How do teeth evolve?

Teeth are bones, they are not exactly inorganic. They form, they grow. They are controlled by genes. Among the variations in genes (and the resulting teeth), some may be better attuned to survival and are transmitted to later generations. Genetic drift or sexual selection (lady T-Rexes like a nice smile) may also be at work.

essentialsaltes said:

Teeth are bones, they are not exactly inorganic.

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Being pedantic for a moment . . .

If memory serves, teeth are not true bones because they develop from the ectoderm. Bones develop from the mesoderm. Teeth are more closely tied to skin and hair than they are bones.

OldWiseGuy said:

This article reveals that T-Rex and some other dinosaurs had very complex serrated teeth. How do teeth evolve if there is no biofeedback to the cpu of natural selection due to the inorganic composition of teeth? Or were these teeth 'designed' this way from the getgo?

http://www.msn.com/en-us/news/world...th-had-secret-weapon/ar-AAdBeeg?ocid=U147IDHP

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How did you determine that there is no biofeedback?

OldWiseGuy said:

If the shape of teeth evolve there must be some 'organic' connection to relay the 'need for change' to the genome. The outer surfaces of teeth are inorganic/without nerves or blood vessels, so how does the tooth send this signal?

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Do you understand natural selection?

"Among the variations in genes (and the resulting teeth), some may be better attuned to survival and are transmitted to later generations."

The tooth does not need to send any signals. The proof is in the pudding. Some animals with teeth like this leave more offspring than the animals that have teeth like that.

Clearly organic cells and structures build the tooth. Genes are responsible for this. Different genes produce different teeth. Different tooth-genes may lead to different reproductive success, producing evolution of the tooth genes (and the physical form of teeth they produce).

OldWiseGuy said:

If the shape of teeth evolve there must be some 'organic' connection to relay the 'need for change' to the genome. The outer surfaces of teeth are inorganic/without nerves or blood vessels, so how does the tooth send this signal?

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There's no signal. There's no signal for "need for change" to the genome for any of this stuff. Natural selection is the driving force behind evolution, not signals.

OldWiseGuy said:

They must have received a signal that there was indeed food deeper in the ground.

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Really, the signal is death. Those with short bills died. Those with long bills could reach the food, and survive to reproduce, and pass on their long-billed genes. There is no signal to living creatures that they can react to. Once they are born, their genes are fixed. Some will survive, and others will die.

Do you understand natural selection?

OldWiseGuy said:

But Darwin said that those birds (on Galapagos) needed longer bills to get at food deeper in the ground in order to survive (which is strange because their shorter billed cousins are still around). They must have received a signal that there was indeed food deeper in the ground. They should have taken a tip from the robins who instead of growing a longer beak just wait until the worms come closer to the surface.

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As essentialsaltes rightly says, if there is a "signal," it's death. The finches' beaks changed, not because signals were traveling through their blood vessels, but because slight differences in beak shape led to different rates of passing on genes.

Some of those with short bills adapted to have powerful bills, for cracking hard nuts. Other adapted with long bills for reaching hard to get food. The long bills don't have the mechanical advantage to crack nuts, and the short bills don't have the reach to get hard to reach food. These different varieties have started down different paths, with different typical foods, and the different selection pressures produced different results. This is what Darwin saw, and recognized that once they had been set down different paths, adaptation would continue to separate them, so that one species could become many, each adapted to its own way of life.

Those with long bills might evolve toward shorter bills, if the environment favored it. If the environment changed too quickly, it might not be possible.