Natural selection does not explain all traits of all organismsby John Tyler Bonner / August 21, 2013 / Leave a comment
It is hard to explain the huge variety of diatoms—a microorganism that has 100,000 species—in terms of natural selection, says Bonner
There are good reasons why natural selection has become widely accepted as an explanation of evolutionary development. When applied to mammals and other large animals, it fits perfectly. But we cannot assume that all evolutionary steps arise from selection, particularly when looking at smaller animals.
The reason for natural selection’s great success is that it provides a satisfying explanation of how evolution might have occurred: individual organisms vary and if those variations are inherited, the successful ones will survive and propagate and pass down their desirable traits to succeeding generations.
But this process alone does not explain all of evolution; all it can claim is that it could do so in theory. To argue for its total universality one would have to prove that each instance of a trait that characterises such a step in evolution arose through selection. This is an impossible task. It has been shown that indeed this has occurred in many instances that have been examined—the assumption that it is true for all traits of all organisms is more problematic.
What happened in the last century was a deserved blossoming of Darwin and his theory of natural selection, which led to a popular form of ultra-Darwinism: the idea that natural selection did everything. This became the only view—I know this because, along with every other biologist, I succumbed.
Evolutionary biology differs substantially from other branches of biology, including my own area of expertise, developmental biology. I do not mean that the objects of study differ; I mean that the attitudes and psychology of the practitioners is different. One generally assumes that all scientists work on the basis of an identical “scientific method,” whereby a scientific statement is accepted or dismissed according to confirmation by experiment. But they do not.
Biology is riddled with assumptions, hypotheses, guesses and models, as we try to paint as rounded and complete a picture as possible. Scientists fill in the unknown gaps with conjecture. In today’s literature, one of the most common phrases is, “these data suggest…” which is followed by a guess. All science is expanding and it grows with a mixture of new facts and evolving speculations.
The view that natural selection accounts for every feature of all…