 One hypothesis postulates that the breasts grew as a frontal counterpart to the buttocks as primates became upright to attracting mates, a model first developed in 1967.Other hypotheses include that by chance breasts act as a cushion for infant heads, are a signal of fertility, or elevate the infant's head in breastfeeding to prevent suffocation.Paradoxically, there is even a school that believes that they are an evolutionary flaw, and can actually suffocate a nursing infant.