The ape that is closely related to man is the chimpanzee.

Chimpanzees, scientifically known as Pan troglodytes, are the closest living relatives to humans. They share a common ancestor with humans, with whom they have a high degree of genetic similarity. Here is an explanation of why chimpanzees are considered to be closely related to humans:

1. Genetic Similarity:
- Humans and chimpanzees share approximately 98.7% of their DNA.
- This high degree of genetic similarity indicates a close evolutionary relationship between the two species.

2. Common Ancestor:
- Humans and chimpanzees diverged from a common ancestor around 6 to 7 million years ago.
- Over time, this common ancestor gave rise to two distinct lineages, one leading to humans and the other to chimpanzees.

3. Physical Similarities:
- Chimpanzees and humans share several physical characteristics, such as opposable thumbs, forward-facing eyes, and complex social behaviors.
- These similarities suggest a common evolutionary history and a close relationship.

4. Behavioral Similarities:
- Chimpanzees exhibit complex behaviors, including tool use, hunting, and communication.
- These behaviors are similar to those observed in early human ancestors, providing further evidence of a shared ancestry.

5. Social Structure:
- Chimpanzees live in social groups, similar to human societies.
- They form complex social hierarchies, maintain social bonds, and engage in cooperative activities.
- These social behaviors parallel many aspects of human social organization.

In conclusion, the chimpanzee is closely related to humans due to the high degree of genetic similarity, shared ancestry, physical and behavioral similarities, and similar social structures. Studying chimpanzees helps scientists gain insights into human evolution, behavior, and biology.