busted or rotten teeth as an adult, there's no replacement, but while the teeth are there, they work very, very well.
Reply:Yes, they do.





Monkeys, remember, split off from what would become the ape progenitors, long before the ape progenitors split into apes and humans.





Actually, nearly all placental mammals have deciduous teeth.





So what that tells us, evolutionarily, is one of two things:


1) Convergent evolution allowed for nearly all mammals to develop the growth of baby teeth.


or


2) Early mammals had deciduous teeth, and that trait was passed on to all evolutionary decendants.





Choice 2 is the simplest explanation, and therefore the most likely, and is borne out by fossil records.



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