The Human brain is amazing. It uses around 25% of many of our body's metabolic resources (such as oxygen) to operate. This aspect does not, intuitively, seem like an adaptation that would have helped us out if it didn't happen gradually over a long period of time so that the benefits could justify the resource use. But it didn't happen (on an evolutionary scale) over a long period of time.

Its divergence from the slow, expected progress of evolution when compared to other primates' brains seemed to have rapidly occurred over the past 300,000 years or less. This appears to some to defy the basic principle of incremental change over time. Was it was the result of a single mutation - perhaps mitochondrial Eve? If so, a big brain that is uneducated (imagine the first super-genius) isn't as useful as might be imagined. And such a visible mutation might have made that baby a target for destruction by the 'community.'

In any case - I am fascinated by my recent introduction into this aspect of evolution and am hoping people can share scholarly articles and educated insight into this puzzling aspect of evolution. Here's my contribution:

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Actually - I find the timeline on this page useful - not so certain about and concurrent philosophical underpinnings of the site itself. I read some and am mildly confused about where they stand on certain ideas ... interesting - but needs more study - or just ignore the opinions, I guess.
Good thread! I read a book called "The Evolution of Consciousness." The premise was that our large brain was a by-product of the problem of overheating. All those extra neurons are just... insulation!
Now that would be the ultimate irony. Neural matter is fat, is it not?
I thought it was pretty clever... intelligence, just an unintended side effect
Not according to quantum babblebrain - Deepak Chopra!

Check out Shermer and Harris Vs Chopra and Houston
http://abcnews.go.com/Nightline/video/chopra-time-upgrade-science-1...
Yeah - he's nuts when he tries to tuck the soul into the quantum realm AFTER demonstrating and claiming that he understands the Scientific Method, Occam's razor, falsifiability, etc.

He did the one thing (though joking) that drives me nuts about New Age Western 'Past Lives' believers do all the time - claimed to have been one of the very few notable figures from antiquity in a past life - and he takes it further by claiming to be a mythical one at that. It drives me nuts how many women I've met who ALL used to be Cleopatra.
I watched the video. It frustrates me that the "average" viewer doesn't have the critical thinking skills to distinguish between accurate information (evidence based) from woo woo, when presented by likable, articulate speakers.
There's a clip on Youtube (Slaves to superstition) which has Dawkins interviewing Deepak Chopra - and you can see how hollow and ineffective, Chopra's use of scientific jargon, is when scrutinised. His use of the word "quantum" is entirely "poetic".

He is openly hostile to "modern science" - and also takes full credit for the quote "No skeptic, to my knowledge, ever made a major scientific discovery or advanced the welfare of others." I am yet to find another quote more astounding in it's stupidity and absurdity.

He's one more product my country should be ashamed of. Apologies to the rest of the world (which chooses to think)
I do have to say that, at some point, the side-effect started intending things that led to more deliberate intent.
I could see that.... The more intelligent folks could exercise dominance over the less intelligent.
It seems plausible that an arid climate change in eastern Africa some millions of years ago caused the previously forested areas to become more savannah like. To tree dwellers (such as proto-humans) who feed primarily off fruit and relied on the sanctuary of trees for protection, a rapid change had to occur or extinction would surely be the only option.

The first adaptation may have been a more carnivorous diet; as neo-ground dwellers there would have been protein available not from direct hunting, but from scavenging. As an aid to scavenging, having the upper limbs free to grab and carry would be a distinct advantage however that adaptation would require an upright stance (a fairly 'expensive' adaptation) requiring among other things keen balancing, narrower pelvis, head moving forward on top of the spine, and longer legs.

But, it was apparently a good adaptation technique trade-off; a few problems had to be resolved however. The narrower pelvis meant that the maximum size of an offspring's head was a fixed maximum, and even them it was a tight squeeze. To compensate for this, babies were born before they were fully developed to the point that a much longer time of external mental (and physical) growth became necessary. This mental growth outside of the womb meant that the developing brain would be exposed to all the sensory information that was absent in the womb. The brain would accordingly become more complex as it grew as it now was pressed to create 'circuitry' to resolve all the stimuli it now was exposed to in addition to the normal growth that would have occurred had the brain more fully developed within the womb.

The more complex the brain circuitry became, the bigger the eventual head volume became and again requiring an earlier age to be born to compensate for fixed pelvis size. This positive feed-back eventually lead to a brain developing during a much longer period of time where the stimuli presented to it required abstract thinking circuits being laid down to make sense of the non-womb environment.
Once the brain had the potential for abstract thinking, it was possible to use this quirky method of input processing to resolve some of the survival activities necessary in the rapidly changing environment.

A slow positive feed back selection began and those who had keen animalistic thinking processes but limited potential for playing out scenarios within the mind were at disadvantage to those who could. The odd new way of processing sensory information did not come cheap. More and more of the bodies energy was required to run the expanse of new brain circuitry; overheating became a problem. A new way to rapidly cool a large volume of blood was needed. A radiator was needed - and created - in the form of passing the warm blood close to a cool external temperature; and to cool the external body an expensive adaptation was created - sweating. Evaporating water from a surface does indeed cool it, however the efficiency is hampered by any obstacle to the process such as hair growth. Again, an expensive adaptation was needed to accommodate this newly enlarged, resource demanding, excess heat-producing brain, so the protective coat of hair had to dispensed with.

So now we were an upright, awkward balanced, forelimb-free, long legged, big brained naked ape. The
arms that were now need to aid in walking and were useful in grab-and-run scavenging were also free for other uses that might be beneficial for survival purposes, such as weapon wielding. To commandeer a caucus from formidable predators to whom it rightly belonged, an extension arm made of a hard non-inanimate material was just the thing. And it turned out that if there was a shortage of salvageable food, and it seemed that the non-related clan of humans living 'over there' did have resource, the weapon was also as useful to dislodge food from them as it was from the prime predator.

Another adoption seemed necessary to compensate for the extended period of time for the offspring to develop outside of the womb. The amount of care needed to be provided by the female seriously reduced her ability to hunt or find food. She needed a protector/provider who would (at his own expense) continually offer these services. The only currency to ensure this rather heavily priced service was . . .sex. The female offered continual availability to sex during non-estrus and even during pregnancy. Such a scheme was novel, and unknown in the animal world. As our sense of smell was diminished (the neural circuitry was reduced to make room for the ever expanding brain) pheromones were no longer the communication route of sexual readiness. Sight was now the available medium and complex flirting signals developed as well as permanently swollen milk glands caught to catch the attention of ever-ready-for-sex males.

So, to accommodate survival of a rapidly changing climate, tree dwelling apes became upright-walking, big brained, weapon/tool using, same species depriving, naked, over-sexed, abstract-thinking animals with the runaway brain capability to articulately communicate, plan, build, destroy, worry and dream.
Very thought provoking and thoughtful. I heard an anthropologist explain once that the maturation period of humans has been inordinately long for a very long time and, because of this, the tribes that took care of the 'orphans' were the ones that survived major cataclysms (such as ice ages.)

I had not heard of the pelvis to head size ratio adaptation idea before. That totally makes sense - including the dual purpose of the 'soft spot' on a baby's head. A vaginally delivered baby has a cone shaped head for a time after birth in fact. We used to call our daughter our little conehead and reffered to the early stage when she couldn't even hold her head up as the 'worm stage.'

Meanwhile, most other mammals are walking around very soon after birth. Birds learn to fly faster than we learn to crawl. Interesting.

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