The immortal MRS GREN
The teaching of the biological sciences begins with a consideration of the characteristics of life. In the memorable form of MRS GREN, the National Curriculum suggests an acronym that can be drilled into fresh-faced secondary school students to enable them to recite these characteristics on request (i.e. in a GCSE examination). My rather over-zealous biology teacher, however, had formed his own longer and less memorable acronym, DOCMERRING (1). In a rather macabre way to start thinking about life, the ‘D’ (not present in MRS GREN) stood for death - all things of flesh and blood perish.
Why do we grow old and die? Jared Diamond, in The Rise and Fall of the Third Chimpanzee, summarises:
We constantly invest resources in the repair of our bodies, just as we do with our cars. Unfortunately for us and for all other animals, there is a limit to the resources that natural selection found it worthwhile to programme into our self-repair [whilst maximising our reproductive output]. As a result, we eventually grow old and die, but at least we age more slowly than our ape relatives. (2)
Yet humans have never been satisfied with their three score and ten years, and tales of great feats of longevity have been celebrated throughout history - like that of Methuselah, who is quoted in the Hebrew bible as being 969 years old when he died in the year of the Great Flood (Genesis 5:27). Moreover, according to Kant, ‘God, freedom, and immortality are the three great objects of speculative thought,’ although his ‘immortality’ is an ethereal one.
Caloric restriction, ageing and pha-4
As far back as the 1930’s, a link between caloric restriction and longevity has been known: mice subsisting on a calorie-restricted diet (reduced food intake but still healthy) have been shown to live longer than those on a normal diet by up to 40%. Only now though, 70 years later, does a new study from the Salk Institute in California provide the link between caloric restriction and longevity (3). Using the nematode worm, C.elegans, a workhorse of modern cell biology, researchers have found that a gene called pha-4 plays a key role. Loss of this gene resulted in worms that showed no enhanced longevity while on the calorie-restricted diet; conversely, over-expression of the gene (putting in more copies) led to a significant increase in lifespan. Dr. Dillin, the principal investigator, explained that, “Pha-4 may be the primordial gene to help an animal … live a long time through dietary restriction conditions.”
The pha-4 gene has orthologues (relatives) in humans and the identification of this link between caloric restriction and ageing may allow the development of drugs that mimic the effects of a calorie-restricted diet without having to forgo your double cheeseburger with fries.
Immortality: not what Nature intended
Steve Connor, reporting in The Independent, has hailed pha-4 as “the gene that decides how long we live”. That’s a little simplistic, though. This discovery, by itself, is also not going to allow the human race to realise immortality any time soon, but perhaps, with stem cell therapy developments and the like, one day we might.
But would immortality be such a good thing? It may be because I am an atheist but I have nightmares over living forever in Heaven; living forever on an imperfect Earth is positively terrifying!
A solemn appreciation of death brings meaning to one’s life. Mortality is a humbling condition and the knowledge of our future death allows us to put our lives into perspective and plan to give them meaning and substance. A life with no end would surely be a wretched one.
However, we have to put life extension in perspective. If a man on his death-bed were offered the opportunity to live for another 20 years, he may well say yes. If a man were asked at the beginning of his life whether he wished never to die, he may well have doubts. What is certain is that an ability to considerably enhance our lifespan above what is naturally possible, or in the extreme, become immortal, would leave us with a difficult decision of when to end it.
In a way, though, Nature, and its mechanism of evolution, has already provided us with an ability to achieve (impersonal) immortality through reproduction in our mortal lives. As Diotima explains to Socrates in the Symposium, “The mortal nature is seeking as far as possible to be everlasting and immortal. [Men hope that offspring] will preserve their memory and give them the blessedness and immortality which they desire in the future.”
1. DOCMERRING: Death, Osmo-regulation, Cells, Movement, Excretion, Reproduction, Respiration, Irritability (sensitivity), Nutrition and Growth.
2. Opening to chapter 7.
3. PHA-4/Foxa mediates diet-restriction-induced longevity of C. elegans Siler H. Panowski, Suzanne Wolff, Hugo Aguilaniu, Jenni Durieux & Andrew Dillin (2007) Nature Advanced Online Publication, doi:10.1038/nature05837