Are human beings intrinsically good but corruptible by the forces of evil, or the reverse, innately sinful yet redeemable by the forces of good? Are we built to pledge our lives to a group, even to the risk of death, or the opposite, built to place ourselves and our families above all else? Scientific evidence, a good part of it accumulated during the past 20 years, suggests that we are all of these things simultaneously. Each of us is inherently complicated. We are all genetic chimeras, at once saints and sinners — not because humanity has failed to reach some foreordained religious or ideological ideal — but because of the way our species originated across millions of years of biological evolution.
Don’t get me wrong. I am not implying that we are driven by instinct in the manner of animals. Yet in order to understand the human condition, it is necessary to accept that we do have instincts, and will be wise to take into account our very distant ancestors, as far back and in as fine a detail as possible. History is not enough to reach this level of understanding. It stops at the dawn of literacy, where it turns the rest of the story over to the detective work of archaeology; in still deeper time the quest becomes paleontology. For the real human story, history makes no sense without prehistory, and prehistory makes no sense without biology.
Within biology itself, the key to the mystery is the force that lifted pre-human social behavior to the human level. The leading candidate in my judgment is multilevel selection by which hereditary social behavior improves the competitive ability not of just individuals within groups but among groups as a whole. Its consequences can be plainly seen in the caste systems of ants, termites and other social insects. Between-group selection as a force operating in addition to between-individual selection simultaneously is not a new idea in biology. Charles Darwin correctly deduced its role, first in the insects and then in human beings — respectively in “On the Origin of Species” and “The Descent of Man.”
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