Along with our many human propensities, we evolved a huge cerebral cortex with which we make decisions.

The human brain is built to compare; it's Darwinian to consider an alternative when one presents itself.

We evolved in a tropical climate where the smells of plants and flowers were all around us. We spent a lot of time in the trees with a lot of sunlight and no clothes.

I think romantic love evolved to enable you to focus your mating energy on just one individual at a time, thereby conserving mating time and energy.

Real competition can drive up testosterone, which boosts libido.

There exists no culture in which adultery is unknown, no cultural device or code that extinguishes philandering.