(Santa Barbara, Calif.) -- 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
Contact: Andrea Estrada
University of California - Santa Barbara