Let's look at it like a debate. Premises and arguments.

Our diet before the advent of agriculture would probably have been adequate for us, if not perfect. We would have been fully adapted to this diet. All other species would also have been fully adapted to their diet.

Our physiology is the result of literally millions of years of natural selection. It follows that it's doubtful that such evolution would have resulted in less than perfect genetic adaptation. Consider all the other species who are perfectly adapted to their environment. But consider how they too obviously suffer the consequences when they try to live in an environment that is different to any significant degree. Diabetic cats and dogs for example.

The DOCs appear 10,000 years ago. Agriculture appears at the same time. We know what causes the DOCs today, it explains our recent past: Agriculture, grains, sugar, etc.

We are no different today genetically than we were 10,000 years ago. We are not fully adapted to our current agriculture diet in all aspects of our physiology.

All aspects of our physiology are regulated by hormones one way or another. It's doubtful that the size and shape of our skeleton, thus the birth canal, escapes this regulation.

The reason our diet causes the DOCs is because it acts on the hormones that regulate our health.

It follows that the problems of pregnancy birth are affected by our diet because this same diet also acts on the hormones that regulate pregnancy and birth and all the related mechanisms and systems. After all, fuel regulation should constitute an integral part of the growth of the fetus. Why not the regulation of the width of the birth canal too?

Put the question differently. Why would our genes be programmed for a difficult, and possibly fatally dangerous birth? This doesn't agree with the whole idea of natural selection. If anything, these millions of years of natural selection would have quickly killed off anybody who couldn't give birth on their own and live, or could not produce healthy babies and live. Because ultimately, we are the descendants of those who lived.


This puts modern medicine and OBGYN in a totally different perspective, doesn't it.

I agree about the shape and size of the pelvis. That makes sense to me but cranial capacity isn't limited by bone structure. Infants with hydrocephalus have large heads and are usually born by cesarean. What about the woman who's pregnant with twins and can have nourished up to two times the brain mass of a single fetus?

Not helping me decide that I want kids..

The greatest part of our growth occurs after we're born. The effect of our diet on growth occurs over that time too. Brain size would be affected by our diet over that period. Even if it's twins (or more) and birth size is smaller than for a single child, there's enough time to catch up, if diet allows of course.

Talking about bone development, pelvises and the ramifications of having a large-brained baby... Even premature babies and multiples (of Neolithic women) catch up (even formula-fed). Neolithic women, pregnant with multiples, can provide more nutrients for brain development than a single baby would require. In other words, they'd be able to provide enough nourishment for a single large-brained baby.

Why don't we have larger-brained babies to begin with anymore? With the advent of the c-section, we might start seeing larger-brained babies born in the Neolithic.

I think your right about the pelvis but not necessarily about the brain.

Back to the I Caveman show. Remember that lady who refused to eat elk meat because it freaked her out? Well, get this: She drank the water that was sterilized using the skin of a dead animal. She was dressed with the skins of dead animals. She slept inside a shelter and on a bed made with the skins of dead animals. Who is she kidding?

Our brains may be smaller, but I wonder if it is overall smaller or if there is a specific part that has significantly become smaller over the years.

Wow! I've read that Australian Aborigines have a 25% larger visual cortex than Caucasians. This is treading into deep water. Who knows what kind of mind is "better." My guess would be that all minds would be beneficial to a society.

I think we need to remember, infant mortality isn't just about birth, but for the few years after that, also, when the child is very vulnerable. I think there would have been some birthing problems, but not as many as are assumed.

The trade off for evolving into big brained humans is that we have a much longer vulnerable infant stage. Even in other species living in direct competition with other predators, for instance big cats, the mortality rate of the cubs is very high - between 40% and 80%, I read, and this is with only 2 years from birth to full maturity.

I think, for evolutionary purposes, infant mortality is supposed to be high - as has already been said, it should be the strongest who survive to adulthood, the ones most adapted to live in that environment. And even though care would have been taken of the not so able, the pressures of the environment would mean that the least intelligent, and the physically weak would not make it to adulthood, so breeding would only happen from the strongest, most intelligent and best adapted, pushing evolution in the right direction for the changing conditions.

Genetic selection for brain development is not so good right now. We live in a society where the weakest are protected (which is good, don't get me wrong), but there is no selection for intelligence or skills or adaptability - most make it to adulthood now, and breed - what does this mean for the development of our species?

Lee

Most of our great grandchildren are going to be small headed and dumb in a few hundred years?

That's right. This is our future:
http://www.imdb.com/title/tt0387808/

Hehe.

Thanks for expressing exactly what I was trying to say Leemack

Yes it is. How could it not be?

Sorry, but I've seen babies delivered with their brains sticking out of their head- always fatal.

That's true. But this means there's no more natural selection. We now have human selection. And this new selection applies not only to ourselves, but to everything we control, cattle, plants, trees, fish, rodents, bugs, and basically everything affected by our activities. We are not only the top of the food chain, but the new designers of the food chain. As you point out though, human selection doesn't produce better humans, it produces worse humans, humans often incapable to deal with existing conditions yet still able to survive them because we protect the weak, the slow, the deformed, the stupid, etc. And we call ourselves the apex of evolution.

It's a true paradox that the ultimate best that evolution could produce is now actively working against it, and going backwards on the evolution scale.

Funny.

As my mamma used to say, "There's one in every crowd." She might have been talking about A-holes, but drama queens also seem to fit into this category.

And they have been breeding heavily in the last 20 years cause I see a lot more of them now then ever before.