Why are skull bones soft in infants?

The softness of skull bones in infants serves a crucial purpose: to permit passage through the birth canal. During delivery, the flexibility of the skull allows the bones to overlap and compress slightly, which facilitates a smoother, safer passage for the baby without causing harm to both the infant and the mother. This characteristic is particularly important given the size of the newborn's head relative to the maternal pelvic structure.

Once outside the womb, the soft spots, known as fontanelles, gradually close and the bones harden over time as the child grows. While other factors such as support for brain development are significant, the primary reason for the flexibility and softness of the skull in infants during birth takes precedence, aligning with the necessity for safe delivery.