Why is giving birth so painful for women?

The pain women feel when giving birth is a very intense one when compared to the pain females from other species feel. Why is this so?
Question sent by ENRIC CABRERA (Alcoi). CARLOS LORENZO answers:

In the morphology of the human pelvis there is a conflict between its two main functions— the biomechanics of our musculoskeletal system and the fact that children go trough it when they are born. In order to have an effective biped locomotion it is best to reduce the gap between the two femur joints. The closer our legs were to the centre of our bodies, the less energy we would use in walking. But our two femurs cannot be very close to each other because babies have to go through it when they are born. The result is a compromise of the human pelvis to combine these two vital needs. Besides, we have to take into account that humans have big brains and, therefore, the size of our babies’ brains is relatively big. When we are born, the size of our heads is very similar to the size of the birth canal and that is what causes the pain

Carlos Lorenzo. Catalan Institute for Human Palaeoecology and Social Evolution, Rovira i Virgili University (Tarragona).

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