Final answer:
Chimpanzees and bonobos are each other's closest relatives, having separated from a common ancestor about 2 million years ago, and humans share a common ancestor with both, differentiating earlier at about 5 to 7 million years ago.
Step-by-step explanation:
Based on the evolutionary tree and the provided information, the two organisms that are most closely related are chimpanzees and bonobos. Genetic evidence suggests that the lineages of humans and chimpanzees separated approximately 5 to 7 million years ago. However, the split between chimpanzee (Pan troglodytes) and bonobo (Pan paniscus) lineages occurred much later, about 2 million years ago, making them each other's closest relatives.
Furthermore, chimpanzees and humans share 99 percent of their DNA, a sign of close evolutionary relationship, but it is the DNA homology between chimpanzees and bonobos that is most compelling for their close relationship. The behavior and social structures of chimpanzees and bonobos differ, with bonobos known for their peaceful and egalitarian social structure, contrasting with the more hierarchical and aggressive nature of chimpanzee society. Regarding the relationship between chimpanzees and humans, the most accurate description is that chimpanzees and humans evolved from a common ancestor. Despite sharing a high percentage of DNA, they are not the same species and did not evolve directly from one another.