While the Breast Size of Male and Female Primates Are the Same Why Do Women Have Large Breasts?
Scientists have difficulty in explaining why human females have large breasts. Because, male and female breasts are the same size in other primates.
Even so, a chimpanzee and a human can produce the same amount of milk. Therefore, there isn’t a parallel between breast size and milk production.
They try to explain this problem as when humans stood upright, they started to develop face to face social relations.
Namely; as people socialize, their interactions become more face to face. It triggers evolutionary mechanisms to create something similar to buttocks, which is the source of the “sexual” stimuli, at the front of women’s body.
So, evolution allows breasts to get bigger as a substitute for buttocks.
Of course, the vagina, which is normally far behind in other primates, becomes more oriented to the front of the body of women during this socialization process, and the lips thicken as a reflection on the face.
Also, thick lips are a characteristic specific to only humans.