Skip to content

Research highlight: Sexual dimorphism in the relationship between the gut and pelvis

We test the notion that pelvis dimensions can yield accurate estimates of gut size in fossil hominins by looking at today's people.

2 min read
A plot showing the inferior transverse outlet versus gut volume in men and women.

Citation: Uy, Jeanelle, John Hawks and Caroline VanSickle. Sexual dimorphism of the relationship between the gut and pelvis in humans.American Journal of Physical Anthropology. e24084.

Many researchers in human evolution have been interested in the idea that early hominins may have had large guts for digesting poor-quality diets. They have thought that the large pelvis size of hominins like Australopithecus afarensis might reflect gut size, because the pelvis supports the gut in bipeds like humans.

But almost nobody had looked to see whether pelvis size gives any predictive value about gut size in humans or other primates. Jeanelle's research shows that in men the pelvis-gut size relation is entirely explained by body size, with no significant relationship in women. In fact men and women vary in opposite directions, which puts the idea of estimating ancient hominin gut sizes in a different light.

This is an innovative piece of work built on direct measurements of gut sizes from CT scans of living research participants. Previous studies have relied on a handful of dissections of primates across several species, and have not been able to look at the variation within species. When we are trying to understand the anatomy of fossil hominins, the variation within humans is much more relevant than the sizes of small monkeys.

Sexual dimorphism of the relationship between the gut and pelvis in humans
ObjectivesObstetric demands have long been considered in the evolution of the pelvis, yet consideration of the interaction of pregnancy, the pelvis, and the gastrointestinal tract (gut) is lacking....
Research by John Hawksbipedalismdiet
John Hawks

John Hawks Twitter

I'm a paleoanthropologist exploring the world of ancient humans and our fossil relatives.

Related Posts

Members Public

Guide to Sahelanthropus, Orrorin and Ardipithecus

These fossil species between 8 million and 4.4 million years old include some of the earliest members of the hominin lineage.

Ardipithecus hand skeleton next to a human hand X-ray image
Members Public

The real story of myosin, jaw muscles, and ancient brains

The provocative idea that our genus arose with a deactivated muscle gene turned out to be wrong.

Bonobo and gorilla head and neck, showing ecorché muscles on the left side of each
Members Public

Research highlight: Growth and development in human origins

A report from a Wenner-Gren-supported workshop innovating ways forward for understanding hominin ontogenies

A reconstruction of a Homo naledi child skull with bone and teeth indicated.