As an old Chinese saying goes, "A woman at thirty is like a wolf, at forty is like a tiger, and at fifty or sixty she sits on the ground and sucks earth", which is needless to say to an old driver. The so-called sitting on the ground and suckling earth is a way for some people to boast about women's desire for love. If we take this matter seriously and combine it with physiology, it is reasonable. We might as well see how scientists explain it. Elders aged 20 to 30 are always saying that people in their 20s are eight or nine o'clock