True or false? It is uncertain when human life begins

An article printed and distributed by the National Abortion Rights Action League (NARAL) describes as “anti-choice” the position that “human life begins at conception.”  It says that the prochoice position is, “Personhood at conception is a religious belief, not a provable biological fact.”

It is uncertain when human life begins; that’s a religious question that cannot be answered by science.

If there is uncertainty about when human life begins, the benefit of the doubt should go to preserving life.  Suppose there is uncertainty about when human life begins.  If a hunter is uncertain whether a movement in the brush is caused by a person, does his uncertainty lead him to fire or not to fire?  If you’re driving at night and you think the dark figure ahead on the road may be a child, but it may just be a shadow of a tree, do you drive into it or do you put on the brakes?  Shouldn’t we give the benefit of the doubt to life?

Medical textbooks and scientific reference works consistently agree that human life begins at conception.  There are simply too many sources to cite!  I have dozens that cite life begins at conception.  They state not a theory or hypothesis can certainly not a religious belief–every one is a secular source.