What happens to people when they age? Why do we get old and die?
Over the millions of years of evolution, most living organisms have been programmed to reach the pinnacle of their capabilities at the ages when they reproduce. Such organisms can be regarded as having completed their mission after they have reproduced and the next generation has reached maturity. The same is true of human beings. Our hard drive, by which I mean our genes and the way they are connected with one another, achieves optimal fitness between the ages of 25 and 40. Evolution doesn’t concern itself with what happens after that (except for the low evolutionary utility of the grandparents helping to bring up the grandchildren). So aging begins after the reproductive years have passed. The nerve cells in the brain begin to lose their plasticity and stop forming synapses, stem cells stop dividing, and the ability of organs to regenerate themselves decreases. Simultaneously, the number of mutations and defects increases. In the meantime, proteins clump together and toxic substances lead to chronic inflammation in nearly all body tissues. Aging begins when this loss of cell and organ functioning sets in.