User:DrSculerati/sandbox

Upright posture with bipedal locomotion means that the human pelvis has an architecture that is fundamentally different than other primates. Since the female pelvis provides the bony limits to the birth canal, this means that the narrower canal limits the size of the newborn human. The head of the neonate is the largest portion that must pass and the size of the head is the brain case.

Where as the head size of many vertebrate newborns is similar to that of the adult, this is not true of human beings. Our species head size at birth is only about X of the adult, in terms of circumference, a normal newborn ranges from X to Y, but an adult is W to Z.

It is not until about age 3 years that the cranium reaches adult size. Maturation of the brain does not occur until the third decade of life.

Otitis media is particularly common in children under the age of 3 years. The size and angle of the Eustachian tube has a quantum change as the brain case enlarges and the teeth erupt, the entire human head changes shape between the newborn and the three year old, with the