From Primitive Parts, A Highly Evolved Human Brain

From one perspective, the human brain is a masterpiece. From another, it's 3 pounds of inefficient jelly. Both views are accurate, and that's because our remarkable brain has been assembled from some very primitive parts.

"Although the things it can do are very wonderful and impressive, its design is very poor engineering in many respects," says David Linden, a professor of neuroscience at Johns Hopkins University in Baltimore, the author of The Accidental Mind.

Linden says there's a simple explanation: evolution.

"In evolution, you never build something new if you can adapt something you've already got," he says. "It's the ultimate tinkerer and the ultimate cheapskate."

Our brain has been put together with parts from jellyfish and lizards and mice, Linden says. These parts may have been OK for their original owners, he says, but they aren't ideal for us.

Take brain cells, for example.

"They are slow. They are inefficient. They leak signals to their neighbors," Linden says. "Consequently, if you want to build clever human us with these very suboptimal parts, the only way to do it is to build a brain that is simply enormous and massively interconnected."

And that means it's very slow. Linden says getting a simple message from our feet to our brain can take a remarkably long time. To get a sense of just how long, he says, imagine a giant with her head in Baltimore and her toe off the coast of South Africa. If a shark bit that toe on Monday, Linden says, "she wouldn't feel it until Wednesday, and she wouldn't jerk her toe until Saturday."

Why the lag? Linden says it's because we're still using a communication system developed 600 million years ago by jellyfish.

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