Final answer:
Humans and chimpanzees share a last common ancestor approximately 6 million years ago, which is true according to genetic studies and fossil evidence like Sahelanthropus tchadensis.
Step-by-step explanation:
The statement that humans and chimpanzees share a last common ancestor approximately 6 million years ago is true. Genetic studies and fossil evidence such as the discovery of Sahelanthropus tchadensis support the idea that the divergence of humans and chimpanzees from a common ancestor occurred sometime between 5 and 7 million years ago. This period is when Sahelanthropus lived, indicating its potential as the last common ancestor. Additionally, humans and chimpanzees share more than 97% of their DNA, emphasizing their close evolutionary relationship. It's important to note that humans did not evolve from chimpanzees, nor did chimpanzees evolve from humans; instead, both species evolved from a shared ancestor that lived during this period.