Immortality

It is a well-known fact that humans and other developed lifeforms such as animals age and die. But is this inevitable?

This is a legitimate question because simple lifeforms are potentially immortal. For example, single-cell organisms 3.7 billion years ago multiplied by fission and were immortal if the environment was suitable. Nowadays, we observe a different picture: Humans, animals, but also seed-producing plants pass on the genetic information by sexual reproduction. The survival of a species hence did not anymore rely on the longevity of its members.

Nature decided that mortality is her favourite model, and ageing and dying is now programmed at the cellular level. And here is the science bit: Telomeres at the end of chromosomes shorten each time they replicate. After about 50 cell doublings, the telomeres are critically short, and cell division stops. This is today known as the Hayflick limit.

Is this the last word on immortality? Of course not. Nature has examples of animals we believe do not age: for some lobsters, the common cause of death is a disease, not old age. The most bizarre example is Turritopsis dohrnii, more commonly known as the ‘immortal jellyfish’. This jellyfish heals damaged areas by transforming its cells into a younger state, eventually overcoming the injury and growing into adulthood all over again. Even human cells can lose mortality: cancer cells are immortal if the conditions are right. But, as we all know, uncontrolled growth is not a healthy option and not a principle nature would want to advance for us any time soon.