It costs a lot too grow and "feed" a proportionally human sized brain.
The maintenance of brain tissue requires a huge consumption of protein. (If you're not a ruminant that can turn cellulose into protein, and they have to spend so much time eating that cellulose that they wouldn't have much use for high intelligence.) Dogs and wolves are a single species. But over the 15,000 years since dogs chose to live in our multi-species community, they have adapted to a more scavenging and less carnivorous diet than wolves, and as a result their average brain size is smaller.
I Think it takes a rather specialist pelvis to pop a baby head out of, I'm not that educated in this region but I also believe that human birth is rather dangerous to the mother and that advanced pregnant women have a below average mobility range then most animals, also human children are in practical terms extremly stupid for a enormous amount of time (5 years or so) unable to defend themself or run away, hide, find food a even bare the climate.
That's a hard limit we're running up against. Human babies are born at a qualititively much more primitive stage of development than any other mammal, in order for the head to fit through the birth canal. As a result they're utterly helpless for several months after birth and continue to require extensive care and education for many years. That is quite a liability for the baby and quite a burden on the parents compared to almost all other mammals, who leave home during their first year.
I would assume that humans are under a very large evolutionary pressure to adapt to the changed and changing social environment, and that the selection will result in rather extensive changes in both the brain and human behavior.
But it will be slow. As i said, it took fifteen thousand years for dogs to diverge as little as they have from wolves. It took sixty thousand years for the polar bear to diverge from the grizzly; AFAIK that's the most rapid speciation we're aware of.
Our social and technological environment changes much too quickly for our biological evolution to keep up. We're going to have to do it with reason and learning instead of nature, which is the way we've been doing it ever since the Neolithic Revolution.
Some argues that with vegetation food only we wouldnt be in this stage since in dawn of history mankind they surely couldnt understand meaning of protein, in sense that where in vegetation they could extract enough protein.
Humans couldn't extract protein from vegetation until we learned how to cook it. (Only nuts and seeds yield their protein without cooking.) Our ancestors lost the ability to break down cellulose, probably at the same time they learned how to hunt meat. Even so, our metabolism isn't very compatible with a vegatarian diet. The life expectancy at the end of the Mesolithic Era for an adult who had survived childhood was more than 40 years. After the Neolithic (agricultural) Revolution when we became dependent on grains for nutrition, the life expectancy dropped down into the low 20s during the Roman Era. Even 150 years ago it was only in the 30s. Only the advances in the science of biology in the last century--the discovery of the role of vitamins, minerals, amino acids, etc. in nutrition--made possible the current life expectancy of 70+ in the West.
What, other than intelligence and community, do we have? What advantages do we have for survival? We are slow, fat, lazy, not terribly good swimmers, not terribly fast runners, relatively hairless (unprotected from the elements), no natural defenses, no natural fighting implements (sharp teeth or claws). All we have for survival is intelligence and cooperation - without them we would not have survived.
You said a mouthful there. We have transcended our nature and overridden our pack-social instinct, and built gigantic communities: civilization. Civilization has become an artificial organism in its own right that is extremely robust and has defied all of our seemingly concerted efforts to destroy it. It is now 10,000 years old and continues to grow both in size and capability. It's even a recursive phenomenon: civilizations have continually joined forces to become still larger super-communities, to the point that we're probably only one or two hundred years away from a single global civilization.
Why aren't all animals growing flippers?
It is clearly a tremendous evolutionary advantage for mammals to re-adapt to aquatic life. Warm-blooded air-breathers absolutely rule the water. In every aquatic ecological niche where a mammal or bird has reentered, for its size it is usually the apex predator. This includes those who have become completely aquatic and can no longer live on land like the cetaceans, those who can only barely function on land like seals and penguins, those who come to feed like otters and pelicans, and those who just drop in for tasty snacks like bears.
Apparently that readaptation is a difficult process for evolution to provide because it is not common. Of all mammals only the cetaceans have completed it, and they still have vestigial floating pelvises.
The controversial aquatic ape theory--which has been discussed at great length on SciForums if you want to go back a couple of years--suggests that when we came down out of the trees we went into the water first and hunted fish before we came back out onto the land ready to hunt zebras. That would explain the vestigial webs between our fingers and our very un-primate-like buoyancy.
A theory I find attractive suggests that since living in a three-dimensional universe (like swimming or flying) requires your brain to develop more computing power to think in up and down rather than just front, back and sides, that may have been the stimulus for our extraordinary intelligence among all the apes. Just swinging through air between the trees got us partway there to start with.
How did you manage that? I annually insult them, point out their defects, (with specific references to their short comings) etc. and then against the rules call for the banning of someone (Billy T) for his arrogance and disrespect of the moderators. Yet the worst that has happened to me is someone threatened to make me a moderator if I continue that behavior. (It is my annual fun with them, at start of the new year. - I am looking forward to 1/1/08 to do it again.) Last year I set up a pole calling for the ban, and the vote was close, so probably will not do that again!
Personal insults against any member are a violation of the SciForums rules but the moderators have to judge whether it's serious or just wicked fun. I haven't been paying attention to you (sorry dude, you're not a linguist) but apparently you make it obvious that it's all a big joke. Just pick on S.A.M., that's what we all do.
I personally will vote against you unless you tighten up on your spelling, so perhaps you're safe.
