Beautiful Minds—For How Long

O ver the past few years, the evidence has been building intensively that there is a story to be told about the relationship between cetaceans and primates. More significantly, the nature of this relationship carries implications about more general principles of behavioral evolution and convergence, the process by which similarity between species occurs because of adaptation to similar environments rather than genetic relatedness. Throughout the years, various authors, including myself, have spilled a lot of ink pointing out the striking convergence between cetaceans and primates [1]. At first glance, it might seem that cetaceans and primates evolved in anything but similar environments. However, the concept of an " environment " encompasses the totality of selective pressures on an organism, comprising both the physical setting and the behavioral, ecological, and social milieu. The case of convergence in primates and cetaceans is a compelling example of the primacy of social pressures over physical demands in producing similarities. Now, in Beautiful Minds, Maddalena Bearzi and Craig B. Stanford have written the book that I've been hoping to see for a long time, translating these arguments into an accessible and engaging account for the public [2]. Evolutionary convergence is a complex multilayered phenomenon that must be treated with subtlety and sophistication. It is often easy to see it in terms of " black and white " when it is actually a " figure–ground " issue, which depends upon holding two perspectives at the same time and alternating back and forth between them. In one regard, convergence has never occurred on Earth because, at a fundamental level, all life on Earth evolved from a common ancestor. Taking another view, one can observe convergence as a ubiquitous phenomenon in nature. Which is it? Well, both. It depends upon the level and form of convergence one chooses to focus upon. Some critics have said that primate– cetacean comparisons are not a real example of convergence because, after all, both are mammals with mammalian brains underwritten by a shared set of genetic regulatory mechanisms. True enough. But the fact that primate and cetacean brains did take distinctive cytoarchitectural routes to increases in size against the backdrop of these mechanistic similarities demonstrates that shared phylogeny (and genotypes) can still result in evolutionary phenotypes that are quite divergent. This is what I mean when I say that convergence can occur at different levels. Convergence can also take different forms. Convergence …