Scientists fear C-section births are altering human evolution

Before anyone gets too carried away I want to warn you up front that this is a story about evolution. But don’t worry… it’s not the Darwin sort or any discussion of the original origins of man. This science tale deals with “evolution” happening on a much shorter scale. In fact, when compared to the traditional view of the evolution of lifeforms it’s taking place virtually overnight. At least one group of doctors believes that the practice of doctors performing Caesarean section births is affecting human evolution in a negative way. (BBC)

The regular use of Caesarean sections is having an impact on human evolution, say scientists.

More mothers now need surgery to deliver a baby due to their narrow pelvis size, according to a study.

Researchers estimate cases where the baby cannot fit down the birth canal have increased from 30 in 1,000 in the 1960s to 36 in 1,000 births today.

Historically, these genes would not have been passed from mother to child as both would have died in labour.

Researchers in Austria say the trend is likely to continue, but not to the extent that non-surgical births will become obsolete.

This is a curious story to be sure. I suppose the science underlying it is valid enough… in theory. And an increase of 0.6% in the number of C-sections performed in hospitals over a fifty year period might be large enough to call it statistically significant. But right off the bat I have to wonder if they took other factors into account. For one, as the procedure became increasingly common and viewed as almost always safe, did some mothers and doctors opt to choose that route when the going got tough after twelve hours of labor when they might have slugged it out longer in the old days? Hey… I’m just tossing that out there.

But going back to the premise of this theory, I’m not sure “evolution” is really the right word to use here. We’re talking about a relatively short period of time. Yes, there are ancient records of C-section births going back to before the time of Christ, but as far as a practice where the mother was generally expected to survive the process we’re only dealing with the past couple of hundred years maximum and frankly, only since the 20th century when it could be considered “routine.” That’s not very much time for a species to “evolve.”

That’s not to say that humans don’t evolve, and sometimes fairly quickly. There’s compelling evidence that people in western nations have grown, on average, four inches taller in just the past 200 years. We’re also more prone to certain diseases than we used to be. But a lot of that might be attributable to environmental factors as much as or more than genetics. And even the height factor affects the entire herd. C-sections are still comparatively rare. Plus, the selection mechanism of survival of the fittest seems to be strained by definition here. It’s not as if you’re gaining that much of an advantage being born through surgery rather than conventional delivery. Their argument seems to be that bigger infants would usually die in childbirth (generally along with the mother) before the surgery was widely and safely available.

So now we’re pumping a larger number of infants who have bigger skulls and larger overall bodies at birth into the gene pool. But they’re not that much bigger, right? And there aren’t that many of them that would really qualify as “giants” by comparison to the larger babies historically. As I said above, I suppose there’s some truth to the numbers they’re citing, but is this actually an example of “evolution” taking place before our eyes? Only if you stretch the definition a bit.