As mentioned yesterday I’m working my way through Matt Ridley’s Genome – I mean reading the book, not deciphering his actual genetic code – and it has taken me down some mighty interesting and often unexpected intellectual alleyways. Genetics and evolution have been subjects which have captured my imagination for some time, ever since reading The Selfish Gene for no apparent reason during my university years. The idea that so many facets of our lives can be captured by the phrasings constructed from a mere 4-letter alphabet, that this code has been around since the beginning of life on the planet and that it is shared by almost every living organism is beyond incredible. To people who decry science for snatching all the mystery and wonder from life I just say try actually reading some fucking science writing – it’ll give your brain a minor meltdown and you’ll never look at the world in the same way.
It does have its downsides however. A chapter optimistically entitled “Immortality” informs us of two of the main reasons why we grow old and eventually die – one due to our genes and which I’d never previously encountered, the other a simple consequence of natural selection, one which should be obvious but you’ve probably never though of before.
The genetic reason is little more than a pain in the arse. Basically the machines that copy our genes and transcribe them into proteins (I’m simplifying a tad here) can’t, for some reason, start at the beginning of the gene, instead skipping a few letters and effectively chopping them off. For this reason the genes get progressively shorter with each copy and this obviously will lead to malfunction and cell death in the future. Now our systems are a bit smarter than that and have tacked on bits of code called telomeres to the start of the genes – essentially senseless repeating chinks of code which serve no apparent purpose other than being sacrificed every time a copy is made. A plentiful supply of telomeres means the information can be replicated a healthy number of times before we start eating into the useful parts.
The bad part is that there isn’t always enough to last the distance. The example Matt gives is of arterial tissue. It spends its existence under extremely high pressure, much more so than encountered by veins, and as such requires constant repair and constant genetic copying. This means telomeres run out rapidly here, arterial tissue dies and thus we die of hardening of the arteries rather than of the veins. Our death is written into our genes (okay, so that’s a gross oversimplification).
The good news is that there’s an enzyme called telomerase whose job is simply to add extra telomeres to genes, to keep them going. The bad news though? Telomerase is absolutely vital to keeping cancer cells multiplying like viagra-infused rabbits. It’s a no-win situation.
Now for the second reason, and this one is actually quite funny in a grim kind of way. We all know how natural selection works right? All that ‘survival of the fittest’ stuff was complete bollocks and it really means that genes whose vehicles (i.e. our bodies) survive long enough to reproduce and create healthy offspring which themselves reach reproductive age will generally increase in proportion in the gene pool. Or words to that effect.
What follows from this? Well, basically any gene that positively affects your chance of survival through reproductive age to the point where your offspring are no longer dependent on you will be positively selected for. Any genes deleterious to that end will soon disappear. Common sense really.
But what happens after that age? What about those years when you’re finished with the kids and fancy a long, relaxed retirement, perhaps a bit of study or travel, maybe nothing more than chilling in the garden and the odd pint down your local? Tough. Beyond the point where the chicks leave the nest there is no longer any selective pressure whatsoever. Natural selection no longer gives a shit because you have become, to all intents and purposes, a useless meatsack. All manner of nasty genes can feel free to invade your chromosomes and as long as they don’t switch themselves on till your autumn years they’re given free rein and there’s not a damn thing you can do about it.
So what do we take from this lovely Sunday sermon? Well, nothing particularly new to be honest. The ‘knowledge sucks’ part of the title is a little facetious because actually this knowledge should spur us on to bigger and better things. Much like the knowledge that there is no afterlife, reincarnation, etc what it really tells us that we have one shot at life and, barring some utterly amazing advances in medical knowledge over the next few decades, it’s a frighteningly limited shot at that. It’s therefore incumbent on us to make the most of it while we’re still around, to stop procrastinating and making excuses, to do things now because we do actually have a limited number of tomorrows – not a predestined exact number but not far off it.
PS If anyone wants to crochet a moustache hat for me I’ll be eternally grateful. I mean oral-favours grateful…