Saturday, April 11, 2009

Taking Home Darwin's Species Concept

I found, through our discussions of the Origin, that I was able to get a better grasp of what Darwin meant be 'species' and perhaps what many biologists really mean by 'species'. It is hard to describe what I have established in my head as Darwin's picture of how a phylogeny would really look versus how we present it. It is more an image than anything verbal. At some point I will do a painting of it, scan it, and put it on here so you can share in my take home. For now, though, all I can do is declare that Darwin's concept of species still makes more sense to me than any of those I have heard in the Philosophy of Biology thus far. The continued applicability of Darwin's ideas never ceases to impress me.

Friday, April 10, 2009

Darwin's egg

You never know what you'll find in the back of a drawer.

Wednesday, April 8, 2009

Someone else's reflections

If you need additional inspiration for your reflections on the Origin, have a look at John Whitfield's final thoughts at Blogging the Origin.

He makes the excellent point that Darwin can be, and has been, claimed as a founding father by different schools of evolutionary thought. One is what John aptly names the 'lean and mean' school of evolutionary theory (R. A. Fisher, Bill Hamilton, John Maynard Smith, George Price, with Richard Dawkins as their most famous popularizer). This line of thinkers (mostly skinny Englishmen, as Whitfield points out) tends to focus on elegant mathematical models that strip evolution to its bare essentials, and views natural selection as both the most powerful and most interesting evolutionary force. This group appreciates Darwin for his ability to see the simple general principles underlying the polyglot diversity of nature. By contrast, the more loosely defined 'let a thousand flowers bloom' school (think Stephen J. Gould) admires Darwin the natural historian (the fact hound rather than the theoretician), and tends to see the polyglot complexity of nature as the net outcome of many complex interacting factors, of which natural selection is only one. I'm mostly a 'lean and mean' man myself, though I think there are interesting questions about the interplay of natural selection and other factors that both schools of thought tend to ignore.

In a previous post, Whitfield also notes, correctly I think, that a big part of Darwin's genius is his ability to see how patterns in space (say, biogeographical patterns in the distribution of species) can be generated by processes operating over time. Darwin had an extraordinary ability to visualize past sequences of events and how they could've resulted in present-day spatial patterns.


Having asked everyone else to reflect on the Origin and post their reflections, it's only fair that I should do so too.

I enjoyed the book tremendously, and I'm glad I no longer have to embarrass myself by admitting I hadn't read it. I'm even secretly proud of having read the first edition, when most other people have read the sixth. It's a bit like being able to boast that you saw the original version of a great foreign film rather than the Hollywood remake.

I've come away hugely impressed with Darwin's prescience. It's just stunning (even a little scary) how many modern ideas in ecology and evolution are already there in Darwin, and how they all fit together in his mind in pretty much the same way they do for us today. And his error rate is so low--that surprised me. I expected to see that Darwin would have a firm grasp of the core idea of evolution by natural selection, and he does. But I expected that his thoughts on peripheral details and specific examples would often be somewhat wonky. They're mostly not. It's rare that you catch Darwin failing to extend an idea to its logical conclusion (as in his failure to see that what we now call antagonistic pleiotropy can explain vestigial organs in cave dwellers as well as in parasites), or just proposing a strange-sounding hypothesis (as in his explanation for brood parasitism in birds). I'm sure some of this is luck, but I don't see how all of it could be. Darwin's just too right, too often. As the saying goes, it's best to be good and lucky. And it's extraordinary that he managed to see all this without knowing anything about transmission genetics or developmental biology. Even Wallace, who had the same basic idea, never came close to working out all its implications or marshaling all the various lines of evidence given by Darwin.

Ironically, the one area where Darwin's reasoning disappoints me a bit is in the explanation of the origin of species. Darwin's terrific on the origin of adaptation, on how you get Design without a Designer. And he's terrific on the evidence for evolution, and on how his theory ties together a huge body of apparently-disparate facts in fields as different as embryology and biogeography. But as I've described in another post, I don't think he had a sufficiently strong appreciation for how selection pressures could vary from place to place, and I think this is what led him to propose the Principle of Divergence. This principle is clearly crucial to his understanding of how natural selection leads to speciation, but it doesn't stand up to empirical or conceptual scrutiny, and I think its flaws could've been seen even at the time.

I'm also impressed with Darwin the fact hound. He's determined to get things exactly right, even if that means rejecting an idea he'd worked his butt off on for years. I'd like to read some of his letters to get a sense of how much of this impression is just a rhetorical pose. Surely he wished and hoped that evolution by natural selection was The Answer, right? But how could he wish that and at the same time put that wish to one side and truly take seriously all possible criticisms of his idea? My experience is that science proceeds on a sort of adversarial model (what philosopher David Hull called "science as a selection process"), whereby competing theories each have their advocates and the court of scientific opinion sits in judgment, with peer review "selecting" for the best theories. Of course, I do try to criticize my own ideas, if only because I worry that if I don't I'll get trashed by peer reviewers, and I think other scientists do as well. But I'm not sure that Darwin's self-critical approach is a dominant one.

Closely associated with Darwin the fact hound is Darwin the polymath. The age of specialization began before Darwin (Leibnitz was said to be the last man who was an expert in every field of human knowledge), but it hadn't yet gotten to the point where one couldn't be expert in all the fields Darwin draws on: geology, paleontology, ecology, etc. I flatter myself to think I'm slightly more widely read than my fellow community ecologists, at least in certain fields. But I'm absolutely a dilettante compared to Darwin.

Going in, I had no idea that Darwin took "special creation" as a serious alternative hypothesis, or that his argument against it isn't so much that it's falsified by the data as that it explains and unifies nothing. This is rather different from the arguments you see deployed against various versions of creationism today. And of course, those arguments are only deployed in the context of political debates today. It's interesting to be transported to a time when creationism really was a viable scientific hypothesis.

Darwin's reticence on the implications of his theory for people (and God) strikes me as very wise. It's a rational choice for someone like Darwin, who always wants to be completely sure of his ground. But it strikes me as an ethical choice, too. It shows respect for those with other, possibly conflicting ideas. Richard Dawkins has many virtues, but one of his vices is failure to take seriously alternative points of view with which he disagrees. Dawkins doesn't suffer fools gladly, but he also gives the distinct impression that he has all the answers and that anyone who disagrees with him is foolish.

So if I admired Darwin before (and I did), he's one of my heroes now. Evolutionary biologists are sometimes accused of "worshiping" Darwin, as if he were a god himself (this is the "Darwin the Myth" of Mott Greene's recent lecture). I can see why now, and I couldn't before.

The Ethics of Culture

Totally non-Darwinian post: If you want to check out Samuel Fleischacker's The Ethics of Culture, it's out of print but still available through various sellers at There's also a brief but highly positive review of the book from "A Customer" whose identity you may be able to infer...

Mistaken identity

I have been mistaken for someone who knows a lot about Darwin and the Origin (this happens a lot), and so have been invited to speak on these topics at the next meeting of Nature Calgary (aka the Calgary Field Naturalists' Society). The talk is on May 20 at 7:30 pm at Ft. Calgary. Apparently the meetings are open to the public if you want to come along. But if you'd rather not spend an evening listening to an illustrated synopsis of the class you've just taken, you may want to give it a miss.

Add this to your reading list

This week's Nature includes a review of God - Or Gorilla: Images of Evolution in the Jazz Age. It's a book about how images and diagrams were used to communicate evolutionary ideas to the general public in the run-up to the Scopes "monkey" trial. Sounds very interesting. Pictures are powerful but dumb: one's reaction to them is very sensitive to one's prior experience, knowledge, values, and expectations, so it's tough to use pictures to convey exactly what you want to convey. The review is very positive--apparently it's a good read as well as a thought-provoking one.

As the reviewer points out, a comparative analysis of religious and evolutionary imagery would probably be fascinating. Someone should go do it!