If the ancestors of humans, chimps, and gorillas parted company earlier than expected, it would give more validity to claims that the fossils purporting to be the earliest members of the human family, such as the 6 million to 7 million-year-old
Sahelanthropus tchadensis from Chad, really are hominins, the group that includes humans and their ancestors but not the African apes. The longer generation times will also influence evolutionary models on skeletal and dental development that assume that human ancestors had more rapid growth patterns, similar to apes, than to living humans.
The study has yielded "the most accurate estimates of generation length yet possible for wild chimpanzees and gorillas," says paleoanthropologist John Hawks of the University of Wisconsin, Madison, who was not involved in the work. While these precise dates for both generation times and the split between lineages may be modified as more data is collected from more apes, adds evolutionary biologist Wen-Hsiung Li of the University of Chicago, the new work is significant because it "provides a novel approach to the long-standing issue of the divergence time between human and chimp."
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