Human variation in the shape of the birth canal is significant and geographically structured.


Type
Article
Change log
Abstract

The human birth canal shows a tight fit with the size of the neonate, which can lead to obstetric complications. This is not the case in other apes, and has been explained as the outcome of conflicting evolutionary pressures for bipedal locomotion and parturition of a highly encephalized fetus. Despite the suggested evolutionary constraints on the female pelvis, we show that women are, in fact, extremely variable in the shape of the bony birth canal, with human populations having differently shaped pelvic canals. Neutral evolution through genetic drift and differential migration are largely responsible for the observed pattern of morphological diversity, which correlates well with neutral genetic diversity. Climatic adaptation might have played a role, albeit a minor one, with populations from colder regions showing a more transversally oval shape of the canal inlet. The significant extent of canal shape variation among women from different regions of the world has important implications for modern obstetric practice in multi-ethnic societies, as modern medical understanding has been largely developed on studies of European women.

Description
Keywords
birth canal, climate, human, neutral variation, obstetrical constraints, pelvis, Biological Evolution, Female, Genetic Drift, Geography, Humans, Pelvis
Journal Title
Proc Biol Sci
Conference Name
Journal ISSN
0962-8452
1471-2954
Volume Title
285
Publisher
The Royal Society