[robbedpeter]

One end of the spectrum of reasonable possibilities is that evolution selected for genes that cause and or favor death the older an organism gets, through implicit mechanisms like lack of regenerative capacity, such as heart tissue, or explicit mechanisms, of which I'm not aware of any. Are there any genes that explicitly produce a timing mechanism, and thereby create a built-in notion of aging?

To my knowledge, it's all implicit, resulting from wear and tear, the gradual degradation of DNA because of the nature of chemistry on the surface of the planet, and not because any gene or biological mechanism moves an organism through some programmatic notion of mortality.

This seems true to the extent that given molecular level control of an organism, current knowledge would be sufficient to maintain lifespan to an arbitrary degree. Barring sci-fi nanotechnology, genetics and anti-aging have to figure out more robust repair and damage prevention to extend lifespan.

[cantrevealname]

> Are there any genes that explicitly produce a timing mechanism, and thereby create a built-in notion of aging?

Yes, telomeres.

Telomeres set a count on how many times a cell can divide before it ceases to divide and becoming old and useless; in humans, the count is 40-60 divisions and then the cell essentially dies.

There may be other timing mechanisms that haven't been discovered as well.

[outworlder]

It's less of a timing and more like of a "TTL" of a network packet. If you don't divide you don't use them up, even if you could live a thousand years. If you keep dividing like crazy, it will eventually reach useful DNA and the cell will die.

They seem to be quite specifically an anti-cancer measure.