Long-life gene, at a price

Evidence to support the theory that long life comes at a price has been produced by UK scientists.

Researchers have found that nematode worms with greatly extended lifespans were less able to survive food deprivation than normal worms.

The finding lends weight to the idea that there is a genetic trade-off between fitness and longevity. According to the theory, genes that act beneficially early in life may have detrimental effects late in life, leading to ageing. Natural selection permits this situation to exist because after reproducing, it does not matter if an organism lives or dies. Genes that are harmful late in life, are still passed on if they benefit youthful animals at a period when they are reproductively active.

Conversely, any genetic alteration that increases lifespan, might be expected to reduce fitness.

The idea was tested at the University of Manchester, on nematode worms carrying a gene mutation that extends lifespan by up to 80%. Given enough food, the modified worms and ordinary worms did equally well. If the worms went hungry, as often happens in the wild, the population of long-lived worms declined rapidly. This was because young adult worms carrying the longevity gene laid fewer eggs if starved.

Scientists concluded that the extension of lifespan, by mutation of a single gene, is associated with reduced fitness. This fitness cost is apparent in an environment thought to mimic natural conditions.