The mathematics of immortality

Imagining a world where we could cheat ageing and cure disease

By Nicholas Folidis

Immortality has been a subject of imagination in popular culture for many years. From novels like José Saramago’s “Death with Interruptions” and Oscar Wilde's "The Picture of Dorian Gray" to movies and TV series such as “Groundhog Day,” “Peter Pan” and “Doctor Who,” death and immortality have a central role in our cultural narrative.

Ageing has been a natural part of life since the beginning of the Universe. However, that has not stopped scientists embarking on efforts to try and find the secret of eternal life or ways to reverse or slow down the natural process of ageing.

Over the last five decades, life expectancy has increased dramatically and the population has more than doubled worldwide. For every 150,000 people that die roughly every day all over the planet, around 360,000 more people are born. Advances in medicine and technology within the last 50 years have significantly improved our quality of life by curing diseases and making healthcare and lifesaving treatments more widely available. Despite all the efforts of the scientific community and the advances in science, only two diseases, according to the World Health Organization, have been completely eradicated; smallpox and rinderpest.

Nevertheless, one cannot help but wonder what would happen in a world where all diseases could be eradicated.

Scientists believe that even if we managed to cure all diseases and we never suffered any serious injuries, we would only manage to extend our life expectancy by a few more years and, eventually, we would still die due to ageing. So why hasn’t evolution put a stop to the process of ageing?

Our evolutionary history has always depended on a continuous race against the pathogens that plague us. Evolution is all about organisms surviving long enough to reproduce and create more offspring for the continuation of their species. This constant battle has, over the years, ensured the survival of the fittest and weeded out traits that make organisms more likely to die. Human intervention to the process of natural selection may have a negative effect on our evolutionary robustness, although there are no certain indications that this would be the case.

Furthermore, according to researchers at the University of Arizona, immortality is mathematically impossible for complex multicellular organisms, like humans. It all comes down to two major changes taking place in ageing cells: the cell growth rate slows down, making cells more sluggish and poorly functioning – a process known as senescence – or cell growth rate speeds up, causing cancer cells to form. Controlling either one of these two processes will negatively affect and eventually enhance the other. If we manage to stop cells from slowing down, we could get rid of problems like wrinkles and grey hair, but fast-growing cells will take over and eventually kill us; if we manage to stop cancer cells from proliferating, poorly functioning, sluggish cells will accumulate and, again, kill us. This means that human beings would either die due to a cancerous growth or the failing of cells, which would eventually lead to the dysfunction of organs.

Scientists have also investigated, at least in theory, the possibility of extending human life by cheating ageing. There are, after all, examples of various organisms that can live for hundreds – even thousands – of years. By making cells healthier with the help of insulin signalling genes, for example, natural selection could be forced to choose these healthier cells over non-functioning ones.

Another avenue that has been explored is the prevention or reversal of the shortening of telomeres, the regions at the ends of our chromosomes that protect them from fraying and fusing with neighbouring chromosomes. Telomere shortening occurs as our cells continuously divide and age, until they become unviable. This phenomenon of growth arrest after a period of normal cell proliferation is known as the Hayflick limit. When cells reach their Hayflick limit they then enter a senescence phase before eventually dying. The process of telomere shortening could be reversed with the use of the enzyme, telomerase, which counteracts the shortening of telomeres and is active in normal human stem cells and reproductive cells. Unfortunately, however, telomerase is also active in most cancer cells and allows them to replicate indefinitely, without their chromosomes getting damaged, which is what leads to the formation of tumours.

Although, there is a lot more research that needs to be done in order to better understand biological phenomena such as ageing, that probably will not help us to avoid death. We can definitely improve the quality of human life, and some scientists predict that the average life expectancy will continue to increase; however, for now the best we can do is embrace the finite time we have and make the most of it.

From Issue 17