I think I kin, I think I kin

Human beings are capable of killing a sister because she does not behave according to a code of behavior, and refusing to traffic with a brother who has abandoned a religion. We are also capable of treating unrelated strangers as if they were family, as when people take in a ``fellow American'' or a ``veteran just like me'' or a ``fellow child of God'' when those people need help.

This raises a question: If we can treat any human being as a relative, are we immune to the rules that seem to govern other animals? Those rules seem to dictate that the degree of relatedness between two creatures will guide how much they help one another.

In this week's Nature, the evolutionary psychologists Leda Cosmides, John Tooby and Debra Lieberman argue that human beings do have innate psychological mechanisms for detecting who is kin.

Such a claim does not, of course, eliminate the need for explanations for why human beings are so nice to non-kin, but it suggests that people might be susceptible to treat as kin people who feel like kin because they satisfy the unconscious mind's template for a relative. Such a mechanism might be part of why many of us our susceptible to the rhetoric of kinship: All those ``bands of brothers'' who aren't related, those offices ``where we're like family,'' those religions that declare that we are all children of God.