Wednesday, June 08, 2011

Teleological Explanations in Biology

Biologists tend to use teleological language in explaining the origin and evolution of living organisms and their characteristics. As John Reiss has pointed out (Reis, J. Not by Design: Retiring Darwin's Watchmaker, University of California Press, 2009), this entails the idea that evolution is necessarily a teleological process. This entails the idea that evolution is not a "natural" process, like gravity or oxidation, and that therefore there is some "non-natural" component (i.e. "magic") in biology that fundamentally distinguishes it from the other natural sciences.

Evolutionary biologists like Richard Dawkins try to make this distinction when referring to the problem of human free will (see "Let's all stop beating Basil's car"), but unless they are careful about how they talk about evolution (especially natural selection) they revert to the same teleological descriptions and explanations that Reiss so decries. What is the problem, here?

I believe that the underlying problem is the tendency by most evolutionary biologists to think of natural selection as a "force" or "mechanism". As John Endler has pointed out (Endler, J. Natural Selection in the Wild, Princeton University Press, 1986), natural selection is not a "force" or "mechanism", it is an outcome. To be precise, it is the outcome of four separate, but related processes:

Variety: structural and functional differences between individuals in populations,

Heredity : the inheritance of structures and functions from parents to offspring (either genetically or epigenetically),

Fecundity : the ability to reproduce, especially (but not necessarily) at a rate that exceeds replacement, and

Demography : some individuals survive and reproduce more often than others.

As a result of these four processes, the heritable characteristics of some individuals become more common in populations over time.

Notice that the same list of processes can be used to explain non-adaptive evolutionary change (e.g. genetic drift). Also notice that the only source of new phenotypic variations is what I have called the "engines of variation": all of those processes that produce heritable phenotypic changes in phylogenetic lines of organisms in populations. There are at least fifty such processes (you can see a summary list here). While it is the case that "random mutation" is included in this list, there are many other processes in this list that do not involve "mutation" (in the genetic sense) and which also are not "random" (at least insofar as that term is often used).

Is there a real distinction between non-teleological and teleological processes, or are all processes either teleological or not? If all processes (i.e. changes over time) are teleological, as asserted by Aristotle (and some of the commentators), then there is no point in talking about it. However, if some processes are teleological and some are not (as most people, including presumably most of the commentators here, now believe), then the question becomes "how can one distinguish between teleological and non-teleological processes, and what explains the differences between them?"

In his comprehensive analysis of teleology, Andrew Woodfield (Woodfield, A. Teleology, Cambridge University Press, 1976) pointed out that all teleological descriptions can be reformulated to conform to the linguistic formula " x happens in order to/for y outcome." He also asserted that such linguistic formulations describe metaphysically real processes. That is, some processes are genuinely teleological – they involve pre-existing designs or plans that cause processes to tend toward particular outcomes, regardless of perturbations or outside interference – while other processes only seem teleological – they involve laws of nature, such as gravity, that result in particular outcomes, without responding actively to perturbations or outside interference.

This distinction is essential when considering whether "genuine" teleology exists. To be precise, teleological descriptions sound "reasonable" when they are applied to genuinely teleological processes, but sound ridiculous if they are applied to non-teleological processes. For example, does it sound reasonable to say that when you drop a rock, it falls "in order to" reach the ground? By contrast, does it sound reasonable to say that birds have wings "in order to" fly? Is there a difference between the "reasonableness" of the first teleological explanation and the second?

When I pose this question to my students, almost all of them say yes: the first is ridiculous and the second isn't. I then point out that this implies that the origin of the wings of birds therefore seems to be the result of a teleological process. I then point out (reprising Aristotle) that there are at least four ways of explaining the presence of wings:
• "this bird has wings because it is composed of materials that are assembled and operated as wings" (Aristotle's "material" cause);
• "this bird has wings because its parents had wings" (Aristotle's "efficient" cause);
• "this bird has wings because birds have wings" (Aristotle's "formal" cause); and
• "this bird has wings in order to fly" (Aristotle's "final" cause).

Since at least the 17th century (and mostly because of Newton), natural scientists have stopped using formal or final causes to explain natural phenomena...except in biology. This was first pointed out by Colin Pittendrigh (Pittendrigh, C. S. Behavior and Evolution) (ed. by A. Rose and G. G. Simpson), Yale University Press, 1958), who coined the term "teleonomy" to refer to the kind of teleological phenomena observed in biological processes. Francisco Ayala modified and extended Pittendrigh's analysis (Ayala, F. J. 'Teleological Explanations in Evolutionary Biology', Philosophy of Science, vol. 37 pp. 1-15, 1970). Ernst Mayr finally sorted the whole thing out in 1974 in "Teleological and teleonomic: A new analysis" (Boston Studies in the Philosophy of Science, vol. XIV, pp. 91 -117). According to Mayr, the difference between the "behavior" of dropped rocks and genuinely purposeful processes is the presence or operation of a pre-existing information-containing program in the latter. Rocks do not fall because there is an encoded program in nature that makes them fall. They fall because there is a force (i.e. a law of nature) that causes them to fall. However, a bird has wings because there is a program encoded within its genome which, as the result of interactions between the "phenome" of the bird and its environment, causes the construction and operation of wings.

To say that natural selection is teleological would therefore require that there be a pre-existing encoded program somewhere that would cause natural selection to bring about its effects. This is ridiculous for at least two reasons:
• there is no such program as far as we can tell (where would it be encoded?), and
• this would require that natural selection be a process in and of itself, rather than the outcome of the four processes listed above.


As always, comments, criticisms, and suggestions are warmly welcomed!


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At 6/08/2011 08:43:00 PM, Blogger NAL said...

Explaining a preference for Teleological Explanations.

Inferring Design (pdf)

At 6/10/2011 12:23:00 PM, Anonymous DNW said...

Enjoy your site. You seem to be able to consider certain controversial issues without the kind of commissar-like and hyper-vigilant emotionalism that oddly (from my perspective), seems to shape the responses of supposedly dispassionate and rational persons.

It's disquieting to see some practitioners of science showing some of the same signs of religious fanaticism as their opponents. It's almost as if they are more committed to some kind of political utility they believe can be derived from their beliefs - as they have formulated them - than to the scientific project itself.

Question for you.

Mayr who you cite in another blog entry, remarks that those who think of evolution as being at base a kind of a tautological formulation are mistaken.

Why (and this question contains its own obvious assumption) from what is a presumptively ultimately monist-materialist perspective, would this be the case?

Life or non-life it's all basically the same material after all ... just patterns pointlessly interacting; some of which persist and spread for a time.

At 6/11/2011 03:59:00 AM, Blogger Unknown said...

I found a typo: 'd'enetic drift.
Very good explanation anyway.

At 7/08/2011 02:26:00 PM, Anonymous Techne said...

Hi Allen,

I am looking forward to your book, sounds interesting!

Thanks for this post. Some of this (e.g. the nature of natural selection) has been discussed before. With regards to “random mutation”, I don’t think the claim that it is truly random or truly disordered or chaotic in any ontologically significant sense can be defended simply because "there is no agreed definition of randomness among mathematicians or other scientists". In this case the effects of the mutations are "random" with regards to the fitness or phenotype of the organism and not necessarily completely chaotic and disordered.

With regards to teleological processes:
I think I agree more with Aquinas’ version of such a linguistic formula:
“Every agent acts for an end” (Summa Theologiae I.44.4)
An agent can be described in terms of the four causes. Let’s take your rock and gravity example.
From a Scholastic view, gravity has a “standing tendency” or a “second potentiality” or a "first actuaity" to certain kinds of behaviour as Aristotle and Aquinas would say.

Gravity has the potency or power to attract objects of mass with a force proportional to their mass. This potentcy is derived from what kind of thing it is, its formal cause. It’s potentiality is also “restricted” in a sense by its formal cause, meaning it does not have certain potentialities like for example to push masses away from each other or attract massless objects.
So gravity is an efficient cause of the rock falling to the ground. The fact that gravity is an efficient cause of the falling rock (actually the attraction of two objects of mass with a force proportional to their mass) entails that generating the effect of the falling rock is the final cause of gravity. “And in general, if there is a regular efficient causal connection between a cause A and an effect B, then generating B is the final cause of A.”

Gravity can thus be described as follows:
Material cause: What does loop quantum gravity or M-theory suggest?
Efficient cause: Again, this depends on what physics discover.
Formal cause: An agent that gives weight to objects of mass and attracts them with a force proportional to their mass.
Final cause: Attracts objects of mass with a force proportional to their mass.
From a Scholastic view we seem to know more about the formal and final causes of gravity than its material and efficient causes. Final causality is still relevant to gravity and it is not as a result of “pre-existing designs or plans that cause processes to tend toward particular outcomes” but as a result of immanent and intrinsic properties of gravity.

With regards to natural selection, well, I can certainly agree that natural selection is not a force or a cause or something that plays a causal role in the trajectory of evolution. It is logically impossible if it is just a descriptive term or an outcome of a process such as evolution.

At 7/28/2011 01:26:00 AM, Anonymous Anonymous said...

Have you considered the possibility of a natural basis for teleology?

I discussed this a while ago on my blog.

At 8/19/2011 02:46:00 PM, Blogger Unknown said...

This bird has evolved to use its wings for flying - it has acquired that purpose for their use. So in that sense, all biological purposes were at some time and place acquired. And all are to that extent teleological. The question remains as to what extent the presently formed bird strategically evolved itself and/or otherwise took advantage of random accidents.

At 12/15/2011 08:09:00 PM, Anonymous rigadoon said...

I just saw your blog and agree with others that your attitude is to be commended. You wrote, "Since at least the 17th century (and mostly because of Newton), natural scientists have stopped using formal or final causes to explain natural phenomena". This goes back at least to Francis Bacon in his "Advancement of Learning".

I would argue it is one thing to focus on two causes but another to say they are the only causes that can be known. The latter is a prescription for ignorance.

At 10/08/2012 05:58:00 PM, Blogger Unknown said...

The most important item that enables evolution, and one that you left out entirely, is intelligence. All life forms have at least a minimal amount of trial and error analytical ability with choice making purposes. It;s that ability that evolves, with forms that are evolved intelligently to follow.


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