That all living things age and then die has been of interest ever since the dawn of abstract thought. With the advent of molecular biology the prospect of studying the ageing process has become a scientific reality that casts aside random speculation.
A multi institutional study from the UK just published in Nature, Somatic mutation rates scale with lifespan across mammals, examined somatic mutations in 16 mammalian species: black-and-white colobus monkey, cat, cow, dog, ferret, giraffe, harbour porpoise, horse, human, lion, mouse, naked mole-rat, rabbit, rat, ring-tailed lemur, and tiger. The investigators found that all these mammalian species end their lives with roughly the same number of somatic mutations. The shorter the lifespan, the faster the annual rate of mutations. Thus, a mouse which live on average 4 years undergoes 800 mutations a year while the longer an animal lives the less mutations per year – dogs averaged 250, lions 160, giraffes 99, and humans 47.
While the correlation is striking the explanation is still opaque. It appears that the more mutations, the more opportunity for one or more things to go bad resulting in somatic mischief. Thus, the slower the mutation rate the better off the organism is regardless of the mechanism responsible.
Another issue is ‘Peto’s Paradox’. “A decades-long hypothesis on the evolution of somatic mutation rates pertains to the relationship between body mass and cancer risk. Some models predict that the risk of cancer should increase proportionally to the number of cells at risk of transformation. However, there appears to be no correlation between body mass and cancer risk across species. This observation, known as Peto’s paradox, suggests that the evolution of larger body sizes is likely to require the evolution of stronger cancer suppression mechanisms. Whether evolutionary reduction of cancer risk across species is partly achieved by a reduction of somatic mutation rates remains unknown.”
The mechanisms responsible for ageing seem a scientific problem capable of solution. The NIH has an entire institute devoted to it. While laboratories are working on the problem with speed and intense focus, there doesn’t seem to be much attention directed at what the solution to this problem will impose on human society. Ask yourself what would happen to the planet were eternal youth available? Who would get it and at what cost? How many Green New Deals would we need?
