Ontogeny Recapitulates Phylogeny
Claire Filloux '07
Department of Physics
Evolutionarily, to be human is ordinary and incredible. In eight weeks after fertilization, a single human embryo traces our entire evolutionary past. The first weeks we start simple, a sponge maybe, or the translucent ghost of a hydra. Within the next few days a notochord descends. The origin of the vertebrate. Gills streak our sides by week four, and we begin to breathe the amniotic fluid of our motherís uterus like an ancient jawless fish. Week five, our hands web into the ray-like fin of a perch. Then a spine. A red lattice of veins. A mouth that sucks fluid into the soaked lungs of something amphibian. Week seven we sprout the first hair follicles of a mammal. Only in week eight are we human. We can never escape our ancestry because we play it back in ourselves. But with the same neurons that make a kingfisher dive or a deer start at the fall of a footstep he feels foreign, we can marvel as the whole living kingdom rises in a single human cell. We are not special because we can look down on other forms of life, but because we can see the connection. A deer looks into our eyes and sees a stranger. We look into the eyes of a deer and see ourselves.