Northern Illinois University

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News Release

Contact: Tom Parisi, NIU Office of Public Affairs
(815) 753-3635

April 22, 2003

NIU anthropologist sinks teeth
into study of how primates grow up

DeKalb, Ill.- Northern Illinois University anthropologist Gary Schwartz has won a major grant from the National Science Foundation for a study that aims to shed light on how evolution tinkers with the process of growth and development in primates.

NSF is awarding $307,000 over three years to Schwartz and his partner in paleontology, Laurie Godfrey of the University of Massachusetts.

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 more than 500 years ago.

Lemurs have a unique evolutionary story to tell, Schwartz says. 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 explains. "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 adds. "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 says.

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 says.

"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," Schwartz adds. "Once the framework is in place, then we can turn our eyes to the human fossil record."

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