1965, Japanese scientist Yukio Sugiyama published a paper entitled "On the social changes of Ha Numan langur (Presbytis Entellus) under natural conditions", which for the first time rigorously unveiled the veil of harmony that had enveloped the animal kingdom for a long time. The langur is a gregarious monkey. Generally speaking, a group of monkeys consists of an adult male monkey, several adult female monkeys and several young monkeys. Wandering bachelor langurs always seize every possible opportunity to challenge the dominant male monkeys with wives and concubines. This kind of struggle is extremely fierce. Once the challenger wins, he will kill all the flesh and blood of the old monkey king in the group.

Once this bloody scene was disclosed, it immediately caused an uproar in human society. People instinctively resist this kind of thing, so that the research of pioneers like Sugiyama has been suppressed in academic circles for a long time. Glenn Hausfater, an animal behaviorist at Cornell University in the United States, believes that infanticide was not widely accepted at that time, because people thought it was a very evil behavior, and some even thought it was evil to imagine it.

But the fact will not change because of people's likes and dislikes. More and more field observations have confirmed that many animals have similar behaviors. On the other hand, a new generation of evolutionists, represented by Dawkins Richard Dawkins, put forward the shocking concept of "selfish gene" in the late 1970s, which shocked the whole biology and even social sciences. Dawkins believes that every organism is just a carrier of gene transmission, and the process of evolution will allow organisms to transmit their genes by hook or by crook.