The evolutionary struggle for survival is really a self-serving series of blows and stabs, and yet it can lead to extremely social animals like dolphins, wolves or, for that matter, primates.

Empathy probably started out as a mechanism to improve maternal care. Mammalian mothers who were attentive to their young's needs were more likely to rear successful offspring.

The intuitive connection children feel with animals can be a tremendous source of joy. The unconditional love received from pets, and the lack of artifice in the relationship, contrast sharply with the much trickier dealings with members of their own species.

I have often noticed how primate groups in their entirety enter a similar mood. All of a sudden, all of them are playful, hopping around. Or all of them are grumpy. Or all of them are sleepy and settle down. In such cases, the mood contagion serves the function of synchronizing activities.

Most exotic animals are not particularly interested in people, which makes it hard to provoke them. Human-rearing gets them used to and sometimes imprinted on humans, which makes them potentially dangerous.

If we look straight and deep into a chimpanzee's eyes, an intelligent self-assured personality looks back at us. If they are animals, what must we be?

Exclusive homosexuality is not very common in nature.