On the genetic roots of human disease

The New York Times carried this intriguing report by Nicholas Wade.

In brief: the theory used to be that some genetic mutations exert their bad effects only late in life, after people have had their children, and so were not eliminated by natural selection.  So some small set of common variants of genes were taken to underlie various diseases, and there was a hope that understanding the genes would lead to understanding the disease and from that to effective methods of treatment.

But improvements in genomics seems to show that very large numbers of rare genetic mutations are responsible for diseases.  So the situation is lots of genetic variants lead to common diseases, i.e., many different causes lead to similar effects.  The downside of this new understanding is that interpreting our genes is more difficult that we had hoped, that understanding and treating diseases influenced by genes is going to be hard.

At a meta level, it is interesting how such a simple and satisfying theory, and very respecting of Ockham's Razor,  is likely to be wrong.