Evolution: fish select for the survival of the fittest

An important breakthrough has been made in determining the forces responsible for the evolution of populations in nature. By studying wild populations of grayling (a close relative of salmon), Mikko Koskinen and Craig Primmer at the University of Helsinki and Thrond Haugen at the University of Oslo found that natural selection, a force suggested by Charles Darwin in `The Origin of Species`, was responsible for up-to 90% of grayling evolution.

In their study, published in Nature on October 24, the team stated that their findings were in fact the reverse of what many people expected: As the grayling originated from a common source only about a century ago and were very small in number, a random process known as genetic drift was expected to be the driving evolutionary force. However, by comparing the evolution of important biological features of the fish (such as growth rate) with the evolution of sections of DNA not affected by natural selection, the team found that natural selection was in fact much more important than genetic drift. This finding agrees with the hotly debated view of a British geneticist Sir Ronald Fisher, one of the founders of the field of population genetics.