Malaria

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 entitled “An epistatic ratchet constrains the direction of glucocorticoid receptor evolution”. ( http://tinyurl.com/yeq2cy8 ) 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. ( http://tinyurl.com/yba6vba ) This is the last of three posts discussing it. 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 20thcentury paleobiologist, was interested in discerning phylogenies. He maintained that one could always distinguish ancestral forms from descendant Read More ›

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 entitled “An epistatic ratchet constrains the direction of glucocorticoid receptor evolution”. ( http://tinyurl.com/yeq2cy8 ) 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. ( http://tinyurl.com/yba6vba )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 selection Read More ›

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 entitled “An epistatic ratchet constrains the direction of glucocorticoid receptor evolution”. ( http://tinyurl.com/yeq2cy8 ) 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 points Read More ›

Dear Readers, An interesting paper appeared recently in the New England Journal of Medicine. (1) The workers there discovered some new mutations which confer some resistance to malaria on human blood cells in the lab. (Their usefulness in nature has not yet been nailed down.) The relevance to my analysis in The Edge of Evolution is that, like other mutations that help with malaria, these mutations, too, are ones which degrade the function of a normally very useful protein, called pyruvate kinase. As the workers note: “[H]eterozygosity for partial or complete loss-of-function alleles . . . may have little negative effect on overall fitness (including transmission of mutant alleles), while providing a modest but significant protective effect against malaria. Although speculative, this situation Read More ›