In an earlier post in this series, I listed the three stages involved in natural selection, each of which seemed to have seemingly small probabilities. In the previous post, I showed how because of the large numbers of organisms and long time scales involved, the first item got converted into a very high probability event.
The next item in the list, the issue of how a mutation with a small advantage in the properties of an organism can end up with that property dominating the species, was both Darwin’s greatest challenge and his greatest triumph.
The triumph came from a crucial insight that Darwin had concerning the importance of varieties within species. Recall that Platonic ideas were dominant at that time, and that laid the emphasis on the idealized forms of things. So for example while a real triangle drawn on paper would contain imperfections, these were considered incidental, the drawing being a mere approximation to the idealized triangle that one could envision in some abstract space.
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There is a strong (negative) correlation between infant mortality and life expectancy, as can be seen from this graph, where each dot represents the data for a country, along with a linear regression line. The implication is clear that the best way to improve life expectancy is to reduce infant mortality. The reason that many developing countries have high infant mortality rates and resulting low life expectancy is that lack of access to clean water results in diarrhea and this leads to dehydration, which is often fatal for infants. (As an aside, the international conglomerate Nestle deserves widespread condemnation for its