This is an atavism. Long tail? It is a congenital malformation, with one case in about 10 thousand people, and the incidence rate of boys is significantly higher than that of girls. The child's long tail is a hint of central nervous system malformation and a dangerous signal. It is likely that the boy existed when he was still in his mother's womb, and gradually separated from his body as he grew up. Over time, children with long tails will have serious problems such as urinary incontinence, arch, crutches, hydrocephalus, syringomyelia and nerve asymmetry. There are two explanations about atavism in modern genetics. First, because two or more genes separated in the process of speciation were recombined through hybridization or other reasons, a certain trait was determined, and the traits of ancestors were re-expressed; Secondly, the gene that determines this ancestral trait has been blocked by histone-based repressors for a long time in the evolution process, and as a result, the blocked gene has resumed its activity, re-transcribed and translated, showing the ancestral trait.
It is also said that it may be a genetic mutation or a genetic mutation. People have tails in the embryonic period, but they usually disappear gradually, and those who are underdeveloped will leave tails. In short, this is rare ...? According to the survey, in order to prevent this? Atavism? Expectant mothers can get enough folic acid during pregnancy.
In fact, many scientific studies show that our current state is not the final form we can evolve into, and we humans will continue to evolve over time. I wonder what human beings will be like in millions of years.