Another reason to love the Harry Potter books
On to other topics...
Via Stupid Evil Bastard, I've found another reason to love the Harry Potter books. British geneticists Jeffrey M. Craig, Renee Dow, and Mary Ann Aitken examined the chromosomal basis of being a wizard or a muggle, suggesting that wizarding ability is inherited in a Mendelian fashion as a recessive. Last month, they even got their idea published as a Letter to Nature. They speculated:
I like it. Too bad I missed the original letter, which Panda's Thumb pointed out when it was originally published. (I think the reason I missed this one is because it came out while I was on vacation and I never quite caught up on the journals that piled up in my absence, ending up just filing many of them away mostly unread.) In any case, although I know a lot about genetics, I'm not a geneticist. Even so, I realize that this proposed explanation is probably too simplistic. Fortunately for my ability to blog on this without seeming a month and a half out of date, another group of scientists, not to be outdone, agree. They fired off a retort that was published in Nature last week:Wizards or witches can be of any race, and may be the offspring of a wizard and a witch, the offspring of two muggles ('muggle-born'), or of mixed ancestry ('half-blood').
This suggests that wizarding ability is inherited in a mendelian fashion, with the wizard allele (W) being recessive to the muggle allele (M). According to this hypothesis, all wizards and witches therefore have two copies of the wizard allele (WW). Harry's friends Ron Weasley and Neville Longbottom and his arch-enemy Draco Malfoy are 'pure-blood' wizards: WW with WW ancestors for generations back. Harry's friend Hermione is a powerful muggle-born witch (WW with WM parents). Their classmate Seamus is a half-blood wizard, the son of a witch and a muggle (WW with one WW and one WM parent). Harry (WW with WW parents) is not considered a pure-blood, as his mother was muggle-born.
There may even be examples of incomplete penetrance (Neville has poor wizarding skills) and possible mutations or questionable paternity: Filch, the caretaker, is a 'squib', someone born into a wizarding family but with no wizarding powers of their own.
We believe that, with the use of these examples, the concepts of mendelian genetics can be introduced to children as young as five, and then built on by gradually introducing specific terms such as 'gene' and 'allele', and relating these to chromosomes and DNA. At every stage, the children's familiarity with the Harry Potter characters can be used as a hook to engage them in discussing concepts of heredity and genetics.
Following Craig and colleagues' analogy, Hermione, as a muggle-born witch, must have WM parents. However, as Rowling fans could point out, Hermione's parents were muggle dentists who lack any family history of wizarding. It's true, of course, that chance may not have thrown up a witch or wizard for many generations, or that any who did have magical powers may have kept them secret to avoid a witch hunt.
What about Neville's apparently poor wizarding skills? These cannot be explained by incomplete penetrance, as Craig and colleagues suggest. In incomplete penetrance, individuals either display the trait or not: they do not display an intermediate degree of the trait. Poor wizarding skills might be indicative of variable expressivity of an allele. However, both variable expressivity and incomplete penetrance are associated with dominant alleles. If the wizarding allele were dominant, rather than recessive as suggested, wizarding children such as Hermione could not be born to non-wizarding parents.
Neville's clumsiness may, perhaps, be an individual characteristic unrelated to his potential powers. However, it is not possible, from the evidence presented so far, to conclude that wizarding is a heritable trait.
Of course not! What fun would that be? In any case, the discussion in the comment section after the original Panda's Thumb article has some entertaining speculation:
Wizardy is clearly a quantitative, multigenic trait with variable expressivity and incomplete penetrance. I wouldn’t discount a role for epigenetic effects either.
Possibly the magic ability is only partly inherited. One explanation for squibs and muggle-born wizards/witches would be that the allele(s) for magic are fairly common in the population, but that they are expressed only when they are triggered by some external factor. This factor would have to act sometime in the early years (wizards and witches develop their abilities slowly up to around age eleven, and there is no mention in the books of someone gaining magical powers as an adult.) This factor could simply be exposure to magic, or to some microorganism that is endemic to the wizarding community. Muggle-born wizards/witches could come from accidental exposure to either of these. If it is a microorganism, squibs could be explained by immunity from an earlier infection by a related organism. It would be an exciting topic for a research project!
Of course, there is yet another upside to this idea, if it ever caught on. Teaching genetics also implies implies the acceptance of evolution and could even provide an "in" to introducing basic concepts of evolution. As SEB and Clive both point out, that's another reason for the Christian right to hate Harry Potter. Not only would they accuse J. K. Rowling of indoctrinating children into witchcraft, but they could accuse her of something many of them probably view as even worse: introducing them to concepts of evolution.