What is a human being?

When we think of a human being, we think of a man or a woman. In biology, a living organism is something that can reproduce itself, among other things.

Suppose you want to send a human being to a distant planet, in order to colonize that new world. Do you send a man? Or a woman? Or two men? Or five women? Obviously you have to send a man and a woman at the very least. So in a sense, a man-woman pair make up a single unit of homo sapiens.

Just as a heart isn't a human being by itself, and a brain isn't a human being by itself, so too a man by himself or a woman by herself are only half a human being. Is an unfertilized egg a human being? Of course not. Is a sperm cell a human being? No. Only when they come together do they form a person, and even that person is only half a human being until he or she grows up and forms a relationship with a person of the opposite gender.

People speak jokingly of "my other half" when referring to a spouse, and yet it's more true than anyone realizes.