DSSS - The evolution of evolvability

I will discuss the hypothesis that life may have evolved to evolve — a provocative idea given that it appears to require foresight on the part of natural selection. The controversy arises because evolvability is a property of lineages, not individuals, and thus implies that selection can operate at levels above single entities. To probe the mechanisms underlying evolvability, we conducted a long-term evolution experiment in bacterial populations. Over three years, lineages evolved under a selective regime in which success depended on the capacity to mutate between two phenotypic states. Lineages capable of generating the necessary phenotype for future environmental conditions displaced those lacking this capacity. After a series of 46 mutations, a type emerged that appeared to 'anticipate' the future via localised hyper-mutation — a mechanism analogous to contingency loci in pathogenic bacteria. I will describe the stepwise emergence of this capacity and present experiments demonstrating that the locus itself is evolvable. Additionally, I will highlight an unanticipated consequence of enhanced evolvability: its facilitation of secondary adaptive mutations. In closing, I will argue that selection acting on lineages may be more prevalent and consequential than currently recognised.