And Finally by Henry Marsh

Author:Henry Marsh [Marsh, Henry]
Language: eng
Format: epub
ISBN: 9781473560970
Publisher: Random House
Published: 2022-07-08T00:00:00+00:00

12

I do not want to die – but then, who does? But nor, to state the obvious, do I want to become old and decrepit. It used to be thought that human life came with a fairly specific time limit and that there was something ‘natural’ about dying in your seventies, but trying to arrest or even reverse ageing is now serious science, and no longer the exclusive preserve of cranks or quacks. We are part of Nature, and everything we do – including all the technology that is so much a part of human life – is as natural as sex and trees. It is no good saying that trying to extend human life is against Nature, though whether it is sensible or not is a different matter. I find the idea of extending human lifespan appalling but can’t deny it is a prejudice on my part, which I must overcome, if only to understand the science behind it.

There are enormous differences in the lifespans of different creatures – from insects that might live a matter of hours to Greenland sharks and bowhead whales that can live for hundreds of years. Some – like the Galapagos tortoise – show few signs of ageing even in old age. There are various theories as to why we age, but they all must be accounted for in terms of evolution and natural selection, in accordance with Theodosius Dobzhansky’s famous dictum in 1973 that ‘nothing in biology makes sense except in the light of evolution’.

One of the main theories of ageing is ‘antagonistic pleiotropy’ – in simple terms, of evolutionary neglect. It is now understood that the same gene can have different effects – pleiotropy – in different circumstances. A gene which increases reproductive success in youth may have a damaging effect in later life. But this gene will be selected for and spread, despite resulting in cellular decay later in the organism’s life. Evolution by natural selection is simply a mechanism, but I am unable to avoid the pathetic fallacy of attributing purpose and intent to it. Natural selection has no interest in the sufferings of old age. It has abandoned me.

There are exceptions to this – there always are: fish, for instance, and, to some extent, humans, as we live much longer than other primates. Women live well beyond their reproductive age. The most plausible explanation for this phenomenon in humans is the so-called grandmother hypothesis. It seems that humans are unique (although there is evidence that whales might be an exception) in the way that grandmothers are involved in the rearing of the next generation, and it is suggested that this explains our long lifespan compared to other primates. Grandmothers enable their daughters to have more babies and so genes that prolong a grandmother’s life will be relatively successful compared to those that don’t.

Reproduction is not just about having babies, but equally about childcare, and doing our best to see that our children and grandchildren reach reproductive life themselves. If we do not take care to avoid danger and possible death, our children and our genes will not survive.

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