A host cell line is a microorganism that was until fairly recently a part of some higher organism – roughly speaking, a contagious cancer. We know of one good example, transmissible venereal tumor, also known as canine venereal sarcoma or Sticker’s sarcoma, a contagious neoplasm of dogs. It is not contagious in the same sense as liver or cervical cancer, which are (usually) consequences of viral infections. In those cases, it is the virus that is infectious; here it is the cancer itself. Viable cells become engrafted onto mucous membranes and grow in the new host animal. Transmission is usually sexual, but licking or inhaling sometimes causes oral or nasal tumors. Chromosomal and genetic studies indicate that all cases of TVT share a common origin – all share a particular pattern of chromosomal rearrangement and carry characteristic insertions.
Greg goes on to speculate that the cell line derived from a cervical adenocarcinoma in Henrietta Lacks in 1951, HeLa, might be something like a host cell line. Descended from a homo sapiens, but a new species. Since I just happen to be reading Dune, this reminds me of the Bene Gesserit belief that not everyone who happens to be a homo sapiens counts as a human.
Which further reminds me of one of my favorite ideas of John Reilly's: humans, homo sapiens, and persons, are different things. Discoveries like this just reinforce my conviction that John was right. However, I've found that right-thinking people seem obscurely scandalized when I repeat this. I think this is probably a good thing, because de-humanizing people is usually the first step in justifying doing something bad to them. To say that a human being and a person are not logically identical is not the same thing as saying we should de-personalize some human beings. However, it does open that up as a possibility. Thus I am not surprised when people seem off-put.
However, it does not therefore follow that those three things are logically identical. They cannot be, because they are different kinds of things. It is a category mistake to identify them. John summarized thus:
A human is an essence (if you don't believe in essences you don't believe in human beings); a homo sapiens is a kind of monkey; and a person is a phenomenon. Perhaps I read too much science fiction, but it is not at all clear to me that every human must necessarily be a homo sapiens. As for person, which is an entity, conscious or otherwise, that you can regard as a "thou," is conflated with the notion of person, as an entity able to respond in law, either directly or through an agent.
I think that the human beings we know of are homo sapiens, and that homo sapiens are persons. I just think you have to make an argument that these things are true, rather than making an indefensible assumption about it.
The last distinction John makes in the quote above often trips people up. If you conflate the two senses of the word person, and then further identify that with human being, I can see how that idea might be offensive. The problem is, it isn't true. If you can look past the controversies of contemporary American politics, the idea that a corporation can be a person has allowed institutions to flourish in the West, as opposed to tribes, nations, or dynasties, which are defined by common descent. An institution can continue through time once the founder has died, regardless of the familial relations of the people who comprise them.
Societies that lack the ability to create groups with a common purpose that do not depend on ties of kinship are weaker than those that can. We shouldn't cast that aside blithely.