We are beasts, you and I. Total animals. As sophisticated as we might fancy ourselves, we are as zoological as dingoes, goldfish, and llamas. This empirical fact, which is the first principle of the fledgling science known as evolutionary psychology, may seem obvious, but its implications and manifestations are staggering. In Why Beautiful People Have More Daughters, Alan S. Miller and Satoshi Kanazawa detail with fascinating clarity how and why our genes are responsible for just about everything we do.

We accept that salmon spawn, peacocks strut, and dogs howl at the moon because it's part of their innate nature—something in their genes tells them to. Until the advent of evolutionary psychology, scientists agreed that every animal operated this way—except humans. We supposedly emerged as slimy tabula rasa, and our empty brains were instantly filled with socially fabricated gender roles. This means that genitalia aside, men and women are otherwise identical, which should have been clue number one that this was a flawed theory.

Evolutionary psychology contends that the brain is a biological organ that has adapted, much like our hands or eyes, to ensure maximum survival and reproduction. And since spreading your genes around is the primary goal of evolution, it's no surprise that nearly everything boils down to getting laid.

From the biological determinants that dictate why women have fewer affairs, why newborns will stare at photos of pretty women longer than at ugly ones, why guys love porn, and why most suicide bombers are Muslims, evolutionary psychology boils it down to genetic hardwiring that has been propagating the human species for the past 10,000 years.

Of course, there are plenty of exceptions to these guiding principles, which the authors address, and they also confess to huge gaps in the field: Homosexuality, for instance, has yet to be "explained" with evolutionary psychology. Beautiful People is sure to upset some people (liberals and feminists, particularly), but the authors have written a science book, and frequently remind us that this is biology, not morality. Even if some of their findings are startlingly politically incorrect, it's impossible to read this book and not see yourself throughout. You can't help it: It's in your genes.