The central idea of the author of "Human Zoo" is that whether life is advanced or not often depends on whether there is loneliness. The more advanced animals are, the lonelier they are and the less noisy they are.

Some people think this statement is too extreme. Taking lions and ants as examples, the different performances of high-level animals and low-level animals are explained. At the same time, it alludes to the mentality of two different types of people in human society, and this emotion lies here.