Life-history evolution: understanding the proximate mechanisms

Abstract

Several years ago as a fresh graduate student in a laboratory focussed on life-history evolution, I was required to write a term paper for a course on ‘Advanced evolutionary biology’. Having worked in the laboratory for about six months and read through numerous papers on life-history evolution, I was convinced that nothing in life-history was more important than ‘trade-offs’. So, I choose to write my term paper on trade-offs in life-history evolution. In the course of writing that term paper I realized that while studies had established the ubiquity and importance of trade-offs through a multitude of approaches, there was frustratingly little material about the proximate causes of such trade-offs. The general assumption in most studies was that trade-offs were somehow related to the partitioning of limited resources. Now, after several years of having read the book edited by Flatt and Heyland, I wish that I had access to this excellent book as a fresh graduate student! For this book does something that has long been overdue—try and bridge the gap between the ultimate and proximate explanations of life-history evolution. Life-history, the timing of onset and distribution of reproductive output of an organism over its entire lifespan is of central importance in evolutionary biology since it is the lifehistory that forms the interface between an organism and its Darwinian fitness. Life-histories are extremely variable within and across species and explaining such variation is the primary goal of research into life-history evolution. Research within this area focusses on life-history traits such as agespecific mortality and fecundity which are directly related to the fitness of the organism and several other life-history related traits that are only indirectly related to fitness. Previously several books have synthesized the research in this field from the point of view of ultimate questions. The present