Saturday, April 11, 2009
Taking Home Darwin's Species Concept
I found, through our discussions of the Origin, that I was able to get a better grasp of what Darwin meant be 'species' and perhaps what many biologists really mean by 'species'. It is hard to describe what I have established in my head as Darwin's picture of how a phylogeny would really look versus how we present it. It is more an image than anything verbal. At some point I will do a painting of it, scan it, and put it on here so you can share in my take home. For now, though, all I can do is declare that Darwin's concept of species still makes more sense to me than any of those I have heard in the Philosophy of Biology thus far. The continued applicability of Darwin's ideas never ceases to impress me.
Friday, April 10, 2009
Wednesday, April 8, 2009
Someone else's reflections
If you need additional inspiration for your reflections on the Origin, have a look at John Whitfield's final thoughts at Blogging the Origin.
He makes the excellent point that Darwin can be, and has been, claimed as a founding father by different schools of evolutionary thought. One is what John aptly names the 'lean and mean' school of evolutionary theory (R. A. Fisher, Bill Hamilton, John Maynard Smith, George Price, with Richard Dawkins as their most famous popularizer). This line of thinkers (mostly skinny Englishmen, as Whitfield points out) tends to focus on elegant mathematical models that strip evolution to its bare essentials, and views natural selection as both the most powerful and most interesting evolutionary force. This group appreciates Darwin for his ability to see the simple general principles underlying the polyglot diversity of nature. By contrast, the more loosely defined 'let a thousand flowers bloom' school (think Stephen J. Gould) admires Darwin the natural historian (the fact hound rather than the theoretician), and tends to see the polyglot complexity of nature as the net outcome of many complex interacting factors, of which natural selection is only one. I'm mostly a 'lean and mean' man myself, though I think there are interesting questions about the interplay of natural selection and other factors that both schools of thought tend to ignore.
In a previous post, Whitfield also notes, correctly I think, that a big part of Darwin's genius is his ability to see how patterns in space (say, biogeographical patterns in the distribution of species) can be generated by processes operating over time. Darwin had an extraordinary ability to visualize past sequences of events and how they could've resulted in present-day spatial patterns.
He makes the excellent point that Darwin can be, and has been, claimed as a founding father by different schools of evolutionary thought. One is what John aptly names the 'lean and mean' school of evolutionary theory (R. A. Fisher, Bill Hamilton, John Maynard Smith, George Price, with Richard Dawkins as their most famous popularizer). This line of thinkers (mostly skinny Englishmen, as Whitfield points out) tends to focus on elegant mathematical models that strip evolution to its bare essentials, and views natural selection as both the most powerful and most interesting evolutionary force. This group appreciates Darwin for his ability to see the simple general principles underlying the polyglot diversity of nature. By contrast, the more loosely defined 'let a thousand flowers bloom' school (think Stephen J. Gould) admires Darwin the natural historian (the fact hound rather than the theoretician), and tends to see the polyglot complexity of nature as the net outcome of many complex interacting factors, of which natural selection is only one. I'm mostly a 'lean and mean' man myself, though I think there are interesting questions about the interplay of natural selection and other factors that both schools of thought tend to ignore.
In a previous post, Whitfield also notes, correctly I think, that a big part of Darwin's genius is his ability to see how patterns in space (say, biogeographical patterns in the distribution of species) can be generated by processes operating over time. Darwin had an extraordinary ability to visualize past sequences of events and how they could've resulted in present-day spatial patterns.
Reflections
Having asked everyone else to reflect on the Origin and post their reflections, it's only fair that I should do so too.
I enjoyed the book tremendously, and I'm glad I no longer have to embarrass myself by admitting I hadn't read it. I'm even secretly proud of having read the first edition, when most other people have read the sixth. It's a bit like being able to boast that you saw the original version of a great foreign film rather than the Hollywood remake.
I've come away hugely impressed with Darwin's prescience. It's just stunning (even a little scary) how many modern ideas in ecology and evolution are already there in Darwin, and how they all fit together in his mind in pretty much the same way they do for us today. And his error rate is so low--that surprised me. I expected to see that Darwin would have a firm grasp of the core idea of evolution by natural selection, and he does. But I expected that his thoughts on peripheral details and specific examples would often be somewhat wonky. They're mostly not. It's rare that you catch Darwin failing to extend an idea to its logical conclusion (as in his failure to see that what we now call antagonistic pleiotropy can explain vestigial organs in cave dwellers as well as in parasites), or just proposing a strange-sounding hypothesis (as in his explanation for brood parasitism in birds). I'm sure some of this is luck, but I don't see how all of it could be. Darwin's just too right, too often. As the saying goes, it's best to be good and lucky. And it's extraordinary that he managed to see all this without knowing anything about transmission genetics or developmental biology. Even Wallace, who had the same basic idea, never came close to working out all its implications or marshaling all the various lines of evidence given by Darwin.
Ironically, the one area where Darwin's reasoning disappoints me a bit is in the explanation of the origin of species. Darwin's terrific on the origin of adaptation, on how you get Design without a Designer. And he's terrific on the evidence for evolution, and on how his theory ties together a huge body of apparently-disparate facts in fields as different as embryology and biogeography. But as I've described in another post, I don't think he had a sufficiently strong appreciation for how selection pressures could vary from place to place, and I think this is what led him to propose the Principle of Divergence. This principle is clearly crucial to his understanding of how natural selection leads to speciation, but it doesn't stand up to empirical or conceptual scrutiny, and I think its flaws could've been seen even at the time.
I'm also impressed with Darwin the fact hound. He's determined to get things exactly right, even if that means rejecting an idea he'd worked his butt off on for years. I'd like to read some of his letters to get a sense of how much of this impression is just a rhetorical pose. Surely he wished and hoped that evolution by natural selection was The Answer, right? But how could he wish that and at the same time put that wish to one side and truly take seriously all possible criticisms of his idea? My experience is that science proceeds on a sort of adversarial model (what philosopher David Hull called "science as a selection process"), whereby competing theories each have their advocates and the court of scientific opinion sits in judgment, with peer review "selecting" for the best theories. Of course, I do try to criticize my own ideas, if only because I worry that if I don't I'll get trashed by peer reviewers, and I think other scientists do as well. But I'm not sure that Darwin's self-critical approach is a dominant one.
Closely associated with Darwin the fact hound is Darwin the polymath. The age of specialization began before Darwin (Leibnitz was said to be the last man who was an expert in every field of human knowledge), but it hadn't yet gotten to the point where one couldn't be expert in all the fields Darwin draws on: geology, paleontology, ecology, etc. I flatter myself to think I'm slightly more widely read than my fellow community ecologists, at least in certain fields. But I'm absolutely a dilettante compared to Darwin.
Going in, I had no idea that Darwin took "special creation" as a serious alternative hypothesis, or that his argument against it isn't so much that it's falsified by the data as that it explains and unifies nothing. This is rather different from the arguments you see deployed against various versions of creationism today. And of course, those arguments are only deployed in the context of political debates today. It's interesting to be transported to a time when creationism really was a viable scientific hypothesis.
Darwin's reticence on the implications of his theory for people (and God) strikes me as very wise. It's a rational choice for someone like Darwin, who always wants to be completely sure of his ground. But it strikes me as an ethical choice, too. It shows respect for those with other, possibly conflicting ideas. Richard Dawkins has many virtues, but one of his vices is failure to take seriously alternative points of view with which he disagrees. Dawkins doesn't suffer fools gladly, but he also gives the distinct impression that he has all the answers and that anyone who disagrees with him is foolish.
So if I admired Darwin before (and I did), he's one of my heroes now. Evolutionary biologists are sometimes accused of "worshiping" Darwin, as if he were a god himself (this is the "Darwin the Myth" of Mott Greene's recent lecture). I can see why now, and I couldn't before.
I enjoyed the book tremendously, and I'm glad I no longer have to embarrass myself by admitting I hadn't read it. I'm even secretly proud of having read the first edition, when most other people have read the sixth. It's a bit like being able to boast that you saw the original version of a great foreign film rather than the Hollywood remake.
I've come away hugely impressed with Darwin's prescience. It's just stunning (even a little scary) how many modern ideas in ecology and evolution are already there in Darwin, and how they all fit together in his mind in pretty much the same way they do for us today. And his error rate is so low--that surprised me. I expected to see that Darwin would have a firm grasp of the core idea of evolution by natural selection, and he does. But I expected that his thoughts on peripheral details and specific examples would often be somewhat wonky. They're mostly not. It's rare that you catch Darwin failing to extend an idea to its logical conclusion (as in his failure to see that what we now call antagonistic pleiotropy can explain vestigial organs in cave dwellers as well as in parasites), or just proposing a strange-sounding hypothesis (as in his explanation for brood parasitism in birds). I'm sure some of this is luck, but I don't see how all of it could be. Darwin's just too right, too often. As the saying goes, it's best to be good and lucky. And it's extraordinary that he managed to see all this without knowing anything about transmission genetics or developmental biology. Even Wallace, who had the same basic idea, never came close to working out all its implications or marshaling all the various lines of evidence given by Darwin.
Ironically, the one area where Darwin's reasoning disappoints me a bit is in the explanation of the origin of species. Darwin's terrific on the origin of adaptation, on how you get Design without a Designer. And he's terrific on the evidence for evolution, and on how his theory ties together a huge body of apparently-disparate facts in fields as different as embryology and biogeography. But as I've described in another post, I don't think he had a sufficiently strong appreciation for how selection pressures could vary from place to place, and I think this is what led him to propose the Principle of Divergence. This principle is clearly crucial to his understanding of how natural selection leads to speciation, but it doesn't stand up to empirical or conceptual scrutiny, and I think its flaws could've been seen even at the time.
I'm also impressed with Darwin the fact hound. He's determined to get things exactly right, even if that means rejecting an idea he'd worked his butt off on for years. I'd like to read some of his letters to get a sense of how much of this impression is just a rhetorical pose. Surely he wished and hoped that evolution by natural selection was The Answer, right? But how could he wish that and at the same time put that wish to one side and truly take seriously all possible criticisms of his idea? My experience is that science proceeds on a sort of adversarial model (what philosopher David Hull called "science as a selection process"), whereby competing theories each have their advocates and the court of scientific opinion sits in judgment, with peer review "selecting" for the best theories. Of course, I do try to criticize my own ideas, if only because I worry that if I don't I'll get trashed by peer reviewers, and I think other scientists do as well. But I'm not sure that Darwin's self-critical approach is a dominant one.
Closely associated with Darwin the fact hound is Darwin the polymath. The age of specialization began before Darwin (Leibnitz was said to be the last man who was an expert in every field of human knowledge), but it hadn't yet gotten to the point where one couldn't be expert in all the fields Darwin draws on: geology, paleontology, ecology, etc. I flatter myself to think I'm slightly more widely read than my fellow community ecologists, at least in certain fields. But I'm absolutely a dilettante compared to Darwin.
Going in, I had no idea that Darwin took "special creation" as a serious alternative hypothesis, or that his argument against it isn't so much that it's falsified by the data as that it explains and unifies nothing. This is rather different from the arguments you see deployed against various versions of creationism today. And of course, those arguments are only deployed in the context of political debates today. It's interesting to be transported to a time when creationism really was a viable scientific hypothesis.
Darwin's reticence on the implications of his theory for people (and God) strikes me as very wise. It's a rational choice for someone like Darwin, who always wants to be completely sure of his ground. But it strikes me as an ethical choice, too. It shows respect for those with other, possibly conflicting ideas. Richard Dawkins has many virtues, but one of his vices is failure to take seriously alternative points of view with which he disagrees. Dawkins doesn't suffer fools gladly, but he also gives the distinct impression that he has all the answers and that anyone who disagrees with him is foolish.
So if I admired Darwin before (and I did), he's one of my heroes now. Evolutionary biologists are sometimes accused of "worshiping" Darwin, as if he were a god himself (this is the "Darwin the Myth" of Mott Greene's recent lecture). I can see why now, and I couldn't before.
The Ethics of Culture
Totally non-Darwinian post: If you want to check out Samuel Fleischacker's The Ethics of Culture, it's out of print but still available through various sellers at amazon.com. There's also a brief but highly positive review of the book from "A Customer" whose identity you may be able to infer...
Mistaken identity
I have been mistaken for someone who knows a lot about Darwin and the Origin (this happens a lot), and so have been invited to speak on these topics at the next meeting of Nature Calgary (aka the Calgary Field Naturalists' Society). The talk is on May 20 at 7:30 pm at Ft. Calgary. Apparently the meetings are open to the public if you want to come along. But if you'd rather not spend an evening listening to an illustrated synopsis of the class you've just taken, you may want to give it a miss.
Add this to your reading list
This week's Nature includes a review of God - Or Gorilla: Images of Evolution in the Jazz Age. It's a book about how images and diagrams were used to communicate evolutionary ideas to the general public in the run-up to the Scopes "monkey" trial. Sounds very interesting. Pictures are powerful but dumb: one's reaction to them is very sensitive to one's prior experience, knowledge, values, and expectations, so it's tough to use pictures to convey exactly what you want to convey. The review is very positive--apparently it's a good read as well as a thought-provoking one.
As the reviewer points out, a comparative analysis of religious and evolutionary imagery would probably be fascinating. Someone should go do it!
As the reviewer points out, a comparative analysis of religious and evolutionary imagery would probably be fascinating. Someone should go do it!
Sunday, April 5, 2009
Saturday, April 4, 2009
readings for april 8
1) Christ and a Bicycle by Andrew Brown. Apparently delivered as part of his advertising or publicity for his book Darwin Wars: The Scientific Battle for the Soul of Man.
2) Charles Darwin on Religion by John Hedley Brooke, an invited contribution to the website for The International Society for Science & Religion
3) Dawkins, R. 1997. Obscurantism to the rescue. The Quarterly Review of Biology 72(4):397-399. (pdf available)
4) portions of "Natural selection not inconsistent with natural theology", by Asa Grey, as published in the Atlantic Monthly in a series of articles for July, August, and October 1860.
2) Charles Darwin on Religion by John Hedley Brooke, an invited contribution to the website for The International Society for Science & Religion
3) Dawkins, R. 1997. Obscurantism to the rescue. The Quarterly Review of Biology 72(4):397-399. (pdf available)
4) portions of "Natural selection not inconsistent with natural theology", by Asa Grey, as published in the Atlantic Monthly in a series of articles for July, August, and October 1860.
Friday, April 3, 2009
Blogging Mott Greene
Last night was historian Mott Greene's seminar in the public lecture series Introducing Darwin, which I've organized along with Maggie Osler, Tony Russell, and Jessica Theodor. Thanks to Shari and CJ for helping with the mikes and to CJ for taking some pictures.
Mott's talk was very good--first half some biographical remarks on "Darwin the man", then moving on to some very interesting remarks on "Darwin the myth", particularly the various ways in which Darwin has been enlisted by a wide range of people to support a wide range of ideas (he's been claimed as a justification for both unregulated capitalism and communism, for instance). As we've discussed, Darwin himself is notable for his insistence on getting his facts right and in his extreme reluctance to make inferences beyond what the facts will support. I'm sure this is why he was always very reticent about the implications (if any!) of his ideas for religion, economics, etc.
The point that will stick with me the most is Mott's remark that both religious conservatives and secular liberals today tend to resist Darwinian-style explanations for social phenomena. For instance, one can argue that the rise since the 1960s of feminism and gay liberation is not ultimately attributable to individuals making and responding to arguments about justice or equality. Rather, the ultimate drivers are economic pressures and reproductive imperatives. Appeals to justice and equality are at best the proximate mechanisms by which individuals happen to respond to those ultimate drivers of human behavior. The point is not that this explanation of the rise of feminism and gay rights is right or wrong, it's that people from across the liberal-conservative spectrum tend to dislike this kind of explanation, independent of any evidence.
One point Mott didn't make, which I got the chance to make briefly in response to a question from the audience afterwards, is that non-biologists who've developed "evolutionary" theories of economics or society (think of Hegel, Marx, Comte, and many others) tend to conflate Darwinian evolution with organismal development. That is, they tend to think of growth of an individual organism from child to adult as "evolutionary". It's not just famous thinkers like Comte who thought this way--the recent remarks from our own federal science minister indicate that he believes in "evolution" in the sense of individual development and change. To a biologist, this is a serious confusion. Darwinian evolution doesn't have a direction or goal or purpose (see Mayr's remarks in his introduction to the Origin). But the development of an individual organism does have a predetermined goal--to convert a fertilized egg into a functioning adult organism. If you claim that human societies are like developing organisms, that's a very different claim from the claim that human societies are like evolving populations.
This confusion between evolution and development has three obvious sources. One is that both involve "change over time", which is what "evolution" means in a colloquial sense. Second is that there are indeed directional trends in the history of life (e.g., increase in the average "complexity" of organisms since the origin of life), and it's natural (but incorrect) to think of such trends as analogous to the directional development of a newborn into an adult. Third is that it's very hard for non-specialists to grasp that the notion of "fitness" in Darwinian evolution is "relative fitness". All that matters in Darwinian evolution is your ability to survive and reproduce, relative to the other current members of the population. This notion of relative fitness does not imply that absolute fitness will increase over time (even in a constant environment), or that there is some "maximally fit" or "ideal" or "perfect" state toward which a population tends to evolve. I think this is the key Darwinian insight that even very smart non-biologists seem to find very difficult to fully absorb (though in fairness, evolutionary biologists don't help them by talking about evolution using engineering and hill-climbing metaphors that are fine in many respects but are subtly and importantly misleading in other respects). Evolution by natural selection is change over time that both lacks a goal or endpoint, but that is not simply random either (random evolution is genetic drift). Directional, non-random change--but the direction isn't "towards" anything. That's Darwinian evolution. As Mott noted, it's this kind of explanation that many people either misunderstand or find unpalatable.
Mott's talk was very good--first half some biographical remarks on "Darwin the man", then moving on to some very interesting remarks on "Darwin the myth", particularly the various ways in which Darwin has been enlisted by a wide range of people to support a wide range of ideas (he's been claimed as a justification for both unregulated capitalism and communism, for instance). As we've discussed, Darwin himself is notable for his insistence on getting his facts right and in his extreme reluctance to make inferences beyond what the facts will support. I'm sure this is why he was always very reticent about the implications (if any!) of his ideas for religion, economics, etc.
The point that will stick with me the most is Mott's remark that both religious conservatives and secular liberals today tend to resist Darwinian-style explanations for social phenomena. For instance, one can argue that the rise since the 1960s of feminism and gay liberation is not ultimately attributable to individuals making and responding to arguments about justice or equality. Rather, the ultimate drivers are economic pressures and reproductive imperatives. Appeals to justice and equality are at best the proximate mechanisms by which individuals happen to respond to those ultimate drivers of human behavior. The point is not that this explanation of the rise of feminism and gay rights is right or wrong, it's that people from across the liberal-conservative spectrum tend to dislike this kind of explanation, independent of any evidence.
One point Mott didn't make, which I got the chance to make briefly in response to a question from the audience afterwards, is that non-biologists who've developed "evolutionary" theories of economics or society (think of Hegel, Marx, Comte, and many others) tend to conflate Darwinian evolution with organismal development. That is, they tend to think of growth of an individual organism from child to adult as "evolutionary". It's not just famous thinkers like Comte who thought this way--the recent remarks from our own federal science minister indicate that he believes in "evolution" in the sense of individual development and change. To a biologist, this is a serious confusion. Darwinian evolution doesn't have a direction or goal or purpose (see Mayr's remarks in his introduction to the Origin). But the development of an individual organism does have a predetermined goal--to convert a fertilized egg into a functioning adult organism. If you claim that human societies are like developing organisms, that's a very different claim from the claim that human societies are like evolving populations.
This confusion between evolution and development has three obvious sources. One is that both involve "change over time", which is what "evolution" means in a colloquial sense. Second is that there are indeed directional trends in the history of life (e.g., increase in the average "complexity" of organisms since the origin of life), and it's natural (but incorrect) to think of such trends as analogous to the directional development of a newborn into an adult. Third is that it's very hard for non-specialists to grasp that the notion of "fitness" in Darwinian evolution is "relative fitness". All that matters in Darwinian evolution is your ability to survive and reproduce, relative to the other current members of the population. This notion of relative fitness does not imply that absolute fitness will increase over time (even in a constant environment), or that there is some "maximally fit" or "ideal" or "perfect" state toward which a population tends to evolve. I think this is the key Darwinian insight that even very smart non-biologists seem to find very difficult to fully absorb (though in fairness, evolutionary biologists don't help them by talking about evolution using engineering and hill-climbing metaphors that are fine in many respects but are subtly and importantly misleading in other respects). Evolution by natural selection is change over time that both lacks a goal or endpoint, but that is not simply random either (random evolution is genetic drift). Directional, non-random change--but the direction isn't "towards" anything. That's Darwinian evolution. As Mott noted, it's this kind of explanation that many people either misunderstand or find unpalatable.
Thursday, April 2, 2009
The Martyrdom of Man
I forgot to mention this yesterday in class: If anyone is interested in reading an application of selection theory on the development 'human tribes' and a 'natural' history of Western civilisation then take a look at Winwood Reade's Martyrdom of Man (1872). It is an account of the West's development that draws a great deal from social Darwinism and was a pinnacle work during the age of Empire. It was highly influential upon a great many British figures from Cecil Rhodes to Winston Churchill. Reade was a renowned atheist and tried to devise a secular conception of human destiny that also appears in a dialogue in Churchill's novel Savrola. The book is largely devoid of the racism that would dominate later Continental and American works, and focuses predominantly upon cultural selection. Obviously it has many of the typical biases of late Victorian writing, neverthless is an early and interesting exercise of parochial altruism and group selection, roughly along the lines of the Bowles article of last Wednesday. It is most interesting in its predictions for the distant future.
A copy is available at your friendly university library.
A copy is available at your friendly university library.
Wednesday, April 1, 2009
Further reading on group selection
I'm posting in advance of class today because I likely won't have time afterwards. Looking forward to today's discussion on group selection and altruism, as it raises a fascinating tangle of empirical and conceptual issues at the interface of biology, sociology, and philosophy.
Group selection and altruism is a topic on which my thinking has been very much shaped by reading a few key people. So if you're keen on reading more on this topic, I suggest you have a look at:
The work of young British philosophy hotshot Samir Okasha, especially his terrific 2006 book Evolution and the Levels of Selection. This book is already becoming the standard reference on the topic. Most of his papers can be downloaded from his website, so if you don't want to buy or read the book you can easily access individual papers to get snapshots of Okasha's views on key issues.
The work of philosopher Eliot Sober (Marc Ereshefsky's doctoral supervisor), especially his book Unto Others with evolutionary theoretician David Sloan Wilson. Sober basically invented contemporary philosophy of evolutionary biology (in his classic 1984 book The Nature of Selection), and David Sloan Wilson did as much as any biologist to revive group selection as a respectable idea.
The exchange of views between Eliot Sober and evolutionary biologist John Maynard Smith in The Latest on the Best (MIT Press, 1987) is a good non-technical introduction to certain key issues such as what counts as a "group" (yes, that's actually a non-trivial issue).
Richard Dawkins' The Selfish Gene. At the time it was published (1976), this was the final nail in the coffin of group selectionist thinking. Wonderfully clear and forcefully argued, even if some of the conclusions aren't widely held today (which isn't to say that today's group selectionist thinking bears more than a passing resemblance to the naive views that Dawkins was attacking).
Finally, I'll share a little anecdote. As a grad student (this was in the late '90s), I was fortunate enough to have the chance to discuss group selection with Dick Lewontin. Lewontin and Sober wrote a famous 1982 paper about group selection, which addressed the issue that one can often build mathematically-equivalent group-selectionist and individual-selectionist models of the same biological situation. That is, the models make the same predictions about future evolution, but do so by making different assumptions about the underlying causal processes driving evolution. The existence of such predictively-equivalent models could be taken to suggest that the distinction between group and individual selection is merely conventional, a matter of choosing one heuristic perspective over another. In contrast, Sober and Lewontin took a realist view and argued that, in the case of a specific example (heterozygote advantage), the group selectionist model "gets the causal facts right" while the individual selectionist model is simply a mathematical fiction that gives the right predictions for the wrong causal reasons. I'd read the paper and thought a lot about it, and so I was excited to ask Dick Lewontin himself if he still took the same view. He didn't. He'd changed his mind and decided that, at least in the case of the example of heterozygote advantage, that there were no "causal facts" that one could appeal to in order to motivate a choice of one model over the other. I don't know that Lewontin has ever published his revised view, so I don't know if it's widely known that he changed his mind.
Postscript: In Evolution and the Levels of Selection, Samir Okasha argues that Lewontin and Sober's example of heterozygote advantage has actually been misinterpreted by both sides in this realist/conventionalist debate. Okasha argues that Lewontin and Sober arrive at the right (realist) conclusion, but for the wrong reasons. This is a nice example of what I think is Okasha's greatest strength--he's very precise and analytical, and he's good at drawing distinctions that need to be drawn. Okasha's book convinced me that much of the debate and confusion in the group selection literature has arisen because of people failing to draw key distinctions.
Group selection and altruism is a topic on which my thinking has been very much shaped by reading a few key people. So if you're keen on reading more on this topic, I suggest you have a look at:
The work of young British philosophy hotshot Samir Okasha, especially his terrific 2006 book Evolution and the Levels of Selection. This book is already becoming the standard reference on the topic. Most of his papers can be downloaded from his website, so if you don't want to buy or read the book you can easily access individual papers to get snapshots of Okasha's views on key issues.
The work of philosopher Eliot Sober (Marc Ereshefsky's doctoral supervisor), especially his book Unto Others with evolutionary theoretician David Sloan Wilson. Sober basically invented contemporary philosophy of evolutionary biology (in his classic 1984 book The Nature of Selection), and David Sloan Wilson did as much as any biologist to revive group selection as a respectable idea.
The exchange of views between Eliot Sober and evolutionary biologist John Maynard Smith in The Latest on the Best (MIT Press, 1987) is a good non-technical introduction to certain key issues such as what counts as a "group" (yes, that's actually a non-trivial issue).
Richard Dawkins' The Selfish Gene. At the time it was published (1976), this was the final nail in the coffin of group selectionist thinking. Wonderfully clear and forcefully argued, even if some of the conclusions aren't widely held today (which isn't to say that today's group selectionist thinking bears more than a passing resemblance to the naive views that Dawkins was attacking).
Finally, I'll share a little anecdote. As a grad student (this was in the late '90s), I was fortunate enough to have the chance to discuss group selection with Dick Lewontin. Lewontin and Sober wrote a famous 1982 paper about group selection, which addressed the issue that one can often build mathematically-equivalent group-selectionist and individual-selectionist models of the same biological situation. That is, the models make the same predictions about future evolution, but do so by making different assumptions about the underlying causal processes driving evolution. The existence of such predictively-equivalent models could be taken to suggest that the distinction between group and individual selection is merely conventional, a matter of choosing one heuristic perspective over another. In contrast, Sober and Lewontin took a realist view and argued that, in the case of a specific example (heterozygote advantage), the group selectionist model "gets the causal facts right" while the individual selectionist model is simply a mathematical fiction that gives the right predictions for the wrong causal reasons. I'd read the paper and thought a lot about it, and so I was excited to ask Dick Lewontin himself if he still took the same view. He didn't. He'd changed his mind and decided that, at least in the case of the example of heterozygote advantage, that there were no "causal facts" that one could appeal to in order to motivate a choice of one model over the other. I don't know that Lewontin has ever published his revised view, so I don't know if it's widely known that he changed his mind.
Postscript: In Evolution and the Levels of Selection, Samir Okasha argues that Lewontin and Sober's example of heterozygote advantage has actually been misinterpreted by both sides in this realist/conventionalist debate. Okasha argues that Lewontin and Sober arrive at the right (realist) conclusion, but for the wrong reasons. This is a nice example of what I think is Okasha's greatest strength--he's very precise and analytical, and he's good at drawing distinctions that need to be drawn. Okasha's book convinced me that much of the debate and confusion in the group selection literature has arisen because of people failing to draw key distinctions.
Tuesday, March 31, 2009
Evolution Obliterates Morality?
There was a quote put forth in Ruse in an effort to discern whether Darwin ever flirted seriously with the concept of group selection. It nevertheless carries other implications that caught my interest. I reproduce it here:
"It is extremely doubtful whether the offspring of the more sympathetic and benevolent parents, or of those which were the most faithful to their comrades, would be reared in greater number than the children of selfish and treacherous parents of the same tribe. He who was ready to sacrifice his life, as many a savage has been, rather than betray his comrades, would often leave no offspring to inherit his noble nature. The bravest men, who were always willing to come to the front in war, and who freely risked their lives for others, would on an average perish in large number than other men."
Does evolution obliterate morality? Are the noblest and greatest of service to the group destined to sacrifice themselves for the survival of those who indulge in a shallow life of self-preservation? Or is morality, a noble character, a learned rather than an evolutionary trait, and could the stuff of heroes spring from a brood of spoiled children and a bloodline of thoroughly spoiled adults?
"It is extremely doubtful whether the offspring of the more sympathetic and benevolent parents, or of those which were the most faithful to their comrades, would be reared in greater number than the children of selfish and treacherous parents of the same tribe. He who was ready to sacrifice his life, as many a savage has been, rather than betray his comrades, would often leave no offspring to inherit his noble nature. The bravest men, who were always willing to come to the front in war, and who freely risked their lives for others, would on an average perish in large number than other men."
Does evolution obliterate morality? Are the noblest and greatest of service to the group destined to sacrifice themselves for the survival of those who indulge in a shallow life of self-preservation? Or is morality, a noble character, a learned rather than an evolutionary trait, and could the stuff of heroes spring from a brood of spoiled children and a bloodline of thoroughly spoiled adults?
Wednesday, March 25, 2009
readings for april 1
Further thoughts on challenges to the Modern Synthesis
Very good papers this week. Rose and Oakley are actually much more knowledgeable about evolutionary biology sensu stricto than are many modern systems biologists and evo-devo folks who see their fields as challenging the Darwinian orthodoxy. Lots of interesting conceptual issues to chew on here, including:
1. If we want to say whether Darwinism, or the Modern Synthesis, or the possible Postmodern Synthesis, is a 'paradigm shift', we need to define what we mean by 'paradigm shift'. Infamously difficult, due in no small part to ambiguity in the writing of Thomas Kuhn, the physicist/historian/philosopher who came up with the idea of paradigm shifts. Kuhn used 'paradigm' in lots of very different ways, and philosophers have been arguing about his ideas ever since. I do think it's pretty clear that some senses in which Kuhn used the term don't really apply to Darwinism or the Modern Synthesis. As Mike indicated, there was no failure of communication between Darwin and his opponents, or between the developers of the Modern Synthesis and their opponents. People weren't talking past one another. They mostly agreed on what the questions were and simply disagreed about the answers. That means those paradigm shifts, if that's what they were, weren't like 'gestalt switches', contrary to some of Kuhn's claims. (A gestalt switch is like when you look at an ambiguous drawing such as the famous one that can look like either a rabbit or a duck, and switch from seeing it one way to seeing it the other way. The two different perspectives are just that--different. Neither is incompatible with the other, and so the choice between them isn't rational but rather is merely a matter of preference).
2. The distinction between proximate and ultimate explanations, and the relationship between them, seems to me to absolutely indispensable for understanding the relationship between evolutionary biology and molecular biology/genetics/biochemistry. This distinction is, or should be, familiar to biologists. Ethologist Niko Tinbergen wrote a classic 1963 paper on four kinds of questions in ethology, which basically draws this distinction. Unfortunately, a lot of unproductive argument and attempts at synthesis in science basically boil down to arguments over which of these kinds of questions is "best".
3. Following on from 2, it's very interesting to think about how proximate and ultimate explanations relate to one another, both in general and in specific cases. Simple reduction of ultimate to proximate explanations generally isn't possible or desirable. This is in part because of supervenience--properties like "fitness" are not physical properties like "mass" or "charge". So statements about fitness cannot be translated into, and thereby reduced to, statements about physical properties, although an organism's physical properties obviously affect its fitness. This kind of "translation problem" crops up in other fields. It's the basis of the mind-brain problem the prevents psychology from being reduced to neuroscience. States of mind (e.g., "happy", "sad") can be correlated with states of the brain (patterns of neuron firing), but that doesn't mean the mind "is nothing but" the brain.
I actually think there are a lot of really cool scientific questions that are inspired by our new genetic knowledge. But those questions seem to me to fall within the conceptual framework of the Modern Synthesis. For instance, much of the mathematical theory of quantitative genetics developed by Fisher, Haldane, and Wright assumes that a quantitative phenotype of an organism(e.g., its weight or length) is determined in part by its genotype at each of infinitely many loci, each of which has a very small, additive effect on phenotype. This assumption is mathematically convenient, because it turns out to predict that phenotypic variation will be normally distributed (i.e. follow a bell curve), and normal distributions are easy to work with mathematically. This assumption is also empirically supported, in that we do indeed observe that phenotypic variation of quantitative traits like height often is normally distributed, even when all individuals are grown in a shared, controlled environment. But recently, modern molecular biology has falsified the genetic assumptions on which the mathematical theory is based. We can now identify most of the genetic loci that affect, say, height, and we can estimate the additive effect of each genotype at each locus. And it turns out that genetic variation in quantitative traits is mostly due to variation at only a few loci, each of which has a big rather than a small effect on phenotype. But this doesn't mean we should just chuck quantitative genetic theory and start over, since (again) it's a matter of empirical fact that phenotypic variation is normally distributed. So quantitative genetics gives the right answer for the wrong reasons, and it's a very interesting question to try to work out how that's possible. We now know the genome isn't at all like we thought--so how can it be that false assumptions about the genome nevertheless give the right answer?
4. Closely related to ideas about proximate vs. ultimate explanations and supervenience is the idea of "screening off". This is the idea that, if A (an event or state of affairs) causes B and B causes C, B "screens off" C from A. That is, in order to predict C, I only need to know B. Knowing A doesn't help predict C, because A only affects C indirectly, via B. But that doesn't mean one never wants to know anything about A. For instance, once I've explained C by appeal to B, it's natural to ask "What explains B?", which leads me to work backwards along the causal chain. I leave it to you to think about how this idea relates to the ideas discussed in class today.
5. We didn't talk about Gould today, but I hope it's clear that objections to Darwinism as wrong or incomplete tend to run to type. The claim that development imparts some kind of directionality to adaptive evolution (or so strongly constrains it that the constraint is really the main story) resonates with much earlier ideas about orthogenesis and the "bauplan".
6. Objections to Darwinism and the Modern Synthesis also run to type in caricaturing Darwinians as believing that natural selection is all powerful and entirely unconstrained. My experience is that evolutionary biologists focus so much on natural selection not because they think it can produce any adaptation, but because they think it's the only thing that can produce what adaptations exist. And so if you're interested in explaining adaptation, you have no choice but to be interested in natural selection--it's the only game in town. That doesn't mean you don't care about constraints on adaptation. But those constraints aren't interesting in and of themselves, they're only interesting by virtue of their effects on adaptive evolution. Of course, scientists prefer to argue about objective empirical claims rather than subjective claims about what's "interesting". So if you want to argue against the Modern Synthesis, you can't accuse its proponents of making uninteresting claims, you have to accuse them of making false claims.
1. If we want to say whether Darwinism, or the Modern Synthesis, or the possible Postmodern Synthesis, is a 'paradigm shift', we need to define what we mean by 'paradigm shift'. Infamously difficult, due in no small part to ambiguity in the writing of Thomas Kuhn, the physicist/historian/philosopher who came up with the idea of paradigm shifts. Kuhn used 'paradigm' in lots of very different ways, and philosophers have been arguing about his ideas ever since. I do think it's pretty clear that some senses in which Kuhn used the term don't really apply to Darwinism or the Modern Synthesis. As Mike indicated, there was no failure of communication between Darwin and his opponents, or between the developers of the Modern Synthesis and their opponents. People weren't talking past one another. They mostly agreed on what the questions were and simply disagreed about the answers. That means those paradigm shifts, if that's what they were, weren't like 'gestalt switches', contrary to some of Kuhn's claims. (A gestalt switch is like when you look at an ambiguous drawing such as the famous one that can look like either a rabbit or a duck, and switch from seeing it one way to seeing it the other way. The two different perspectives are just that--different. Neither is incompatible with the other, and so the choice between them isn't rational but rather is merely a matter of preference).
2. The distinction between proximate and ultimate explanations, and the relationship between them, seems to me to absolutely indispensable for understanding the relationship between evolutionary biology and molecular biology/genetics/biochemistry. This distinction is, or should be, familiar to biologists. Ethologist Niko Tinbergen wrote a classic 1963 paper on four kinds of questions in ethology, which basically draws this distinction. Unfortunately, a lot of unproductive argument and attempts at synthesis in science basically boil down to arguments over which of these kinds of questions is "best".
3. Following on from 2, it's very interesting to think about how proximate and ultimate explanations relate to one another, both in general and in specific cases. Simple reduction of ultimate to proximate explanations generally isn't possible or desirable. This is in part because of supervenience--properties like "fitness" are not physical properties like "mass" or "charge". So statements about fitness cannot be translated into, and thereby reduced to, statements about physical properties, although an organism's physical properties obviously affect its fitness. This kind of "translation problem" crops up in other fields. It's the basis of the mind-brain problem the prevents psychology from being reduced to neuroscience. States of mind (e.g., "happy", "sad") can be correlated with states of the brain (patterns of neuron firing), but that doesn't mean the mind "is nothing but" the brain.
I actually think there are a lot of really cool scientific questions that are inspired by our new genetic knowledge. But those questions seem to me to fall within the conceptual framework of the Modern Synthesis. For instance, much of the mathematical theory of quantitative genetics developed by Fisher, Haldane, and Wright assumes that a quantitative phenotype of an organism(e.g., its weight or length) is determined in part by its genotype at each of infinitely many loci, each of which has a very small, additive effect on phenotype. This assumption is mathematically convenient, because it turns out to predict that phenotypic variation will be normally distributed (i.e. follow a bell curve), and normal distributions are easy to work with mathematically. This assumption is also empirically supported, in that we do indeed observe that phenotypic variation of quantitative traits like height often is normally distributed, even when all individuals are grown in a shared, controlled environment. But recently, modern molecular biology has falsified the genetic assumptions on which the mathematical theory is based. We can now identify most of the genetic loci that affect, say, height, and we can estimate the additive effect of each genotype at each locus. And it turns out that genetic variation in quantitative traits is mostly due to variation at only a few loci, each of which has a big rather than a small effect on phenotype. But this doesn't mean we should just chuck quantitative genetic theory and start over, since (again) it's a matter of empirical fact that phenotypic variation is normally distributed. So quantitative genetics gives the right answer for the wrong reasons, and it's a very interesting question to try to work out how that's possible. We now know the genome isn't at all like we thought--so how can it be that false assumptions about the genome nevertheless give the right answer?
4. Closely related to ideas about proximate vs. ultimate explanations and supervenience is the idea of "screening off". This is the idea that, if A (an event or state of affairs) causes B and B causes C, B "screens off" C from A. That is, in order to predict C, I only need to know B. Knowing A doesn't help predict C, because A only affects C indirectly, via B. But that doesn't mean one never wants to know anything about A. For instance, once I've explained C by appeal to B, it's natural to ask "What explains B?", which leads me to work backwards along the causal chain. I leave it to you to think about how this idea relates to the ideas discussed in class today.
5. We didn't talk about Gould today, but I hope it's clear that objections to Darwinism as wrong or incomplete tend to run to type. The claim that development imparts some kind of directionality to adaptive evolution (or so strongly constrains it that the constraint is really the main story) resonates with much earlier ideas about orthogenesis and the "bauplan".
6. Objections to Darwinism and the Modern Synthesis also run to type in caricaturing Darwinians as believing that natural selection is all powerful and entirely unconstrained. My experience is that evolutionary biologists focus so much on natural selection not because they think it can produce any adaptation, but because they think it's the only thing that can produce what adaptations exist. And so if you're interested in explaining adaptation, you have no choice but to be interested in natural selection--it's the only game in town. That doesn't mean you don't care about constraints on adaptation. But those constraints aren't interesting in and of themselves, they're only interesting by virtue of their effects on adaptive evolution. Of course, scientists prefer to argue about objective empirical claims rather than subjective claims about what's "interesting". So if you want to argue against the Modern Synthesis, you can't accuse its proponents of making uninteresting claims, you have to accuse them of making false claims.
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