About Rationally Speaking
Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.
Tuesday, November 14, 2006
Making Sense of Evolution (the book)
The first thing to know about the book is that, although it is in fact a critique of the limitations of the so-called Modern Synthesis, i.e. the current incarnation of evolutionary theory that has held sway since the 1940s, it should not in any reasonable way be construed as ammunition for creationism, intelligent design, and other such nonsense (of course, if someone wishes to unreasonably so construe the book, be my guest).
What the book (written in collaboration with my philosopher colleague, Jonathan Kaplan) attempts to do is a critical examination of the logic, consistency and applicability of some of the fundamental concepts used by evolutionary biologists. Some of these concepts include basic ones such as natural selection and biological species, as well as more esoteric ones like “adaptive landscapes” and “genetic constraints.” Jonathan and I claim that some of these ideas are problematic in the sense that they either can be construed in a variety of not necessarily clearly compatible ways, or they have a troubled relationship with what evolutionary biologists actually do in the course of their empirical research.
Take natural selection as an example. It can be thought of as a physical process resulting from the direct interaction between organisms and the environments in which they live. This is certainly the way Darwin thought about it. But in most modern biological literature it is actually defined (and empirically measured) as a statistical covariance between traits and measures of fitness, i.e. as an abstract property of populations. Jonathan and I go into great detail to show that biologists may be unaware of all the not-so-trivial complications that arise when one wishes to connect Darwin-style, individual-level natural selection with the way contemporary biologists use the “same” concept at the level of entire populations.
A second example, a bit more technical, concerns the idea of “adaptive landscapes.” This is a standard conceptual tool in evolutionary theory, and refers, well, Jonathan and I point out that it seems to refer to several things, not themselves easily connected to each other. The idea was introduced by Sewall Wright in the 1930s to present to a non-mathematical audience of biologists his way of thinking about the relationship between the genetic make-up of individuals and populations on the one hand and the corresponding fitnesses of the same genotypes on the other. To make the story short (for the longer version you'll have to read the book), Jonathan and I claim that the idea was fraught with problems and inconsistencies from the beginning, and that it has now been radically modified by the work of a mathematical biologist named Sergey Gavrilets. Sergey actually showed that the mathematical (and biological) properties of realistic (i.e., highly multidimensional) “landscapes” are very different from those of the 2- and 3-dimensional versions usually presented in textbooks and examined in most of the literature. Indeed, these differences are such that some old questions to which biologists have dedicated a large amount of effort ought to be rethought in an entirely different fashion, and may in fact cease to be relevant to our understanding of how evolution works. For example, the classic adaptive landscape problem is how does a population “move” from one adaptive peak to a higher one, i.e. how can evolution re-shape the genetic makeup of populations to increase their average fitness. The problem is that the “peaks” of the classic rendition are separated by maladaptive “valleys,” i.e. by combinations of genes that have lower fitness than the combinations currently present in the population. By definition, natural selection cannot bring a population “down” such a valley to reach a nearby peak, because it (selection) doesn't have forethought, it cannot sacrifice the immediate advantage for the long-term gain. Several ingenious (but largely unworkable) solutions have been proposed over a course of decades, until Gavrilets demonstrated that if the landscape is highly-dimensional (as must be the case for real organisms with tens of thousands of genes) the problem largely disappears because there are no “peaks” and “valleys,” but rather large continuous multidimensional hyper-planes of high fitness punctuated by occasional “holes” of low fitness (hence the term “holey landscapes” to refer to Gavrilets' theory). All natural selection has to do is keep the populations from falling into the holes, i.e. to evolve genetic constitutions that would drive the population to extinction. As I said, if you need more than this, read the book...
The main reason I liked working on this book, though, is because it represents a fairly rare (though certainly not unheard of) example of collaboration between a philosopher and a scientist, and I assure you it was much fun to get past (or around) the inevitable cultural barriers that separate the two cultures of the humanities and the sciences. Especially when the cross-cultural exchange is helped by some excellent wine from Jonathan's exceedingly well-stocked cellar.