Biologist Ann Gauger finds this reply wanting because it reduces evolution to the process of natural selection, but, as she argues in a piece at Evolution News and Views, there is more to evolution than just natural selection:
Evolutionists often challenge us for referring to Darwinian evolution as "random." They point to the fact that natural selection, the force that supposedly drives the train, always selects more "fit" organisms, and so is not random. That is only part of the story, though, and to understand why evolution can indeed be called random, the rest needs to be told.The last two aspects of evolution are natural selection, which Gauger acknowledges is not random, and environmental change, which is. Thus, she concludes:
Evolution can be considered to be composed of four parts. The first part, the grist for the mill, is the process by which mutations are generated. Generally this is thought to be a random process, with some qualifications. Single base changes occur more or less randomly, but there is some skewing as to which bases are substituted for which. Other kinds of mutations, like deletions or rearrangements or recombinations (where DNA is exchanged between chromosomes), often occur in hotspots, but not always. The net effect is that mutations occur without regard for what the organism requires, but higgledy-piggledy. In that sense mutation is random.
The next part, random drift, is like a roll of the dice that decides which changes are preserved and which are lost. As the name implies, this process is also random, the result of accidental events, and without regard for the benefit of the organism. Most mutations get lost in the mix, especially when newly emerging, just because their host organisms fail to reproduce, or die from causes unrelated to genetics. It can also happen that new mutations are combined with other mutations that are harmful, and so get eliminated.
The random effects of drift are large enough to overwhelm natural selection in organisms with small breeding populations, less than a million, say. New mutations are not born fast enough to escape loss due to drift. There is a fractional threshold in the population that must be crossed before a new mutation can become "fixed," that is, universally present in every individual. A new mutation generally is lost to drift before that population threshold is crossed.
The sum of all these factors is what is responsible for evolution, or change over time. Mutation, drift, selection, and environmental change all play a role. Three out of these four forces are random, without regard for the needs of the organism. Even selection can be random in its direction, depending on the environment.. The challenge for the proponent of naturalistic evolution, as opposed to proponents of some form of guided, or telic, evolution, is to explain how, against all odds, something as complex and specific as protein synthesis or DNA replication could have ever arisen purely by chance in the earliest cells. Any explanation that just assumes that it could have is ipso facto disqualified. There are no fairies waving magic wands allowed in scientific explanations.
So tell me. Is evolution random? Most of the processes at work definitely are. Certainly evolution won't make steady progress in one direction without some other factor at work. What that factor might be remains to be seen. I personally do not think a material explanation will be found, because any process to guide evolution in a purposeful way will require a purposeful designer to create it
