Abortion

The basis of Roe v Wade:

"We need not resolve the difficult question of when life begins . . . the judiciary at this point in the development of man's knowledge, is not in a position to speculate as to the answer."

So when Roe v Wade was ruled upon, the SCOTUS said that it could not be determined when life begins (nor was it its jurisdiction). However:

"If this suggestion of personhood is established, the appellant's case [i.e. "Roe" who sought the abortion], of course, collapses, for the fetus' right to life is then guaranteed specifically by the [14th] Amendment."

So if scientists could ever determine when life begins, the 14th Amendment would protect the fetus' right to life. Thanks to the advent and understanding of science decades later, that has now been determined.

Human Life Begins at Conception (this is science, not religion):

Life Begins at Fertilization
Scientists Attest To Life Beginning At Conception