Wednesday, November 02, 2005

Some implications of probability bounds

It is argued that ID has little impact on anything in the world of “real science”. However, to consider at least one issue, there are some conclusions that can be drawn on the basis of work on probability bounds. The bounds place constraints on the starting point for evolution, and would perhaps assist in showing how evolution might happen – and also establishing whether evolutionary explanations are plausible.

For example, take as a starting point a random sequence of DNA bases. It is unclear from literature whether this is assumed to be a basis of evolutionary progress – whether having a random sequence of bases would be a starting point for natural selection. Actual proposed mechanisms by which novel proteins might appear is rarely addressed. But let's assume, for the sake of argument, that the engine of evolution is random DNA sequences which are then modified by natural selection.

However, three out of 64 of the DNA base codons code the STOP sequence – that is, if one of these codons is found, they will terminate a protein chain. Now, the probability of three bases NOT coding for STOP is thence 61/64 – or 0.953. The probability of two lots of three bases NOT coding for STOP is 0.953 squared – 0.908. The significance of the universal probability bound is that we can exclude chance as a reasonable explanation for an event if the probability of an event is less than this bound. And it turns out that the probability of 7000 lots of three bases NOT coding for stop is close to Dembski's conservative value for the universal probability bound of 10 to the power of -150.

In other words, we can exclude the possibility that a protein with a chain of over 7000 amino acids arose on its own. The likelihood of a DNA sequence of the required length arising at random can be excluded, using the universal probability bound – such a protein would have to arise by other mechanisms - perhaps as a consequence of adding together smaller components. Obviously, if as I suggested in an earlier post, higher probability bounds ought to apply to biological systems, then the maximum number of amino acids that could be present in a protein as a starting point for natural selection would be consequently smaller.

I would like to explore some further implications of the probability bounds in future posts.