Really Sciency

Visit my other blog 'Really Sciency' looking at Climate Science and its portrayal, misrepresentation and denial in the media.

Saturday, 15 January 2011

Natural selection

 Most people, except probably the mis-educated or ignorant, accept that the process of natural selection, the main driver of evolution, exists. But how did it begin?

It isn’t very satisfying to just say, "So natural selection just happened”.

I believe the idea of natural selection has become a bit of a tautology; whatever is better at surviving and reproducing, survives and reproduces more than whatever isn't as good at surviving and reproducing. 

Once you have replicators and some source of variation, natural selection has to happen. The very scientifically interesting question is how the first replicators arose.

It is scientifically interesting because there are no definitive answers. There are plenty of hypotheses, but evidence about what actually happened is (understandably) difficult to come by (it is highly unlikely that they would have left physical traces).

So any anti-evolutionist will now jump in and ask; How did life come into existence if not by chance?

The concept of chance needs careful handling, as it's not straightforward. If you toss a coin over and over again indefinitely, you will eventually get a run of ten heads. Does that happen by chance, given that it's inevitable?

Some scenarios have a vast number of possible outcomes. Each one of them is highly unlikely, but one of them is going to happen. Whichever one it is, will it be reasonable to say after the event that the winning outcome is too unlikely to have happened by chance? To put it another way, the chances of winning the lottery are remote, but people win it all the time.

The concept of life also needs careful handling. It's not necessarily the case that there has to be a clear division between life and non-life. Purely chemical replicators exist. There could have been many intermediate stages that can't be classified by the usual definitions. Evolution by natural selection doesn't require life as we know it; it only needs replication and selection of some kind to be going on. 

Life as we know it could have evolved in a system which in some way met the requirements for evolution without containing anything that we'd recognise as a living organism.

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