Causes of parallel molecular evolution: A fundamental question in evolutionary genetics concerns the extent to which adaptive phenotypic convergence is attributable to parallel changes at the molecular sequence level. This has important implications for understanding the inherent repeatability and predictability of molecular evolution. In my seminar I will report a comparative analysis of hemoglobin function in high-altitude vertebrates to assess the extent to which replicated evolutionary transitions in biochemical phenotype involve parallel sequence changes. I will describe insights into mechanisms of biochemical adaptation to high-altitude hypoxia and the nature of genetic 'constraints'.