Gary Schwartz

NIU anthropologist sinks teeth
into study of how primates grow up

Gary Schwartz and colleague land $307,000 NSF grant

by Tom Parisi

NIU anthropologist Gary Schwartz might have been on the road less traveled, but he never lost his sense of direction - or purpose.

Each morning for a month last summer, he made an hour-long trek over primitive dirt roads leading from his campsite, located in the South African bush, to cyber-civilization.

Schwartz was helping run a field school in South Africa's Limpopo Province, the site of 3 million years of human evolution. "I'd drive the students into town, and while they picked up supplies, I would send frantic e-mails from the Internet café," he said.

Working with NIU's Office of Sponsored Projects and his partner in paleontology, Laurie Godfrey of the University of Massachusetts, Schwartz was able to meet his deadline on a major grant proposal.

Suffice it to say the effort paid off.

The National Science Foundation is awarding Schwartz and Godfrey $307,000 for a three-year study that aims to shed light on how evolution tinkers with the process of growth and development in primates.

The study will focus on a highly diverse group of primates known as lemurs.

The creatures, which resemble a cross between a monkey and ferret, are indigenous to Madagascar, an exotic island off the eastern coast of Africa. Schwartz and Godfrey will examine growth and development patterns among both living and extinct lemurs. Living lemurs range in size from one ounce to 15 pounds, while the extinct giant lemurs weighed as much as 400 pounds. Humans drove the giants to extinction some 2,000 years ago.

Lemurs have a unique evolutionary story to tell, Schwartz said.

For many decades, paleontologists have adhered to a general rule regarding growth and development: The bigger the mammal, the slower its growth. A mouse, for example, will reach maturity quicker than an elephant, a chimpanzee faster than a human. Eruption of wisdom teeth, typically at age 18 to 22 in humans, is seen as the final marker of physical maturity in primates.

In an article last year in the Proceedings of the National Academy of Sciences, Schwartz and Godfrey announced their pilot-study discovery that giant lemurs had incredibly fast dental development, much like their smaller living relatives. The finding throws a major wrench into growth and development theory.

"All mammals have two sets of teeth," Schwartz explained. "Baby teeth fall out and are replaced by adult teeth. But the giant lemurs we studied were born with a mouthful of adult teeth, essentially chewing their way out of the womb. Their last molars were in place before six months, even though their bodies weren't nearly fully developed.

"What this shows is that nature can select for accelerated dental growth without accelerated body growth," Schwartz added. "The rules are different than we thought."

The new study will address questions never before asked of extinct primates: How long was gestation in giant lemurs? How rapidly did they grow? At what age did weaning occur? The researchers will chart not only the pace of dental development, but also brain development and cranium growth in differently sized lemur species.

"Ultimately, this study will provide the evolutionary developmental framework for understanding the rules that govern how animals grow up," Schwartz said.

Schwartz's first semester teaching at NIU was this past fall. He is considered a top expert in dental anthropology.

"A specially trained anthropologist can determine how long it took a given animal to grow up by studying its teeth or dental fossils," Schwartz said.

"We can do this with living animals or with 45-million-year-old fossils because teeth preserve a record of growth in a way that's somewhat analogous to tree rings. The cells that produce teeth generate a new line or layer each day. By looking at these lines, we can figure out the length of growth to maturation or even the gestation length of an animal."

Schwartz's study of one complete skull of an adult giant lemur allowed him to pinpoint its gestation to the week. "The next step is to determine the fundamental evolutionary rules of prolonged growth and development, so unique to modern humans," he added. "Once the framework is in place, then we can turn our eyes to the human fossil record."

Schwartz will hire a postdoctoral student for his new project and plans to involve both undergraduates and graduate students in his research. He also hopes to take NIU students to the Limpopo Province for next summer's field school.

See http://www.asu.edu/clas/iho/field.htm for more field-school information.

2-10-2003