The evolutionary perspective in medicine describes the ultimate or upstream cause of disease. This contrasts with pathology and pathophysiology, which are concerned with the proximate or downstream mechanisms. Evolutionary medicine tries to answer the "why" questions of disease and proposes new hypotheses to give a more complete understanding of the reasons why we get sick.Evolutionary medicine asks: why do certain disease susceptibility genetic variants (alleles) persist in human populations? These genetic variants are increasingly forming the basis for genomic diagnostic testing and have the potential to lead to better treatments through pharmacogenomics. By showing how millions of years of evolution have left human bodies susceptible to devastating diseases such as cancer, stroke, autoimmune disease, and infection, the book lays out a new way of thinking about disease that should help students find success in medical practice and research.An Introduction to Evolutionary Medicine is written by two physicians, Alan Penman and Joe Alcock, with years of combined experience teaching evolutionary medicine to medical students. The book is aimed at health professionals and students and could serve as a foundational preclinical course for medical students. The chapters are organised by body system, with each covering a specific disease or disorder, introduced by a clinical case. Examples at the end of each chapter demonstrate how an evolutionary perspective can lead to new diagnostic tools, better risk stratification, and new therapies.