Describe the sex differences in body growth. How does this help explain girls' lower infant and childhood mortality rates?

What will be an ideal response?

In infancy, girls are slightly shorter and lighter than boys, with a higher ratio of fat to muscle. These small sex differences persist throughout early and middle childhood and are greatly magnified in adolescence. But the best estimate of a child's physical maturity is skeletal age, a measure of bone development. It is determined by X-raying the long bones of the body to see the extent to which soft, pliable cartilage has hardened into bone, a gradual process that is completed in adolescence. When skeletal ages are examined, girls are considerably ahead of boys. At birth, the sexes differ by about 4 to 6 weeks, a gap that widens over infancy and childhood. This greater physical maturity may contribute to girls' greater resistance to harmful environmental influences.