 |
| This illustration is from Björn Ostman's blog. |
Gavrilets (2004), however, only shows these images at the very beginning of his book, in order to prove them wrong. As fitness landscapes are multidimensional (not 3 dimensional), there are many connections between peaks. As a mental picture imagine bridges between the peaks bridging valleys. Therefore Gavrilets concludes that fitness landscapes are very different from ordinary landscapes and that populations form networks within them, where much of the variation is neutral in terms of fitness. Nevertheless Behe presents the rugged landscape as if it was the state of art in research and makes a lot of fuss about the impossibility of a population crossing valleys in the landscape.
How is that to be judged? In my eyes, it is either gross negligence or dishonesty. If Behe took the images from Gavrilets without taking even a superficial look at the context and what Gavrilets was showing, it would be gross negligence. If, however, he knew what Gavrilets was about, it would be dishonest.
Given that on page 114, Behe falsely credits Fisher (not Wright) with conceiving the idea of a fitness landscape, I conclude that he is only negligent or just ignorant. Otherwise he would have known that Wright already proposed drift in small sub-populations as a means of crossing valleys that requires no ID.
Regardless of who made the comments about the problems of moving from peak to peak, it really is a problem. Not a problem that cannot be overcome, of course, but also not one that is solved by arguing that there really are paths between peaks that don't involve a decrease in fitness, because there most emphatically are peaks, no matter what the dimensionality is. However, valleys can be crossed, depending on the mutation-supply rate (population size times mutation rate) and on the depth of the valleys. Wright's Shifting Balance Theory offers another way to cross valleys, by fragmenting the population geographically, whereby demes (subgroups) can drift across valleys (because smaller populations are less restricted by selection).
ReplyDelete@Bjørn,
ReplyDeletesure, science only gets interesting when there is a problem in the first place. But Behe always wants to make an in principle impossibility out of a problem. Same with his argument concerning irreducible complexity. He starts with a definition and ends with claiming the in principle impossibility of irreducibly complex things to evolve.
However, even for mousetraps it is not impossible in principly to come up with an evolutionary account of their history (see here), even if tastes concerning the Darwinization of culture may differ.
The Fitness landscape is not static. I changes (peaks migrate or fade/intensify) as the organism's environment (physical and biological) changes. Change in phenotype can be regarded as tracking a moving peak.
ReplyDelete-djlactin
Moreover, the fitness landscape also changes as the organisms themselves change genetically. Each advantageous mutant will automatically become the new local peak. It's hard to imagine a fitness landscape existing before any organism occupies/creates it.
ReplyDelete