Final answer:
Sahelanthropus tchadensis, a skull nicknamed “Toumai,” is the specimen found in Chad around 6-7 million years ago, potentially representing a common ancestor of humans and chimpanzees.
Step-by-step explanation:
The specimen found in Chad around 6-7 million years ago (mya) is known as Sahelanthropus tchadensis. This fossil, often referred to by the nickname “Toumai,” is a skull discovered in 2001-2002. It is considered a crucial finding in the study of human evolution due to its age and the mix of both primitive and evolved characteristics. Some scientists posit that Sahelanthropus tchadensis could be the last common ancestor of humans and chimpanzees, although its exact place in the human lineage is debated. The cranial capacity of this specimen is roughly 350 cubic centimeters, similar to that of a chimpanzee, and aspects of its skull suggest it may not have been bipedal.