Dental traits may lead to the missing link.

• Position: Anthropology - Fossil hominids

A dental study of fossilized remains found in South Africa provides new support that the species Australopithecus sediba is one of the closest relatives to early humans. The teeth indicate that it also is a close relative to the previously identified Australopithecus africanus. These species clearly are more closely related to humans than other australopiths from East Africa, according to research appearing in Science, which reveals that both sediba and africanus share about the same number of dental traits with the first undeniably human species.

"Our study provides further evidence that sediba is indeed a very close relative of early humans, but we cannot definitively determine its position relative to africanus." says Debbie Steinberg, professor of anthropology at Ohio State University, Columbus, and coauthor of the study.

Teeth are an excellent way to study relationships among different species. They are well preserved in the fossil record, and researchers can compare large samples, at least for many ancient species. In addition, most of the dental traits the researchers used in this analysis do not 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 did not...