Different chimp species suspected

August 26, 1994|By Newsday

Like chambermaids cleaning up after departed guests, scientists have climbed trees and scoured branches in Africa seeking chimpanzee hair, hoping to figure out who's who among all the world's chimps.

In the first large study of genetic variation among wild chimpanzees, researchers from the University of California, San Diego, used tiny bits of deoxyribonucleic acid, or DNA, from hair as a guide to chimpanzee relationships, mating preferences and social structure.

The biggest surprise was that chimps from West Africa are genetically distinct from chimps in Central and East Africa, so much so that they may even be a separate species. There are chimps, pygmy chimps and now, maybe, West African chimps.

The discovery should spur a deeper look at chimpanzees -- at behavioral and physical differences, for example -- that could indicate a truly separate species.

Equally as significant, the research found that the more than 2,000 chimpanzees in U.S. biomedical research colonies, long considered genetically equivalent to each other, are more genetically diverse than had been thought.

In other words, not all chimps are the same, so research that assumes genetic uniformity may yield errors that are important in human medicine.

"This discovery suggests that some biomedical research based on chimps may have to be reassessed," said David Woodruff, a conservation biologist at UC San Diego and a member of the research team.

The findings are "intriguing and significant," said Dr. Kenneth Gould of the Yerkes Primate Research Center in Atlanta and a member of the Great Ape Taxon (Genetic) Advisory Group. "They used a relatively novel and developing technology to prove things which otherwise would have been rather hypothetical."

Among other findings reported in today's Science magazine:

* Males in wild chimp communities are more closely related to one another -- as brothers, cousins, etc. -- than are the females. This may explain why cooperative behavior is seen more often among males than among females, who usually leave the troupe during adolescence.

* Female chimps spread a community's genes widely by leaving their own groups to join other communities. As a result, their genes have spread hundreds of miles over long periods of time. Males are more likely to stay put.

The scientists studied wild chimpanzees at the Gombe National Park in Tanzania by watching where individual animals nested at night in trees, then collecting hair samples in the morning, eventually from all 43 members of one chimp community.

They also studied and compared chimp hair collected from 20 sites across Africa. The tactic works because each chimp makes a new bed every night and leaves behind hair that has been shed. Hair fibers usually include a few cells -- and thus some DNA -- from the animal.

Such work represents "the first step in understanding the diversity and the similarities among chimpanzee communities, populations and subspecies," the research team wrote.

More important, the same methods "are immediately applicable to many other . . . [species] of concern," offering a powerful new way to study wildlife biology.

Geneticist Phillip Morin, now at the University of California, Davis, explained that studying chimpanzee DNA "tells us a lot about the history of the animals. Genetics tells us about the social structure of natural populations: how many males reproduce, how closely related animals in a group are, or whether females mate with the males in their own or a neighboring group."

This is useful because "almost nothing is known about genetic variation of the chimpanzee," the team wrote.

After testing their ideas on captive chimps' hair, the researchers visited Gombe in Tanzania. A band of chimps, the Kasakela community, was studied because it was already well known after three decades of work by anthropologist Jane Goodall, who participated in the new research.

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