A new study on 45 human cadavers has discovered significant differences in the gut anatomy between bodies, concluding that females have “consistently and significantly longer small intestines than males”. They say the discovery, though based on a small sample, could support the hypothesis that the energetic demands of pregnancy and breastfeeding have led to females adapting to absorb more lipids from their diet.
The rubbery ropes that make up our intestines are arguably the most vital organs in the gut for nutrient absorption, explain the authors of a new paper. As such it figures that an animal’s life history could influence the way they grow and behave.
To look for signs of “hidden diversity” between sexes, they gathered data from a group of 45 cadavers, 21 females and 24 males. Comparing the results revealed significant differences in the size of certain organs.
Non-human species including rats, pigs, and bullfrogs were also dissected for the research, and – taken with the human data – showed that morphological variation along the gastrointestinal tract was associated with the organs’ roles in food processing, with their lengths being influenced by feeding strategy.
One example of this is the small intestines of humans. This organ is vital for absorbing nutrients from our food – and while both males and females need to eat, there were significant differences between the cadavers’ intestinal lengths. On average, the males’ small intestines were a little over 4 meters (13 feet), but the females’ were around 30 centimeters (11.8 inches) longer.
One possible explanation for this difference is that it ties in with pregnancy and breastfeeding. Both of these processes require enormous amounts of energy, and so it could be that adapting to have longer small intestines helps females to get as much fat and nutrients from their diet as is physiologically possible.
Sex differences in anatomy have long been overlooked, as we discussed with Prof. Claire Smith, Head of Anatomy for Brighton and Sussex Medical School in the UK. Smith was a leading contributor to the Complete Anatomy by Elsevier model of female anatomy that aims to color in the incomplete picture of human anatomy that’s historically been built on the bodies of white, European males.
Discovering the hidden diversity between humans builds towards a more accurate understanding of what goes on underneath our skin. Diving into Homo sapiens variation could have implications for improving medical therapies, too, so research like this is a promising step in the right direction.
So, wear your slightly longer small intestines with pride, human females of the world. Science marches on.
The study is published in PeerJ.
[H/T: New Scientist]
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