Professor has bone to pick with skeleton

A 3.3 million-year-old child skeleton found in Ethiopia may not be what some claim it to be,… A 3.3 million-year-old child skeleton found in Ethiopia may not be what some claim it to be, a Pitt professor said last week.

The child’s skeleton was found in 2000, but was only recently unearthed enough to begin studying it. Zeray Alemseged, a researcher with the Max Planck Institute for Evolutionary Anthropology, identified the child, found in the Dikika area of Ethiopia, as a member of the species Australopithecus afarensis.

But Pitt professor Jeffrey Schwartz said that there are questions as to what species the child represents, and he questioned the classification of human bones as that species.

“The human fossil record has not been sorted out so definitively,” Schwartz said.

At issue is the way paleoanthropologists classify human ancestor remains and the manner in which they decide what defines a species. Experts don’t dispute the age of the fossils or the location of their discovery. They dispute the species classifications that the bones represent.

Schwartz noted a recent study of virtually all of the fossils from the region called Hadar, where other human remains have been found.

This study, conducted by Schwartz and Ian Tattersall, curator of anthropology at the American Museum of Natural History in New York, revealed that the Hadar fossils are not similar in any detail to the fossils from Laetoli, the region of Tanzania, where the prime example of Australopithecus afarensis species was uncovered.

But Tim White, professor in the Department of Integrative Biology at the University of California at Berkley, disagreed.

“All of the specimens found in Hadar so far are Australopithecus afarensis, except one, which is 2 million years old,” he said.

He said it is true that Australopithecus afarensis come from Laetoli in Tanzania and not Ethiopia, but it’s also misleading. Afarensis was first recognized based on fossils found in Chad, Ethiopia, Kenya and Tanzania. This region includes the site where White works, which is 50 miles south of the site where the Dikika child was found.

“[White] is very committed to identifying species largely on the basis of time rather than what they actually look like,” Schwartz said. “The school of thought he comes from is that everything in this 3- to 4-million-year period would be the same species. I come from different training.”

Schwartz looks at the shapes and details of what the remains are. He said that the way a systematist decides what defines a species involves the study of a broad sample of remains to determine what is unique about the species.

To draw the conclusions made in his book, “The Human Fossil Record,” Schwartz and his co-author, Tattersall, began with one specimen and checked to see if others look like it. If a group of specimens had a unique shape or feature, they called it a morph.

“The purpose of the human fossil record project was to open up the field from a medieval kind of guild of a few [human ancestor] specialists to a broader audience,” said Schwartz.

Many photos of specimens were included in the book in order to enable this larger audience to see the specimens and decide for themselves.

“When you make these public declarations in journals like Nature and media reiterates it, it becomes fact,” said Schwartz. “People don’t question it.”

He went on to say that he would like people to take the claims of paleoanthropologists with a grain of salt. He said it is important to separate discussions of interpretation from discussions of function.

“Once we figure out what species it really represents, not the one it’s claimed to represent, it could help provide us with more information on the growth and physical development of an early human relative,” Schwartz said.