Organelle Transplant

Yesterday on Twitter, Razib Khan remarked that he hadn't realized pro-life Christians relate genetics to souls.

Since I wasn't party to the conversation, I have no idea what was said. I have heard things like this however, and it made me go hmmm....

I decided to respond in a blog post, since Twitter sucks for anything moderately complicated.

The bigger context for this is a proposal to treat mitochondrial disease that was approved by the Human Fertilisation and Embryology Authority in the United Kingdom. In what seems like an attempt to annoy the maximum number of people possible, this procedure is usually described as a 'three-parent baby'. While there is a germ of truth in this description, you could also call it an organelle transplant, since the intent is to replace defective mitochondria with working ones.

The germ of truth is this: the replacement mitochondria should breed true, because the technique referenced in the article, pronuclear transfer, removes the male and female pronuclei from one fertilized egg [the one with defective mitochondria in the cytoplasm] and moves them to another fertilized egg [whose pronuclei have been removed] with different mitochondria. These new mitochondria are in fact from a third person, and are genetically distinct from the other woman's.

I use organ transplant as a reference point, because a donated organ also contains DNA different from the recipient's. The key difference here is that your donor liver's DNA cannot be passed down to future descendants.

So why does anyone care? People care because 1) pro-life Christians are generally essentialists, meaning that essences or forms [in the Platonic or Aristotelian sense] define what things are, and 2) popular science accounts of genes or DNA usually describe these things as our 'essence' [in the loose popular sense of the word]. Thus our genes probably seem real important to some folks, and tampering with them is tantamount to playing God. I think this is a misunderstanding, albeit a predictable one.

In my opinion, I don't think the fact of getting DNA from a different source matters at all in its own right. One reason is much the same one Razib talks about in his tweet:

Some of our genes are indeed from viruses and stuff. There is a theory that mitochondria were once separate organisms that have become symbiotes. A lot of genes are common to all life on Earth. Strictly considered, a gene is just a way of encoding information about proteins. Any gene that works in some fashion is a real gene, although some clearly work better than others.

The second reason is that I think a lot of pro-life Christians have made a philosophical mistake in conflating the terms we use to talk about people. John Reilly said it, and I just stole it:

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.

Human ≠ homo sapiens. It just ain't. Popular science accounts are correct insofar as homo sapiens is a biological concept, it can be usefully defined using genes. Human is a philosophical concept, moreover one that is dependent on a specific context to really be cogent. I think that at the very least Neanderthals were humans too, and possibly other hominins. Hell, if we were consistent, pygmies might be considered a separate species from homo sapiens, because they split off from other humans 300,000 years ago, which is before the currently defined date of the origin of anatomically modern humans

I have my doubts about the current theories, but that doesn't matter. Human is a status that is in principle independent of lineage. In practice, it isn't, but that is different from saying that they are identical.

Now, what about this mitochondrial replacement therapy? I'm still opposed. The reason has nothing to do with genes. In my philosophical tradition, there are three criteria an act must meet to be considered good:

  1. Right act
  2. Right end
  3. Right circumstances

The techniques in the Wikipedia article all involve IVF, which means creating embryos using harvested eggs and sperm, which has a pretty horrible success rate [10-20%]. That in itself isn't damning, but the way in which unused embryos are discarded [that essentialism again], and the way in which sperm and eggs are collected are objectionable in their own right. Only criterion 2) is met: preventing disease is a very good thing, especially if you can help reduce future occurrences. Anyone who doesn't share my premises about human embryos [if you don't believe in essences, you don't believe in humans], will likely not agree with my objections to IVF, although I do note that even people who are in theory in favor of it tend to find it icky and horrible when they see it.