Knobi watches intently as University of California, Santa Cruz researcher Dr. Nathaniel J. Dominy tests saliva samples for the enzyme amylase. Great Ape Trust photo.

Des Moines, Iowa – July 29, 2008 – What makes an ape's mouth water? Some scientists think the answer is starch. The saliva of humans and great apes is unusual among mammals for being rich in amylase, an enzyme that converts starch to sugar. The drool of the world-famous bonobos and orangutans at Great Ape Trust of Iowa could shed new light on the evolution of humans, according to a pair of researchers from the University of California, Santa Cruz who visited the scientific research institute in southeast Des Moines earlier this month.

Dr. Nathaniel J. Dominy, a noted anthropologist whose research is at the intersection of anthropology, ecology and genetics, and his student, Andy Cunningham, analyzed the apes' saliva to measure the amount of amylase. Cunningham just finished undergraduate work at UC Santa Cruz.

Their pilot study, which will measure salivary amylase levels across the primate order, is important because it can shed more light on when and why early human ancestors began consuming foods requiring starch hydrolysis, such as tubers, bulbs, roots and corms. The enzymes have been found in humans (high levels) and chimpanzees (moderate levels), but extensive testing of orangutans or bonobos has never been attempted – though high levels were detected in a single orangutan at the Yerkes Primate Center in 1982. With the opportunity to do more extensive testing of orangutans, and test the saliva of bonobos that were never tested before, Great Ape Trust offered opportunities for researchers not available elsewhere, Dominy said.

Before the invention of cooking, starchy foods were typically famine foods, so high levels of salivary amylase in a species could give scientists a greater understanding of past selection pressures – that is, the intensity with which an environment eliminates an organism and its genes, or gives it an adaptive advantage. For example, it is known that starch intake varies considerably among human populations – amylase levels are generally high in agricultural populations with a starch-rich diet such as American-Europeans and Japanese, while levels are generally low in some hunter-gatherer populations that do not rely much on starch – but information on the amylase levels among bonobos and orangutans is practically non-existent. In the wild, orangutans often crack seeds and chew on the starchy tree bark, so salivary amylase levels are expected to be high.

"In one week," Cunningham said, "we collected the only five data sets for bonobos, and tripled the known data on orangutans."

The study by the UC Santa Cruz researchers was a collaboration with Great Ape Trust scientist Dr. Serge Wich, who has extensive field experience on the islands of Sumatra and Borneo, the only places on Earth where wild orangutans remain. Their conservation status is precarious, and without intervention, they could become extinct within a decade.

"It's a good example of how to integrate lab work and field work, and tells us more about orangutan evolution and human evolution," Wich said. "The more we can stimulate field work, the better it is in general for conservation."

Ultimately, the information could help conservationists predict how wild orangutans might respond to a change in their food availability due to logging, he said.

BACKGROUND INFORMATION

Great Ape Trust of Iowa is a scientific research facility in southeast Des Moines dedicated to understanding the origins and future of culture, language, tools and intelligence. When completed, Great Ape Trust will be the largest great ape facility in North America and one of the first worldwide to include all four types of great ape – bonobos, chimpanzees, gorillas and orangutans – for noninvasive interdisciplinary studies of their cognitive and communicative capabilities.

Great Ape Trust is dedicated to providing sanctuary and an honorable life for great apes, studying the intelligence of great apes, advancing conservation of great apes and providing unique educational experiences about great apes. Great Ape Trust of Iowa is a 501(c) 3 not-for-profit organization and is certified by the Association of Zoos and Aquariums (AZA).