When we conceived our children, my wife and I had to give them genetic instructions on how to build their bodies, including such developmental issues as nose placement and skin color. Egg and sperm split the instructional task. My March 2003 column celebrated the 50th anniversary of the discovery of DNA (deoxyribonucleic acid) located in the nucleus of each body cell. DNA is the genetic recipe book on body organization, development, and maintenance that parents give to their children.

But providing such genetic information is only part of the human parenting charge. We also have to teach our children how to become decent, productive, reproductive human beings. Our upright stance and consequent narrow female birth canal results in a child whose birth brain can only be one-third its adult size. Most human cognitive development thus occurs after birth (as compared to other mammals whose female birth canal is slightly larger than the almost fully developed brain that passes through it).

We begin life as a wet noisy pet and require 20 years at best to move into an autonomous adulthood. Our long juvenile dependency has of necessity turned us into a highly interdependent social species that must master complex cultural information and communication systems. Further, our upright stance frees our forelimbs from mere body movement and so creates grasping, handling, throwing, and signaling capabilities that materially expand the complexity of learned human culture.