There is an interesting post over at Alex Palazzo's blog, The Daily Transcript, on the distinction between proximal and ultimate causes in biology. As he notes proximal causes and (proximal explanations) deal with how things work where as ultimate explanations are evolutionary explanations: why was a certain structure or behavior selected for-what causes certain genes to spread as opposed to others in a population.
This distinction sometimes creates as Alex notes a divide among scientists in terms of their view points. For example when I was a graduate student there was a lot of interest in "r" vs "K" selection. Populations that are r selected invest heavily in reproduction and reproductive structures whereas K selected species or populations invest in structures that give them a competitive advantage. I went to a dissertation defense of a graduate student working on r and K selection in populations of a certain plant and the evidence seemed to support the student's hypothesis that in unstable environments with fewer competitors the plant should show attributes of an r selected species and in stable environments with more competitors the plant should show attributes of a K selected species.
To make a long story short, the poor graduate student was savaged by a plant physiologist in the audience who argued that the results were just due to physiological responses of the plant and had nothing to do with evolutionary explanations at all. There were weaknesses in the study and the student should have anticipated this sort of criticism. But the physiologist did not pick up on these weaknesses in terms of what the student needed to do to really test the hypothesis, instead ultimate causation was not even on his radar screen.
I have always been bothered by the use of the terms proximate vs ultimate causation explanations in biology and wrote a response to Alex's post. Basically my concern is with the use of ultimate. To me, ultimate implies teleology. Teleology implies directedness toward some sort of final goal, usually some sort of cosmological goal, or metaphysical goal, as opposed to intentional behavior on the part of an individual organism. To illustrate: my goal in writing this article is intentional but not teleological in the sense the word is usually used. I suppose were some one to say "water tends to seek it's own level" ,as students often do by the way, that is a sort of teleological statement, again seeming to imply intent.
So here is the scheme I proposed in my comments to Alex (cribbing heavily from my response on his blog, and correcting typos).
Teleological causality and explanations involve progression toward a final goal (teleos). This is metaphysics and outside the scope of science...at least science has found no empirical evidence that the universe's unfolding involves this sort of intentional movement toward a final goal.
Scientific causality and explanations are about the universe in terms of natural causation. These are "how questions" and it doesn't matter whether you are talking about cells or evolution. It their core all scientific explanations are explanations about mechanism-they are" how explanations."
Scientific causality and explanations in biology (I will ignore physics here) would include:
1. Proximal explanations-explanations about the immediate operation of organisms.
2. Evolutionary explanations-historical explanations about how the structure and adaptations of organisms and groups of organisms came to be in terms of modification with descent and the mechanisms by which modification with descent operates.
So in my scheme, ultimate is relegated to the sort of explanation that is outside the realm of empirical science because how do you know what the final goal is. What I am proposing is related to the problem of design since design implies intent. Evolutionists, myself included, often talk about the adaptations that organisms show as giving the illusion of design. After all, evolution is not intentional. It is not as Darwin realized, directed toward some sort of final goal. Evolution is not teleological, even though it has given rise to creatures that show intent and directedness toward immediate goals-teleonomy.
Whether or not teleology exists, or is an illusion is really what the intelligent design advocates are asking. The problem is that teleological explanations have not proven useful in terms of understanding the universe. Since they have never proven useful -water seeking it's own level is after a pretty useless explanation of fluid dynamics, the intelligent design advocates have a very difficult task ahead of them if they believe that teleological causality and explanations are needed to understanding the universe. If they have not been shown useful in biology whether we are talking cells or evolution, why should teleology even be on our radar screen as scientists?
Setsuya Fujita (2001) Evolution of the Brain and the System of Value - Origin of Morality in
Bioethics and the Impact of Human Genome Research in the 21st Century pp 161-169