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9. DEATH Previous | Next

Evolution’s problem with self-destruction

WHY do living things die? Obviously, things kill each other – that’s part of the natural order. But what causes “natural” death? It is a question that splits biologists. It has become like a game of ping pong – over the years, theories have been batted back and forth as new evidence comes to light.

One answer is that death is simply necessary – to avoid overcrowding, for instance. But evolution doesn’t – can’t – select for a “death switch” because evolution is supposed to be all about the individual. And yet there does seem to be a death switch – researchers have managed to locate genetic switches that massively extend the lifespan of some nematode worms.

That might seem a long way removed from where we’re at, but there are vertebrates that live a very, very long time. Blandings Turtles, just don’t seem to get old and decrepit, for example. Teasing out why that might be is a tricky job – but potentially worth it.

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#1 - Posted: 11/08/2008 06:23

I must have missed the class when the professor's argument made sense. In fact, I got in trouble for displaying logic, during a presentation, that showed how the "death switch" made our own personal lives better.  Maybe missing a few classes is exactly what I needed to get just enough Biology and not too much paradigm.  

Quite obviously, for a novel mutation to make its way through evolution, it needs to be passed on from the parent.  But if a mutation causing a cell to die is to be selected for, it must be passed on at the time of reproduction. Long term effects on the individual aren't always of importance. Recall that the Salmon dies shortly after spawning. Surely his novel gene made it to the roe, or it would be lost.  So why the immediate death then? I don't think this is the right question. "Why should the animal live longer?"  is the question. It turn out that there is no benefit to live longer. Even if the organism could adapt to live longer, at that point, the selection to do so is lost. Sometimes the ability to live longer ensures the proper maturation of the young. This is easy to understand. So why do the "death genes" exist then? Because they also help the chances of survival of the young, and/or the individual itself. Biology is definitely conservative. The proper message to allow programmed death for effective development may just be the same gene that causes death.  Don't forget that we are living twice as long as our great great grandparents. And at the same rate, cancer is a rising consequence. Somehow a little internal cell death doesn't seem so bad now does it. 

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