In January there has been a discussion about differences in dietary adaptations between human populations. I have a similar question: Is it imaginable, that there are gender differences in dietary adaptations?

Anatomically the digestive tracts of humans and great apes are very similar (1). Allometric scaling however shows, that the human gut is markedly small in relation to body size and in comparison with our closest relatives (2). This suggests, that we are adopted for a relatively high-energy diet, for instance meat.

If dimensions of the digestive tract are indicators of dietary adaptations, how can we explain the following? In the experience of many endoscopists colonoscopy in women is more difficult than in men. To investigate a possible anatomic basis for this finding Saunders et al. analysed barium enemas of more than 300 patients (3). Results: Total colonic length was greater in women (median, 155 cm) compared to men (median, 145 cm), despite women´s smaller stature (p<0.0001). This difference is most prominent in the transverse colon and these findings are in keeping with those of Sadahiro et al. (4). 

Some other observations: Dispite food-sharing behavior the per capita consumption of meat by male chimpanzees is greater than the amount of meat eaten by females (5). Similar differences may be observed in humans: Data from the 1987 National Health Interview Survey (and from my own family) show that women eat more fruits and vegetables and less meat.

Are the observed differences in colonic length accidental findings without any significance, acquired modifications, or could it be, that they are the result of (at least) 2 million years "man the hunter" and "woman the gatherer"?

1. Stevens CE & Hume ID (1995). Comparative physiology of the vertebrate digestive system. Cambridge, Cambridge University Press.
2. Martin RD et al. (1985). Gastrointestinal allometry in primates and other mammals. In: Size and scaling in primate biology (Jungers WL, ed.). New York, Plenum Press.
3. Saunders BP et al. (1996). Why is colonoscopy more difficult in women? Gastrointestinal Endoscopy 43/2:124-126.
4. Sadahiro S et al. (1992). Analysis of length and surface area of each segment of the large intestine according to age, sex and physique. Surgical and Radiologic Anatomy 14:251-257.
5. Stanford CB (1996). The hunting ecology of wild chimpanzees: Implications for the evolutionary ecology of Pliocene hominids. American Anthropologist 98:96-113.
6. Patterson BH (1995). Food choices of whites, blacks, and Hispanics: data from the 1987 National Health Interview Survey. Nutrition and Cancer 23:105-119.