Look at the comments on this paper.
from Aristotle's Generation of Animals (Book 5, Chapter 8)
It is possible to learn much about Aristotle (384-322 B.C.) and his point of view concerning what we would call biology by examining his discussion on teeth. Aristotle uses reason, logic, and empirical observations to formulate his system of biology. He proposes questions and then reasons out the answers using empirical observation as well as logical reasoning. In this short "paper", I shall discuss and clarify the basic ideas and topics that Aristotle puts forth in his section on teeth.
According to Aristotle there are two types of teeth:
1) front teeth, or dividing teeth
2) grinders, or flat teeth, or crushing teeth.
Aristotle asks four questions in relation to teeth:
First, let us assume based on what we see that nature generally does not do things in vain.
Next, if an animal must stop receiving its nourishment via mother's milk, then the animal needs some method of dealing physically with food. Hence, we have teeth. But teeth may not be useful solely for the purpose of obtaining nourishment; teeth may also be used in some animals to aid in vocal speech or for fighting.
Why is it that the front teeth form before the back teeth?
In answers to question one and two, Aristotle reasons that since dividing comes before crushing, then the dividing teeth must come in first. As added proof, he offers that a smaller thing develops more quickly than a larger thing, even when they start growing at the same time. Since the front teeth are smaller than the grinders, they develop more quickly. But why are the front teeth smaller? That would be because the greater part, or larger part, of the jaw is in the back of the mouth where the grinders are, while the smaller part is in the front of the mouth. More bone can hold more nutrients. Therefore, there exists more nutritive substance in the back part than the front part, so the grinders are allowed to grow larger than the front part.
Now onto questions three and four.
Why do some teeth fall out (and are replaced) while others stay in?
There are two reasons why teeth might be shed (i.e. when one loses one's baby teeth):
a) it is better
b) it is necessary
Aristotle proposes that since what is sharp becomes dull with use, as with an ax or a knife, it becomes advantageous to replace the dull with the fresh and sharp. An ax or a knife can just be sharpened, but it would be rather painful to try sharpening your teeth. So, it is better that front teeth, dulled from use would come out allowing new and fresh teeth to come in and replace the old ones. Flat teeth cannot be become dull since they are flat, but their surfaces do become smoother with time, as a path becomes worn as many people walk over it.
Since the jaw is flat where the grinders are, those teeth may be well rooted in the bone. However, since front teeth are in the thin part of the jaw, the bone is weak, and the teeth are easily moved. So, it becomes necessary that the front teeth are shed. Luckily, the animal is young enough at the time of the shedding that more teeth may grow. As part of Aristotle's proof that more teeth may grow, he mentions that some flat teeth take a long time in growing, and they do not appear until a person is about twenty or even older. He is, of course, referring to wisdom teeth. The reason that this is possible is that the bones contain the nutrients necessary for the growth of teeth. As teeth grow, these nutrients are used up. The larger part of the bone has more nutrients than the smaller part. So, the front teeth have used up all of their nutrients by adulthood, whereas the back teeth still have enough nutrients for another set of grinders.
Thus, Aristotle reasons out the four questions he had first proposed, and it seems logical that
A) the front teeth be developed before the grinders are developed, and
B) the front teeth may shed and be replaced while the grinders may not.