{'fraction_non_alphanumeric': 0.023622047244094488, 'fraction_numerical': 0.011023622047244094, 'mean_word_length': 4.868360277136259, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
On the Adaptive Significance of the Female Breast

The evolution of the rounded or protuding breast in the human female has recently been reassessed by Crook (1972). Opinions differ whether the breast functions as a mimic device to arouse sexual activity (Morris 1967; Crook and Garthlan 1966), or is simply a sexual display unassociated with mimicry (Eibl-Eibesfelt 1970). Alternatively, the rounded form could be universally appealing to the human male and the present shape a result of sexual selection by males (Crook and Garthlan 1966; Campbell 1966). In sum, breast form is hypothesized as relating to sexual activity, but the exact nature of this relationship is disputed. As Montague (1965) pointed out, these hypotheses suffer from ethnocentrism. He rejects sexual selection as an explanation and suggests that the reduction of prognathism in humans has required a change in breast shape. While not discounting this factor, we feel the protuberant breast is a direct physiological consequence of two major differences between man and other primates: bipedalism and prolonged infant immaturity. Both these changes make the primate modes of carrying infants-ventral with the infant clinging, or backriding-either very inefficient or impossible for man. Man as a biped (in part because of the resulting flare of the ilium) generally carries infants on the hip or over the shoulder. The infant is carried and does not cling (although there is a clinging response). This is because the infant is immature for a long period and because of the lack of human body hair. We argue that braless females have sagging, not rounded, breasts and that a sagging breast lowers the nipple height, and increases its flexibility, allowing the human infant to nurse more easily. This modification is necessary because a nursing baby is held on the hip or on the lap, and is not directly ventral to the mother. Thus, the distance between the hip or lap and the breast is too great to allow infants to reach the nipple. Also, without having hair to cling to and not being directly against the mother's chest, an infant has difficulty retaining hold of a nonprotuding nipple. With a sagging flexible breast, the mother can feed or placate an infant while sitting, standing, or walking and still have one arm free for other activities. Thus, the sagging breast can be explained as a response to the selection for bipedalism, prolonged infancy, and hairlessness; it does not appear necessary to hypothesize a universal sexual attraction to the human breast.