Newborn babies have no teeth because the development of teeth begins before they are born. The process of tooth formation, or odontogenesis, starts during fetal development, typically around the sixth week of pregnancy. However, the teeth do not fully erupt until much later.
Here’s a brief overview of the stages of tooth development:

1. Embryonic Stage: The first signs of teeth development occur during the embryonic stage. The oral structures begin to form, and the germinative cells that will become the teeth (tooth buds) are established.
2. Fetal Stage: Tooth buds continue to develop, and by the end of the fetal period, the basic structure of the teeth is in place. The enamel, which is the hardest substance in the human body, starts to form, but the teeth remain embedded in the gums.
3. Postnatal Development: After birth, the teeth continue to develop below the gums. The enamel matures, and dentin, a hard tissue that makes up the bulk of the tooth, is formed. However, the teeth do not erupt until the baby is between 6 months to 3 years old.

The timing of tooth eruption can vary greatly among individuals, but the first teeth to appear are usually the lower central incisors, followed by the upper central incisors, lateral incisors, and canines. The molars come in later.

Newborns lack teeth because the eruption process takes time, and the bones and gums of a baby’s mouth are not ready to support the teeth until they have reached a certain level of development. Additionally, the lack of teeth is a normal part of human development, and babies are designed to nurse or bottle-feed without the hazard of sharp teeth.

It’s important to note that while babies are toothless, they still need proper oral care. Regular cleaning of the gums can help prevent oral health issues later in life.