• UCSBgauchos twitter avatar
    .@UCSBMensSoccer puts up a fight vs. No. 2 Clemson, but falls 3-2 in Sweet 16. RECAP >>> https://t.co/oqnHQnJzTn https://t.co/vgP5NNdQpL
    8 hours 15 min ago
  • UCSBgauchos twitter avatar
    UCSB Falls at Arizona State on Last Second Shot, 70-68 https://t.co/J0qqsxzgGY
    9 hours 13 min ago
  • UCSBgauchos twitter avatar
    And that'll do it. They battled valiantly, but @UCSBMensSoccer's season comes to and w/ a 3-2 Sweet 16 loss at Clemson. Great season guys!
    10 hours 31 min ago
  • UCSBgauchos twitter avatar
    2 mins left here, rain is really pouring now. C'mon Gauchos!
    10 hours 33 min ago
  • UCSBgauchos twitter avatar
    Goal for Clemson. Tic-tac-toe passing leads to a tap-in goal for Kyle Murphy. 3-2 now w/ 11 mins to go #LetsGoGauchos
    10 hours 44 min ago
  • UCSBgauchos twitter avatar
    GOALLLLLLLL! Sloppy back pass from Clemson to the keeper, Kevin Feucht pounces on it and taps into an empty net. 2-2 w/ 20 mins left to go.
    10 hours 54 min ago
  • UCSBgauchos twitter avatar
    Clemson goes up 2-1 on a goal by Diego Campos. 22 mins left for UCSB to equalize.
    10 hours 58 min ago
  • UCSBgauchos twitter avatar
    63' - Yellow card for Clemson, #6 Paul Clowes
    11 hours 4 min ago
  • UCSBgauchos twitter avatar
    62' - Nice build up for UCSB leads to a shot from the right side from Ismail Jome, but he hits the sidenetting.
    11 hours 5 min ago
  • UCSBgauchos twitter avatar
    Tactical foul leading to the YC for Clemson leads to a short-side opportunity for Randy Mendoza, but his shot stays wide left.
    11 hours 12 min ago
  • UCSBgauchos twitter avatar
    58' - Yellow card for Clemson, #11 Aaron Jones
    11 hours 12 min ago
  • UCSBgauchos twitter avatar
    51' - Jome sends one to the far post from inside the 18, but his curler goes just wide.
    11 hours 19 min ago
  • UCSBgauchos twitter avatar
    Second half for @UCSBMensSoccer starting now, tied w/ No. 2 Clemson 1-1! Catch the end of the game here: https://t.co/R9FRG70Get
    11 hours 26 min ago
  • UCSBgauchos twitter avatar
    Halftime stats for UCSB/Clemson (tied 1-1) Shots: 8/5 Shots on Goal: 3/4 Corners: 3/2 Fouls: 13/8 Yellow cards: 1/0
    11 hours 34 min ago
  • UCSBgauchos twitter avatar
    Clemson equalizes late in the first half through an Aaron Jones strike. It's 1-1 heading into halftime.
    11 hours 41 min ago

UCSB Study on Sibling Detection Mechanism Highlighted in 'Nature'

Thursday, February 15, 2007 - 16:00
Santa Barbara, CA


Leda Cosmides and John Tooby

Photo Credit: 

Djamoul E. Ramoul

Fundamental theories in evolutionary biology have long proposed that biological kinship is the foundation of the family unit. It not only creates the sense of altruism that exists among genetically related family members, but also establishes boundaries regarding sexual relations within the nuclear family. Questions have persisted, however, regarding the means by which humans recognize family members -- particularly siblings -- as close genetic relatives.

A team of researchers at the University of California, Santa Barbara, has found evidence of a nonconscious mechanism in the human brain that identifies genetic siblings on the basis of cues that guided our hunter-gatherer ancestors. Their findings will be published in the February 15 issue of the science journal Nature. In a study involving more than 600 test subjects, the researchers found that people felt more altruistic toward individuals this mechanism recognized as siblings, and, at the same time, felt a greater aversion to engaging in incestuous sexual relations with them.

"The old thinking was that Darwinism applied to humans physically, but not socially. Now we see the evolution of a mechanism that finely regulates important aspects of human social behavior," said John Tooby, professor of anthropology and co-director of the Center for Evolutionary Psychology at UCSB. He completed the study with Leda Cosmides, professor of psychology and also co-director of the Center for Evolutionary Psychology, and Debra Lieberman, a former student at the center and now a professor of psychology at the University of Hawaii. Mechanisms such as the one identified in the current study have been found in many species, he added, but their existence in humans had been a matter of controversy.

According to the researchers, the development of altruism between siblings is a result of natural selection, as are their aversions to sexual relations with one another and their aversion to sexual relations among siblings in general. The study's findings indicate these sensibilities are not primarily a result of socialization by parents or peers, but of motivational systems that evolved to respond to cues of genetic relatedness.

The question the researchers sought to answer was how siblings recognize their close genetic matches. Drawing on the socioecology of ancestral human foragers they found the answer in a set of cues that enable humans to identify their brothers and sisters as siblings. For older siblings, what the researchers refer to as "maternal perinatal association" -- seeing their mothers care for infant siblings -- activates the mechanism in the brain, which, in turn, increases feelings of both altruism and sexual aversion toward younger brothers and sisters.

This cue, however, is unavailable to younger siblings whose birth order precludes the opportunity of watching their mothers care for older brothers and sisters. For these siblings, the mechanism is triggered by the amount of time they live together as

a family during the period from the younger siblings' infancy through adolescence. The researchers found that this "co-residence" regulates sibling altruism and sexual aversion toward adopted and step-siblings as well -- individuals whom the subjects consciously believe to be genetically unrelated. "This shows that the mechanism operates independently of our beliefs about kinship," Cosmides said. "The cues regulate sibling altruism and sexual aversion, no matter what we believe."

The discovery of a mechanism designed to make family relationships non-erotic casts doubt on Sigmund Freud's view that family members are the first and most powerful objects of sexual desire, say the authors.

It also helps to settle a long-running debate in anthropology about whether family relationships are socially created purely by culture, or whether evolved mechanisms in the brain play a role.

The results of the study could also have implications for health care professionals such as psychiatrists and psychologists who treat victims of incest and those who commit it.

"The theory gives a means of identifying who might be at risk," said Tooby. "Siblings who have lived separately for long periods of time have not been exposed to the cues the brain uses to determine who is a sibling. This may offer an explanation as to why someone might have an inclination toward incest."

It also suggests, he says, ways of building families that would be more strongly and reliably linked together by bonds of affection.

Nature Article

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