My co-blogger attempts to draw a line between debating the personhood of fetuses and the personhood of slaves:
The claim that undergirded slavery--and really Jim Crow--wasn't simply that blacks lacked "personhood" it was that they either weren't human, were sub-human, or were a lower order of human. This wasn't simply an ethical debate--whole reams of bad science sprung up to back up this notion. Eventually, better science prevailed. I'm arguing that that's a lot more cut and dry than abortion, and that religion was a constant on both sides, and basically dominant among those who defended slaveholding. Science, which rose above the level of alchemy, on the other hand, was not.
I don't think this works, for a number of reasons. Mr Coates is intermingling a scientific definition of humanity with the social definition--what I called "personhood". They happen to be contiguous in America right now, but that's by no means a universal cultural constant. Our Victorian ancestors were perfectly capable of recognizing that Africans met the basic scientific requirements to be counted in the human being--whites and blacks could interbreed and produce viable offspring. That's one of the reasons that I'd dispute that either slavery or Jim Crow were overthrown by science--it would be nice if this were so (I think), but the debate wasn't fundamentally scientific. It was a debate over what entities are included in the social definition of "person".
Every society has its own definition of what makes a person. Personhood, broadly defined, is what grants you the basic complement of rights to which everyone is entitled. That definition is usually based on genetic affinity, but what degree of genetic affinity varies greatly. Ta-Nehisi is using a fairly modern definition, "every adult whose genes class them as homo sapiens". We think that anyone who meets that criteria is entitled to a broad array of negative rights--you can't rob tourists just because they're German.
But that's hardly a universal constant. Western society has been expanding its definition of personhood for centuries--an ancient Roman wouldn't understand the notion that everyone who happened to find himself inside Roman territory should be entitled to the rights of a Roman citizen. Indeed, most non-Christian societies would have been puzzled at the notion that infants were people with a right not to be killed even if their family found them inconvenient. Nor would Tamerlane easily comprehend the notion that the citizens of the cities he sacked had a basic human right not to be raped and/or dismembered. For that matter, I doubt the African slavers who captured and sold most of the people who were sent to America as slaves thought that they were doing anything wrong; my understanding is that they were taking captives from other tribes and nations, who probably fell outside their mental definition of what constituted a person.
As an aside, we do need to credit religion for much of this. The Church has certainly committed its share of religious atrocities, but it was also, as I understand it, the main force eliminating practices like infanticide, "honor guards" and even human sacrifice in Western Europe. It was also where the anti-slavery movement started--the 16th century Catholic Church spoke out against it, and William Wilberforce, the father of the British abolitionist movement, was inspired by religious passion. The Congregationalist church in New England and the Quakers in Pennsylvania were the backbone of the abolitionist movement in early 19th century America. It's not relevant that churches in the south supported slavery. Support for slavery would have existed without the church. Opposition to it wouldn't have, without the churches that preached their conscience and gave the movement a ready-made base for organization. Or such is my understanding of the history.
Back to personhood. In at least one place we've contracted that definition. We used to think fetuses were persons, but over the last forty or fifty years, we've decided that they aren't. That's not because the science has changed; the relevant facts were all known in 1960. Rather, various cultural changes have made fetal personhood much harder to sustain socially than it was fifty years ago, so we rescinded it.
I think that in both cases we've got it right, and moreover I don't think that even most pro-lifers actually believe in the full personhood of the fetus, because if they did they'd be for capital punishment for women who have abortions, and against exceptions for rape and incest.
But this is an uncomfortable parallel for pro-choicers, because it makes obvious the fact that we have, in the past, expanded our social definition of personhood--and that a lot of people, many of whom were undoubtedly otherwise pretty good joes, embraced an excessively narrow, evil definition of who was entitled to be called a person. It is possible, though I don't think particularly likely, that 100 years from now our grandchildren will wonder how we could have been such selfish, inhuman monsters as to deny basic human rights to creatures who were obviously human.
That's why, while I'm pretty settled on my opinions of black personhood, I'm less sanguine about my notions of fetal (non) personhood, and frankly puzzled by the pro-choicers who not only believe that their definition is right, but that it has been arrived at by some super-scientific process that could only be disputed by a woman-hating religious nut who has blinded himself to the obvious rational answer. There are two obvious bright lines: conception (or implantation), and birth. Pro-lifers have chosen the former (though as I said above, they don't really fully believe this). A few hard-core pro-choicers are willing to hew to the latter--to say that eight months after conception, outside the womb it's a baby with full personhood, but inside the womb it's a thing with no right to exist save at the sufference of the mother. But most pro-choicers do not. The label "pro-choice" tolerates a very wide degree of disagreement about when personhood begins, from the end of the first trimester all the way to birth. If it's so obvious that pro-lifers must be willfully blind, how come we can't agree?