Saturday, October 20, 2012

Humans Have Brains For Running

Why do humans have brains so much bigger than our bodies, relative to other animals?  As it turns out, maybe not so we can be so smart.  Most theories have to do with the physiology of bipedalism.  You may have heard of similar hypotheses before (the most famous being the radiator hypothesis) but the go-to guy for "human brains are adapted for (bipedal) running" theories is Daniel Lieberman, an evolutionary biologist at Harvard.  Both transcript and video at link with him explaining this increasingly well-supported theory, it but unfortunately the video is not embeddable. 

Brains are very costly. Right now, just sitting here, my brain (even though I'm not doing much other than talking) is consuming about 20- 25 percent of my resting metabolic rate. That's an enormous amount of energy, and to pay for that, I need to eat quite a lot of calories a day, maybe about 600 calories a day, which back in the Paleolithic was quite a difficult amount of energy to acquire. So having a brain of 1,400 cubic centimeters, about the size of my brain, is a fairly recent event and very costly.

The idea then is at what point did our brains become so important that we got the idea that brain size and intelligence really mattered more than our bodies? I contend that the answer was never, and certainly not until the Industrial Revolution.
What is the answer then?  Bipedal locomotion over long distance.  Remarkable that this is part of what made us able to start asking other questions about our existence.  There's a lot more but here's another telling passage.

The other reason we often discount the importance of brawn in our lives is that we have a very strange idea of what constitutes athleticism. Think about the events that we care about most in the Olympics. They're the power sports. They're the 100-meter dash, the 100-meter freestyle events. Most athletes, the ones we really value the most, are physically very powerful. But if you think about it this way, most humans are wimps.

Usain Bolt, who is the world's fastest human being today, can run about 10.4 meters a second, and he can do so for about ten or 20 seconds. My dog, any goat, any sheep I can study in my lab, can run about twice as fast as Usain Bolt without any training, without any practice, any special technology, any drugs or whatever. Humans, the very fastest human beings, are incredibly slow compared to most mammals. Not only in terms of brute speed, but also in terms of how long they can go at a given speed. Usain Bolt can go 10.4 meters a second for about ten to 20 seconds. My dog or a goat or a lion or a gazelle or some antelope in Africa can run 20 meters a second for about four minutes. So there's no way Usain Bolt could ever outrun any lion or for that matter run down any animal.

A typical chimpanzee is between about two and five times more powerful than a human being. A chimpanzee, who weighs less than a human, can just rip somebody's arm off or rip their face off (as recently happened in Connecticut). It's not that the chimpanzee is remarkably strong, it's that we are remarkably weak. We have this notion that humans are terrible natural athletes. But we've been looking at the wrong kind of athleticism. What we're really good at is not power, what we're really phenomenal at is endurance. We're the tortoises of the animal world, not the hares of the animal world. Humans can actually outrun most animals over very, very long distances. 
The marathon, of course, is a very interesting example. A lot of people think marathons are extraordinary, and they wonder how many people can run marathons. At least a million people run a marathon every year. If you watch any major marathon, you realize that most of those folks aren't extraordinary athletes, they're just average moms and dads. A lot of them are charity runners who decided to raise money for some cancer cause or diabetes or something. I think that proves that really your average human being can run 26.2 miles without that much training, or much ability to be a great athlete. Of course, to run a marathon at really fast speeds is remarkable, but again, it just takes some practice and training. It's not something that's really extraordinary.

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