Introductory essay: Evolution, comparative biology, and development

WHY STUDY EVOLUTION? An understanding of the evolutionary origins of the endothelium has important implications for human health and disease. As discussed by Nesse and Weder (Chapter 15), when approaching mechanisms of structure and function, evolutionary explanations (“why”) complement proximate considerations (“how”). They provide important insights into the design constraints, path dependence, trade-offs, and selective pressures that underlie endothelial function and vulnerability to disease. Another critical and often underappreciated consideration is that, in the course of human evolution, our body (including the endothelium) has evolved to maximize fitness in a far earlier era, perhaps tens of thousands of years ago, which is the time it takes for the gene pool to be filtered by natural selection. In Chapter 16, Eaton and his colleagues write about the environment and lifestyle of the hunter-gatherer, and remind us about the importance of cultural (as distinct from genetic) evolution in mediating the modern-day predisposition to atherosclerosis. As another example of how evolutionary theory may be applied to an understanding of human disease, Haig discusses how evolutionary conflicts between maternal and fetal genes may underlie the pathophysiology of preeclampsia (Chapter 17). Piecing together the evolutionary origins of the endothelium is challenging and necessarily speculative. Because the human endothelium does not fossilize, interpretations rely on a combination of molecular phylogeny and comparative biology/physiology, with the assumption that what works for extant organisms may have worked for ancestral species. In Chapter 14, McVey demonstrates how molecular phylogenetic approaches may be used to gain insights into the evolutionary history of the endothelium. In Chapter 3, Burggren and Reiber provide a comprehensive overview of the comparative biology of cardiovascular systems.