Transcription and Translation

Proximal vs Ultimate Causation

There is a divide within the biological sciences, those that are concerned with proximal causes and those concerned with ultimate causes. For every question in biology there are two answers.

Ultimate causes have to do mostly with the “why?”s. Why was this structure selected for? But not always. What advantage did this gene give to the organism? Do synonymous mutations give a selection advantage?

Proximal causes have mostly “how” questions. How does this protein work? How does a cell cycle check point function? How does this synonymous mutation affect protein folding?

Another way of thinking about these two views is that ultimate causes have to do with evolution and proximal causes have to do with the nitty gritty day-to-day operations. Ultimate questions involve intention or teleology and proximal questions have to do with direct, bouncing billiard ball like causation.

Any subject or object that stems from a biological organism will have these two types of questions. So for example a car arose from human needs and engineering. You can ask ultimate and proximal questions for its function. For example the blinker or flasher. The “proximal” explanation for blinkers, or the answer to the “how” question, will involve a lever connected to a circuit and the heating of a light generating filament. You hit the level and a periodic current generates light from a filament with a certain on/off interval. There you’ve explained its proximal function. The “ultimate” explanation, or the answer to the why question will involve the intention of the driver. A blinker or flasher is used by the conductor to signal neighboring vehicle drivers that he/she wishes to switch lanes or make a turn. The ability to signal fellow conductors prevents accidents and facilitates a speedier commute.

Within other realms, such as physics, geology and chemistry, teleological questions are just speculation and do not have any sound basis. Yes some will be hurt by that statement, but teleology, or intention can only arise if a system has some mechanism to generate intention. That system is evolution. Evolution itself can be explained on a proximal level. No such bridge from proximal causation to teleological causation exists outside of biological system and their derivatives such as nests, cars, culture, economies etc.

One further note. You will notice that most biology blogs, culture warriors and science reporting about the biological sciences have tro do with ultimate causation. Why are things the way they are. However my blog has lots of nitty gritty stuff. How does this work and so on. Well it would seem that although the vast majority of biological scientists study proximal questions within biology, many more bloggers and science reporters are concerned with ultimate questions. It’s a shame because right now we are in the midst of a revolution. Proximal biology is advancing so fast it is hard to keep up even within my own field. The beauty of proximal biology is that the cell is full of neat and interesting little toys and devices. Ironically evolution is a diversification machine. Through the process of evolution, genes that encoded machines multiplied and differentiated from each other to create all the neat contraptions in the cell. All that biological “mush” hiding in each cell, that “force vitae”, we’re piecing the inner most mechanisms of life right now! And despite all of the brilliant researchers out there, no one knows what we will find next. No amount of ultimate thinking can currently predict or deduce how cells maintain homeostasis. We are trying. Hence systems biology and other such valiant attempts.

So I encourage all those out there who are investigating all the nitty gritty stuff within the cell, come out and share your thoughts, I would love to read your ideas and your insights.

[Next up: how mushy religious thinking once dominated both proximal and ultimate questions in biology has totally lost the proximal war of ideas.]


  1. #1 Such.Ire
    March 30, 2007

    Within other realms, such as physics, geology and chemistry, teleological questions are just speculation and do not have any sound basis. Yes some will be hurt by that statement, but teleology, or intention can only arise if a system has some mechanism to generate intention. That system is evolution.

    You could say that the physical world has a similar sort of teleology, i.e. the second law of thermodynamics. After all, evolution, fundamentally, is nothing more than the statement that “that which reproduces more will tend to become more common.” It’s a bare-bones logical statement, and everything else is mere implementation, the “proximal” questions, as you say. Similarly, one could say that almost all of physics and chemistry in the natural world can have the teleological purpose to “tend to do things that are more likely to occur” (i.e. maximize entropy). Everything else from there is “proximal.”

    I think fundamentally, whether scientific questions are “why” or “how” are simply a matter of phrasing. We don’t know why things work at all; we simply know that this is how they do work. The logical structure of our universe is such that evolution becomes sort of a given, as does thermodynamics.

  2. #2 Greg Laden
    March 30, 2007

    There are actually four andswers, if you go with Tinbergen’s more comprehensive formulation:

    Ultimate (funcitonal)
    Proximate (mechanisitic … how something works)

    I nurse my young because it’s a good PI strategy (ultimate) but I’m stuck with this strategy because I’m a mammal (phylogenetic), the strategy emerges in me because I develop mamary glands in a certain way (ontogenetic) which function as follows …. (ontogenetic).

    Except that I’m actually a man so I don’t do any of this. The females have to do it (more phylogeny, and a bit of ultimate????)

  3. #3 Sunil
    March 30, 2007

    Really liked this post…..and the way you define proximal and ultimate stuff. Over the past year or so, I’ve found myself writing more and more about “proximal” stuff….about cool little things that happen in science, and am now thorougly enjoying it. And your “nitty-gritty” posts are among those I enjoy reading the most.

    Incidentally….i’m not too big on the present approaches to “systems biology”, and find the idea and present approaches largely flawed. There are way too many assumptions and generalizations and so the interpretations/conclusions drawn leave a little too much to be desired.

  4. #4 Paul Decelles
    March 31, 2007

    Interesting post. Personally I restrict the use of ultimate causation to teleology which is progression toward a goal which implies intent. Evolutionary explanations are also “how” explanations except on a different level of analysis than the sorts of proximal explanations. So I like the following scheme better-

    Teleological explanations-explanations about the universe involving 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 explanations-explanations about the universe in terms of natural causation. These are how questions anf it doesn’t matter whether you are talking about cells or evolution, these are still how questions to me.

    Scientific expalantions in biology 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.

  5. #5 apalazzo
    April 1, 2007


    I’m not sure that the second law of thermodynamics gives physical systems intent. At its most basic, the second law of thermodynamics states that a system will change from the less probable state to the more probable state. Take a pile of cards in a large cardboard box and shake up the box, the cards end up all messed up because there are many more “messed up states” than “neatly piled up” states. Is that intention? It’s just first principals. But talk about a bird’s wing and you can’t easily deduce the ultimate reasons for its shape. It’s not simply due to taking up the most probable configuration but rather a product of selection or as others in this thread have stated due to selection within the context of a series of historical situations.


    I would say that you are subdividing the ultimate reasons into further categories (as far as I understand).


    Yes there is quite a bit of debate over whether the idea of “teleology” is appropriate for evolution. But I’m not using teleology within the context of directionality within evolution, so I agree evolution per se does not have intent, only small incremental changes which further the fitness of the organism at each step. But I am using teleology within the context of an organism’s life. The organism has certain structures and it benefits it by being used in a certain context. Yes the structures may have arose by accident and in the course of evolution may have served different purposes, but now they are used with a particular adaptive “intent” by the organism.

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