Mark E. Borrello

Experimental evolution of multicellularity

Multicellularity was one of the most significant innovations in the history of life, but its initial evolution remains poorly understood. Using experimental evolution, we show that key steps in this transition could have occurred quickly. We subjected the unicellular yeast Saccharomyces cerevisiae to an environment in which we expected multicellularity to be adaptive. We observed the rapid evolution of clustering genotypes that display a novel multicellular life history characterized by reproduction via multicellular propagules, a juvenile phase, and determinate growth. The multicellular clusters are uniclonal, minimizing within-cluster genetic conflicts of interest. Simple among-cell division of labor rapidly evolved. Early multicellular strains were composed of physiologically similar cells, but these subsequently evolved higher rates of programmed cell death (apoptosis), an adaptation that increases propagule production. These results show that key aspects of multicellular complexity, a subject of central importance to biology, can readily evolve from unicellular eukaryotes.

Synthesis and Selection: Wynne-Edwards' Challenge to David Lack

David Lack of Oxford Universityand V.C. Wynne-Edwards of Aberdeen Universitywere renowned ornithologists with contrastingviews of the modern synthesis which deeplyinfluenced their interpretation and explanationof bird behavior. In the 1950s and 60s Lackbecame the chief advocate of neo-Darwinism withrespect to avian ecology, while Wynne-Edwardsdeveloped his theory of group selection. Lacks position was consistent with thedeveloping focus on individual leveladaptation, which was a core concept of themodern synthesis. Alternatively, Wynne-Edwardsviewed the emphasis on populations as the mostimportant development provided by the modernsynthesis. In this paper, I present thedevelopment of these two positions and tracetheir roots in the literature of the synthesis.Through an analysis of Lacks 1966 critique ofWynne-Edwards I conclude that Wynne-Edwardswas, in many ways, justified in his pursuit ofgroup level explanations.

Mutual aid and "animal dispersion": an historical analysis of alternatives to Darwin.

Petr Alekseyevich Kropotkin (1842-1921) and Vero Copner Wynne-Edwards (1906-1997) developed evolutionary theories that emphasized social groups and cooperation rather than the organism-level natural selection of standard Darwinian theory. The most important reason for their alternative interpretations was their experience as field naturalists. Kropotkin and Wynne-Edwards worked in arctic environments and were impressed by aspects of the natural world that differed significantly from those experienced by Darwin or Wallace. These field experiences led to their emphasis on mutual aid and group selection, respectively. Understanding the development of their theories helps to illuminate the continuing debates over evolutionary theory and the current resurgence of interest in group selection.

Parasites and altruism: converging roads

W.D. Hamilton was most known for his work on two topics: social evolution and parasites. Although at first glance these seem to be disparate interests, they share many attributes and have logical connections within evolutionary biology. Nevertheless, Hamiltons contributions in these areas met with very different receptions, with his place in the field of social evolution assured, but his work on the role of parasites perceived as more specialized. We take an historical approach to examine the reasons for this difference.