Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Human vs Animal Sets of Teeth
Name: John D.
Status: student
Age: 10
Location: N/A
Country: N/A
Date: Saturday, June 01, 2002

Is there a good reason, or guess, why humans have only two sets of teeth (baby and adult) while other animals constantly replace them?

As with most questions of "why" things are the way they are in nature, we usually can only guess. Evolution and adaptation have selected for traits that succeed over many generations. Specifically, most mammals have teeth similar to those of humans, with the exception of the incisors (front gnawing teeth) of rodents like beaver, that continue to grow through their lifetimes. Those teeth are not replaced by adults that lose them, though. Some creatures, like sharks and some snakes, replace teeth throughout their lives. Why? We can see that it is a successful survival strategy but how they evolved is hard to say.
J. Elliott

It is generally agreed that the reason humans have two (or three in some cases) sets of teeth deals with growth of the skeleton. Teeth are essential for eating many foods and the early set of teeth are too small as we grow or evolve into adulthood. The jaw grows larger and we drop the smaller teeth for large ones; and more of them too for our jaws are larger. Early humuns did not have the luxury of soft foods so babies need to grow teeth for eating after been weaned. The reason why other animals have other methods of replacing teeth reflects their diet and environmental needs. Humans are omnivores, but many herbivores grind their food continuously and need to replacement constantly. Animals that use their teeth for more than eating such as rodents, have incisors that grow continuously. These animals need to constantly grind their front teeth down, but this normally takes place with their day-to-day activites consisting not only of eating, but building nests and opening hard shelled food, etc. Now there are other information about teeth that you can look up easily. Steve Sample

Click here to return to the Zoology Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory