The Evolutionary Function of Human Breasts

Project leader: Dr Bridget Waller (Department of Psychology, University of Portsmouth)

The study aims to increase our understanding of the function of female breasts. Whilst breasts are obviously used for breastfeeding, scientists have long been interested in why they are also considered to be a sexual characteristic (e.g. Morris, 1967). Humans share many physical and psychological features with other primates, so evolutionists often look to other primate species and make comparisons.

Humans are the only primate to have breasts that are enlarged at all times, in contrast to other primates which have swollen breasts only when breastfeeding. This suggests that human breasts have a unique function that is not shared by other primates. What this unique function is, however, is unknown.

Some evolutionary theories suggest that breasts have evolved as simple by-products of increased fat under the skin in females, and only later became a sexually attractive trait (Mascia-Lees et al., 1986, Pawlowski, 1999, Pawlowski et al., 2004). In order to test these theories, it is important to understand how external appearance is related to fat deposits and glandular breast tissue, and whether this is universally attractive (and not based solely on cultural preferences).

One of the obstacles in this area is that we do not know enough about the normal variation of breasts. Breasts can vary in size and shape, and we need to understand this variation before we can begin to test theories about why they have evolved. It is surprising that the science of such an important part of women?s bodies has been neglected for so long.

Why are we recording variation in breasts?

The aim of the current project is to document the ways in which breasts vary. We will then use these statistics to create a computer generated image of the 'average' breast.

To conduct this research, we are looking for female volunteers who are willing to take photographs of their breasts. The only people who need to see the photographs are the researchers on the project and you will remain totally anonymous at all times.

Once we have the photographs, we will plot, using specialist software, the dimensions of your breasts. This information will be used to create a set of computer generated images of 'average' breasts. Once this process is complete we will create a survey using only the computer generated images. So, your image (and your specific dimensions) will not beused in the final survey.

The findings of this research will greatly inform our understanding of the evolution of the female form, which will have knock on benefits for women's health, body image and well being. For example, can we challenge the current stereotypes that characterise the 'ideal' breast shape and size and consequently help women to feel more comfortable with the way they are?

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