By Maggie Fox, Health and Science Editor
WASHINGTON (Reuters) - Researchers who wanted to find out why it is not only
taboo to kiss your sister, but also disgusting, said on Wednesday they have
discovered why in a discovery that challenges some basic tenets of Freudian
The instinct evolved naturally and cannot be taught, John Tooby and Leda
Cosmides of the University of California Santa Barbara wrote in their report in
the journal Nature.
Spending time in the same household and watching your mother care for your
brother or sister is all it takes. This is all subconscious, of course, reported
the researchers, who worked with Debra Lieberman of the University of Hawaii.
"We went in search of a kin detection system because some of the most
important theories in evolutionary biology said such a thing should exist,"
Cosmides said in a telephone interview.
"It should regulate both altruism and incest disgust."
Humans have an inbuilt system that does both, they found.
"This data shows that the degree to which we feel those things is governed by
these cues that, for hunter-gatherers, predict whether somebody is a sibling.
And it works regardless of your beliefs -- who you are told who your siblings
are," she said. Continued...
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