Tuesday, October 19, 2010

Why do we die?

Why do we die?

Seriously, why do humans die? Yeah, I know about the tree in the Garden of Eden and all, but why biologically do we die? Is it because we've built up a bunch of mutations that gradually kill us as we age? Or is it because we're genetically programmed to live a certain lifespan? I think it's the latter.

This week's PNAS has an interesting article looking at common disease-risk alleles (AKA genes that predispose you to diseases like cancer or heart disease) in young people and old people. Guess what? There doesn't seem to be much correlation between the occurrence of common disease-risk alleles and longevity. The authors of the study, Beekman et al., put it this way: "Longevity in this study population is not compromised by the cumulative effect of this set of risk alleles for common disease."

That's kind of counterintuitive, since you would expect the opposite to be true. Disease alleles should shorten lifespan, right? Not in this case, though. Does this relate to the question of why we die? Possibly, but remember they only looked at a certain selection of genes, so we can't really extrapolate broad conclusions about life and death from their results. It does make me suspicious of this notion that we die as bad mutations build up. At least for these genes, that doesn't seem to be happening.

Beekman et al. 2010. Genome-wide association study (GWAS)-identified disease risk alleles do not compromise human longevity. PNAS 107:18046-18049.

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