I finally got around to reading Londa Schiebinger's Plants and Empire, a fascinating book on colonialist bioprospecting which deals at great length with the controversy over abortifacients in early modern Europe, particularly as regards the slave trade. (Slave women frequently took abortifacient drugs in order to avoid having their children born into captivity.)
The part of the book that's especially pertinent right now has to do with the European views of "ensoulment": the point at which a fetus stops being a blob of protoplasm, and starts being a person. Initially, it seems, ensoulment was often thought to happen in the fourth or fifth month, after "quickening." When the baby started kicking, it was a person. Before that, it was simply biological matter with no special claim to respect or protection. (Though Schiebinger doesn't mention it, versions of this viewpoint were approved by Aristotle and Augustine; the latter drew a clear distiction between the ensouled "embryo animatus," and the unsouled "embryo inanimatus.")
Apparently, the combined authority of Aristotle and Augustine was more than enough for many early modern churches; Schiebinger notes that around 1600,
Church law was more lenient, teaching that "it is lawful to procure abortion before ensoulment of the fetus, lest a girl, detected pregnant, be killed or defamed. It seems probable that the fetus...lacks a rational soul and begins first to have one when it is born; and consequently it must be said that no abortion is homicide."What's really fascinating is that laws specifying that ensoulment came with quickening made the pregnant women herself the arbiter of when a fetus was ensouled. Thus, it seems likely that the dogma that ensoulment occurs at conception was turned into law in order to take from women the authority to declare a child ensouled, which had made them the arbiters of whether or not they'd had a "criminal" abortion.
A very interesting book, and well worth reading given our current controversies. At the least, it provides further evidence that the modern pro-life view of ensoulment-at-conception by no means represents the traditional or scriptural religious view.