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But the largest number of primate species--thirty-four--have a promiscuous system in which females routinely associate and copulate with multiple male...more

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[W]hat makes patriotic and religious fanatics such dangerous opponents is not the deaths of the fanatics themselves, but their willingness to accept t...more

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Recreational sex is thus supposed to function as the glue holding a human couple together while they cooperate in rearing their helpless baby.

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Sex is flagrantly separated from reproduction in a few species, including bonobos and dolphins.

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Sex in social mammals is generally carried out in public, before the gazes of other members of the troop.

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The daddy-at-home theory posits that concealed ovulation evolved to promote monogamy, to force the man to stay home, and thus to bolster his certainty...more