Human beings (and other living things) are a complex arrangement of cells. Cells reproduce through division. However, cells cannot go on reproducing forever. The capacity of a cell to undergo division is known as its Hayflick limit. Human cells can divide only about 50 to 60 times. After that, the cell goes into senescence: it becomes weak and dies.
Certain lifeforms have a very high Hayflick limit. For example, cells of the Galapagos tortoises have a Hayflick limit of 110 — one of the reasons that these turtles can live up to 170 years of age. Lobsters live for well over one 100 years. The oldest specimen of a certain type of clam was found to be 405 years old!
Researchers are studying such creatures to understand the secret behind their longevity. In future, scientists might succeed in developing genetic technology that’ll allow humans to live 200 years or even longer!
Every cell has a built=in biological clock that can run for only about a certain period of time. So this might sound a bit depressing, but we are all programmed to eventually grow old and die. The nuclei of our cells contain chromosomes, which are a kind of genetic code. Chromosomes are long thread-like structures, much like a shoelace.
Just as a shoelace has plastic bits at each end to protect it, chromosomes too are protected by ‘caps’ which are known as TELOMERES. Every time a cell undergoes division, the telomeres become a tiny bit shorter until they are no more.
You have probably noticed that when the end bits come off a shoelace, it becomes frail and useless. Similarly, without telomeres, our chromosomes begin to disintegrate and die.
Scientists have discovered that certain lifeforms (a type of jellyfish, some kinds of corals) produce large quantities of the enzyme telomerase and hence their telomeres do not shorten upon division. Technically, this renders these creatures immortal!
By this principle, if human cells had enough telomerase, they would keep reproducing forever and humans would become immortal too. Sadly, all of this is just a hypothesis as of now.
Telomerase is a double-edged sword. Cancer cells use it to reproduce uncontrollably. This results in ever-expanding tumours which interfere with the functioning of organs and ultimately cause death.
If human cells had a never-ending supply of telomerase, it is likely that they would become cancerous. Despite the risks, telomerase research is considered to be a breakthrough in genetic engineering. It is highly possible that in future, this knowledge will help humans to increase their lifespan.
We’ll now quickly touch on some other theories of aging.