Wednesday, December 8, 2010

Harry Potter and the Question of Heritability

I just saw the new Harry Potter movie and so decided to type the general search term "Harry Potter" into a few science literature search engines just to see what got conjured up. One of the first topics was all about the heritability of magic!

A correspondence in Nature suggests that magical ability is inherited in a Mendelian fashion, with the wizard allele (W) being recessive to the muggle allele (M). The recessive part makes since considering there are so many more muggles, those without magical abilities, than there are witches/wizards. That means that those with magical ability must have two copies of the wizard allele (W W). Take this up the family tree and it means that purebloods will have both parents that are W W while half-bloods and mudbloods will have one or both parents with W M. Although, Harry does have a W W genotype he is not considered pureblood since his mother was muggle-born. Later published comments point out some interesting flaws in this particular hypothesis.

Craig, Jeffrey M., Renee Dow, and MaryAnne Aitken (2005) Harry Potter and the recessive allele. Nature: 436(7052), 776. (DOI: 10.1038/436776a)

Dodd, Antony N., Carlos T. Hotta, and Michael J. Gardner (2005) Harry Potter and the prisoner of presumption. Nature: 437(7057), 318. (DOI: 10.1038/437318d)

Another paper, published in BMJ, discusses in more detail the evidence for a genetic basis to magic. As we discussed above the books, and the movies, to some degree, class people as either muggles, squibs, mudbloods, or purebloods. Most of the world is made up of muggles, a minority of people are witches/wizards, those with magical abilities, and a very small fraction of the magic community are squibs (non-magical people from an otherwise magical family). This suggests that there is some heritability to the trait that is magical ability. Additionally, the environment Harry was raised in, a very non-magical muggle home, further supports that this is a genetic trait, one leaning more towards the nature rather than the nurture.

This particular paper prefers the idea of magical ability not as a dichotomous trait but rather a quantitative attribute that ranges in its ability with some individuals having an exceptional proficiency and others a relative ineptitude. Individual magical skills such as parseltongue (ability to talk to snakes), clairvoyance, metamorphmagus (ability to change physical appearance) are all likely skills that seem to be conferred by specific genes. The authors argue that the best explanation for the inheritance of magic in the world of Harry Potter is best explained by a multilocus model with a dominant gene for magic, the function of which is controlled epistatically by one or more loci, possibly recessive in nature. The genotypes influence total magical abilities with the allele frequencies differing significantly between populations with magical abilities and those without.

Ramagopalan, Sreeram V., Marian Knight, George C. Ebers, and Julian C. Knight (2007) Origins of magic: review of genetic and epigenetic effects. BMJ: 335, 1299. (DOI:10.1136/bmj.39414.582639.BE)

This is a fun topic to get all sciency over. Check out another set of papers on the origins of Harry Potter's headaches:

Sheftell Fred, Steiner Timothy J., and Thomas Hallie (2007) Harry Potter and the curse of headache. Headache 47, 911-916. (DOI: 10.1111/j.1526-4610.2007.00665.x)

Hagen, Knut. Harry Potter's Headache. (2007) Headache: 48(1), 166. (DOI: 10.1111/j.1526-4610.2007.00985.x)
Lewis, Donald and Andrew Hersheym (2007) Harry Potter's Headaches. Headache: 48(1), 167. (DOI: 10.1111/j.1526-4610.2007.00986.x)

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