Resumen

RAMON, Fidel. Obstetric dilemma. Rev. Fac. Med. (Méx.) [online]. 2015, vol.58, n.2, pp.17-35. ISSN 2448-4865.

Darwinian theory indicates that human beings are products of evolution and natural selection, processes that have taken millions of years. During that time animals and humanoids changed in many ways and one of the most remarkable is the transition of a quadrupedal to a bipedal gait. Such a change required numerous adaptations, many of which are in the skeleton and lower limbs, that reduced the diameter of the pelvis in such a way that if the fetus had to wait to be completely developed to be born his large head would not pass through the pelvic channel. This problem is known as the ‘obstetrics dilemma’ and its solution was to allow the birth of an immature fetus, which implies a long process of extra uterus development. Even so, to be born the fetus has many difficulties to negociate the pelvic channel.

At birth the fetus brain is incompletely developed and has to finish developing out of the uterus, a process that takes about 20 years. This delay might explain no only some unpredictable adolescent behaviors, but also the onset of some diseases whose consequences are seen until the adult years, when brain development has finished.

Palabras llave : human evolution; bipedalism; pelvis; birth.