BLAME THE CAVEMEN

Evolution may have catapulted humans to the top of the food chain, but it has also landed us with a range of health problems. this week: Difficult labour

AS OUR ancestors began to walk upright around three million years ago, our hips also narrowed to make the movement more efficient. However, as the pelvis started to slim and the spine started to curve into an S-shape, human babies had to twist and turn to pass out of the body, making birth far more difficult.

Over the same period, our brains became bigger. This has led to babies whose heads are too big to fit through the birth canal — affecting about one in 250 mothers. As a result, they often need a Caesarean section. According to Professor Karen Rosenberg, a biological anthropologist, the average pelvic opening in women today is 13cm at its largest width, and 10cm at its smallest. Meanwhile, the average baby’s head is 10cm and the shoulders are 12cm. Professor Rosenberg says: ‘When the head is large and pelvis restricted, the birth can’t happen without surgical help.’