Sharks grown new teeth, why don't people?

That%26#039;s an interesting question!


The short answer would be %26quot;Different evolutionary paths%26quot;, which is true. But those paths imply adaptive and functional differences.


The teeth of sharks are not too different from those of other tetrapods. Aside from birds, most tetrapods have many generations of teeth (this is called polyphyodonty), and those teeth are usually not strongly attached to the jaws. They`re more or less easily lost and replaced during normal activities. So, why don%26#039;t we mammals have such a useful feature?


The loss of all those teeth replacements was a tradeoff for our acquisition of better tooth occlusion. Occlusion is the way the surfaces of the upper and lower teeth contact each other, and in mammals, our chewing teeth (molars and premolars) have complex occlusal surfaces, which allow for slicing food (shearing like scissors), crushing food (cusps and basins that act like a mortar and pestle), and other ways of basically, disintegrating food items.


The thing is, the precise interlocking of cusps and vales is not easy to achieve (as anybody with occlusion problems has probably heard from the dentist). So the hypothesis is that the evolutionary path of mammals %26quot;focused%26quot; on one generation of perfectly occluding teeth. Thus, molars erupt late in life, grow slowly, and are not replaced. And the other teeth (incisors, canines and premolars) have a first, %26quot;milk%26quot; teeth generation that allows the young mammal to feed while its skull is expanding. Then, by the time its growth has slowed down, the definitive teeth erupt and take their places (they would not fit in the small jaws).


The teeth of man, as those of all primates, are brachydont. This means that they don%26#039;t keep growing once they%26#039;ve erupted completely. However, the enamel that forms the outer cover of the teeth is the hardest substance in our bodies, and is able to endure the wear from our food. However, many other mammals that eat more abrasive foods (plants, and especially grasses) have permanently growing teeth (hypsodonty). This is, in a way, the equivalent of having multiple generations of teeth; their teeth keep growing throughout part of their lives (as in the case of horses) or all of their lives (like many rodents and ruminants). But we cannot %26quot;recover%26quot; the capacity for multiple teeth generations that we %26quot;gave up%26quot; evolutionarily when we became mammals.

Sharks grown new teeth, why don%26#039;t people?
evolution. habitat and enemies
Reply:people do dumbass..hence the name %26quot;baby teeth%26quot;
Reply:Humans and sharks are different, that%26#039;s why.
Reply:sharks could not use toothbrush
Reply:Sharks have a very different system, their teeth are created within their mouth at the rear of the gums and sort of %26#039;fold-up%26#039; into place, the old ones are pushed out by new emerging teeth, and they loose teeth when they bite. Humans do grow new teeth--but only once! We loose our baby teeth, and they are replaced by our adult dentition. Very rarely, some people will have a third set of teeth, or a third tooth somewhere in their mouth.



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