Final answer:
The 6-7 million-year-old primate skull from northern Chad is of Sahelanthropus tchadensis, potentially the last common ancestor of humans and chimpanzees. Discovered by Michel Brunet's team, it holds significant information about early hominid evolution. Other species like Australopithecus afarensis and Australopithecus africanus also provide insights into human ancestry.
Step-by-step explanation:
The 6-7 million-year-old primate skull discovered in northern Chad is that of Sahelanthropus tchadensis, also known as "Toumai". It was found by a French research team led by paleoanthropologist Michel Brunet in 2001-2002. The skull exhibits a mix of primitive and more evolved traits, placing it around the period when the last common ancestor of humans and modern chimpanzees is assumed to have existed. While the cranial capacity is similar to that of a chimpanzee at 350 cubic centimeters, features like a large brow ridge and the position of the foramen magnum (suggesting non-bipedalism) distinguish it. Comparatively, Australopithecus afarensis, which includes the well-known "Lucy" specimen found in Ethiopia, lived around 3 million years ago with a brain volume of about 500 cc. Australopithecus africanus, discovered by Raymond Dart in South Africa, dates to a slightly later period and presents traits closer to modern humans, such as evidence of bipedalism. Meanwhile, Homo naledi and Homo habilis are other important human ancestors that contribute to our understanding of the evolution of the genus Homo.