1) Rose, M. R. and T. H. Oakley. 2007. The new biology: beyond the Modern Synthesis. Biology Direct 2:30. (pdf available)
2) Huxley, J. 1942, 1963. Evolution: The Modern Synthesis. Chapter 1 of First Edition, excerpts from the Introduction of Second Edition.
Sunday, March 22, 2009
Monday, March 9, 2009
Further thoughts on Chapters XIII-XIV
A few--okay, many--further thoughts on the last two chapters. May try to post with further thoughts on the Origin as a whole at some point, but I'll probably wait until around the time of the last class (but don't let that stop you from posting your own lookback on the whole "long argument").
1. The idea that classification was based on evolutionary principles without actually realizing it has intriguing implications. For instance, does that comprise evidence for those evolutionary principles? I'm reminded of the argument (discussed in one of Gould's essays, I believe) that biological species, as classified by taxonomists, are "real" entities because hunter-gatherer tribes classify organisms in the same way (i.e. they recognize each biological species as a distinct kind of organism and give it its own name). Or maybe that thought doesn't stand up to the scrutiny you all will surely apply to it next week as part of your discussion of Darwin's species concept. ;-)
2. I love the final passages of the Origin (from the bottom of p. 480 on) more than I can say. It's so satisfying to see Darwin rising to the occasion and finishing with a flourish. All the caveats and doubts drop away as he drives home the argument and its enormous implications. And it's beautifully written, it just sweeps you along. My highlights (warning: long list!):
(a) p. 481: "But the chief cause of our natural unwillingness to admit that one species has given birth to other and distinct species, is that we are always slow in admitting any great change of which we do not see the intermediate steps." Yup (although I don't know that this is true of today's evangelical creationists; their unwillingness has other sources).
(b) p. 481: "Although I am fully convinced of the truth of the views given in this volume...I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of facts all viewed, during a long course of years, from a point of view directly opposite mine. It is so easy to hide our ignorance under such expressions as the 'plan of creation,' 'unity of design,' &c., and to think that we give explanation when we only restate a fact. Any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject my theory...but I look with confidence to the future, to young and rising naturalists, who will be able to view both sides of the questions with impartiality." Oh no he didn't! This is stunningly direct. He might as well have written "The close-minded old farts who dominate the field are so blind they can't even see that their so-called 'explanations' are empty. I can't hope to change their minds because science advances one death at a time. But history will show that I'm right and they're wrong." I'm sure this would read as arrogant--except that history did indeed prove Darwin right. As Reggie Jackson once said in a different context, "It ain't braggin' if you can do it."
(c) p. 483, the rhetorical attack on the emptiness of special creationist 'explanations': "These authors seem no more startled at a miraculous act of creation than at an ordinary birth. But do they really believe that at innumerable periods in the earth's history certain elemental atoms have been commanded suddenly to flash into living tissues? Do they believe that at each supposed act of creation one individual or many were produced?...and in the case of mammals, were they created bearing the false marks of nourishment from the mother's womb? Although naturalists very properly demand a full explanation of every difficulty from those who believe in the mutability of species, on their own side they ignore the whole subject of the first appearance of species in what they consider reverent silence." Wow. One gets the sense here that deep down Darwin is quite frustrated and even angry with special creationism. I imagine that, if one is an open-minded fact hound like Darwin, if one is absolutely determined to get things right, then one is likely to be very impatient with those who aren't equally open-minded and determined. And one is likely to be especially impatient with those who aren't even sufficiently open-minded to recognize and engage with questions so big as to demand an answer. Clearly Darwin took seriously the mottoes from Whewell and Bacon with which he chose to preface his book.
(d) p. 484: "[P]robably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed." Talk about following the evidence wherever it leads. At the time, it would've seemed like a very good question to ask just how far Darwin's argument goes. One might well have wondered, why couldn't there have been several or even quite numerous events of special creation (say, one per family), with evolution by natural selection merely driving subsequent within-family diversification? But there's no evidence for this, and so Darwin calls it like he sees it: the Tree of Life has one root. When I started reading the Origin, I was most impressed with Darwin's insight regarding the mechanism of adaptive evolution. But this passage really convinces me that his insight regarding the fact of evolution was equally impressive. Not only is there an evolutionary Tree of Life--it has one root! No pun intended here but--my God! I wish I could forget what I know about evolution and read that as it would've read to a Victorian. Because in all likelihood I'll never have the chance to be told something that astonishing about the world--something that runs so counter to my whole picture of how the world works. I'll never get to have my world turned upside down. Then again, if I was told something that would turn my world upside down, I'd probably dismiss it as wrong, if not crazy. I'd have to hope I had the insight of Thomas Henry Huxley, who wrote upon reading the Origin, "How extremely stupid not to have thought of that."
(e) p. 485: "When we no longer look at an organic being as a savage looks at a ship, as at something wholly beyond his comprehension; when we regard every production of nature as one which has had a history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor, nearly in the same way as when we look at any great mechanical invention as the summing up of the labour, the experience, the reason, and even the blunders of numerous workmen; when we thus view each organic being, how far more interesting, I speak from experience, will the study of natural history become!" Great analogy. And a great summary of the modern scientific mind. To a scientist, things become more wonderful, not less, the more we learn about them.
(f) p. 488: "Light will be thrown on the origin of man and his history." Perhaps the most famous understatement of all time.
(g) p. 489. God love him, Darwin saves the best for last. Maybe for some people, the beauty of some famous passages of literature is dulled by familiarity. But for me, the final paragraph of the Origin, with which I was familiar before the term started, will never get old. Indeed, I used to regard it as merely a nice passage. But having read the book I now see it as it was intended, as a summary of everything that came before. And so now this passage impresses and thrills me more than I can say. I am not a religious person, and like many such people if you asked me, "So what do you believe in?" I would struggle to articulate a satisfying answer, by which I mean a spiritually (rather than intellectually) satisfying answer. But although I would struggle to speak for myself, I'm happy to let this passage speak for me. This is the best thing I've ever read:
It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing in the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the direct and indirect action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling according to the fixed law of gravity, from so simple a beginning endless forms most beautiful have been, and are being, evolved.
1. The idea that classification was based on evolutionary principles without actually realizing it has intriguing implications. For instance, does that comprise evidence for those evolutionary principles? I'm reminded of the argument (discussed in one of Gould's essays, I believe) that biological species, as classified by taxonomists, are "real" entities because hunter-gatherer tribes classify organisms in the same way (i.e. they recognize each biological species as a distinct kind of organism and give it its own name). Or maybe that thought doesn't stand up to the scrutiny you all will surely apply to it next week as part of your discussion of Darwin's species concept. ;-)
2. I love the final passages of the Origin (from the bottom of p. 480 on) more than I can say. It's so satisfying to see Darwin rising to the occasion and finishing with a flourish. All the caveats and doubts drop away as he drives home the argument and its enormous implications. And it's beautifully written, it just sweeps you along. My highlights (warning: long list!):
(a) p. 481: "But the chief cause of our natural unwillingness to admit that one species has given birth to other and distinct species, is that we are always slow in admitting any great change of which we do not see the intermediate steps." Yup (although I don't know that this is true of today's evangelical creationists; their unwillingness has other sources).
(b) p. 481: "Although I am fully convinced of the truth of the views given in this volume...I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of facts all viewed, during a long course of years, from a point of view directly opposite mine. It is so easy to hide our ignorance under such expressions as the 'plan of creation,' 'unity of design,' &c., and to think that we give explanation when we only restate a fact. Any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject my theory...but I look with confidence to the future, to young and rising naturalists, who will be able to view both sides of the questions with impartiality." Oh no he didn't! This is stunningly direct. He might as well have written "The close-minded old farts who dominate the field are so blind they can't even see that their so-called 'explanations' are empty. I can't hope to change their minds because science advances one death at a time. But history will show that I'm right and they're wrong." I'm sure this would read as arrogant--except that history did indeed prove Darwin right. As Reggie Jackson once said in a different context, "It ain't braggin' if you can do it."
(c) p. 483, the rhetorical attack on the emptiness of special creationist 'explanations': "These authors seem no more startled at a miraculous act of creation than at an ordinary birth. But do they really believe that at innumerable periods in the earth's history certain elemental atoms have been commanded suddenly to flash into living tissues? Do they believe that at each supposed act of creation one individual or many were produced?...and in the case of mammals, were they created bearing the false marks of nourishment from the mother's womb? Although naturalists very properly demand a full explanation of every difficulty from those who believe in the mutability of species, on their own side they ignore the whole subject of the first appearance of species in what they consider reverent silence." Wow. One gets the sense here that deep down Darwin is quite frustrated and even angry with special creationism. I imagine that, if one is an open-minded fact hound like Darwin, if one is absolutely determined to get things right, then one is likely to be very impatient with those who aren't equally open-minded and determined. And one is likely to be especially impatient with those who aren't even sufficiently open-minded to recognize and engage with questions so big as to demand an answer. Clearly Darwin took seriously the mottoes from Whewell and Bacon with which he chose to preface his book.
(d) p. 484: "[P]robably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed." Talk about following the evidence wherever it leads. At the time, it would've seemed like a very good question to ask just how far Darwin's argument goes. One might well have wondered, why couldn't there have been several or even quite numerous events of special creation (say, one per family), with evolution by natural selection merely driving subsequent within-family diversification? But there's no evidence for this, and so Darwin calls it like he sees it: the Tree of Life has one root. When I started reading the Origin, I was most impressed with Darwin's insight regarding the mechanism of adaptive evolution. But this passage really convinces me that his insight regarding the fact of evolution was equally impressive. Not only is there an evolutionary Tree of Life--it has one root! No pun intended here but--my God! I wish I could forget what I know about evolution and read that as it would've read to a Victorian. Because in all likelihood I'll never have the chance to be told something that astonishing about the world--something that runs so counter to my whole picture of how the world works. I'll never get to have my world turned upside down. Then again, if I was told something that would turn my world upside down, I'd probably dismiss it as wrong, if not crazy. I'd have to hope I had the insight of Thomas Henry Huxley, who wrote upon reading the Origin, "How extremely stupid not to have thought of that."
(e) p. 485: "When we no longer look at an organic being as a savage looks at a ship, as at something wholly beyond his comprehension; when we regard every production of nature as one which has had a history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor, nearly in the same way as when we look at any great mechanical invention as the summing up of the labour, the experience, the reason, and even the blunders of numerous workmen; when we thus view each organic being, how far more interesting, I speak from experience, will the study of natural history become!" Great analogy. And a great summary of the modern scientific mind. To a scientist, things become more wonderful, not less, the more we learn about them.
(f) p. 488: "Light will be thrown on the origin of man and his history." Perhaps the most famous understatement of all time.
(g) p. 489. God love him, Darwin saves the best for last. Maybe for some people, the beauty of some famous passages of literature is dulled by familiarity. But for me, the final paragraph of the Origin, with which I was familiar before the term started, will never get old. Indeed, I used to regard it as merely a nice passage. But having read the book I now see it as it was intended, as a summary of everything that came before. And so now this passage impresses and thrills me more than I can say. I am not a religious person, and like many such people if you asked me, "So what do you believe in?" I would struggle to articulate a satisfying answer, by which I mean a spiritually (rather than intellectually) satisfying answer. But although I would struggle to speak for myself, I'm happy to let this passage speak for me. This is the best thing I've ever read:
It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing in the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the direct and indirect action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling according to the fixed law of gravity, from so simple a beginning endless forms most beautiful have been, and are being, evolved.
Today's Supplementary
The line of demarcation between natural and artificial selection seems to become blurred if one views intelligence as a product of the mind which in turn was developed by natural selection. This point in itself is highly debatable and no doubt some of you will disagree entirely. Nevertheless, let us venture down Dennett's rabbit hole. Cutting to the chase, it does open the door for everything cultural, political, and economic to be explained in the framework of the "Darwinian Algorithm". The 19th century politician did it for national competition in the West and imperialism in the Third World, the 19th century historian did it for cultural transmission, and Margaret Thatcher did it for economics. The algorithm can be applied anywhere because of its unique and ingenious construction allows it to explain anything, (although this does not necessarily mean the explanation is correct, and Dennett even allows for an imaginary super-algorithm being produced someday that does the task even more efficiently.) The point is, it can potentially be applied anywhere. But the question is where it is most usefully applied.
Now I do hope I was not misunderstood in this "ought question". I was not raising an ethical question. That would have been very dull of me. More useful is the question of where the framework is of most use. If every nook and cranny of the living world can be explained along the lines of natural selection, that is all and well. However, an all encompassing theory has a tendency to get a little stale. If the theory potentially explains everything social scientists can all retire, unless they'd like to devote their careers to filling in the details. If so, I eagerly anticipate the doctoral thesis on how does Darwinian theory guides the ability of Midwestern American housewives to make chocolate chip cookies. However, one suspects it is rather inefficient to spend our lives explaining everything. Rather, it is worthwhile to focus on things that need to be explained. In the face of an all-encompassing theory, the fact seems self evident. Therefore, a more pragmatic question seems to be, how does it aid us in pursuing our respective topics? Is, for instance, the transmission of language and culture any better understood by cramming what we now into a Darwinian framework? To a significant degree that would justify a dissertation on the subject? (which, sadly, has already been written more than once) How is any particular topic more greatly elucidated by viewing it through such a lens? That is the question we must ask ourselves. We must selfishly ask whether thinking about it that way profits us and enhances our perspective, in the same way historians today consider the usages of a 'Gender lens' or a 'Marxist lens' when writing their histories. All these algorithms or frameworks belong to what is commonly called the 'methodological toolbox' from which they draw a perspective when it is found useful to the purpose.
Where is the 'Darwinian tool' most useful and best suited? The immediate answer seems to be the obvious one - the study of the evolution of species. Alternately, in the study of human activity from Capitalism and Freedom to Mein Kampf, social and economic theory has been written taking from quasi 'Darwinist' perspectives. Yet these writings deal with topics vastly different from those with which Darwin was concerned. Nor would Darwin have necessarily agreed with how his theory was applied. Not to dismiss the many ideas in the social sciences that could not have been generated without Darwin, many of these explanations of culture seem to be an intellectual exercise at best, and at the worst, a blatant subversion of Darwin's principles. There are many ways Darwin has influenced the social sciences, but his algorithm seems to have made tangible progress seems to have been made in the realm of biology. I cannot even begin to imagine how long that list may be. A lot of quasi-social darwinist prattlings, on the other hand, have turned out to be a highly decorative waste of time. I say this as delicately as I can, with many notable exceptions in mind, as well as bearing in mind the army of scholars who would take offence to such a sweeping remark and seek hang me from a lampost. Nevertheless, if a line of demarcation cannot be clearly made because Darwin's algorithm can be deployed everywhere, to explain even the products of the human mind, perhaps a line of demarcation can at least be drawn pragmatically and opportunistically, like a tool drawn from a toolbox, it is best suited to tackling certain kinds of jobs.
Now I do hope I was not misunderstood in this "ought question". I was not raising an ethical question. That would have been very dull of me. More useful is the question of where the framework is of most use. If every nook and cranny of the living world can be explained along the lines of natural selection, that is all and well. However, an all encompassing theory has a tendency to get a little stale. If the theory potentially explains everything social scientists can all retire, unless they'd like to devote their careers to filling in the details. If so, I eagerly anticipate the doctoral thesis on how does Darwinian theory guides the ability of Midwestern American housewives to make chocolate chip cookies. However, one suspects it is rather inefficient to spend our lives explaining everything. Rather, it is worthwhile to focus on things that need to be explained. In the face of an all-encompassing theory, the fact seems self evident. Therefore, a more pragmatic question seems to be, how does it aid us in pursuing our respective topics? Is, for instance, the transmission of language and culture any better understood by cramming what we now into a Darwinian framework? To a significant degree that would justify a dissertation on the subject? (which, sadly, has already been written more than once) How is any particular topic more greatly elucidated by viewing it through such a lens? That is the question we must ask ourselves. We must selfishly ask whether thinking about it that way profits us and enhances our perspective, in the same way historians today consider the usages of a 'Gender lens' or a 'Marxist lens' when writing their histories. All these algorithms or frameworks belong to what is commonly called the 'methodological toolbox' from which they draw a perspective when it is found useful to the purpose.
Where is the 'Darwinian tool' most useful and best suited? The immediate answer seems to be the obvious one - the study of the evolution of species. Alternately, in the study of human activity from Capitalism and Freedom to Mein Kampf, social and economic theory has been written taking from quasi 'Darwinist' perspectives. Yet these writings deal with topics vastly different from those with which Darwin was concerned. Nor would Darwin have necessarily agreed with how his theory was applied. Not to dismiss the many ideas in the social sciences that could not have been generated without Darwin, many of these explanations of culture seem to be an intellectual exercise at best, and at the worst, a blatant subversion of Darwin's principles. There are many ways Darwin has influenced the social sciences, but his algorithm seems to have made tangible progress seems to have been made in the realm of biology. I cannot even begin to imagine how long that list may be. A lot of quasi-social darwinist prattlings, on the other hand, have turned out to be a highly decorative waste of time. I say this as delicately as I can, with many notable exceptions in mind, as well as bearing in mind the army of scholars who would take offence to such a sweeping remark and seek hang me from a lampost. Nevertheless, if a line of demarcation cannot be clearly made because Darwin's algorithm can be deployed everywhere, to explain even the products of the human mind, perhaps a line of demarcation can at least be drawn pragmatically and opportunistically, like a tool drawn from a toolbox, it is best suited to tackling certain kinds of jobs.
Thursday, March 5, 2009
supplementary reading for march 9
Dennett, D. C. 1995. Darwin's dangerous idea. Sciences 35 (3):34-40 (pdf available to EBSCOhost subscribers here)
Wednesday, March 4, 2009
Further thoughts on chapters XI-XII
A few further musings on the biogeography chapters:
1. After today's discussion, I now want to go and read Mayr (which I've never actually done, embarrassingly), and decide for myself just how firm are the empirical (as opposed to theoretical) foundations of the 'conventional wisdom' that allopatric speciation is the rule.
2. Darwin's own theory of speciation is (in)famously hard to decipher. As was correctly pointed out in class today, much of the biogeography material sounds like it was written by a man who believes in allopatric speciation as the dominant mode of speciation. But the earlier chapters don't read that way. Darwin clearly understood that what we would now call gene flow can prevent lineages from splitting. But his theory of speciation also relies a lot on the 'principle of divergence of character' (see chapter IV). Briefly, this is the idea that the 'fittest' types of organism will be those that produce the most divergent offspring, so that collectively those offspring can occupy a greater number of niches in the economy of nature, thereby allowing more of the offspring to survive than if they were all suited only for a single niche. This principle has several logical and empirical problems with it, although something like it is the basis for one hypothesis to explain the evolution of sexual reproduction (which produces more variable offspring than asexual reproduction).
I wonder if Darwin was drawn to the principle of divergence of character in part because he was afraid that otherwise his theory would predict a world populated only by a very few 'superspecies' rather than the polyglot diversity that we see. There are other ideas that Darwin might have hit on (or emphasized more strongly) to explain why we don't just have a few superspecies, such as the fact that selection pressures vary geographically. But taking that view seriously would've required him to find another way to explain why some species have larger geographical ranges than others besides the simple claim that the wide-ranging species are the 'fittest'. In general, Darwin isn't as sensitive as I expected to the notion that fitness is typically very context-dependent. He talks about the fittest type replacing all other types in its own lineage, and then spreading widely to replace other similar lineages, as if any one type could possibly be the 'best' in very different contexts. Then, to ensure continued maintenance and production of diversity, he appeals to the principle of divergence of character, which introduces an element of self-contradiction. Your offspring can't fill the gaps in the economy of nature (thereby avoiding competition with other species), and at the same time outcompete other species for already-occupied places in that same economy. Your offspring either compete with other species, or they don't.
But Darwin had such a head full of ideas, it's hard to fault him too much if those ideas didn't all quite fit together.
3. A rare instance of Darwin just getting it wrong: Darwin refers at multiple points to species failing to evolve in response to climate change because they all shift their ranges as a group, so that each continues to live with its coevolved fellows. There are a number of problems with this view, starting with the fact that it's false. Empirical research has now shown that, while species do generally migrate north (and up mountain slopes) in warming periods, and the reverse in cooling periods, they do so at very different rates. Many ancient ecosystems therefore were comprised of combinations of species that don't currently exist. But in fairness, Darwin's suggestion is a perfectly reasonable one given the evidence available to him at the time.
1. After today's discussion, I now want to go and read Mayr (which I've never actually done, embarrassingly), and decide for myself just how firm are the empirical (as opposed to theoretical) foundations of the 'conventional wisdom' that allopatric speciation is the rule.
2. Darwin's own theory of speciation is (in)famously hard to decipher. As was correctly pointed out in class today, much of the biogeography material sounds like it was written by a man who believes in allopatric speciation as the dominant mode of speciation. But the earlier chapters don't read that way. Darwin clearly understood that what we would now call gene flow can prevent lineages from splitting. But his theory of speciation also relies a lot on the 'principle of divergence of character' (see chapter IV). Briefly, this is the idea that the 'fittest' types of organism will be those that produce the most divergent offspring, so that collectively those offspring can occupy a greater number of niches in the economy of nature, thereby allowing more of the offspring to survive than if they were all suited only for a single niche. This principle has several logical and empirical problems with it, although something like it is the basis for one hypothesis to explain the evolution of sexual reproduction (which produces more variable offspring than asexual reproduction).
I wonder if Darwin was drawn to the principle of divergence of character in part because he was afraid that otherwise his theory would predict a world populated only by a very few 'superspecies' rather than the polyglot diversity that we see. There are other ideas that Darwin might have hit on (or emphasized more strongly) to explain why we don't just have a few superspecies, such as the fact that selection pressures vary geographically. But taking that view seriously would've required him to find another way to explain why some species have larger geographical ranges than others besides the simple claim that the wide-ranging species are the 'fittest'. In general, Darwin isn't as sensitive as I expected to the notion that fitness is typically very context-dependent. He talks about the fittest type replacing all other types in its own lineage, and then spreading widely to replace other similar lineages, as if any one type could possibly be the 'best' in very different contexts. Then, to ensure continued maintenance and production of diversity, he appeals to the principle of divergence of character, which introduces an element of self-contradiction. Your offspring can't fill the gaps in the economy of nature (thereby avoiding competition with other species), and at the same time outcompete other species for already-occupied places in that same economy. Your offspring either compete with other species, or they don't.
But Darwin had such a head full of ideas, it's hard to fault him too much if those ideas didn't all quite fit together.
3. A rare instance of Darwin just getting it wrong: Darwin refers at multiple points to species failing to evolve in response to climate change because they all shift their ranges as a group, so that each continues to live with its coevolved fellows. There are a number of problems with this view, starting with the fact that it's false. Empirical research has now shown that, while species do generally migrate north (and up mountain slopes) in warming periods, and the reverse in cooling periods, they do so at very different rates. Many ancient ecosystems therefore were comprised of combinations of species that don't currently exist. But in fairness, Darwin's suggestion is a perfectly reasonable one given the evidence available to him at the time.
Darwin and art
I continue to be proven wrong in my claim early in the term that Darwin had little or no influence on art. This week's Nature contains a review of an exhibition on the response of artists to Darwin's ideas. Darwin: Art and the Search for Origins is running at the Shirn Kunsthalle in Frankfurt, Germany. Above is Monkey Before a Skeleton by Gabriel von Max (1840-1915), one of the artists featured in the exhibition. von Max was a convinced Darwinist and a prolific zoological collector.
I hate it when Nature runs reviews of things that I can't go to see. Sigh. I miss living in London...
Wednesday, February 25, 2009
Further thoughts on Chapters IX-X and the suppl. reading
Good discussion today, and a good supplementary reading. Most of the issues I wanted to raise were touched on in class, so I don't have too much more to add. I'll recapitulate some points I enjoyed chewing on, and folks can comment if they have further thoughts.
1. Dealing with the unknown in science. The debate between Darwin and Kelvin on the age of the earth is a fascinating case study of the informal, heuristic strategies scientists use to estimate unknown quantities and bound the uncertainty of those estimates. The strategies on display include:
(a) 'Back of the envelope' calculations to roughly estimate an unknown quantity. This is how Darwin estimated the time required to denude the Weald. The trouble is that it's hard to say how much confidence we should have in such estimates. What's the range of plausible estimates?
(b) One way to determine the plausibility of a back of the envelope calculation is via a second, independent back of the envelope calculation. If both calculations give you the same answer, it's either a huge coincidence, or it's because both calculations are giving an approximately-correct answer. This was Kelvin's strategy for estimating the age of the earth. I had known Kelvin estimated the age of the earth, but hadn't known he'd made two independent estimates. So I now have much more respect for him as a scientist and a much greater appreciation for the pressure his calculations put on Darwin. Of course, Kelvin's calculations weren't entirely independent; they were based on some shared assumptions, which perhaps should've been cause for caution (though recognizing shared, implicit assumptions is often hard, as William Wimsatt's discussions of "independent" models of group selection point out). In hindsight, we know that Kelvin's calculations were way off, because he didn't know about radioactivity. But don't be too hard on Kelvin; there was no way for him to know his picture of how the world works omitted a hugely important, unknown factor (radioactivity). Such factors can never be ruled out, but it's never reasonable, or even possible, to allow for the possibility of them in our science. Telling scientists to "always keep in mind that your theory could be totally wrong because of some hugely-important factor nobody's ever thought of" isn't a useful guide to action.
(c) Simply admitting ignorance and calling for more research. This is basically the strategy Darwin ended up with by the 6th edition of the Origin. It seems to me to be a reasonable strategy, given that there were many reasons for treating evolution by natural selection as a working hypothesis useful for guiding further research, even lacking a good estimate of the age of the earth (lack of viable alternatives, independent evidence favoring natural selection, curiosity about how evolution by natural selection might proceed in the future, etc.) Part of being a good scientist is being a good judge of when to keep pursuing an imperfect or incomplete hypothesis, and when to drop it (either in favor of a competing alternative, or in favor of pursuing a completely different research topic). Philosopher of science Thomas Kuhn (in)famously thought that such decisions were entirely irrational, but this claim can be questioned on various grounds.
3. Ironically, debate about the correctness of uncertain calculations (regarding the age of the earth) was itself predicated on an (implicit) uncertain calculation (regarding the time required for natural selection to produce certain results). I'm a little surprised that apparently no one recognized this at the time. Or perhaps Darwin discussed in his letters why he thought natural selection needed more time than Kelvin's calculations allowed?
4. Turns out the hierarchy of sciences (aka "physics envy") goes back at least as far as Victorian times. So does the intimidating effect of mathematical calculations on those who don't know math.
5. Darwin's writing in the Origin hints at an implicit philosophy of theory testing, but it's not a philosophy Darwin actually adhered to in practice. Darwin says of many objections to his theory that they would be "absolutely fatal" if true. I assume he writes this way because these objections really did seriously concern him; it's not just a rhetorical technique he's deploying to make himself look brilliant when he refutes the objections. Darwin often sounds like a fairly strict Popperian falsificationist when he's discussing objections to his theory. That is, he sounds like he'd be prepared to junk the whole theory if even one fact could be shown to be inconsistent with the theory. The history of science shows that most scientists don't operate that way, and for good reason (science needs working hypotheses and so can't go chucking entire theories at the first sign of trouble). And arguably, Darwin himself didn't operate that way. His response to Kelvin was to modify his theory to include a greater role for rapid Lamarkian evolution, not to throw his theory out and start fresh.
6. Many of Darwin's arguments about the imperfection of the geological record are exactly the same as those deployed against Gould and Eldredge's modern idea of punctuated equilibrium (roughly speaking, the idea that evolution is characterized by bursts of rapid change associated with speciation events, separated by periods of stasis). We may talk about this more in the session on the Modern Synthesis and its critics.
7. A tangential issue: You might think there's a tension between my suggestion that scientists need working hypotheses (even imperfect ones), and my suggestion that it's ok to just admit ignorance on the question of the age of the earth, pending further research. Doesn't further research on the age of the earth itself need to be based on some working hypothesis, so that confessing ignorance on this question is a non-starter? I don't think so (write a comment if you disagree!) To estimate the age of the earth, I don't think you need a working hypothesis about its age. The question is a purely descriptive, empirical one, rather than a theoretically-motivated one. It's like estimating the height of a mountain, or the average depth of the ocean. To pursue those kinds of purely descriptive questions, you need to have working hypotheses about the sources of error and bias in one's estimation method, so that you can minimize or eliminate those errors and biases. But to identify and study the mechanisms of evolution and work out the consequences of those mechanisms, one needs to have some working hypothesis about the identity of those mechanisms. That is, one needs to have an underlying theory of evolution. (We could argue about whether it's ok to think of that theory as a purely instrumental predictive tool rather than as a true description of how the world actually is, but that's a whole other ballgame...)
1. Dealing with the unknown in science. The debate between Darwin and Kelvin on the age of the earth is a fascinating case study of the informal, heuristic strategies scientists use to estimate unknown quantities and bound the uncertainty of those estimates. The strategies on display include:
(a) 'Back of the envelope' calculations to roughly estimate an unknown quantity. This is how Darwin estimated the time required to denude the Weald. The trouble is that it's hard to say how much confidence we should have in such estimates. What's the range of plausible estimates?
(b) One way to determine the plausibility of a back of the envelope calculation is via a second, independent back of the envelope calculation. If both calculations give you the same answer, it's either a huge coincidence, or it's because both calculations are giving an approximately-correct answer. This was Kelvin's strategy for estimating the age of the earth. I had known Kelvin estimated the age of the earth, but hadn't known he'd made two independent estimates. So I now have much more respect for him as a scientist and a much greater appreciation for the pressure his calculations put on Darwin. Of course, Kelvin's calculations weren't entirely independent; they were based on some shared assumptions, which perhaps should've been cause for caution (though recognizing shared, implicit assumptions is often hard, as William Wimsatt's discussions of "independent" models of group selection point out). In hindsight, we know that Kelvin's calculations were way off, because he didn't know about radioactivity. But don't be too hard on Kelvin; there was no way for him to know his picture of how the world works omitted a hugely important, unknown factor (radioactivity). Such factors can never be ruled out, but it's never reasonable, or even possible, to allow for the possibility of them in our science. Telling scientists to "always keep in mind that your theory could be totally wrong because of some hugely-important factor nobody's ever thought of" isn't a useful guide to action.
(c) Simply admitting ignorance and calling for more research. This is basically the strategy Darwin ended up with by the 6th edition of the Origin. It seems to me to be a reasonable strategy, given that there were many reasons for treating evolution by natural selection as a working hypothesis useful for guiding further research, even lacking a good estimate of the age of the earth (lack of viable alternatives, independent evidence favoring natural selection, curiosity about how evolution by natural selection might proceed in the future, etc.) Part of being a good scientist is being a good judge of when to keep pursuing an imperfect or incomplete hypothesis, and when to drop it (either in favor of a competing alternative, or in favor of pursuing a completely different research topic). Philosopher of science Thomas Kuhn (in)famously thought that such decisions were entirely irrational, but this claim can be questioned on various grounds.
3. Ironically, debate about the correctness of uncertain calculations (regarding the age of the earth) was itself predicated on an (implicit) uncertain calculation (regarding the time required for natural selection to produce certain results). I'm a little surprised that apparently no one recognized this at the time. Or perhaps Darwin discussed in his letters why he thought natural selection needed more time than Kelvin's calculations allowed?
4. Turns out the hierarchy of sciences (aka "physics envy") goes back at least as far as Victorian times. So does the intimidating effect of mathematical calculations on those who don't know math.
5. Darwin's writing in the Origin hints at an implicit philosophy of theory testing, but it's not a philosophy Darwin actually adhered to in practice. Darwin says of many objections to his theory that they would be "absolutely fatal" if true. I assume he writes this way because these objections really did seriously concern him; it's not just a rhetorical technique he's deploying to make himself look brilliant when he refutes the objections. Darwin often sounds like a fairly strict Popperian falsificationist when he's discussing objections to his theory. That is, he sounds like he'd be prepared to junk the whole theory if even one fact could be shown to be inconsistent with the theory. The history of science shows that most scientists don't operate that way, and for good reason (science needs working hypotheses and so can't go chucking entire theories at the first sign of trouble). And arguably, Darwin himself didn't operate that way. His response to Kelvin was to modify his theory to include a greater role for rapid Lamarkian evolution, not to throw his theory out and start fresh.
6. Many of Darwin's arguments about the imperfection of the geological record are exactly the same as those deployed against Gould and Eldredge's modern idea of punctuated equilibrium (roughly speaking, the idea that evolution is characterized by bursts of rapid change associated with speciation events, separated by periods of stasis). We may talk about this more in the session on the Modern Synthesis and its critics.
7. A tangential issue: You might think there's a tension between my suggestion that scientists need working hypotheses (even imperfect ones), and my suggestion that it's ok to just admit ignorance on the question of the age of the earth, pending further research. Doesn't further research on the age of the earth itself need to be based on some working hypothesis, so that confessing ignorance on this question is a non-starter? I don't think so (write a comment if you disagree!) To estimate the age of the earth, I don't think you need a working hypothesis about its age. The question is a purely descriptive, empirical one, rather than a theoretically-motivated one. It's like estimating the height of a mountain, or the average depth of the ocean. To pursue those kinds of purely descriptive questions, you need to have working hypotheses about the sources of error and bias in one's estimation method, so that you can minimize or eliminate those errors and biases. But to identify and study the mechanisms of evolution and work out the consequences of those mechanisms, one needs to have some working hypothesis about the identity of those mechanisms. That is, one needs to have an underlying theory of evolution. (We could argue about whether it's ok to think of that theory as a purely instrumental predictive tool rather than as a true description of how the world actually is, but that's a whole other ballgame...)
Tuesday, February 24, 2009
my favourite brief snippet of Darwin
OTOOS has a lot of great lines, but the first (and now second) times I have read through it, one particular section really hit me. It's hiding in plain view really early in Chapter 9.
"He who can read Sir Charles Lyell's grand work on the Principles of Geology, which the future historian will recognise as having produced a revolution in natural science, yet does not admit how incomprehensibly vast have been the past periods of time, may at once close this volume."
He spends page after page trying to convince both scientists and lay people of his time how small inheritable changes could lead to complex behaviours and new species and all the biodiversity on the planet, and shows an astounding amount of patience in that endeavour.
But when he's faced with a young-earth creationist... he recognizes they are hopeless, can not be reasoned with, and that there is no way he can argue his science with them, because they can't even recognize deep time.
For a statement from Chuck D, it's fairly confrontational. But it's so true. If you can't accept that the Earth is billions of years old, then it's no use trying to teach you that common descent is the overarching law of biology. You are willingly ignorant, and if geology can't sway you, then neither can biology.
And yet we as scientists, as palaeontologists, or geologists, or evolutionary biologists, or some Frankenstein's monster combination thereof, are willing to jump through their hoops and "debate" them. To defend our position as if they have any science to stand on. We have to fight them at school board meeting after school board meeting to make sure they don't poison science education for the next generation.
So it's just refreshing to remember that Darwin was fighting the same forces of ignorance 150 years ago. And depressing that the same battles still exist, since some people are not using their naturally selected brains.
"He who can read Sir Charles Lyell's grand work on the Principles of Geology, which the future historian will recognise as having produced a revolution in natural science, yet does not admit how incomprehensibly vast have been the past periods of time, may at once close this volume."
He spends page after page trying to convince both scientists and lay people of his time how small inheritable changes could lead to complex behaviours and new species and all the biodiversity on the planet, and shows an astounding amount of patience in that endeavour.
But when he's faced with a young-earth creationist... he recognizes they are hopeless, can not be reasoned with, and that there is no way he can argue his science with them, because they can't even recognize deep time.
For a statement from Chuck D, it's fairly confrontational. But it's so true. If you can't accept that the Earth is billions of years old, then it's no use trying to teach you that common descent is the overarching law of biology. You are willingly ignorant, and if geology can't sway you, then neither can biology.
And yet we as scientists, as palaeontologists, or geologists, or evolutionary biologists, or some Frankenstein's monster combination thereof, are willing to jump through their hoops and "debate" them. To defend our position as if they have any science to stand on. We have to fight them at school board meeting after school board meeting to make sure they don't poison science education for the next generation.
So it's just refreshing to remember that Darwin was fighting the same forces of ignorance 150 years ago. And depressing that the same battles still exist, since some people are not using their naturally selected brains.
Thursday, February 19, 2009
supplementary reading for 02/25/09
Burchfield, J.D. 1974. Darwin and the dilemma of geological time. Isis 65(3):301-321. (pdf available to JSTOR subscribers)
For anyone looking for term paper ideas...
...this might be of interest. It's an essay contest being run by the Darwin Correspondence Project, looking for the best student essay on science and religion that uses material from Darwin's letters (which the Project makes available online). Essays that engage closely with Darwin's correspondence and connect with 19th century debates about science and religion are encouraged. First prize is 1000 pounds sterling, which is currently about $1800 Canadian. That would buy you, um, $1800 worth of something.
Thursday, February 12, 2009
Wednesday, February 11, 2009
Special issue of Nature on evolution
This week's Nature is a special issue on evolution. You can access it through the library website (electronic journals). There are a couple of news articles looking at recent research on the evolution of human culture, a debate on whether scientists should research the link between race and IQ, a fanciful article asking what would've happened if Darwin's publisher had asked him to rewrite the Origin as a popular book about pigeons, an article about how Darwin's anti-slavery views shaped his scientific ones, reprints of the poetry of Darwin's great-great-granddaughter, and a bunch of review articles on various evolutionary topics by various famous evolutionary biologists.
Chapter VII
Permit a humble supplicant to pose a question to the biologists of this outfit. In regards to warning calls, it was said the caller announcing his location to the predator by making noise isn't too much of a disadvantage. I would agree. Even if it is a disadvantage, it probably isn't so much of a disadvantage that the trait would be deselected. Callers rarely are killed as a result of their behaviour. Therefore, even if the behaviour isn't advantageous to the individual (while it is undoubtedly advantageous to the group) would not the trait still be passed down because it is not so disadvantageous as to warrant deselection - especially if it confers a general advantage to the whole?
Cannot this logic be applied to those species that produce sterile offspring? If giving birth to some sterile offspring does not destroy utterly the parent's prospects of reproductive success, since they may produce other offspring that are fertile, why should a variation with the tendency to produce some sterile offspring be wiped out of existence if producing sterile offspring does not hinder their fitness as an individual and enhances the fitness of the family or group?
I throw this question out into the void.
Cannot this logic be applied to those species that produce sterile offspring? If giving birth to some sterile offspring does not destroy utterly the parent's prospects of reproductive success, since they may produce other offspring that are fertile, why should a variation with the tendency to produce some sterile offspring be wiped out of existence if producing sterile offspring does not hinder their fitness as an individual and enhances the fitness of the family or group?
I throw this question out into the void.
Further thoughts on Chapters VII-VIII
I don't have much else to say on chapters VII-VIII that I didn't say in class, though some of these points were raised after some folks left so I'll repeat them here for everyone's benefit.
1. I love chapter VII, full of really interesting stuff. So full, in fact, that on p. 237-238 Darwin can just toss off the idea of kin selection/group selection as an explanation for the evolution of altruistic (self-sacrificing) sterile workers, and then move on to focus on what he considers the really difficult problem of explaining the evolution of distinct worker castes. We'll return to the ideas of kin and group selection, the distinction between them (or lack thereof), and their implications for humans, nearer to the end of the term (Darwin himself did come back to kin/group selection in Descent of Man). Darwin also notes in passing that the existence of distinct castes of sterile workers refutes Lamarckism ("oh by the way, I've refuted one of the most important biological ideas of all time"). And the long discussion of how bees could build complex, geometrically-perfect, wax-economizing honeycombs by following simple behavioral rules is extremely modern-sounding, perhaps the most modern-sounding passage in the entire book so far. The idea that simple biological rules, followed by 'dumb' individual agents, can yield complex, apparently-intelligent outcomes, and that we can demonstrate this by mathematical modeling, is not just a modern point of view but a cutting-edge point of view. That is, both the hypothesis, and Darwin's way of evaluating it, are bang up-to-date. They should hire Darwin at the Santa Fe Institute. The discussion of the evolution of brood parasitism is mostly off-base, but even Darwin's incorrect hypotheses are at least imaginative.
2. In contrast, I found chapter VIII a slog. It's Darwin's upteenth argument against the idea that species were specially created and are qualitatively different than varieties. It's ok, we believe you, please stop! What struck me most about this chapter is that it's perhaps the first time I've seen Darwin miss a clear opportunity to foreshadow a very important modern idea. Darwin thinks that hybrid sterility is just 'incidental'. But if hybrid matings don't lead to fertile offspring (either because they lead to no offspring at all, or only to sterile offspring), then selection will favor any trait that prevents hybrid matings in favor of productive matings (i.e. "assortative mating"--mating with those who are similar to you). Selection will also disfavor hybrid mating if hybrid offspring are fertile, but are less fit than their parents, for instance because the hybrids are intermediate between the parents and so aren't well-adapted to the 'niche' of either parent (or to any other niche--they're 'jacks of all trades and masters of none'). In short, it's very common that selection will favor what are now called isolating mechanisms. We need to understand how those mechanisms work, because they're the flip side of the origin of species. If you want to understand how species split, you need to also understand what keeps them from merging. Writing in the the 6 Feb. issue of Science, UBC's Dolph Schluter reviews evidence for what's now called "ecological speciation", which is essentially the modern version of Darwin's own idea about how species originate. Schluter highlights the importance of isolating mechanisms.
1. I love chapter VII, full of really interesting stuff. So full, in fact, that on p. 237-238 Darwin can just toss off the idea of kin selection/group selection as an explanation for the evolution of altruistic (self-sacrificing) sterile workers, and then move on to focus on what he considers the really difficult problem of explaining the evolution of distinct worker castes. We'll return to the ideas of kin and group selection, the distinction between them (or lack thereof), and their implications for humans, nearer to the end of the term (Darwin himself did come back to kin/group selection in Descent of Man). Darwin also notes in passing that the existence of distinct castes of sterile workers refutes Lamarckism ("oh by the way, I've refuted one of the most important biological ideas of all time"). And the long discussion of how bees could build complex, geometrically-perfect, wax-economizing honeycombs by following simple behavioral rules is extremely modern-sounding, perhaps the most modern-sounding passage in the entire book so far. The idea that simple biological rules, followed by 'dumb' individual agents, can yield complex, apparently-intelligent outcomes, and that we can demonstrate this by mathematical modeling, is not just a modern point of view but a cutting-edge point of view. That is, both the hypothesis, and Darwin's way of evaluating it, are bang up-to-date. They should hire Darwin at the Santa Fe Institute. The discussion of the evolution of brood parasitism is mostly off-base, but even Darwin's incorrect hypotheses are at least imaginative.
2. In contrast, I found chapter VIII a slog. It's Darwin's upteenth argument against the idea that species were specially created and are qualitatively different than varieties. It's ok, we believe you, please stop! What struck me most about this chapter is that it's perhaps the first time I've seen Darwin miss a clear opportunity to foreshadow a very important modern idea. Darwin thinks that hybrid sterility is just 'incidental'. But if hybrid matings don't lead to fertile offspring (either because they lead to no offspring at all, or only to sterile offspring), then selection will favor any trait that prevents hybrid matings in favor of productive matings (i.e. "assortative mating"--mating with those who are similar to you). Selection will also disfavor hybrid mating if hybrid offspring are fertile, but are less fit than their parents, for instance because the hybrids are intermediate between the parents and so aren't well-adapted to the 'niche' of either parent (or to any other niche--they're 'jacks of all trades and masters of none'). In short, it's very common that selection will favor what are now called isolating mechanisms. We need to understand how those mechanisms work, because they're the flip side of the origin of species. If you want to understand how species split, you need to also understand what keeps them from merging. Writing in the the 6 Feb. issue of Science, UBC's Dolph Schluter reviews evidence for what's now called "ecological speciation", which is essentially the modern version of Darwin's own idea about how species originate. Schluter highlights the importance of isolating mechanisms.
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