Where does anything begin? Regardless of its specific form or context, our human experience seems to center around a notional perception of continuity. Each day we awaken to a belief that we existed yesterday, and each and every moment before the present. It’s easy for this to seem like a needless distinction. Obviously, we can make any number of delineations on events or distinctions: when we are conceived, or our heart first beats, or we are born, or our first memory. Any one of these may constitute one's opinion on the beginning of a human life, but each and every one requires a prior existence that makes the decision that this distinction designates the "beginning" seem rather insouciant. The meaning of a beginning for humanity is equally perplexing if not equally peripheral. Our love of continuity prefers to accept the prevailing theory of evolution, but this only serves to raise the "species problem." Nature does not construct boundaries with bright lines;...