If our bodys renew itself all the time - why do we grow old, why does it decide to just die?
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The human brain doesn't renew itself. It starts dying from about the age of twelve. It has plenty of spare capacity but eventually we cannot continue.
The selfish gene theory, suggests that we exist to perpetuate our DNA. Under this theory once we have produced children, and natured them to adulthood, we have served our purpose. Its a miserable view of the world which I don't agree with. Our relationship with the world is far more complicated than that.
Interestingly in the ocean's there are creatures which never grow old. It is impossible for us to know how old they are because of this.
Body does not renew itself all the time. The process slows down with the age which is called decay. The decay ends up at death.
Yes, we're programmed by our genes to do that.
The body changes with aging because changes occur in individual cells and in whole organs. These changes result in changes in function, in appearance, and thus in the experience of aging.
As cells age, they function less well. Eventually, they must die, as a normal part of the body's functioning.
Cells may die because they do not divide normally or because they are damaged. Cells may be damaged by harmful substances in the environment, such as radiation, sunlight, and chemotherapy drugs. Cells may also be damaged by certain by-products of their own normal activities. These by-products, called free radicals, are given off when cells produce energy.
Many cells die because the genes they contain program a process that, when triggered, results in death of the cell. This programmed death, called apoptosis, is a kind of cell suicide. Reasons for cell suicide include replacing old cells with new ones and eliminating excess cells.
Also, cells die because they can divide only a limited number of times. This limit is also programmed by genes. When a cell can no longer divide, it grows larger, exists for a while, then dies. The mechanism that limits cell division involves a structure called a telomere. Telomeres are used to move the cell's genetic material in preparation for cell division. Every time a cell divides, the telomeres shorten a bit. Eventually, the telomeres become so short that the cell can no longer divide. The telomeres of cancer cells, unlike those of normal cells, do not shorten each time the cell divides. Consequently, cancer cells can divide forever.
Different cells do renew themselves, but less efficiently every time.
So skin loses its elasticity, hence wrinkles, hair loses its colour, bones find it increasingly difficult to replace lost calcium, in short ageing takes place.
The exception to this is the brain, which loses cells at an astonishing rate after maturity, so as we grow older we get slower mentally.
Eventually somewhere or other along the line vital cells cease to function and we die.
There isn't a 'body-clock' as such, just myriads of 'cell-clocks' if you like.
As for living forever, science has made so many incredible leaps forward in the past 40 years that it would be fool who who say definitely either way.
But when you are young, which I guess you are, the thought of living for ever seems attractive.
But as you get a lot older, which I am, it's not as attractive as you might thin k.
We don't renew ourselves all the time. When you're young and healthy, your cells do regenerate. But that process slows as you get older. Science is advancing in anti-aging products. Our life expectancies have gone up compared to previous years because of medicine and science. And every day it seems they learn something new about preventing aging. The best thing you can do for your body is eat healthy (lots of fruits, veggies, and whole grains) and exercise. The compounds in healthy food actually tell your cells to replicate. But eating trans fats and other harmful things tells your cells not to replicate. So take care now and you'll live longer.
The body renews itself but it is coded into our DNA that renewal slows down and eventually stops. Not all body parts continually renew themsleves. Brain cells start dying pretty early and just keep reducing with age. Some disorders cause it to happen faster (Parkinsons). Death is coded into our DNA and it's unlikely we'll ever be able to remove it. Also removing it wouldn't be very helpful. The earth can't support unlimited human inhabitants. Living forever would defeat progress since evolution would become impossible. Also it would be rather boring. I guess you've heard of stem cells. Well stem cells from a fetus can become any other sort of cells. They are therefore capable of completely renewing any damged parts. Stem cells in adults on the other hand are very limited in what they can become. That's why when you get a cut and it heals it forms a scar instead of forming perfect new skin. Also many people suggest that the part of our genetic code that controls aging also connects with reproduction. It's actually quite simple and based on observation. Animals with longer life spans get sexually mature at a later age and have fewer young. Animals that have shorter life spans have more young and mature faster. Some say this is simply because they need to. Of course that's a fact but there is a possibility that they live longer because they mature later. Anyway, the kind of advancements you are speculating about will probably not happen and definitelt not in our lifetimes.
Many cells don't work like this, for example we are born with our full compliment of brain calls. We then loose some every day and there are no replacements. Additionally we seem to have a built in obsolescence and we get older replication becomes less perfect, our skin for example ages visibly with loss of elastic tissue.
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