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 ›

Nature Paper Reaches “Edge of Evolution” and Finds Darwinian Processes Lacking

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 second of several posts discussing it. Using clever synthetic and analytical techniques, Bridgham et al (2009) show that the more recent hormone receptor protein that they synthesized, a GR-like protein, can’t easily revert to the ancestral structure and activity of an MR-like protein because its structure has been adjusted by Read More ›

Nature Publishes Paper on the Edge of Evolution

Nature has published an interesting paper recently which places severe limits on Darwinian evolution. This is the first of several posts discussing it. 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. Nonetheless, like the important work over the years of Michigan State’s Richard Lenski on laboratory evolution of E. coli, which has shown trillions of bacteria evolving under selection for tens of thousands of generations yielding just broken genes and minor changes, the new work demonstrates the looming brick wall which confronts unguided evolution in at least one system. And it Read More ›