Fertilization for all animals takes place in some form of water; embryos float in the womb; human blood has almost the same concentration of salts as seawater. “Those animal species that fully adapted to the land did so through the trick of taking their former environment with them,” the evolutionary biologist Lynn Margulis writes. “No animal has ever really completely left the watery microcosm…. No matter how high and dry the mountain top, no matter how secluded and modern the retreat, we sweat and cry what is basically seawater.”
