It turns out Sir Mix-a-lot wasn’t lying, and science now knows why. In a string of findings to be published as a comprehensive study, scientists have found that large bums in women serve an essential evolutionary purpose – to develop healthy and smart offspring.
Over the course of thousands and thousands of years of evolution, this has led to a general preference in men towards women who possess this beneficial child bearing ability, which means Nicki Minaj isn’t waving her bum for nothing. Men have been selected to prefer large backsides.
The fat stored in the buttocks and on the hips of women contains a compound called docosahexaenoic acid, or DHA. DHA, it turns out, is essential for the growth and functional development of the brain in infants.
The inclusion of plentiful DHA in the diet improves learning ability, whereas deficiencies of DHA are associated with deficits in learning.
“The fat in these areas is a depot for building a baby’s brain,” Professor Lassek, who has published a number of science papers and a book on the subject, Why Women Need Fat, told the UK’s Sunday Times.
This phenomenon, however, is unknown among the rest of the primates, where females do not have significantly different body-fat ratios to males. In humans this instance of sexual dimorphism is, comparatively, immense.
Professor Lassek explained it has always been a “complete mystery” why women have so much fat. “Mammals’ and primates’ bodies typically have about 5-10 per cent of fat, but in human women that rises to 30 per cent on average,” he said.
DHA is prevalent in only 1% of fat, and a large amount is thus necessary to supply meaningful amounts to a fetus. This would, then, explain why women (in general!) have so much more fat than men.
“Women have traded muscle for fat, so [now] they are about a third as strong,” Lassek noted.
There is some reprieve for aspiring mothers though.
Since around 80% of the DHA a fetus requires comes from the mother’s fat stores, it is common for a lactating mother to lose up to half a kilogram of fat per month as these stores find their purpose during simple breastfeeding*.
*PM is unaware of any research that has been done on whether this also explains why so many wet-nurses were employed to rather breastfeed children than mothers in the height of the patriarchal societies of the 19th century.