Friday, December 3, 2010

If Biology Had Schools of Thought Like Economics Does

In this post I discuss how silly arguing from the perspective of "schools of thought" is in economics. Let me clarify, I don't think all economists do this. It's most problematic among macroeconomists, and particularly among macroeconomists that can't distinguish between their politics and their economics. This isn't an issue at all among microeconomists. Microeconomists differ over specific findings, but there are no great over-arching "schools of thought".

Anyway, by means of illustration I wanted to sketch out how silly it would be for evolutionary biologists to do what macroeconomists do. Imagine these schools of thought:

The Foodians: The Foodians strongly maintain that evolution is primarily driven by access to food sources. When climate changes, the kinds of food growing in an area changes and organisms who are best suited to survive eating the new collection of food available are the ones that survive and propagate successfully. Food drives evolution.

The Climatists: The climatists regularly accuse the Foodians of ignoring underlying causes (despite regular references in Foodian articles to things like changing climates). Climatists argue that it's wrong to say that food supply drives evolution - ultimately changes in the climate cause evolution. Organisms that are more prepared to survive in colder weather, or wetter climates, or what have you are going to survive and propagate successfully. Climate drives evolution.

The Dispersionists: The Dispersionists, on the other hand, think that both the Foodians and the Climatists are barking up the wrong tree. Evolution depends on the availability of lots of genetic variation in a population and this is going to depend on how dispersed or concentrated, large or small the population of a species is. If there are just a bunch of small colonies of an organism scattered widely across the planet with little contact between each other, genetic variation is not going to be as wide as if a lot of organisms of the same species congregated together and could easily travel through the population and mate with each other. Population dispersion is what drives evolution. Moreover, the other schools have a fatal flaw: they consider population variation to be homogeneous! They aggregate too much! Despite the regular mention of variations in the preparedness of organisms to eat certain foods or deal with certain climates, the Dispersionists still accuse Foodians and Climatists of genetic aggregationism... no one quite understands why they accuse them of this. Presumably its because Dispersionists are smitten with the way they talk about genetic disaggregation and like to feel special.

The Asteroidists: The Asteroidists argue that the biggest episode that life has to deal with on a planet is surviving being hit by an asteroid or other incoming rock. Large rocks flying into Earth drive evolution because the impact is so violent and the resulting climatic changes are so all-encompassing that only organisms designed to deal with the extreme cold after the impact blocks out the sun, or those who can burrow deep underground, or even those who are simply lucky enough not to live directly in the impact zone can survive. Impact events drive evolution.


Can you imagine how goofy that would be? The disagreements I outlined above are largely based on caricatures of the other positions. There's very little that is obviously mutually exclusive in any of this, and whatever is mutually exclusive can be explained by acknowledging "yes, X is a process that operates sometimes and excludes the prospect of Y process occuring, but at other times Y may occur without X occuring".

The reason why economists do this is probably mostly because of politics and ideology, but it's allowed to perpetuate itself because we also have a very weak commitment to the idea that (1.) we are scientists - primatologists, in fact, and (2.) we are studying a complex phenomenon that involves multiple simultaneously operating processes.

I think it would be legitimate to say "I study this particular extinction episode a lot, which was caused by an asteroid strike so I emphasize the role of asteroids in my own research but I recognize all the other forces". That's fine. It is also legitimate to have a preference for what explains a large portion of the subject at hand in general, without thinking of other forces as illegitimate or mutually exclusive. What's wrong is to pretend that what we're dealing with should be treated as warring schools of thought. This isn't to say there can never be warring schools of thought. I'm not sure what a good example in biology would be - punctuated equilibrium vs. gradualism? That seems like it might fit the bill. But they should not be as common as they are in economics.


  1. When you say "and particularly among macroeconomists that can't distinguish between their politics and their economics," what do you mean by the word "politics"?

    Do you think that the positive statements economics seeks to determine to be true or false are different from those who study politics (whatever you have in mind for that word).

    Economics is a science that searches for true positive statements about how individuals interact in a social context to satisfy virtually unlimited wants. That's my definition of economics.

    Give your definition of politics, and let' talk again.

  2. I don't mean to reference political science, DLK, which is what I think you're getting at. Political science has valid positive questions to answer. I was refering to macroecnomists' own normative political ideology or philosophy. Sorry for the confussion.

    Your definition of "economics" is a little broader than I would use. I think of economics as encompassing what you're talking about, but focusing primarily on exchange and distribution arrangements. There is a lot of non-economic want-satisfaction as well that I think is more under the purview of political science, sociology, or psychology. But as a first cut I think your definition is fine.

  3. Welcome to the blog, by the way! I think I've seen you post at Bob Murphy's blog before - is that correct? Please visit more often! Do you run a blog, by any chance?

  4. @Daniel, the definition of economics I use is broad, but I believe generally in line with what other economists use.

    My question was not intending to evoke a definition for "political science." My real question is how you mean the word "politics" in the sentence in which it appears. People use the word "politics" all the time, but I am quite certain I have no idea what meaning the word has for them. That's why I asked.

    In my view, economics and politics are searching for the same true positive statements about human behavior. But the axioms, hypotheses, and methods are quite different.

    You probably know that the discipline of economics used to be called political economy. I think that was a better name, since the intersection of the two fields of study is enormous.

    I have gone so far as to tell my students that the study of economics is quite uninteresting if one does not include the normative questions about how humans should behave in a social context. That notion is more than a bit out of step with most of my fellow economists in the profession, but that doesn't make my observation incorrect.

    Just lately I have started reading Bob Murphy's blog, Cafe Hayek, Econlog, Scott Sumner's blog, and the Marginal Revolution. Very time consuming, to say the least.

    Yes, I do have a blog @ I have seen your posts recently on the other blogs. Now that we've met, I will pay closer attention to your posts.



  5. I think the normative questions are interesting as well - but I do think we should be careful not to confuse them with the positive questions. This is not to say we should favor one sort of question over the other - only that we should distinguish them.

  6. Definitely. In fact, I believe that people disagree about normative issues for one or all of three reasons. First, people may be ignorant of certain true positive statements. Second, people may have different values. Third, people may have the same values, but weight them differently.

    In my experience, the first reason is the most prevalent. Much of what we take ourselves to know cannot withstand close or critical scrutiny.


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