Posted by: Dan | February 4, 2007

Behe’s Distortions on the Evolvability of Complex Features

Being that I went to undergrad at Lehigh and took a couple classes under Behe (not very good classes mind you), I emailed this to the Cornell IDEA listserv in an attempt to spark some discussion. The local IDEA club is fairly lifeless these days however, so I’m sharing my email with a slightly broader audience…

Michael Behe contributed this to the Discovery Institute’s “media complaints division”: “The evolutionary puzzle becomes more complex at a higher level of cellular organization.” No kidding.

Behe attacks high-profile papers in Science and Nature with such words as “very modest paper was puffed,” “hype otherwise-lackluster work,” and “breathless papers like this” – he certainly has a lot of chutzpah to say such things, considering his publication record in favor of intelligent design – nada. Behe has written one paper on related issues, using a computer simulation, to demonstrably refute a hypothesis based upon “irreducible complexity” of proteins. Other than that one paper, he has written hardly anything other than opinion pieces. So if one were to compare “lackluster work” (Science and Nature) with “zero work” (Behe), I’ll take the lackluster.

To wit, Behe continues:

My general reaction to breathless papers like this is that they vastly oversimplify the problems evolution faces. Consider a very rugged evolutionary landscape. Imagine peaks big and small all packed closely together. It would of course be very difficult for a cell or organism to traverse such a landscape.

He can imagine whatever he wants; he hasn’t attempted to actually put his imagination to the test, has he? One can question Poelwijk et al., but one thing can be said about such papers that can’t be said of Behe – they’re trying to actually test their models, ideas, and imaginations.

But Behe’s fraudulent argument doesn’t stop there. He argues: “Nonetheless, they, like most Darwinists, assume that larger changes involving more components are simple extrapolations of smaller changes.”

Of course I find it odd that he calls them Darwinists (why not biologists?; we don’t even know that all points on the fitness landscape need be adaptive – in fact there’s observations in the literature aplenty that neutral mutations, gene duplications and neofunctionalization abound – so why does he attack an already superceded theory?). But whatever.

The larger point is that he’s addressing the issue of so-called macroevolution – the idea that speciation is proven fact, but phylogenies constitute changes that are too overwhelming for gradual change to traverse. Specifically, he says:

Quite unsurprisingly, the current paper shows that microevolution can happen. Small changes in a protein may not destroy its activity. If you start out with a protein that does something, such as bind DNA or a hormone, it’s not surprising that you can sometimes find a sequence of changes that can allow the protein to do something closely similar, such as bind a second sequence of DNA or a second, structurally-similar hormone.

But what do the editors of Nature actually say:

Despite the plethora of modern genetic tools, something that is little changed since Darwin’s time is our reliance on evolutionary outcomes to unravel the process of evolution. The lack of evolutionary intermediates leaves the door ajar for the proponents of intelligent design. But a new technique could help fill the gaps. It involves the construction of evolutionary intermediates in the lab, and the search for viable paths between them. The resulting ‘fitness landscapes’ map viable routes between accessible evolutionary paths.

I would suggest that Behe pick up a copy of Sean B. Carroll’s Endless Forms Most Beautiful. Or any book on Evo-Devo for that matter; or any paper on the phylogenetic reconstruction of protein superfamilies from yeast to man; the list goes on. The point that can be broadly supported by those books and articles is that microevolution does happen, as Behe agrees, but also that macroevolution is nothing more than many microevolutionary changes. Time leads to change; lots of time leads to lots of change. And as all of biology resoundingly agrees – we’re filling in the list of “little changes” that happened hundreds of millions of years ago.

Lastly, Behe wraps it up with:

A good reason to be extremely skeptical of that is the work of Richard Lenski, which they cite. Lenski and his collaborators have grown E. coli in his lab for tens of thousands of generations, in a cumulative population size of trillions of cells, and they have seen no building of new systems, just isolated mutations in various genes.

Behe’s referring to this paper (Lenski and Travisano, 1994), with the abstract (emphasis mine):

We followed evolutionary change in 12 populations of Escherichia coli propagated for 10,000 generations in identical environments. Both morphology (cell size) and fitness (measured in competition with the ancestor) evolved rapidly for the first 2000 generations or so after the populations were introduced into the experimental environment, but both were nearly static for the last 5000 generations. Although evolving in identical environments, the replicate populations diverged significantly from one another in both morphology and mean fitness. The divergence in mean fitness was sustained and implies that the populations have approached different fitness peaks of unequal height in the adaptive landscape. Although the experimental time scale and environment were microevolutionary in scope, our experiments were designed to address questions concerning the origin as well as the fate of genetic and phenotypic novelties, the repeatability of adaptation, the diversification of lineages, and thus the causes and consequences of the uniqueness of evolutionary history. In fact, we observed several hallmarks of macroevolutionary dynamics, including periods of rapid evolution and stasis, altered functional relationships between traits, and concordance of anagenetic and cladogenetic trends. Our results support a Wrightian interpretation, in which chance events (mutation and drift) play an important role in adaptive evolution, as do the complex genetic interactions that underlie the structure of organisms.

Also, if Behe’s going to cite Lenski, one can’t forget this more recent paper (Lenski et al., 2003), with the abstract (emphasis mine):

A long-standing challenge to evolutionary theory has been whether it can explain the origin of complex organismal features. We examined this issue using digital organisms—computer programs that self-replicate, mutate, compete and evolve. Populations of digital organisms often evolved the ability to perform complex logic functions requiring the coordinated execution of many genomic instructions. Complex functions evolved by building on simpler functions that had evolved earlier, provided that these were also selectively favoured. However, no particular intermediate stage was essential for evolving complex functions. The first genotypes able to perform complex functions differed from their non-performing parents by only one or two mutations, but differed from the ancestor by many mutations that were also crucial to the new functions. In some cases, mutations that were deleterious when they appeared served as stepping-stones in the evolution of complex features. These findings show how complex functions can originate by random mutation and natural selection.

More can be read at The Questionable Authority.

References:

  • Poelwijk,F.J., Kiviet,D.J., Weinreich,D.M., and Tans,S.J. 2007. Empirical fitness landscapes reveal accessible evolutionary paths. Nature 445:383-386. Pubmed
  • Bridgham,J.T., Carroll,S.M., and Thornton,J.W. 2006. Evolution of hormone-receptor complexity by molecular exploitation. Science 312:97-101. Pubmed
  • Lenski,R.E. and Travisano M. 1994. Dynamics of adaptation and diversification: a 10,000-generation experiment with bacterial populations. Proc Natl Acad Sci U S A. 91(15):6808-14. Pubmed
  • Lenski,R.E., Ofria,C., Pennock,R.T. and Adami,C. 2003. The evolutionary origin of complex features. Nature 423, 139-144. Pubmed

Responses

  1. Excellent post, and thanks for the references too! Behe’s quote of

    “My general reaction to breathless papers like this is that they vastly oversimplify the problems evolution faces. Consider a very rugged evolutionary landscape. Imagine peaks big and small all packed closely together. It would of course be very difficult for a cell or organism to traverse such a landscape.”

    seems to be an awfully flimsy metaphor (much like the “jumping gaps” one in DBB), with the cell actually traversing mountain ranges. I used to at least respect that Behe willingfully and calmly engaged evolutionists who wanted to interview him, but the more I read by him the more I realize what an absolute tool he can be.

  2. By the way, I like the new banner.


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