When we first learned basic reproductive science, giggling behind our hands in school, we learned that a vast number of tadpole-like sperm swim up to a round, floating egg somewhere in the mysterious geography of the female reproductive tract. Voila! An embryo is made, which (blah, blah, blah) becomes a person in roughly 40 weeks (give or take). While this is not untrue, it is a remarkable simplification of processes that we can barely wrap our minds around. Consider that when the sperm and egg meet, they carry with them half of the genetic information for an entire human being. According to the National Institutes of Health Human Genome Project, human DNA contains about 20,000 genes on 23 pairs of chromosomes — half from each parent. All starting with that ridiculous-looking sperm and egg. In terms of just the physical length, every human cell has about five feet of DNA…