Cross-species studies of animal populations have shown that cubs who are isolated from their mothers within a month of birth often show strong aggression  For example, when looking for food, he is aggressive and fighting for food, while other cubs give in and he is still fighting for food
Chimpanzees who grew up in the socialized training environment of their parents were much less aggressive in mating conflicts than chimpanzees who did not grow up in this environment.
 The hypothesis that explains this phenomenon is that the aggressive problem is due to the lack of social training guided by parents at the newborn stage