* Earliest known potential hominid species, discovered in Chad in 2001.

* Dated to be between 7 and 6 million years old, making it the oldest known hominid.

* There is some debate as to whether it is actually a hominid or a close relative of the common ancestor of humans and chimpanzees.

* Some scientists believe it is a distinct genus, Sahelanthropus, while others believe it is a member of the genus Orrorin.