Why people are not born with a ready-made set of teeth?
If the answer in short, children are born without teeth, because the teeth newborns are unnecessary and even dangerous.
Now consider this question in detail.
The function of the teeth - grinding solid food. A newborn is nothing to grind in the mouth is not necessary, they only eat liquid food - milk. Their digestive system is not yet fully developed, and recycle solid food they can't.
Babies grow quickly, and by 5-6 months of liquid food they start to miss: for all its nutritious mother's milk or infant formula is not enough calories (i.e. do not contain enough energy to ensure continued growth. Just then the kid starts to erupt first milk teeth. A full set of milk teeth, the child gets to 2 years.
The beginnings of deciduous teeth in a child are pledged at 7-13 weeks of pregnancy, and even the mineralization of teeth is already in utero. But these teeth are not in a hurry to erupt because for a child with a full set of teeth in the mouth birth process would have been much more problematic than for toothless baby. To the child it was easier to pass through the birth canal, wise nature made it so that even the bones of the baby is soft and more flexible than adult bones. But even with such precautions, the nature of birth injuries, unfortunately, not uncommon. And to complicate the situation by the presence in the mouth, excess solid objects completely useless!
You can also find the view that children are born toothless, as the toothed sucker may be damaged in the process of sucking the mother's breast. This explanation also has the right to life, but we must draw your attention to an important point: the teeth and the gums in the process of sucking not involved! On the other hand, toothy baby might bite her mother's nipple or the native tongue of negligence because he had not fully in control of their jaws.