Oooh, I have annoyed Secular Pro-Life so much. I disagreed with the confusion they sow by equating status as a human being with being members of the species Homo sapiens; the former is a property of an entity, the latter a property of a class. It is highly problematic to freely switch between the two, and it is especially misleading to use a class definition to assign rights and privileges to a subset, particularly when it involves denying the existence of clear distinctions between members of the group. It is also dishonest to declare that the authority of science specifies a sharp, clear boundary line in development, when what science actually says is that there is a continuum, and cannot define the instant when a clump of human cells makes the transition into having “fully equal” human status.

Here’s their complaint:

If PZ could give a commonly accepted definition of "species" that debunked the idea that human organisms–including zygotes, embryos, and fetuses–are part of the human species, he would. If he could give a commonly accepted definition of "organism" that did not include zygotes, he would. But he doesn’t give those definitions. He can’t. Because zygotes are organisms, and human organisms are part of the human species. PZ can do a bunch of hand wavy complaining about how he’s not sure what Kristine means (and try to assert that his alleged lack of understanding equals her dishonesty), but that’s all he’s got. There’s no substance here.

He’s right that there are many ways of thinking about the concept of "species." But Kristine’s perspective doesn’t rely on some obscure, slippery definition. How about a group of organisms having common characteristics and capable of mating with one another to produce fertile offspring? You can find that description on the lying, anti-woman, secretly religious website: Biology Online.

Kristine claims "science defines a fetus as a biological member of our species." PZ tries to brush off Kristine’s perspective as "traditional and colloquial" (as if those attributes, in themselves, make an idea anti-scientific), but in reality Kristine’s assertions rely on a very common–and scientific–species concept: the biological species concept. UC Berkeley’s "Understanding Evolution" website describes the biological species concept as the concept used "for most purposes and for communication with the general public." How dare Kristine fail to define that for someone like PZ–he only has decades of background in developmental biology. That must have been very confusing for him.

That’s exactly what I mean! You cannot cavalierly apply a definition appropriate to populations to individuals. Here’s that definition: “The biological species concept defines a species as members of populations that actually or potentially interbreed in nature”. If you take that literally, then sterile individuals are not members of the human species. No one takes it that literally. Even the site they link to spells out problems with the BSC, and lists a small subset of other species concepts.

Another problem with the BSC is that it doesn’t address development, and this really is a problem in developmental biology. What does “potentially interbreed” mean? Are embryos part of the gene pool? How about menopausal women? Do men with vasectomies lose their ontological status with that little snip? If you’re going to say that embryos have the potential to reproduce, then you can’t deny that sperm and ova also have that potential, and SPL’s distinction that sperm don’t count is invalid. Scientists are also crystal clear in defining human sperm and human ova; does the use of the label imply that sperm therefore have all the rights of a human being?

The biological species concept doesn’t apply to this problem, and it is not only scientifically invalid to try and use it that way, it is offensive. We do not and should not define a person’s status in society by their reproductive potential. We do not measure the broader social and familial relationships of individuals by reducing them to biological abstractions — having the right number of chromosomes, complementary sperm-egg recognition proteins, matching genitalia for efficient intromission and docking. The species problem is a whole different problem from the humanity problem! And when your argument rests on a willful conflation of two completely different issues, you’ve got a credibility problem. And claiming that science decrees a simple clear answer when it actually says the answer is murky and complex and ambiguous on multiple levels means you’ve got an honesty problem.

But yes, please do try to imagine a world where your status as a human being was determined by applying the biological species concept to individuals. Dystopias are fun logical exercises, if not so fun to live through.