[annie123 (OP)]

Does anyone know why humans teeth only replace themselves only once, while those of dinosaurs/sharks kept/keep on coming? Why would this advantageous feature disappear as evolution continued?
Is there a gene for tooth replacement (in sharks?) and could this be engineered into humans to give us this useful quality? What is the difference in the genomes of organisms that replace teeth continually and those which don't?

[CliffordK]

Sharks tend to have rows of "backup teeth" that can be moved into place as the need arises, or perhaps they just shed teeth.  However, their mouth is quit different than ours.



There was a recent discussion on TheNakedScientists that tooth decay is about 5x higher now than it was just a few thousand years ago.

http://www.thenakedscientists.com/forum/index.php?topic=41690.0

While ancient man certainly had a few cavities, they just weren't as bad as it is today.  The average lifespan for prehistoric man was also much less...  perhaps 30 to 40 years.  So, again, less chance to loose all of one's teeth.

Perhaps one day there will be a method to culture and implant teeth customized to an individual.  However, it likely will not be inexpensive.

There is active research on re-activating the genes that cause the baby teeth to be replaced with new permanent teeth.  Perhaps the alternative will be to tell the body to naturally regrow certain teeth, or even a full set.

[grizelda]

Teeth are a constant source of bacterial entry to the body. As we age, our saliva becomes less antibacterial, and the bacteria become a source of chronic inflammation causing many ailments. Probably best to get rid of our teeth at the earliest opportunity.