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Monday, July 16, 2012

Genetic Evidence of Cannibalism?

In Blogging the Human Genome in Slate today, Sam Kean is on chromosome 20, and he tells how the  the "prion" gene -- and mutations thereof -- could provide evidence of cannibalism in our past.  We all have two copies of the gene, but in some of us, one copy is slightly different, either as a result of heredity or the environment.  One kind of mutation leads to horrible brain disorders, which can be transmitted to someone who eats your brain.  The other kind of mutation actually prevents the brain-eater from getting the disorder.   Although this is considered "highly conserved" DNA -- DNA that nature does tinker with much -- the protective mutations in it are reasonably common.  Apparently this same thing came up in the mad cow disease scenario in the 1990s, where all but one of the people who died from eating "mad cow" did NOT have the beneficial mutation (I think we'd need to know more to understand how this proves anything -- since only 100 people died, perhaps that just means that one in a hundred people have the mutation).

So a 2003 study suggests that the presence of the mutation that protects cannibals from getting the disorder is evidence of widespread cannibalism in our past.  Other researchers have questioned this conclusion.  I'm neutral, and haven't read either competing side, but from the blog I'm having trouble understanding why this necessarily has to be correlated with cannibalism -- why can't it protect people who eat bad meat (e.g. mad cows?).

BTW, I ate some very tough and stringy beef (at least that's what they said it was) at a Vietnamese restaurant last night, on one of my occasional breaks from vegetarianism.  It wasn't worth it (practically inedible; I left much of it), and it will be a long time before I eat beef again.

I learned something else about mad cow disease from the article:  the cause of it was that the cows were forced to eat each other on factory farms.  Here again, Shakespeare was prescient:

ROSS
And Duncan's horses--a thing most strange and certain--
Beauteous and swift, the minions of their race,
Turn'd wild in nature, broke their stalls, flung out,
Contending 'gainst obedience, as they would make
War with mankind.
Old Man
'Tis said they eat each other.
ROSS
They did so, to the amazement of mine eyes
That look'd upon't. Here comes the good Macduff.
--

In other words, when hoofed animals start eating each other, you know there's something wrong with society, as in MacBeth.

And here's a Family Guy take on another factory farming practice.

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