Final answer:
We do not conclusively know which hominid is the last common ancestor of humans and chimpanzees, but Sahelanthropus tchadensis is a candidate from around the estimated divergence time. However, debates continue due to its mixed features that do not clearly align it directly with hominins. Our extended family, Hominidae, includes species more closely related to us than to chimpanzees, and understanding these relationships is crucial to studying human evolution.
Step-by-step explanation:
No, we do not know exactly which hominid specimen is the last common ancestor of humans and chimpanzees. While the discovery of the Sahelanthropus tchadensis cranium in 2002 by French paleoanthropologist Michel Brunet and his team provided significant insight into our understanding of human evolution, it is still debated whether this species is in fact the last common ancestor. Genetic studies suggest a divergence between humans and chimpanzees somewhere between 5 and 7 million years ago (MYA), coinciding with the era in which Sahelanthropus tchadensis existed. However, with a cranial capacity of only 350 cubic centimeters, akin to that of a chimpanzee, and anatomical features such as a pronounced brow ridge and the positioning of the foramen magnum indicative of non-bipedal locomotion, there is still uncertainty in classifying Sahelanthropus tchadensis as our direct ancestor.
Further understanding of human evolution also includes a discussion on hominins, which are species that evolved after the split from the chimpanzee lineage. Bipedal hominins such as Australopithecus, Homo habilis, and Homo erectus played a part in the evolutionary pathway to modern humans. In contrast, Homo sapiens, our own species, is unique with our large and complex brain leading to significant technological and abstract advancements compared to our primate cousins.
When examining the evolutionary tree, we see that extinct great apes and their ancestors, including humans and chimpanzees, belong to the biological family Hominidae. Our closest relatives within this family include not only chimpanzees but also gorillas and orangutans. With over 97% of DNA shared amongst gorillas, chimpanzees, and humans, the study of our common ancestors is a vital part of understanding our place in the natural world.