As it turns out, there are good reasons to believe we can or will be able to control our aging, at least to some extent and within the limits imposed by our genetic endowment.
Previous research done with a variety of lower animals has shown that their lifespans can be lengthened by caloric restriction — that is, by significantly limiting their food intake for periods of time. And this may well prove to be true for humans. However, because it would be unethical to conduct such experiments in humans, it will be more difficult to clearly demonstrate this effect in us.
But recent research has given us some additional clues as to why we age and thus opened up other possibilities for slowing the aging process. Some of these studies have focused on a tiny organelle that lives within almost all living cells of higher organisms. This organelle, called a mitochondrium, is thought to have been acquired early on in the evolution of life on Earth as a result of primitive cells ingesting a bacterium that could use oxygen to generate useful energy.
This bacterium, instead of being fully digested and destroyed by the primitive cell, set up residence there and became a mutualistic symbiont with its own genetic material. In turn, it provided its host with the ability (in an oxygen-rich atmosphere) to efficiently obtain energy from its stored calories. Thus was born an ancestor of all living plants and animals that rely on oxygen for life. An interesting aspect of these tiny organelles (of which there are many in each of our cells and which are inherited only from our mothers) is that they can digest themselves (a process called autophagy) when they become defective either from injury or disease. They are then replaced through the synthesis of new mitochondria (by a process akin to cell division). In much the same way, whole cells can and do replace themselves in various tissues of our bodies.
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