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Diet & Nutrition

How C-sections might be changing human evolution

Will giving birth get harder as time goes on?

New research suggests that the increasing number of caesarean sections are causing evolutionary changes with regard to babies' heads and the size of a woman’s pelvis.
According to a study by medical experts from Austria and the US, published in Proceedings of the National Academy of Sciences earlier this week, they found that the number of cases where a baby is unable to fit down the mother’s birth canal has increased 20 percent worldwide from 30 in 1,000 to 36 in 1,000 since the C-section procedure became commonplace in the ’50s.
Scientists have known for quite some time that humans have more trouble giving birth than most other animals—this is because of the passage of proportionally larger babies' heads through a relatively small birth canal. When a baby has a head that is too big to pass through (known as fetopelvic disproportion), surgeons manually remove the baby through an incision in the mother's lower abdomen—a procedure known as a Cesarean or C-section (believed to be named after Julius Caesar, who was thought to have been cut from his dying mother's womb.)
So what’s the evolutionary impact of opting for a C-section every time a baby can’t be delivered vaginally?
Basically, in the past a woman with a narrow pelvis giving birth to a baby with a big head would have been a struggle that would have often resulted in death. Now, because of the C-section option both genes for a narrow pelvis and a big head are being passed on instead of dying out.
“Women with a very narrow pelvis would not have survived birth 100 years ago. They do now and pass on their genes encoding for a narrow pelvis to their daughters,” Dr Philipp Mitteroecker from the university told the BBC.
Researchers also note that the trend of having a bigger baby, with a bigger head, might be due to the modern diet and lifestyle, which is more inactive and calorie rich than that of past generations.

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