In fact, it’s really only been considered Biblically “true” since 1979 — before that, Evangelicals held widely varying positions, and even some of the most vocal “life begins at conception” voices today didn’t think that zygote life was the equivalent of born-human life in the 1960s and 70s. But political necessities change, and with them Bible interpretations. Read that whole piece; it’s fascinating. Also worth considering the role played by the new Right, and the need to replace full-throated support for segregation with other issues that could rally racist whites, particularly in the South.
Thanks, Lauren, for the link!