“Above all, don’t lie to yourself. The man who lies to himself and listens to his own lie comes to a point that he cannot distinguish the truth within him, or around him, and so loses all respect for himself and for others. And having no respect he ceases to love.” – The Brothers Karamazov

One of a number of debates that rages among biologists, social scientists, and various other disciplines is the role of evolutionary theory in explaining behaviour. Almost everyone respects the power of evolutionary theory to describe humanity, but the trick lies in using it properly. Evolutionary biologists like Trivers or Steven Pinker use it widely, and point out that many of the criticisms of their work seem to consist of dislike of the conclusions, not critical argument. There may or may not be difference between the sexes, they say, but disapproving of them doesn’t make them nonexistent.

More sensible critics, however, have a legitimate source of concern. Choose any behaviour, and a reasonable sounding justification from evolution can be concocted to explain it. Of course, such explanations can’t be tested, and it’s usually pretty easy to come up with multiple, conflicting explanations of any such behaviour. Given that, evolutionary explanations may be cute and fun, but it’s not clear they’re much use for anything.

In Deceit, Trivers makes a fairly simple argument: that we have evolved to deceive ourselves, and that such self-deception helps us deceive others and improve our lives. The rest of the book is stories and anecdotes illustrating that point, from the animal kingdom, from politics, and from human behaviour. In West Africa, for example, there are five species of poisonous butterflies. One species has evolved to mimic them: all of them. The mimetic females lay five different kinds of eggs, each of which will mimic a different poisonous species. That way, instead of doubling the frequency of a single poisonous species and making it worthwhile for birds to learn to tell the difference, in any given forest the frequency of each mimic matches the frequency of the model. Some caterpillars, in contrast, curl up like ant larvae and wait to be taken in the nest and fed: once there, they emit the scent of newborn queens, to ensure they get more food than the real ant larvae.

The book is entertaining and has some engaging anecdotes, but you already know the main thesis: it comes as no surprise to anyone who reads fiction that we deceive ourselves, given the essential role it plays in much great literature. If you’d like a deeper look, though, you can get the book here.