Okay - for those of you that like to talk about human evolution.

"Neoteny - a slowing of the rate of development with the consequent retention in adulthood of a feature or features that appeared in an earlier phase in the life cycle of ancestral individuals: Neoteny in the ostrich has resulted in adult birds sporting the down feathers of nestlings."
Also called pedogenesis

The result is usually the elimination of what was previously the adult morph. The pheonomenon is most common in modern species of amphibians - particularly some salamanders. The larval stage (or immature individual) acheives sexual maturity - with the resultant loss of the adult stage.

Humans retain throughout adulthood the comparatively large head and lack of hair that is common in very young primates. It is thought to be caused by environmental stresses that interrupt hormone production, and thus, interrupt the natural progression of life stages. (Human example: Lack of iodine needed for the thyroid gland.)

Is the idea that humans are a neotenous form of an ancestor that was much more "ape-like" a valid possibility?

Is the idea that humans are a neotenous form of an ancestor that was much more "ape-like" a valid possibility?I thought this was accepted as part of the process by which humans had evolved. The lactose tolerance that allows most adults to consume milk is another instance of this. Perhaps I've picked up the wrong idea, and this isn't a widely acceepted idea. What is your take on this?

I think that what is thought to have happened with humans is a more special and gradual case of neoteny/heterochrony (not depending on a single gene, like in some salamanders). And certainly not determined by environmental stresses, but nearly totally a different regulation of the growth by the organism itself, even though it does have some environmental inputs.

That is, even though you can do things like, by the modification of environmental inputs, make boys or girls to reach pubescence faster (or delay it somewhat), you wouldn't be able to change something in the environment of a growing person and make it "completely" develop into a chimp-like animal.

There's genetic restriction on the "species-level" possible degree of change by environmental variables, and a level beyond that would require either very extraordinary "environmental" changes (perhaps yet on the womb) or genetic changes.

Scientists were able to made chicken develop teeth, as some early birds (and dinosaurs) had, feathers instead of a sort of scale in their feet (and vice-versa, I guess), and I think I've read that they even made them develop somewhat longer tails, rather than their relative lack of bony tail (not it all in a single individual animal). Even though these changes were induced by environmental factors, they're very well targeted, nothing expected from usual environmental variations.

I think it had something to do with sexual selection.

Scientists were able to made chicken develop teeth, as some early birds (and dinosaurs) had, feathers instead of a sort of scale in their feet (and vice-versa, I guess)Birds never had feathers on their feet. Scaly feet are one of the vestiges of their reptilian ancestry. It also gives them better traction so it would have been selected for. Only penguins have feathers on their feet so they can stand on ice without losing all their body heat. If they can grow feathers on chicken feet, they're moving them forward, not backward.

Just like most mammals don't have hair on the soles of their feet, it would make it hard to walk.

I've always heard "neoteny" used in a narrower sense, for adults reverting to the behavior of childhood. That's the reason given for cats becoming social in captivity, when they're solitary hunters in the wild. Our caring for them and picking them up makes them feel like they're kittens being handled by their parents, so they revert to kittenhood, and kittens are social.

Birds never had feathers on their feet. Scaly feet are one of the vestiges of their reptilian ancestry. It also gives them better traction so it would have been selected for. Only penguins have feathers on their feet so they can stand on ice without losing all their body heat. If they can grow feathers on chicken feet, they're moving them forward, not backward.

Both ptarmigan and snowy owls have feathers on their feet, and they're likely separated by millions of years of evolution.

The genes regulating that sort of stuff wouldn't be very hard to mess with, as it's most likely a handful of regulatory transcription factors, rather than novel protein coding genes.

Sort of like how mutations in BMP4 (aka Gremlin), which is a hox gene, I believe, can turn a chicken foot into a duck foot and vice versa

snow owls (http://images.google.com/images?svnum=10&um=1&hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=snowy+owl+feet&btnG=Search+Images)

ptarmigan (http://images.google.com/images?svnum=10&um=1&hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=ptarmigan+feet&btnG=Search+Images)