Magazine article Science News

Humanity's Roots May Lie in Single, Diverse Genus

Magazine article Science News

Humanity's Roots May Lie in Single, Diverse Genus

Article excerpt

Six newly discovered fossil teeth from the hominid Ardipithecus, which lived in eastern Africa more than 5 million years ago, have sharpened the scientific debate about our evolutionary origins.

Analyses of the 5.6-to-5.8-million-year-old specimens indicate that they belonged to a previously unidentified species, which anthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History and his colleagues are calling Ardipithecus kadabba. Previous fossil finds from the same genus had suggested that the hominids called kadabba were instead a subspecies of the only other known Ardipithecus species, Ardipithecus ramidus (SN: 7/14/01, p. 20).

Even more provocatively, Haile-Selassie's group concludes that 6-to-7-million-year-old fossil teeth that have been attributed by other researchers to two separate hominid genera, Sahelanthropus (SN. 7/13/02, p.19) and Oworin, resemble those of Ardipithecus and probably belonged to members of that genus. That would put all of the Homo sapiens ancestors of 5 to 7 million years ago in one genus, which evolved gradually.

"It appears that the evolution of dentition in these early hominids occurred through a slow evolutionary process resulting in [anatomical] changes through time," Haile-Selassie says.

The new fossil teeth show one facet of gradual evolution, the investigators report in the March 5 Science. The upper canines curved to the outside of the lower canines and were sharpened by premolars adjacent to the lower canines. This arrangement was intermediate between that of fossil apes, as well as living chimpanzees, and later hominids. …

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