a. If there is uncertainty about when human life begins, the benefit of the doubt should go to preserving life. b. Medical textbooks and scientific reference works consistently agree that human life begins at conception. c. Some of the world’s most prominent scientists and physicians testified to a U.S. Senate committee that human life begins at conception. d. Many other prominent scientists and physicians have likewise affirmed with certainty that human life begins at conception. e. The possibility of human cloning does nothing to discredit the fact that all humans conceived in the conventional manner began their lives at conception.