How long will you live? 10,000 years ago, the average human life lasted just over 30 years, and then a hundred years ago that number was up to 50. If you were born in the last few decades in the developed world, then your life expectancy is 80 years. But that is of course assuming that no major breakthroughs happen during your lifetime that can slow the process of aging.
That may be a very bad assumption.
According to Dr. Fiona Ginty, aging is not always recognized as a disease. There are plenty of diseases we do acknowledge like diabetes, heart disease, and Alzheimer’s. At their core, aging may be responsible for all of them.
And yet aging seems natural because it’s something that we do from birth and for a while it makes us better. Bigger, stronger, faster, more intelligent. But then at some point in your life it reverses and aging makes our bodies decay and degrade.
Why do we have to age?
Scientists are now realizing there is a fundamental cellular mechanism at the heart of aging. Do we age at the macroscopic level because our cells are aging at the microscopic level? To a great extent, yes. There’s only a finite number of times a eukaryotic cell will divide.
The key discovery was made by a biologist named Hayflick. Like many biology tutors, he was studying normal human cells. He found that they can only divide a finite number of times, usually about 50. Beyond that, the cell becomes senescent, which means it’s an aged cell. It can divide no longer. It lives for a little while but it’s the accumulation of these senescent cells in our bodies that leads to aging on the macroscopic scale.
So it’s as though cells have this little timer inside them that tells them when to stop dividing. But how do they know, and what is that timer?
According to Dr. Ginty, “telomeres are like how your shoelaces have a little bit of plastic at the end to stop them from fraying.” So when your telomeres wear out, the chromosomes stop multiplying. When they work, they keep the chromosome together and stop them from sticking to other chromosomes. Dr. Ginty explains that every time a cell divides, it loses about 200 base pairs of telomere due to the mechanics of the action. “There’s only so much space when DNA polymerase does its job of replicating when it’s copying.”
So the telomere getting shorter is like your molecular clock. The cellular clock inside each cell that tells it how many times it has divided. Would you want to have your telomeres measured?
Well, we can at least lengthen our telomeres!
There have been associations made with lifestyle and exercise showing that longer telomeres are associated with a more active lifestyle.
If we could stop the telomeres from shortening, maybe the cells would live forever. There’s another enzyme involved called telomerase, and it keeps rebuilding.
Telomase rebuilds the telomere, and there is one animal that doesn’t seem to age—the lobster. It just gets bigger over time. It doesn’t get weaker and its chromosomes don’t change. It has long telomeres that do not shorten, so it only dies when it gets eaten by something else like a human. So how can we be more like a lobster?
Well, that answer is a little complicated.
Unfortunately, cancer is a perfect example of telomerase being hyperactive. In the end, it becomes an unregulated growth situation. —This is the double-edged sword of telomeres and telomerase. Cancer cells have really long telomeres, and they can divide indefinitely, and that is the problem with cancer. Cancer is dividing cells that won’t stop and they won’t die. So, in a way, cancer is the immortal cell living within us.
So maybe we have telomeres that shorten for a very good reason; otherwise they could become cancerous. One of the theories there is that the cells divide that limited number of times because it stops them from accumulating damage that may be detrimental. Telomeres might stop cells from becoming cancerous.
Over the past hundred years, developments in medicine have increased human lifespan more than we could have imagined, and I can only expect that the next hundred years will bring similarly incredible results. I’m not sure where or how they will take place, but you can bet that your life expectancy today will not be the actual age at which you die.
Original content by Veritasium