How far back does your family tree go? A hundred years? A thousand years? What about 6 to 7 million years? An ancient skull found in Africa suggests that the human family might be that old.
Discovered in 2001 in the desert of Chad, the skull was nicknamed Toumai by scientists. Toumai is a rare find. The skull is nearly complete; it even includes a few teeth. The Toumai skull is estimated to be between 6 and 7 million years old. Scientists are debating whether the skull is linked to humans.
The finding is not without controversy. Some scientists think that Toumai is the oldest known hominid （原始人类）ever found. Others say Toumai is an ape（猿）.
Most hominids that scientists are aware of lived millions of years after Toumai. The most famous one is called Lucy. She lived in Ethiopia about 3.5 million years ago. While Lucy's face looked like the face of a chimpanzee, Toumai's skull has both human and ape-like features.
Because Toumai's skull looks different from other hominid skulls, some scientists think Toumai represents a whole new species. Toumai's official name is Sahelanthropus tchadensis.
Scientists were surprised to find a human-like face on a skull as old as Toumai's. They thought hominids turned into humans step by step over time. Scientists mark those changes on a timeline, starting with a chimpanzee-like ancestor and ending with modern humans. Toumai's human-like face and chimp-sized brain suggest that the development of hominids was not so simple. There may not be a direct line leading from Toumai to Lucy to us. Instead, the timeline might be similar to a tree with lots of branches. Different species in different places could have evolved human-like features at different time.
Scientists aren't sure where exactly Toumai belongs on our family tree. Toumai could be like a great-great-grandfather — or just a distant cousin. Toumai could also be one of many types of hominids who wandered Earth millions of years ago.
