Evolution of Breasts

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Evolutionary Psychology

The Evolution of Female Breasts and Breasts as Sexual Signals

Female breasts always seem to be a ‘hot’ topic, even from an evolutionary standpoint! Human females have larger breasts than all their nonhuman primates. Many studies have been conducted on the function and purpose of the large female breasts. Human females have breasts that have evolved to always be prominent after puberty, a physical characteristic that has been found to be attractive to our male ancestors and even males in today’s society. As signals of fertility and good health, breasts cause arousal in males hence, increasing a woman’s chances of attracting a mate! Different variations of breast size and shape are preferred all around the world, but it is no mystery that breasts are valued as an attractive sexual signal to people worldwide.

1. Breast size on primates and Homo sapiens.
Throughout evolutionary time breasts have been a clear indicator used to spot a female who is equipped with the physiology necessary for the nurturing of offspring. Breasts have evolved for the obvious reason, to provide breast milk for offspring. However, compared to primates such as chimpanzees, baboons, monkey’s etc., human females have larger breasts. Human female’s breasts begin their growth once puberty begins, however nonhuman primates have a different growth pattern. For nonhuman primates, breasts only enlarge during lactation and pregnancy; however a human female’s breasts enlarge during puberty from the distribution of adipose fat tissue to the breasts (Dixson et al, 2011). Instead of the breasts only swelling during lactation, human females breasts remain enlarged whether they are ovulating or not. It is interesting that human females have evolved to always have the display of swollen breasts however, other primates have not. Many studies have been conducted on nonhuman primates on the hypothesis that their genitals and breasts only swell during lactation periods to attract primates for mating. A study of the Chacma baboon proposes that the hypothesis on swelling during lactation for nonhuman primates is accurate. The findings indicated that the Chacma baboon experienced large swelling of the genitals and breasts a few days before ovulation, and the swelling decreased a few days after ovulation (Bielert, C. & Girolami, L., 1987). Overall, breasts for nonhuman primates and female Homo sapiens can be small, medium, and large, however for human females they tend to be larger because they remain swollen at all times instead of just during ovulation or pregnancy.

2.2 The Nubility Hypothesis
The nubility hypothesis of female breasts proposes that Homo sapiens females have evolved larger breasts because the size and shape of breasts function as a signal of constant reproductive value (Marlowe, 1997). Breasts remaining swollen will indicate to male Homo sapiens that this female is fertile and likely to produce many off spring; hence he should mate with her. Also, large breasts will increase the female’s chances of finding a mate and producing offspring, because of her constantly large breasts used as a signal of reproductive value. It is hypothesized by the nubility hypothesis that once reliable cues to ovulation were lost and long-term bonding became more beneficial for survival, hence human females that displayed greater reproductive value were preferred by males (Marlowe, 1997). In other words the evolution of large breasts may have partly resulted from men’s choices in potential mates from the display of the female breasts themselves. Although a female is more likely to conceive during ovulation, having breasts that always remain swollen is more beneficial and increases her chances of conceiving. Also, finding a long term mate to help raise offspring can be difficult if you are only most attractive during ovulation. Therefore permanently enlarged breasts increase a woman’s chances of finding a...
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