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Why Humans Have Such Big Brains

<img src="/files/u19/images_3.jpeg" align="left" height="96" width="136" /> What

People like many things about the game of basketball. There are those who like the thrill of the slam dunk, the bulls-eye accuracy of a fade-away three-pointer, the relentless thudding of a wide-bodied big men battling it out for rebounds. This list goes on and on.

Last night, mid-way through the first quarter of the Stanford v. Texas game, I saw a reprise of the thing that made me first fall for the sport: a pass.

It was a doosy.

In basketball, it’s a point guard’s job to handle the ball and distribute the ball and generally set up the offense, and Texas has one of the better point guards in the college game in D.J. Augustin. And it was Augustin who made the pass in question, a lightning dart, a perfectly timed ball bounce, sent into the waiting hands of Longhorn’s big man Dexter Pittman.

Sure, Pittman responded with a nice little hook shot of his own to score two, but I almost didn’t notice, such was my awe at the pass.

Perhaps my awe is slightly different from most, but that’s because it’s been informed by a long ago conversation with University of Washington Professor Emeritus of theoretical neurophysiology William Calvin.

Theoretical neurophysiology is a mouthful. Essentially, what Calvin spent his career thinking about is how the human brain evolved. One of the core questions in this field has always been: what triggered the development of the human brain? How did the it triple in size in just over two million years of evolution? Why is it so much bigger than the noggin of other, older primates? What was it that required more thinking power and thus more space for more gray matter to facilitate that thinking power?

These are all very good questions and scientists have proposed a variety of different answers, but most reigning theories begin with RA Fisher’s runaway model of sexual selection.

The idea—at a very basic level—is that random mutation produces random body types, but if, say, at some point in evolution a few female birds decide to take a liking to longer tails in their mates, then their offspring will all have longer tails. If this long tail preference continues over time and through successive generations it can result in something like the peahen’s preference for peacock tails (this is helpful since there is no natural advantage to survival to having a tail the size of a coat closet).

Fisher’s key insight was why future generations would take a liking to such long tails (why that first female’s preference got passed down). The answer is simple: the genes for sexual selection are heritable.

Which means, at a certain point in the mating game, enough of a core starter population inherits this preference so the prefence starts to snowball (to runaway in Fisherian parlance) and thus becomes a ubiquitous desire.

So what was it that set this big-brain ball rolling?

Many scientists feel that language is the answer, but Calvin has a different idea.

Calvin’s thought is that to spur that much brain growth requires more fuel for the fire and more fuel for the fire means more food and better hunting skills. Thus the thing that Calvin decided triggered this whole cascade was our ability to throw a spear.

Here’s why: spear throwing requires not just stabbing—a very in-the-moment activity—but targeting. To throw a spear at an animal that is running away requires planning into the future. Not a great bit, but a few seconds worth of that future.

You sight the animal where it is now, but throw the spear to where it will be moments later. And in Calvin’s opinion it is this time act of dreaming into the future that required more brain power for more trajectory calculation and this requirement is what causes our brains to begin to grow.

Obviously, this ability to throw a better spear made one a better hunter and since everyone likes to eat (and survival depends upon it) spear tossing prowess could become a target of sexual selection. Thus the genes for the desire, right along the genes for the greater brain size to facilitate this desire, would get passed down, and suddenly evolution is off and running.

And it is this same motion, this same thinking into the future throw, that is mostly frequently and most elegantly represented by the pass in basketball (some might argue that football is a better example, but in football most of the plays are scripted some the quarterback knows where the receiver will be ahead of time so a different thing is going on). Thus, my admiration for DJ Augustin’s bounce pass was an admiration for the very thing that made me human in the first place: a big brain at work!

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