An Open Letter to Teachers teaching Natural Selection

2012-03-07 11:35
There is a small controversy brewing over a teacher that is being prevented from teaching natural selection in science classes. Teaching students about natural selection shouldn’t be a problem. The concept of natural selection on the surface appears to be a rather simple concept to grasp. In its simplest form, when you have individuals in a population that have some kind of variation (e.g. genetic) and fitness differences and are able to pass on their traits you have natural selection. Lurking beneath this simple concept, however, are deep philosophical and metaphysical issues. These issues are not resolved up to this day and continue to be debated.

Let’s look at the concept of “fitness” first. Fitness plays a central role in the concept of natural selection. There are at least two ways that scientists and philosophers view fitness. The propensity view of fitness argues that fitness is a probabilistic propensity while a statistical view sees fitness as a subjective probability. The propensity view sees fitness as a causal factor while the statistical view "deprives fitness of any causal or explanatory power". It is an ongoing discussion and here are a view articles discussing the role of fitness in evolutionary biology.
Two ways of thinking about natural selection
Selection and Causation (argues against a causal view)
Fitness and Propensity’s Annulment?
Fitness (Stanford Encyclopaedia)
Matthen and Ariew’s Obituary for Fitness: Reports of its Death have been Greatly Exaggerated (argues for a causal propensity view)
What fitness can't be (argues against a causal view)

What about natural selection itself? One can ask the following four questions about the concept.

Is natural selection used in a prescriptive manner? In this sense natural selection is an actual and real cause or a force that "guides" the interaction or change of traits of biological entities. It "maintains" the prevalence of beneficial mutations. It "limits" or "favours" some variations over other variations. It "steers" biological change toward the local maxima in the "fitness landscape". On this view natural selection is an agent (albeit impersonal and blind, as in non-directional) that causally influences biological change by “maintaining” or “favouring” or “producing fitter” biological entities etc.

Or is natural selection used in a descriptive manner? In other words it is a term that describes what happens when you have individuals in a population that have some kind of variation (e.g. genetic) and fitness differences and are able to pass on their traits.

“But first, since selection is so uncontroversial to Dawkins yet so maligned by F&P, it behooves us to understand what it is. In principle, natural selection is simple. It is neither a "law" nor a "mechanism." It is, instead, a "process"–a process that is inevitable if two common conditions are met.”

“In essence, the modern theory of evolution is easy to grasp. It can be summarized in a single (albeit slightly long) sentence: Life on Earth evolved gradually beginning with one primitive species—perhaps a self-replicating molecule—that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.”

So the question can be stated, “In what way is natural selection a mechanism and what way is it not?"

Professor Dawkins describes natural selection as a "force" and Professor Coyne describes natural selection as a "cause." Whether these terms are used metaphorically or not is unclear. It is also unclear what they mean with the terms "cause" and "force"?

“As John Endler has argued eloquently in Natural Selection in The Wild (1968), natural selection is not a mechanism. Natural selection does not act on anything, nor does it select (for or against), force, maximize, create, modify, shape, operate, drive, favor, maintain, push or adjust. Natural selection does nothing. Natural selection as a natural force belongs in the insubstantial category already populated by the Becker/Stahl phlogiston (Endler 1986) or Newton's "ether". Natural selection is the necessary outcome of discernible and often quantifiable causes.”

“How is natural selection a teleological "force"? I see remnants of two sorts of teleology operating in Darwin. The key to seeing both is within Darwin's concept of natural selection which can be summed up as follows: as a result of individuals possessing different heritable abilities striving to survive and reproduce in local environments, comes an explanation for changes in trait composition of populations through time. Traits become prevalent in populations because they are useful to organisms in their struggle to survive. Aristotle's functional teleology is preserved through the idea that an item's existence can be explained in terms of its usefulness (Lennox 1993). What makes a trait useful is that it provides certain individuals an advantage over others in their own struggle to survive and reproduce. Secondly, the concept of individual striving to survive and reproduce plays the fundamental role in Darwin's explanation for the origins of organic diversity. The same concept reminds us of Aristotle's formal teleology – the striving for self-preservation.”

So the relevance of teleology in the debate about the concept of natural selection is still very much alive.

Some biologists (see above) see it as a process, some see it as an outcome. There appears to be some disagreement over this question.

To be sure, these are metaphysical and philosophical questions related to the nature or essence (what it is?) of natural selection. Students should be wary of any teacher that tries to slip in any metaphysics into the empirical science class.

To the teachers that want to teach the concept of natural selection, how would you answer these questions relating to the concept of natural selection?

5) What is your view of the concept of “fitness”?

6) How would you go about teaching the concept of natural selection without dragging metaphysics and philosophy into the empirical science class?

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