Evolution/design of human teeth

So produce 'em.In evolutionary terms anything that doesn't cause a problem until after the age of reproduction won't get selected against. The prime example of this is Huntington's disease which is inherited in an autosomal dominant manner. It's fatal, yet it continues to be passed on because it only begins to manifest itself well after reproductive age, usually starting in mid forties. By the time someone knows they carry the gene the've already had children, 50% of whom will also carry it.So we're stuck with our teeth that are prone to caries and awful abscesses. They can keep us going long enough to pass on these teeth to our offspring without modification.As to why we don't grow more teeth underneath to replace bad ones, it seems to be something that would be selected against if it had ever happened or started to change. Our bite is very complex. Our teeth are a mixture of carnivore and herbivore and to work well together have a very small tolerance to any change in the size, angle or position of molar cusps. The top molars and bottom molars have to fit together well and all teeth are subject to the same wear so they still function with their partner. A new, unworn tooth appearing would cause havoc. I know this courtesy of an idiot dentist who filled a lower molar, but left the filling too high. The only place in my mouth where my teeth met was the raised filling and the molar above it. I spent a week on soup, none of my other teeth could function at all and even talking and swallowing were difficult. The thought of that happening on a regular basis as replacement teeth grow in makes me shiver.

You need to read more carefully. I was using Huntington's disease(note that Huntington's disease is not Hodgkin's disease nor is it even remotely similar) as as example to illustrate how traits that reduce fitness can be passed down. How does this go against you saying that traits which reduce fitness can be passed down?The reason I used Huntington's disease is that it is inherited in an autosomal dominant fashion, i.e., you only need one copy of the faulty gene to succumb to the disease. The point I was trying to make is that even if a trait is 100% fatal it will not be eliminated from a population if it only manifests itself after reproductive age has been reached.Given that most people manage to get to reproductive age without suffering from terminal dental caries, there is little selective pressure for our teeth to have changed.ABE I hit the "Cheers" button on foreveryoung's post while attempting to hit the "Jeers" button. If his post is an example of how carefully he reads other people's posts before replying, I wonder how carefully he's examined the evidence for the ToE.Edited by Trixie, : Sorting out the "Cheers" and "Jeers" mistakeEdited by Trixie, : Spealing and rypos!