Cordelia's Dilemma, Historical Bias, and General Evolutionary Trends: Catfishes as a Case Study for General Discussions on Phylogeny and Macroevolution

Dec 1, 2006

As noted Gould in his recent and last book «The structure of evolutionary theory», discourses on the high importance and frequency of evolutionary trends have consumed a great part of the research on the history of clades. Although aware that natural selection theoretically yields adaptation to immediate environments, many authors defend such trends as generalised improvements somehow conferring advantages across most or all experienced environments. The high importance given to evolutionary trends is questioned by Gould, who considers that such a high importance given to such evolutionary trends bears no necessary relationship to the relative frequency or casual weight of these events in evolution, but mainly to a major bias: trends tell histories, and evolution is a narrative history. In the present paper I briefly discuss this subject arguing that the case study provided by catfishes, a remarkably diverse group of Vertebrates reputed by its «general evolutionary trends», supports Gould's view according to which careful phylogenetic analysis of a clade often contradicts the supposed importance of general evolutionary trends in that clade's evolution.