Final answer:
Sahelanthropus tchadensis is a candidate for the last common ancestor of all great apes, which lived about 7 million years ago and has morphological features consistent with this timeline. This species, along with others like Samburupithecus and Ouranopithecus, provides insight into the ancestry of modern African apes and humans. Great apes evolved from catarrhines in Africa and are characterized by their large brain and body size, lack of tail, and varying degrees of bipedalism.
Step-by-step explanation:
The last common ancestor of all great apes, including humans, chimpanzees, gorillas, and orangutans, as well as all their immediate ancestors, is a subject of extensive research and debate. One candidate that has emerged is Sahelanthropus tchadensis, a fossil ape discovered in 2002 by French paleoanthropologist Michel Brunet and his team in Chad, West Africa. Sahelanthropus tchadensis lived approximately 7 million years ago (MYA), coinciding with the time humans and chimpanzees are believed to have diverged from one another, based on genetic studies.
The cranium of Sahelanthropus exhibits a small cranial capacity of 350 cubic centimeters, similar to that of a chimpanzee, with a large brow ridge and positioning of the foramen magnum suggesting it was not bipedal. Competing theories for ancestors of modern African great apes include fossils like Samburupithecus, known from northern Kenya, and Ouranopithecus, discovered in Greece. Both show characteristics resembling modern African apes.
Apes, part of the family Hominidae, evolved from the catarrhines in Africa around 25 million years ago. The great apes are distinguished by their large size, taillessness, and increased brain size relative to body size. Apes also include the lesser apes, represented by gibbons and siamangs, while the great apes encompass the genera Pan (chimpanzees and bonobos), Gorilla (gorillas), Pongo (orangutans), and Homo (humans).