Local man studies when we first walked the walk
By using computer technology to analyze the fossil remains of the earliest known human-like creature, a Pittsburgh mechanical engineer has added fuel to the scientific debate about when humans started walking on two legs.
In 2000, a pair of French paleontologists unearthed remains from deep in the heart of Africa’s Great Rift Valley in the Tugen Hills of Kenya.
The fossil bones of this so-called Millennium Man — known in anthropological circles as Orrorin tugenesis — are thought to be about 6 million years old. Until they were found, the oldest human-like fossils discovered were dated at 4.5 million years old.
A well-preserved femur (thigh bone) from Orrorin suggests this chimpanzee-sized creature had strong back legs and possibly walked upright.
Karol Galik, a mechanical engineer at Allegheny General Hospital’s Orthopedic Biomechanics Laboratory on the North Side, has found strong evidence to support this theory by analyzing X-ray scans of cross-sections of the fossil bone.
“We started the project two years ago, and I had some experience with medical imaging and bones from my Ph.D. work,” Galik said. “I looked around for software to make it easier.”
Galik’s findings, published Sept. 3 in the journal Science, suggest that Millennium Man is indeed the earliest known hominid to be bipedal — to walk on two legs. Hominids include humans and extinct near-humans.
A native of Slovakia, Galik, 37, was part of a team of researchers led by his father-in-law, Robert Eckhardt, a Penn State evolutionary biologist who has studied human evolution for more than 30 years.
“Bipedalism is the signature characteristic that defines humans as separate from other hominid primates,” Eckhardt said.
British naturalist Charles Darwin theorized that walking on two legs freed the arms and hands so early hominids could make and use tools. Some scientists argue instead that bipedalism made it possible for male hominids to carry food so the females could focus on child rearing and thereby increase the survival rate of their offspring, Eckhardt said.
Regardless of why bipedalism evolved, most experts had believed it appeared about 4 million years ago. Galik’s findings push this date back by 2 million years.
This means that the ancestors of chimpanzees and humans likely went their separate ways on the evolutionary tree about 2 million years earlier than thought, Eckhardt said.
Galik moved to the United States about 10 years ago and completed his doctorate in mechanical engineering at the University of Pittsburgh, where he studied ankle joint mechanics.
At AGH, the Mt. Lebanon resident is working with orthopedic surgeons to develop a new prosthesis to treat arm bone injuries.
Eckhardt tapped his son-in-law’s expertise in medical imaging technology to analyze CT scans of the interior of Orrorin’s thigh bone.
“If you have children, you have to get them married to the right people to further your career,” Eckhardt joked.
CT scans, or computed tomography, use a rotating X-ray device to create detailed cross-sectional images of body parts.
Galik used specialized software to create three-dimensional models of the femur from CT scans taken of the fossil shortly after it was found.
In today’s apes, the thickness in the upper and lower parts of the thigh bone is roughly the same. In modern humans, the bone is about four times thinner on the top than on the bottom. By taking sophisticated measurements of his 3-D models, Galik found the ratio in the fossil to be one to three, suggesting a transition toward upright posture and bipedalism, he said.
“The story is not the find, but the finding,” Eckhardt said. “The fossils were already found, but we’ve used really powerful modern imaging technology to show something that otherwise wouldn’t have been visible.”
To build consensus among anthropologists that Millennium Man was a biped, it will be necessary to improve the resolution of the CT scans, which were taken several years ago, Galik said.
“The CT scans are not of good quality, and the resolution was low,” he said. “If they had zoomed in, we could have had better resolution — but they didn’t.”
Eckhardt is applying for a grant from the National Science Foundation to go to Kenya to remove the fossils from the museum vault where they are being stored and have them scanned again. Paleontologists also continue to comb the fossil-rich African Rift Valley for more remains from the dawn of human time, he said.
Even if Orrorin walked on two legs, some scientists in the field remain skeptical that it’s a human ancestor.
University of Pittsburgh anthropologist Jeffrey Schwartz agreed that Galik’s findings show Orrorin was bipedal for at least some part of its life. But key structural differences between the fossil bone and modern human femurs make it unlikely that we descended from Millennium Man, Schwartz said.
Instead, Orrorin could have been a forerunner of apes or an evolutionary dead end.
“Whoever owned this femur may have supported itself on two legs at least part of the time,” Schwartz said. “But I don’t think these things can be ancestors of humans. To me, that makes it even more interesting.”