Why We Age and Die

Many scientists are studying the pathways involved with the aging process, or as I like to think of it the breakdown of the “keeping-our-cells-young” process. Why do these processes break down in the first place? This is where you get the evolutionary process. There is no evolutionary benefit to an infinite lifespan in a natural setting. The environment changes all the time as continents move, the sun brightens and dims, the Earth’s rotation around the sun changes, impacts of space objects, and innumerable local condition changes such as landslides, droughts, floods, fires etc. The inability to change and adapt to a different environment would mean death. It is harder to change if you have a long lifespan, because change involves more than just rearranging the genetic bits you have but creating new ones as well. Animals don’t have the natural ability to change their DNA throughout the body. Changes in DNA can only be passed on to offspring. Depending on how fast you have to change your lifespan is adjusted accordingly.

Once one starts having offspring the only things that matter are getting them to reproductive age and having them reproduce. Natural selection breaks down after this. A few examples in humans (in caveman days):

1) A mutation that causes your death at 20. You have already likely passed on your genes to offspring but are still very important to their survival to reproductive age. This mutation has some pressure be selected out because your kids won’t survive as well without you around.

2) A mutation that causes your death at 30. You have already passed this gene onto your offspring, but a couple of them have reached or are almost at reproductive age. Less pressure for this mutation to be selected out since at least a few of your kids should get along fine without you around.

3) A mutation that cause your death at 40. Most of your offspring have started reproducing and are getting along fine. Very little pressure on this mutation since if you die most of your offspring should be fine.

4) A mutation that causes your death at 50. Some of your offspring’s offspring are reproducing. Virtually no pressure on this mutation. If you die now it is unlikely your death will affect three generations.

As one can see it’s hard to get natural selection to "care" about imortality. Eventually there will be something "wrong" with you that will manifest itself. However, the clever apes that we are can fix this. We can fix it one of two ways. We can fix the DNA either as it is broken, or fix the inherent problems with the genetic code since evolution only got us so far. The second way is to develop drugs or treatments that will either force the cells to fix their DNA or mediate the processes that lead to aging. It is just a matter of time.