back to news April 15, 2013

Anthropology Professor’s Dental Findings Offer Insight into Human Ancestor

Debbie Guatelli-Steinberg, professor of anthropology, is co-author of a new dental study of fossilized remains found in South Africa in 2008 that provides support that this species is one of the closest relatives to early humans. The teeth of this species–an ancient offshoot of the human family tree called Australopithecus sediba indicate that it is also a close relative to the previously identified Australopithecus africanus. Both of these species are clearly more closely related to humans than other australopiths from east Africa, according to the new research.

Guatelli-Steinberg is among a team of international scientists who have published a series of papers in Science describing how the hominid Australopithecus sediba walked, chewed, and moved around two million years ago. Their research offers a comprehensive depiction of some of the most complete early human ancestral remains ever discovered.

Guatelli-Steinberg’s study, Dental Morphology and the Phylogenetic “Place” of Australopithecus sediba, revealed that both africanus and sediba shared about the same number of dental traits with the first undeniably human species.

“Teeth are an excellent way to study relationships between different species,” Guatelli-Steinberg said. “They are well preserved in the fossil record and researchers can compare large samples, at least for many ancient species.”

The sediba fossils were found in South Africa in 2008 and first described in a series of articles published in Science in 2010. That study was led by Lee Berger of the University of Witwatersrand in South Africa, who is also a co-author of this new study.

In this study, Guatelli-Steinberg and colleagues extended that work by examining the teeth from sediba and comparing them to eight other African hominin species, which include modern humans from Africa, and extinct species of Homo, Australopithecus, and Paranthropus. In all, the researchers examined more than 340 fossils and 4,571 recent specimens. They also examined teeth from 44 gorillas for comparison.

The focus was on 22 separate traits of tooth crowns and roots that can give clues as to the relationship between the different species studied.

In addition, most of the dental traits the researchers used in this analysis don’t have a selective advantage that could help one species survive over another. That means if researchers see a similar trait in two species, they can be more confident that they shared a common ancestor and that the trait didn’t evolve independently.

Guatelli-Steinberg said their dental analysis showed that both africanus and sediba are more closely related to humans than the famous “Lucy” skeleton fossil found in East Africa in 1974. This fossil represented a species, Australopithecus afarensis, that was at one time was thought to be the closest relative of humans.

“Our study provides further evidence that sediba is indeed a very close relative of early humans, but we can’t definitively determine its position relative to africanus, said Guatelli-Steinberg.

Lucy is estimated to have lived 3.2 million years ago. Sediba lived 1.977 million years ago, while africanus lived between 3.03 and 2.04 million years ago.


Read the entire press release online, courtesy of Jeff Grabmeier, director, research and innovation communications.

Also, read more about the study in The Wall Street Journal (April 11, 2013), The Washington Post (April 11, 2013), and NBC News (April 11, 2013).

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