Why do we die?

I was listening to the Infinite Monkey Cage  on Radio 4 with Brian Cox and Robin Ince.  I’m normally at work when it is on and so it was a rare treat.  Yes, I know it is available as a download and I would certainly recommend it if you haven’t had the chance to hear it. 

They were talking about how to define if something is alive or dead and why animals and plants die.  There were lots of very circular arguments and plenty of laughter to go with them.  That’s the point of the show.  The general conclusion from the studio panel was that death had something to do with sex, or at least procreation as all evolution does.

Of course my mind wandered and I got to thinking that if immortality was an evolutionary advantage then surely some species would have cracked it by now.  There are some animals and plants that live an awfully long time by our standards but not for ever and so I quickly came to the conclusion that it must be death that has the advantage and not immortality but how can this be?  How can the act of not surviving help your species to survive?

Evolution is often referred to as an arms race where competing species need to strive constantly to be one step ahead of each other.  The hunter gets faster or more cunning while the hunted gets even faster or harder to swallow.  Species evolve with each other to the point where they are caught in their own symbiotic existence with neither being able to live truly without the other.

But this arms race depends upon changes in the genetic make-up of species that are passed on through the reproductive cycle.  Animals and plants need to breed and procreate in order to give birth to the next generation that can out run or out smart its predators.  So if you were a species that was immortal, your current crop would be consuming all the resource that any new offspring would require yet would have all of the outdated genetic material within its cells.  They would be last season’s model and if all available resource was being consumed there would be little or no incentive to replicate. Any mutated predator that came along with even the slightest of advantage would be devastating indeed.

So long ago all species must have been selected for the very characteristics that make them get less able to breed as they get older and to eventually die.   Once reproduction is complete and you have more than replaced yourself then, from a biological and evolutionary standpoint you are surplus to requirements.

A sobering thought that could explain why most of my bodily functions are now heading south and why I won’t be living forever.

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