How Is Modern Medicine Impacting Human Evolution?

Researchers from the University of Vienna believe that the increase of Caesarean births could be having an impact on human evolution. Their study, published in 2016 in the Proceedings of the National Academy of Sciences, suggests that more mothers are getting C-sections because babies are getting larger -- and that these larger babies are unable to fit through the birth canals of narrow-hipped women. The researchers say that there has been a 20 percent global increase in the prevalence of babies not being able to fit through the birth canal -- from 30 in 1,000 births in the 1960s to 36 in 1,000 births today. Before C-sections became commonplace, it would have been much less common for the genes for narrow hips to be passed from mother to child, since women with very narrow hips often did not survive labor, particularly when giving birth to a large baby.

When medicine meets evolution:

• Once only an emergency option, now roughly a quarter of new moms in the United Kingdom and about one-third of mothers in the United States give birth though C-section.
• "Women with a very narrow pelvis would not have survived birth 100 years ago,” explains Philipp Mitteroecker, the lead author on the project. “They do now and pass on their genes encoding for a narrow pelvis to their daughters."
• But not everyone is convinced. “Mitteroecker’s team hasn’t produced any evidence that it is (happening),” says Clare Wilson of New Scientist. “The study was theoretical work, based on plugging observed figures for the rate of obstructed childbirth into their models.”