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

TY - JOUR

T1 - Human variation in the shape of the birth canal is significant and geographically structured

AU - Betti, Lia

AU - Manica, Andrea

PY - 2018/10/24

Y1 - 2018/10/24

N2 - 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-encephalised 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.© 2018, The Author(s) Published by the Royal Society. This is an author produced version of a paper published in PROCEEDINGS OF THE ROYAL SOCIETY B BIOLOGICAL SCIENCES uploaded in accordance with the publisher’s self- archiving policy. The final published version (version of record) is available online at the link below. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it.

AB - 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-encephalised 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.© 2018, The Author(s) Published by the Royal Society. This is an author produced version of a paper published in PROCEEDINGS OF THE ROYAL SOCIETY B BIOLOGICAL SCIENCES uploaded in accordance with the publisher’s self- archiving policy. The final published version (version of record) is available online at the link below. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it.

KW - pelvis

KW - climate

KW - neutral variation

KW - obstetrical constraints

KW - birth canal

KW - human evolution

UR - https://doi.org/10.5061/dryad.1gk3014

U2 - 10.1098/rspb.2018.1807

DO - 10.1098/rspb.2018.1807

M3 - Article

SN - 0962-8452

VL - 285

JO - Proceedings of The Royal Society B Biological Sciences

JF - Proceedings of The Royal Society B Biological Sciences

IS - 1889

M1 - 20181807

ER -