Why humans grow old grungily

From The New Scientist:

Old MY ATTIC is a sad sight, a jumble of frayed carpet offcuts, half-empty cans of congealed paint, broken videos, dead computers and inoperative exercise bikes. Just the thought of dragging it all to the dump tires me out. Something similar is happening inside my body’s cells – at least according to a new theory about why we age. The rubbish is piling up, and while I could clear it all out, that would take a lot of effort. So my metabolic cleaning systems are set to “don’t bother”, and the result is that harmful garbage is accumulating.

Junk plays a central role in many theories of ageing. The “free radical” theory, for example, suggests that ageing is caused by highly reactive oxygen species that gradually turn DNA and proteins into toxic rubbish. But now there is a new take on junk, where it comes from, and how it causes us to get old. By analysing unusually long-lived variants of the tiny nematode worm Caenorhabditis elegans, David Gems and Josh McElwee of University College London’s Centre for Research on Ageing have found that free radicals are just one part of a much bigger story.

The story begins in 1993 when Cynthia Kenyon of the University of California, San Francisco, discovered that some strains of C. elegans with mutations in a gene called daf-2 lived more than twice as long as normal. This appeared to show that ageing was controlled by genes, contradicting the widespread view that it was largely the result of wear and tear inflicted by free radicals. Not surprisingly the results caused a stir. Many researchers were puzzled about how genes for ageing could evolve through natural selection.

More here.