What Are The Arguments Against Random Genetic Drift

Most of us are familiar with natural selection as one of the mechanisms of evolution. Another well-known mechanism is random genetic drift. This is a mechanism that results in fixation (or loss) of alleles by purely random processes. The topic is thoroughly covered in all the major textbooks—it is not controversial. Unless you deny the existence of random genetic drift, you must agree that some of evolution is entirely due to chance events.

The controversy is over how much of evolution is due to drift and how much is due to natural selection. Excellent arguments have been advanced to prove that most of evolution is due to random genetic drift and that's the position I take. Thus, in a discussion about the role of chance and accident in evolution I would say that most of evolution is accidental because of the frequency of drift vs. selection. Note that this says nothing about the perceived importance of these mechanisms. That's a value judgement. Some evolutionists think that adaptation, or evolution by natural selection, is the only interesting part of evolution. These evolutionists don't deny that random genetic drift occurs; instead, they simply relegate it to the category of uninteresting phenomena. Others, like me, think that random genetic drift is far more interesting than natural selection because drift is responsible for junk DNA, molecular phylogenies, molecular clocks, and DNA
In some cases this is because they don't even know about drift. Those people are easy to spot because they usually reveal their ignorance of evolution in other ways. In other cases the chance-deniers are well aware of the existence of random genetic drift but they choose to define it out of evolution. Sometimes they specifically say that evolution by drift isn't really evolution. More often, they will use terms like "Darwinism" to describe