The Catechism Versus the Data (Part 2): Much Ado About A Footnote Citing Christian Schwabe
This is the second in a blog series responding to John Timmer's online review of the supplementary biology textbook Explore Evolution. The first part is here.
2. Much Ado About A Footnote Citing Christian Schwabe
One theme of EE addresses differing views among evolutionary biologists about Darwin's Tree of Life, i.e., the theory of the universal common ancestry of all organisms on Earth: more precisely, the monophyly of terrestrial life, rooted in the Last Universal Common Ancestor, or LUCA. While the majority position within evolutionary biology endorses monophyly, a growing minority of workers argue for multiple independent origins, or polyphyly (see below). It's an important controversy, well worth the attention of textbooks.
But Timmer accuses EE of a "bait-and-switch" move in describing this controversy. By "lumping...together in a single footnote" several scientists with very different views about the overall pattern of life's history, he argues, EE tries for "borrowed credibility," misleading its readers about the true outlines of the current mono- versus polyphyly debate.
Timmer is particularly exercised by EE's inclusion of the ideas of Professor Christian Schwabe of the Medical University of South Carolina, whose publications he calls "borderline deranged." Given the space Timmer uses to criticize Schwabe, one might think that the latter's ideas receive significant attention in EE.
No, actually: the book mentions Schwabe exactly once, in a single footnote (which cites three of his papers). Timmer claims that EE lumps Schwabe together with other, better-known scientists, such as National Academy of Sciences member Carl Woese, as advocates of the polyphyletic view, without informing the reader about the different number of separate origins postulated by their respective theories.
But here is the actual EE footnote (p. 11):
Scientists who support a polyphyletic view differ on how many trees one should expect to find in the "orchard" of life. Some, such as microbiologist Carl Woese of the University of Illinois, argue that life on earth is descended "not from one, but from three distinctly different cell types" ("On the evolution of cells," Proceedings of the National Academy of Sciences 99 (2002):8742- 77; 8746). Others, including Malcolm Gordon of UCLA and Christian Schwabe of the Medical University of South Carolina, think there might be a greater number of separate trees.
And that's it. No misdirection or lumping: Woese says three independent origins; Schwabe and Gordon say more. Anyone who reads the EE footnote should grasp that scientific opinions about polyphyly differ.
Let's go back, however, to Timmer's charitable label for Schwabe, "borderline deranged," as it gives us our first opportunity to address the catechism versus data dilemma in more depth.
Timmer acknowledges that "every couple of years, [Schwabe] publishes a paper in which he argues in favor" of his "borderline deranged" ideas. These, however, "are not scientific controversies," Timmer claims, but "actually opinions that have barely registered within the wider scientific community."
Really? To see how Schwabe's research raises challenges to monophyly and universal common ancestry, consider this excerpt from one of his papers cited in EE:
Against this background of high variability between relaxins from purportedly closely related species, the relaxins of pig and whale are all but identical. The molecules derived from rats, guinea pigs, man and pigs are as distant from each other (approximately 55%) as all are from the elasmobranch's [shark's] relaxin. ... Insulin, however, brings man and pig phylogenetically closer together than chimpanzee and man. (Schwabe 1994, 171-2)
According to Timmer's catechism, however, none of this is worth talking about, because Schwabe's ideas are just too crazy for serious consideration.
But someone forgot to tell journal editors and referees. Schwabe's "deranged" ideas -- coming from a tenured professor of biochemistry, and based in part on the puzzling features of relaxin (not "reflexin," as Timmer writes), and its phylogenetic distribution -- have cleared editorial review at the following journals:
• Christian Schwabe and Gregory Warr, "A Polyphyletic View of Evolution: The Genetic Potential Hypothesis," Perspectives in Biology and Medicine 27 (1984):465-85.
• Christian Schwabe, "On the validity of molecular evolution," Trends in Biochemical Sciences 11 (1986):280-3.
• C. Schwabe and E.E. Büllesbach, "Relaxin: structures, functions, promises, and nonevolution," FASEB Journal 8 (1994):1152-60.
• Christian Schwabe, "Theoretical limitations of molecular phylogenetics and the evolution of relaxins," Comparative Biochemistry and Physiology 107B (1994):167-77.
• Christian Schwabe, "Genomic Potential Hypothesis of Evolution: A Concept of Biogenesis in Habitable Spaces of the Universe," The Anatomical Record 268 (2002):171--179.
• Christian Schwabe, "Chemistry and Biodiversity," Chemistry and Biodiversity 1 (2004):1584-9.
Were these papers ignored? No: the relaxin puzzles are well-known; as other biologists who study relaxin observe (Wilkinson et al. 2005, 3),
Relaxin evolution has confounded researchers for decades. High sequence variability in relaxins across closely related species is a well-known feature of this peptide, however startling similarities have been observed between very distant species such as pigs and whales.
Nor have Schwabe's heterodox ideas about the evolutionary process escaped critical notice. His 2004 paper in the journal Chemistry and Biodiversity was followed immediately -- in the very same issue -- with a critical reply, as was the case with Schwabe's 1999 FASEB Journal paper. Hafner and Korthof (2006) argue vigorously against Schwabe's position, and Wilkinson et al. (2005, 9) note that "relaxin evolution has been the centre of much controversy," which they believe their approach has been able to resolve.
"The centre of much controversy" -- but Timmer says (falsely) that no one cares, because it's all "borderline deranged" anyway. Thus, what might be an interesting case study, supported by multiple peer-reviewed publications, pro and con, about how to interpret molecular evidence in relation to the tree of life and its origin, would be tossed aside by Timmer, in favor of the catechism: the "fact" of evolution, never mind the data.
As we mentioned above, EE cites Schwabe in a single footnote. His name never appears in the main text. A reader who followed up the Schwabe citations, however, would find a rich controversy, likely to stimulate thinking.
And that's good, all worries about the complicated data notwithstanding.
Up next: The "Fact" of Evolution
Hafner, Martin and Gert Korthof. 2006. Does a "500 million-year-old hormone" disprove Darwin? The FASEB Journal 20:1290-2.
Schwabe, Christian. 1994. Theoretical limitations of molecular phylogenetics and the evolution of relaxins. Comparative Biochemistry and Physiology 107B:167-77.
Wilkinson, Tracey N., Terence P. Speed, Geoffrey W. Tregear, and Ross A.D, Bathgate. 2005. Evolution of the relaxin-like peptide family. BMC Evolutionary Biology 5:14.