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Science notes / Primatology, epidemiology

Bonobos know how to relax

The striking absence of aggression among one species of ape -- bonobos -- may be hard-wired into their brains, a new study suggests. Though closely related to chimps, the endangered bonobos of central Africa are much mellower.

Male chimpanzees have been documented dispatching infants sired by other males. They also stalk and kill outsider chimps. The much more laid-back bonobos react to stress by sharing, playing and engaging in sex.

In the study, James Rilling of the Yerkes National Primate Research Center in Atlanta scanned the brains of 13 living and dead bonobos and chimps. Compared with those of chimps, bonobo brains displayed bigger, more-developed regions thought to be vital for feeling empathy, perceiving distress in others and feeling anxiety, Rilling said.

Even more notable, he said, is that bonobo brains carry a thick connection between the amygdala, a deep-seated emotional center that can spark aggression, and a higher brain region, the ventral anterior cingulate cortex, which helps control impulses.

The thicker connection may explain why bonobos are "better at regulating aggressive impulses and better at avoiding antisocial behavior," said Rilling, who published the study in the journal Social Cognitive and Affective Neuroscience.

-- The Washington Post


Suicide tied to bad economy

Everyone is familiar with stories of businessmen jumping to their deaths from window ledges during the Great Depression. New data from the Centers for Disease Control and Prevention indicate that those stories, sometimes viewed as apocryphal, have a strong basis in fact: Suicide rates rise during times of economic hardship and decline in periods of prosperity.

The association, however, holds strongly only for adults of working age between 25 and 54, the authors reported in the online version of the American Journal of Public Health. And overall, suicides are only a small proportion of deaths, even at times when rates peak.

"The rates were higher during the Great Depression, but not incredibly high," said Dr. Alexander E. Crosby, a medical epidemiologist in the CDC's Division of Violence Prevention and a co-author of the paper.

Earlier studies examining links between economic conditions and suicide have produced conflicting results. The new CDC study covers 80 years and eight distinct age groups. It found that the suicide rate was 18 per 100,000 adults in 1928, and climbed to 22.1 in 1932, the last full year of the Great Depression. That 22.8 percent jump over a four-year period is the largest in history. Since then, the suicide rate has been dropping, with much smaller increases during the oil crisis (1973-75) and the recession (1980-82).

-- Los Angeles Times

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