Or – too much of a good thing, why something useful when you’re young could harm you later, or basically – the rule that there is a trade-off for everything, nothing is free when nature puts on price tags.
The antagonistic pleiotropy hypothesis is the one proposed by George C. Williams in 1957 as an explanation of senescence or bluntly – why cells and organisms get old and die. Pleiotropy means that one gene determines more than one trait in an organism and at least one of these traits is beneficial and at least one is detrimental. Something that gave you an edge over the otters when you were youngermight come back to bite you on the bottom later on in life. It is believed to be a solid explanation to why we age and why our health deteriorates so rapidly in old age. Because death comes as a necessary side effect of the depletion living brings.
Although there are some species that are “immortal”, which just revert back to the larval state and get young again, it would seem that evolution favours aging. Evolution is a practical lady, concerned with the matters of utmost importance such as continuing on the species and “wanting” to see them thrive. So to evolution you’re most valuable young and ready for procreation and most of genetic mutation that interfere with the development of young organisms towards sexual maturity are weeded out as they fly right against the prime directive. But once you’ve had enough time to have offspring and to raise them until they are able to take care for themselves the number genetic errors rises dramatically. If there is a predisposition in your genetic material for heart disease at 50-60 it is far more likely it will manifest than if there was a proclivity for it at 20. The latter would have been cleaned out from the genetic material. Getting old is a way of relocating resources to the young + you can’t transfer your longevity epigenetics once you can’t procreate any more. Getting old is a drawback of the fitness and abundance of energy when you were young and fertile, where temporary benefit is favoured over permanent damage. Another example is the benefit-cost wobble of a lot of sun exposure. In the short term you’d get a flood of very important and beneficial vitamin D synthesis, yet in the long term the accumulated damage from the sun’s radiation will create irreparable damage to your skin and chromosomes, tear the collagen, and up the chances for disease. We always pay somewhere and nature plays more cruel and more fair than any other man concocted market. You’ll rarely get a free ride, lucky break or an advantage over the others in your species without paying the bill for it at some later time.
It also seems that our enhanced contemporary standard of living, with better hygiene, more resources and medical care is not the only one responsible for a longer lifespan. As we have children later in life our own lifespan lengthens. Experiments have been done with fruit flies where if you don’t let them have offspring for a while, they simple live longer to compensate and after 700 generations they lived four times as long. So age is not a restriction on the body’s cells but a scales game of pros and cons and nature determines the base line. There seems to be correlation of us having children later in life and intelligence, as almost all who have children later are highly educated and intelligence predicts the desire to pursue higher education, so natural intelligence is starting to be slowly favoured by evolution, which makes the new generation also have children later in life than previous generations. Who knows what will happen in another 700 of our generations – we might even breed ourselves a few who could be intelligent enough and live long enough to figure this dying thing out, but for now all living things got the short end of the stick… which is not that bad considering that we at least got a chance to play with sticks and be alive for a few decades. Make them count.