Tuesday, July 28, 2009
In a talk entitled “Darwin's Compass: Why the evolution of humans is inevitable,” Conway Morris will present his argument that evolution has a limited number of “solutions” to particular “needs,” as demonstrated by the numerous cases of parallel evolution observed among living organisms. This argument suggests that evolution is not random, but follows guiding principles, a point of view that leaves room for both science and religion in the study of evolution.
Simon Conway Morris holds an ad hominem chair in Evolutionary Palaeobiology at the University of Cambridge. As a palaeontologist, he is renowned for his insights into evolution and is a leading authority on the Burgess Shale fauna, the rise of multicellular organisms, the Cambrian Explosion, and the topic of evolutionary convergence.
This talk concludes the Royal Tyrrell Museum’s 2009 Speaker Series dedicated to naturalist Charles Darwin.
Admission to the talk is free, however, to visit the galleries regular Museum rates apply.
Friday, April 17, 2009
"Darwin's Origin of Species: A Guided Tour"
Wed. May 20, 7:30 pm
Burnswest Theatre, Fort Calgary
More info here.
Wednesday, April 15, 2009
The event is totally free, so come on by and tell your friends. Chris will speak for about an hour tops, and there'll be question-and-answer with the audience afterwards.
As with Mott Greene's lecture, I need a couple of volunteers to man the microphones for the question-and-answer session that will follow the talk. Email me if you're interested.
After Chris' talk the various Darwin events will be on hiatus until the fall. Watch for more events then, including John Brooke's public lecture on evolution and religion.
Tuesday, April 14, 2009
Maynard Smith, J. 1999. Too good to be true. Nature v. 400, p. 223.
Actually, perhaps this post isn't entirely off-topic: Maynard Smith considers Kelvin's incorrect estimate of the age of the Earth as a candidate, but rejects it as insufficiently clever.
Monday, April 13, 2009
(stops talking like a teenager for a bit)
It's entirely possible to do biology, evolutionary or otherwise, without having the slightest clue who Darwin was, besides:
Just the same as its possible to do physics without knowing who Newton was, or be a political writer without knowing who Machiavelli was, or be a speculative fiction writer without knowing who H.G. Wells was. But it's deeply ironic when people who care about the past (particularly of a prehistorical nature), and spend their time discussing events that occurred to the ancestors of the ancestors of us and our pets and their fleas, are not willing to employ a bit of the same interest in discovering the ancestry of the science they study.
Obviously reading through the Origin is in no way as naturally uplifting as seeing where australopithecines once walked the Great Rift Valley, or seeing the collected corpse of someone who we now know as Turkana boy, or peeking at the flattened skeleton of Eomaia and trying to find the family resemblance between you and a pile of fossilized hair and bones.
And to act like a Hennigian dogmatist for a second (with a slight usage of Dawkinsian lingo thrown in for good measure), of course Darwin can not be proved to be an intellectual ancestral taxon, we can only argue that his memes had unique synapomorphies which are shared with the evolutionary scientist crown group.
But the Origin is the book that brought biology into the materialistic, mechanistic universe that Newton helped introduce to European science. Natural theology, vitalistic forces, special creation, the concept that life was somehow intangibly different than non-life: all of these ideas were slowly or quickly thrown out of biology due to the materialism that Darwin brought to the table and forced everyone to drink.
"A little Learning is a dang'rous Thing;
Drink deep, or taste not the Pierian Spring:
There shallow Draughts intoxicate the Brain,
And drinking largely sobers us again."
Due to his legendary stinging wit, I imagine Pope would say something not nice about me (or maybe my own wits) for using his words to back up the destruction of theological biology. And despite my Dawkins fanboy tendencies, I'm not in anyway insinuating that Chuck D is an atheist icon. His wife would have smacked him.
(Though I will agree with Rick D that, for the most part, the Origin does make it possible to be an intellectually fulfilled atheist. But that's another story.)
Darwin is simply a very good critical thinker who linked together some observations about the world, made some predictions based on those observations, and formulated a simple but powerful mechanism for how large change can happen in small pieces over large pieces of time. Some of his arguments make as much sense now as they did back then, while others (like his insistence to ever talk about use and disuse, ARGH) have faced criticism and been sloughed off.
The intellectual lightweights who consider Darwin to be the devil's lieutenant make a big deal of the man and his works. Reading enough about him to recast the story in a more realistic light is the least an evolutionary scientist should do to honour thine ancestors.
To paraphrase another 19th century European theorist, "Evolutionary scientists of the world, unite, and read Darwin, you have nothing to lose but your chains (and a coupla days)!"
Only a minority of historical tracts actually spend much time focusing on the result of those endeavours. Historians focus on human movements and in their narratives too easily take the progress of science and discovery for granted as a gradual process which forms 'the background' of dramatic tales of battles, corruption, and human frailty. But those people in 'the background' are often some of the most decisive and dynamic of all those who forge human destiny, without whom our story would be completely and irrevocably altered. Darwin was one of those people.
On the Origin of Species drives home, to my mind, how the progress of civilisation, its science and ideas, is entirely dependent on solitary human action. Darwin devoted much of his life to amassing facts and developing his theories. It was a labour of love. He anticipated to a staggering degree modern conceptions of evolutionary thought. What is still more impressive is how many of those ideas remained dormant and largely unappreciated while the debate raged all around him during the nineteenth and early twentieth centuries. Even now, people across the globe are still coming to grips with the full force and significance of his findings.
In reading the Origin I found one of the most impressive aspects of Darwin's theory was his insistence of a common ancestry and his definition of species. For Darwin, a species was defined by its degree of variation from other forms of life. In addition if one goes far enough back, one finds common ancestors for those species. Even while life on earth is constantly changing into wondrous new forms and is locked in a complex struggle for survival, all life itself sprung from a single source. Species may war against one another but their differences are subjective and not eternal, their rivalries and enmity natural, not mortal. The unity of descent is even more profound when narrowed to the human realm, undermining much of the theories of so-called Social Darwinists. In the great clashes of the twentieth century men were too quick to lay emphasis on the significance of being a 'separate race' of man. Little did many of them realise the man whose theory of 'survival of the fittest' they so eagerly espoused had one hundred years earlier concluded a common unity that connects intimately all life found on earth. How meaningless do the small differences between man and man, nation and nation, how trivial does the brief story of our tumultuous history seem next to millions upon millions of years of evolution!
Like all great discoveries, Darwin's theory of evolution raised as many questions as it answered. Perhaps infinitely more. The world after 1859 became a much less familiar place. The indisputable pillars of creation in religious faith were shaken. The nature of the universe became less clear. We have yet, with our ideas, to illuminate more than one bright spark of understanding in a vast darkness of endless space. And while science holds open the possibility of widening our understanding, most, if not all of us, will pass on from our short lives without much extending our sight. The souls of men and nations just as the fires of stars, however brightly they may burn, are destined to one day flicker out. As such skeletons, the ruins of temples and ancient cities, and the wastelands of dead stars and planets are remarkably similar. They are monuments of what was once alive and great but is no more. But what genius can those fires forge while they burn! Darwin's legacy is indicating to us how each passing life is part of a greater more magnificent process, sublime and of vast incomprehensible grandeur:
"There is grandeur in this view of life," he said, "with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."
I was also constantly surprised by how relevant the Origin still is today. Darwin was rarely completely off the mark, which is all the more impressive considering all the advances we have made over the last 150 years, of which Darwin was completely ignorant. It was particularly fun to read statements that in a way were prophetic. I wish I could have seen Darwin’s reaction to the discovery of Archaeopteryx! But then again, that’s one of the things that set Darwin’s theory apart from those of other evolutionary scientists of his time. Predictability! This course gave me a better idea of why (and how) Darwin’s theory was so significant and revolutionary.
Something I had never really thought about until recently is how evolutionary science itself is changing and evolving. Not having an extensive biology background, I had always thought of evolutionary biology as (relatively) immutable and was surprised to realize that the science itself is evolving. It makes complete sense, that in any field of study the more you learn, the more questions you ask, and the new directions you take. I just never really thought about it before.
I was also very impressed with Darwin’s “faith”, for lack of a better term, in his theory. He dedicated a whole chapter to problems with his theory and was fully willing to admit that he didn’t have it all figured out. Despite this and the heavy scrutiny he was under, he stood by his theory and didn’t back step (at least not on the main points?). I haven’t read the later editions.
I also respect the fact that Darwin made a clear distinction between his science and his religion. Considering the topic he was discussing one would expect Darwin’s personal beliefs to be somewhat more on the forefront in the late 1800’s. Even today there is a lot of speculation about Darwin’s personal beliefs, but he kept it separate and private, an incredibly wise move in my opinion.
I have really enjoyed reading the origin and listening to the weekly discussions. They have also made me much more curious about Darwin “the man”, which we got a taste of in Janet Browne’s biography and in some of the discussions. When I have a little more time for myself, I want to read some of Darwin’s letters and his other works. Hopefully they won’t collect too much dust before I crack their spines!
I can say unequivocally that the Origin is the best 490-page argument I’ve ever read. His conclusion in particular is a work of art, and is worth rereading more than once. I was struck by just how subtle and sophisticated Darwin’s actual claims are, compared to the gross caricatures of his views you might be subjected to, both by those who argue for and those who argue against his view. Also, it is funny how some modern creationists (‘intelligent designers’) are just rehearsing objections which Darwin himself brought up in 1859, and fully answered.Perhaps the one thing that will stick in my mind the longest is just how anti-essentialist Darwin was about species. Species, for Darwin, were NOT essentially different from varieties; in fact, varieties could be seen as incipient species. I don't want to put words in his mouth, but he seems very conventionalist: surely there are groups of animals which differ more or less from other groups, but there is no magic criterion which marks groups as different in kind from others - our labels are just that, and our labelling system may be more or less useful. Wonderful!
I won’t rant on and on here about the quality of this book. But I just have to say that I was pleasantly surprised at how accessible it was to me, a non-biologist (there is very little jargon), and that I really think it would be impossible to read it without feeling the full force of the theory of evolution by natural selection; that is, just how many facts it predicts and explains. Darwin took pains to amass ridiculous amounts of evidence for his theory before publishing it, and remember, this book is just an abstract of what he really wanted to say! Darwin himself said that the person who is more impressed by the problems of a theory than with its solutions may at once reject his theory, but of course this would have turned out to be to their detriment in this case. The ‘problems’ have turned into entire (fruitful) research programs, all elucidating and confirming (if we want to be realists) the theory of evolution via natural selection that much more.
Thanks to Jeremy and the other class members for putting up with a philosopher for an entire semester; I feel like I am a much better person for having been able to share the experience of reading the original Origin with you all.
Sunday, April 12, 2009
Anyhow, I have enjoyed this class. It has been interesting to read and listen and think. I would like to read 'The Origin' again - perhaps when I am less busy with school and extracurricular activities, and have more time to really digest it.
Well, like Dr. Fox, I am impressed at the breadth and depth of Darwin's understanding. At how much he was able to piece together and comprehend. And certainly at how much he strove to produce evidence to substantiate his arguments. I am intrigued by the man himself - how he had this brilliant idea, yet wanted to make sure it was fool-proof before he presented it to the world. And then when he was forced into early publication, I am impressed at his civility towards Wallace - in the face of possibly losing recognition for his life's work. One reason why I wanted to read 'The Origin' was to see for myself what it was really about. I believed that Darwin got a bad rap for a lot of stuff that wasn't necessarily true. And in the end, I still believe that. I think that many people (especially religious) have a 'fear' of Darwinisim and evolution - and think that Darwin was an early version of our friend Dawkins. Thankfully (to me, at least!) that is not true. I also think that there are many common misconceptions about the process of evolution - one of the simplest being, "If man descended from apes, why do we still have apes?" People don't seem to understand that the theory is that of a common ancestor.
As for me personally, I found this an interesting time to reflect on my own beliefs. I certainly didn't find anything to cause me to not believe in God. I know that we just can't comprehend everything, but that the more we learn, the more the 'mysteries of God' will be 'unfolded' to us, as it says in scripture. If I can never solve all these questions in this life, I am content to wait to learn the answers in the next. Balance is very important to me, so if I know one side of the argument, then I had better know the other, too.
Thanks to everyone for all your insights.
Saturday, April 11, 2009
Friday, April 10, 2009
Wednesday, April 8, 2009
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.
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.
As the reviewer points out, a comparative analysis of religious and evolutionary imagery would probably be fascinating. Someone should go do it!
Saturday, April 4, 2009
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
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
A copy is available at your friendly university library.
Wednesday, April 1, 2009
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
"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
2) Borrello, M. E. 2005. The rise, fall and resurrection of group selection. Endeavour 29 (1):43-47. (pdf)
3) Bowles, S. 2008. Conflict: altruism's midwife. Nature 456 (7220):326-327. (pdf)
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.
Monday, March 23, 2009
Sunday, March 22, 2009
2) Huxley, J. 1942, 1963. Evolution: The Modern Synthesis. Chapter 1 of First Edition, excerpts from the Introduction of Second Edition.
Monday, March 9, 2009
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.
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
Wednesday, March 4, 2009
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.
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
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
"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
Thursday, February 12, 2009
Wednesday, February 11, 2009
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.
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.
Saturday, February 7, 2009
p81) This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection.
Hmm, I was once told that nothing can be selected for, only against because basically, if you don't have the right stuff you die.
p82) ...a change in the conditions of life, by specially acting on the reproductive system, causes or increases variability...
Lamarkism, or Darwin just trying to make sense of what he didn't know?
p87) What natural selection cannot do, is to modify the structure of one species, without giving it any advantage, for the good of another species.
Maybe not on purpose, but there must be some examples of co-evolving species that shows modifications of one species being good for another?
p106) Generalists versus specialists!
...forms produced on large areas...will give rise to most new varieties and species.
I know you people discussed this but I would really like to see the data on that because even though it sounds logical, maybe it isn't true.
p107) Do all 'living fossils' come from inhabiting a confined area?
p108) That natural selection will always act with extreme slowness, I fully admit.
Opposite of punctuated equilibrium?
p109) I can see no limit to the amount of change, to the beauty and infinite complexity of the coadaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection.
I absolutely love this quote. Is there a limit to the amount of change? I can think of possibly two: 1) organisms will retain their use of DNA; 2) organisms will never be found in a gaseous state. I am iffy on point 1.
The section on extinction gets me excited for some reason :). What IS the maximum amount of species that existed on the earth at one particular time? Min.? How would we ever know? Does the number of species fluctuate with the earth's changing climates and habitats????? Can someone please build me a time machine?
p110) Hence, rare species will be less quickly modified or improved within any given period [compared to common species] and they will consequently be beaten in the race for life by the modified descendants of the commoner species.
This seems like a reasonable assumption for Darwin to make, but how often does this really occur? Maybe sometimes rare species are modified more quickly with changes in habitat.
p119) The modified offspring from the later and more highly improved branches in the lines of descent, will, it is probable, often take the place of, and so destroy, the earlier and less improved branches...
Again, this is always implied but is this really how evolution always works? I know it's hard to get actual data on this but it is really very important. But then Darwin goes on to explain anagenesis, where "the process of modification will be confined to a single line of descent". However, what about multiple lines of descent where the ancestor is not "destroyed". Also on p121, Darwin states "the original parent-species itself, will generally tend to become extinct". Generally, but not always? But then, maybe to hedge his bets, on p122 Darwin states that if "...the modified offspring of a species get into some distinct country, or become quickly adapted to some quite new station, in which [both] do not come into competition, both may continue to exist."
p121) ...the species, which are already extremely different in character, will generally tend to produce the greatest number of modified descendants.
This could easily be tested. Did Darwin already have the data?
p61) I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection, in order to mark its relation to man's power of selection.
It seems that even the name emphasizes (hu)man's power. Was this something Darwin was thinking about when he came up with the name for his idea? Not that humans had any power in natural selection of course, but that people would associate the power of 'nature' with the power already held by humankind?
p62) We behold the face of nature bright with gladness... :)
p63) There are different kinds/gradients of 'struggle'.
p66) ...the average number of any animal or plant depends only indirectly on the number of its eggs or seeds.
Yes, I understand that he is discussing k- verses r- selected organisms but I think this is quite a generalized statement and a lot of other factors determine the average number of them.
p68) Climate plays an important part in determining the average numbers of a species, and periodical seasons of extreme cold or drought, I believe to be the most effective of all checks.
Will this be a check of humans???
p70) ...that a plant could exist only where the conditions of its life were so favourable that many could exist together, and thus save each other from utter destruction.
This statement stood out for me for some reason. Has this been tested? Is this sort of like the school of fish hypothesis? Can anyone elaborate on this for me?
p73) Food Webs!
Nevertheless so profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do not see the cause, we invoke cataclysms to desolate the world, or invent laws on the duration of the forms of life!
"In England, these insects used to be called Humble Bees, and they were the stuff of which legends were made. In The Origin of Species, Charles Darwin related a story that asserted that old maids were the real power behind the British Empire. The reasoning behind this remarkable claim was that the British army lived on beef; to raise beef you must have clover; and clover, particularly red clover, is pollinated only by humble bees. When field mice are abundant, they often break into the nests of humble bees to steal the honey pots, thus killing the bees. Old maids keep cats, and cats kill mice; hence the bee population, the clover crop, and the beef supply all depend on the number of old maids— well, you get the idea. It’s the food chain in action again." B. Meredith
p76) ...but probably in no one case could we precisely say why one species has been victorious over another in the great battle of life.
Any papers on this?