The Threat of Sexual Desire

The threat of having sex with a close relative is that it leads to very unhealthy offspring. We don't know who our relatives are all the time, so there might be cues and other animals can detect them through different senses. But humans as far as I know, aren't very good at doing that. The psychologist Deborah Lieberman found one big predictor is being raised with mistrofen. For instance, watching your own mother nurse another child for a long period might also kind of sit that's kin.