Severe Limits to Darwinian Evolution: Response to Carl Zimmer and Joseph Thornton

The science writer Carl Zimmer posted an invited reply on his blog from Joseph Thornton of the University of Oregon to my recent comments about Thornton’s work. This is the third of several posts addressing it. References will appear in the last post. Now back to Thornton’s first point, the role of neutral mutations (which he sometimes labels “permissive” mutations). At several places in his post Thornton implies I’m unaware of the possibilities opened up by genetic drift: Behe’s discussion of our 2009 paper in Nature is a gross misreading because it ignores the importance of neutral pathways in protein evolution…. Behe’s first error is to ignore the fact that adaptive combinations of mutations can and do evolve by pathways Read More ›

Not So Many Pathways: Response to Carl Zimmer and Joseph Thornton

The science writer Carl Zimmer posted an invited reply on his blog from Joseph Thornton of the University of Oregon to my recent comments about Thornton’s work. This is the second of several posts addressing it. References will appear in the last post. Now to Professor Thornton’s reply. He writes at length but makes just two substantive points: 1) that neutral mutations occur and can serendipitously help a protein evolve some function (“[Behe] ignores the key role of genetic drift in evolution”); and 2) that just because a protein may not be able to evolve a particular function one way does not mean that it, or some other kind of protein, can’t evolve the function another way (“nothing in our Read More ›

Piddling Pebbles and Empty Promises: Response to Carl Zimmer and Joseph Thornton

The science writer Carl Zimmer posted an invited reply on his blog from Joseph Thornton of the University of Oregon to my recent comments about Thornton’s work. This is the first of several posts addressing it. References will appear in the last post. I must say, it never ceases to amaze me how otherwise-very-smart folks like Zimmer and Thornton fail to grasp pretty simple points when it comes to problems for Darwinian mechanisms. Let me start slowly with a petty complaint in Carl Zimmer’s intro to the post. Zimmer is annoyed that I think Thornton’s latest work is “great,” yet I thought his previous work published a few years ago was “piddling.” “Why the change of heart?” wonders Zimmer.

New Work by Richard Lenski

A new paper from Richard Lenski’s group has appeared in Nature and has garnered a fair amount of press attention. Some people asked me for my thoughts about it. The new paper continues the grand experiment that Lenski has been publishing about lo these many years — allowing a culture of the bacterium E. coli to continuously grow and evolve under his close observation. The only really new thing reported is a technical improvement — these days one can have the entire genome of E. coli “re-sequenced” (that is, determine the sequence of the entire DNA of the particular E. coli you’re working with) done for an affordable cost. (There are companies which will do it for a fee.) So Read More ›

Dollo’s law, the symmetry of time, and the edge of evolution

Nature has recently published an interesting paper which places severe limits on Darwinian evolution. The manuscript, from the laboratory of Joseph Thornton at the University of Oregon, is titled “An epistatic ratchet constrains the direction of glucocorticoid receptor evolution”. The work is interpreted by its authors within a standard Darwinian framework, but the results line up very well with arguments I made in The Edge of Evolution. This is the last of three posts discussing it. (see here and here) Bridgham et al (2009) are interested in the reversibility of evolution, and discuss their results in terms of something called “Dollo’s law.” Louis Dollo, an early 20th century paleobiologist, was interested in discerning phylogenies. He maintained that one could always Read More ›