Morphing Evolution

hominid skull missing the lower jaw

Australopithecines haven't roamed the Earth for two and a half million years, but Bob Eckhardt and his students can make them live again: They can simulate the growth processes of this extinct species of early humans, as well as those of other species.

This project actually involves a large-scale move into computer dimensioning, morphing, and imaging," says Eckhardt, who is professor of developmental genetics and evolutionary morphology. He and graduate students Matt Rearick, Bill Dean, and Al Wolstenholme developed their Morph 2 program as a means of delving into the tricky question of human evolution.

The similarities between humans and earlier species, such as the Neanderthal and australopithecine, have long been of interest to Eckhardt. But large enough population samples for a detailed comparative investigation are hard to come by, making for a lot of guess work.

In 1992, however, Eckhardt began working with researchers from Frankfurt, Germany, who had a sample of 280 chimpanzee skulls, all from Central Liberia. A German anthropologist had bought the skulls in 1956 from two Liberian tribes, the Cran and the Dan, who had decorated their houses with the skull trophies." Eckhardt learned about the collection, which the anthropologist had donated to two German universities, after reviewing a journal manuscript for the Frankfurt researchers.

With this population sample, Eckhardt was able track the skulls' different developmental patterns, such as changes in structure and shape. When he realized that the specimens could be used for the study of growth variations in the evolution of early humans, Morph 2 was born. Eckhardt scanned photographs of the Frankfurt skulls into a computer, then used a technique called "critical points" to analyze skull growth.

We can take any two images and merge them together," explains Rearick, who, as a graduate student in kinesiology, studies the principles of mechanics and anatomy in relation to human movement. What you do is pick a critical point on an image, be it the corner of an eye, the tip of the nose—any anatomical feature that stands out. The more critical points you have, the more realistic the on-screen image looks." Once the image is scanned into the computer, it is embellished with a series of green dots, representing the critical points. Each dot corresponds to a dot in every other photo of the differently aged skulls. As Morph 2 runs, the shifting dots stretch and compress the image like a piece of fabric, creating a mini-movie: a chimp skull ages before your eyes, from childhood to adulthood to old age.

3 brown skulls, two green skulls, 5 red arrows
James Collins

Beginning with the 5-year-old Taung Child (far left) and ending with the thirty-something adult female known as Mrs. Ples (or, more formally, STS5 from Sterkfontein; far right), Bob Eckhardt and his students show how the skull of an australopithecine, an early Pleistocene human, changes with age. The large middle skull might be the age of "a high school student or undergraduate," says Eckhardt. The smaller skulls above represent intermediate steps from child to student and student to adult.

Eckhardt's ability to match each step with an age range are useful for age determination, a field previously dependent on dental structure. One aspect of growth, for instance, is the closure of sutures across the skull. Humans as well as chimps are born with these sutures; as we grow older the sutures close up. In chimps, as the sutures close they push the ridge of the nose and lift it up in a process called keeling."

Say some guy in Africa finds a skull and doesn't know how old it was when it died," says Rearick. Eventually, he can give it to us and we can tell him exactly, or very closely, based on the suture growth."

To make Morph 2 more precise, Eckhardt's team has begun work with a large sample of primate skulls from the Yerkes Regional Primate Research Center in Atlanta, Georgia. The center has recorded the exact day and year each primate died, bringing Eckhardt one step closer to recreating the processes of how these animals lived and died—and to solving some of the theoretical problems of human evolution.

All this comes under the heading of using living and fossil populations not for the labeling of species for taxonomy purposes, but to learn about the dynamic processes of growth and development—and of life," Eckhardt says.

Matt Rearick, Bill Dean, and Al Wolstenholme are master's degree students in kinesiology. Their adviser, Robert B. Eckhardt, Ph.D., is professor of developmental genetics and evolutionary morphology in the College of Health and Human Development, 256 Henderson Bldg., University Park, PA 16802; 814-865-1531. Their research is funded by Penn State's Gerontology Center, the Wenner-Gren Foundation for Anthropological Research, and the Eastman Kodak Corporation.

Last Updated January 01, 1997