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Evolutionary principles applied to medical practice: key points
- Medical practice is primarily concerned with preventing and managing ill-health. In turn, this requires an understanding of the determinants of individual phenotype and the factors that lead to variation in disease risk.
- Understanding why one person develops disease while another does not is improved by considering the evolutionary pathways to altered risk.
- The human phenotype at any age is a construct of inheritance and the consequences of developmental plasticity, itself informed by environmental history, and is defined further by the interaction with the current physical, biological and social environments.
- Selection operates to maximise inclusive reproductive fitness, not heath and not longevity.
- Nothing in the human phenotype was selected for a higher purpose. Most traits are present because they were selected for some adaptive advantage in the past.
Depression is predicted to be a leading cause of morbidity in 2030 worldwide (top) and in high-income countries (bottom). There have been enormous changes in our social environment, which for some people have exceeded their adaptive capacities. This environment of the 21st century has many elements of novelty – the way we communicate electronically rather than in person, the high volume of interactions we have, the complexities of changed societal structures of control and increased autonomy and choice. The very changed ability to control reproduction also impacts on our choices and interpersonal behaviours. The changing nature of our society means that the rules of the social game have changed; the nature of family structures, peer perceptions and group dependencies has changed. Our evolved means of identifying and dealing with freeloaders and cheaters are no longer adequate. The contribution of these evolutionary mismatches to mental health disorders and to behaviours that are considered antisocial, such as acting out or delinquent behaviours, is growing.