Jan's question was about "when does life begin" and not about abortion. Although it is understandable how these two topics become linked in people's minds. Taking many....many biology and medical courses, I was taught that a single cell is a living thing. At work, every time I look examine tissues through a microscope, I'm made aware of this simple fact. A sperm is a cell and an egg is a cell (although haploid...uh...half of the full genetic compliment). It takes life to a create life. Life must therefore exist before procreation can begin.

A better question for this topic might be, "at what point does a human being become sentinent or a living being"?