Among humans, we occasionally see children with short tails, people with long hair, women with many nipples and so on. These phenomena indicate that human ancestors may be animals with tails, long hair and many nipples. So atavism is also a kind of evidence of biological evolution.
brief introduction
Atavism is an uncommon phenomenon of biological "degradation". As we all know, domestic chickens, ducks and geese have long lost their flying ability after long-term domestication by human beings. However, in domestic chickens, ducks and geese, sometimes there will be a kind of chickens, ducks and geese with particularly strong flying ability. The chicken, duck and goose regained their flying ability because of atavism.
So far, people's understanding of the causes and essence of congenital mental illness and congenital mental retardation is still relatively backward. Studying the "degeneration" of atavism may explain some reasons of congenital mental illness and congenital mental retardation, and at the same time deepen people's understanding of the process of biological evolution.