Kluge: The Haphazard Construction of the Human Mind (Houghton Mifflin; 2008)

Consider, first, the short span of human existence and what it might mean. Bacteria have lived on the planet for three billion years, mammals for three hundred million. Humans, in contrast, have been around for, at most, only a few hundred thousand. Language, complex culture, and the capacity for deliberate thought may have emerged only in the past fifty thousand years. By the standards of evolution, that's not a lot of time for debugging, and a long time for the accumulation of prior evolutionary inertia.

Meanwhile, even though your average human makes its living in ways that are pretty different from those of the average monkey, the human genome and primate genomes scarcely differ. Measured nucleotide by nucleotide, the human genome is 98.5 percent identical to that of the chimpanzee. This suggests that the vast majority of our genetic material evolved in the context of creatures who didn't have language, didn't have culture, and didn't reason deliberately. This means that the characteristics we hold most dear, the features that most distinctly define us as human beings — language, culture, explicit thought — must have been built on a genetic bedrock originally adapted for very different purposes.

Over the course of this book, we'll travel through some of the most important areas of human mental life: memory, belief, choice, language, and pleasure. And in every case, I will show you that kluges abound.

Humans can be brilliant, but they can be stupid too; they can join cults, get addicted to life-ruining drugs, and fall for the claptrap on late-night talk radio. Every one of us is susceptible — not just Joe Sixpack, but doctors, lawyers, and world leaders too, as books like Jerome Groopman's How Doctors Think and Barbara Tuchman's The March of Folly well attest. Mainstream evolutionary psychology tells us much about how natural selection has led to good solutions, but rather less about why the human mind is so consistently vulnerable to error.

In the pages to come I'll consider why our memory so often fails us, and why we often believe things that aren't true but disbelieve things that are. I'll consider how it is that half of all Americans can believe in ghosts and how almost four million can sincerely believe that they've been abducted by space aliens. I'll look at how we spend (and often waste) our money, why the phenomenon of throwing good money after bad is so widespread, and why we inevitably find meat that is 80 percent lean much more appealing than meat that is 20 percent fat. I'll examine the origins of languages and explain why they are replete with irregularity, inconsistency, and ambiguity — and, for that matter, why a sentence like People people left left ties us in knots even though it's only four words long. I'll also look at what makes us happy, and why. It's often been said that pleasure exists to guide the species, but why, for example, do we spend so many hours watching television when it does our genes so little good? And why is mental illness so widespread, affecting, at one time or another, almost half the population? And why on earth cant money buy happiness?

Kluge, kluge, kluge. In every case, I'll show that we can best understand our limitations by considering the role of evolutionary inertia in shaping the human mind.

This is not to say that every cognitive quirk is without redeeming value. Optimists often find some solace in even the worst of our mental limitations; if our memory is bad, it is only to protect us from emotional pain; if our language is ambiguous, it is only to enable us to say no without explicitly saying "no."

Well, sort of; there's a difference between being able to exploit ambiguity (say, for purposes of poetry or politeness) and being stuck with it. When our sentences can be misunderstood even when we want them to be clear — or when our memory fails us even when someone's life is at stake (for example, when an eyewitness gives testimony at a criminal trial) — real human cognitive imperfections cry out to be addressed.