The last common ancestor of all monkeys and apes lived about 40 million years ago. Proconsul was a species that lived about 17 million years ago. The most recent species ancestral to both humans and chimpanzees lived 6 to 7 million years ago.

evolutionary relationships from degrees of similarity. Using the same logic, other biologists examine similarities in the functions of different organs, in the development of embryos, or in behaviors among different kinds of organisms. These investigations provide evidence about the evolutionary pathways that connect today’s organisms to their common ancestors. Hypotheses based on this evidence then can be tested by examining the fossil record.

Sometimes, separate lineages independently evolve similar features, known as “analogous” structures, which look like homologies but result from common environments rather than common ancestry. For example, dolphins are aquatic mammals that have evolved from terrestrial mammals over the past 50 million

Though dolphins (left) are more closely related to humans than they are to sharks (right), they have evolved bodies adapted to an aquatic environment. This is an example of analogous structures.