[y04nn]

I also have a lots of doubt about this study, the article says '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.' 1960 -> 2016 = 56 years, can natural evolution show signs so fast? Also 'cases where the baby cannot fit down the birth canal' is a subjective, standards may have evolved, maybe babies are also bigger?

[dragonwriter]

> can natural evolution show signs so fast?

Yes, in fact, I think the accepted dominant manifestation of natural evolution is rapid change in trait distribution in response to significant change in enviromental pressure, and near stasis otherwise, not continuous slow change.

Changing a trait from near certain death of mother and child to one which, while it has some increased risk, is normally survivable without lasting adverse consequences for either mother or child is an enormous change in terms of the degree of selective pressure against the trait.

That's not to say there aren't other potential contributors, but it's not unreasonable for natural evolution to have measurable effects in the timeframe in question in those circumstances.

> maybe babies are also bigger?

The article expressly calls that out as a contributing evolutionary trend that was itself limited by the fact that beyond a certain point, that becomes fatal. So, that's certainly true, but in no way a contradiction to the point in the article.

[undersuit]

>maybe babies are also bigger?

Well adults are bigger. Average height has been increasing worldwide and better nutrition is the accepted cause. So maybe(most definitely) a pregnant well-fed mother will produce a larger baby than a mother eating more like those in generations past. We've been evolving for safe delivery of babies while teetering on starvation, not when so well fed that 25% of the US population is obese.