Living in an affluent western society brings many advantages for health, notably security from hunger and from the serious infectious diseases of infancy and childhood that plagued western countries prior to the twentieth century and continue to inflict a heavy burden on populations in poorer countries today. However, as we have seen, westerners suffer from a characteristic set of relatively new non-communicable diseases, and these diseases are seen in non-western populations at increasingly high rates. In this concluding chapter I first summarise what an evolutionary perspective offers to the study of human vulnerability to western diseases. Next, I consider prospects for the future, focusing on what ‘westernisation’ means for the health of the millions of people subject to its influence, and on the insights that an evolutionary perspective provides in relation to possible preventive strategies.

Human vulnerability to western diseases

This book has shown that humans are vulnerable to western diseases because, as a species, we evolved in very different environments from those experienced today. We can summarise these effects in relation to obesity, in many respects the core pathology underlying western diseases. When the genus Homo emerged, selective pressures related especially to having a large brain led to these early hominins becoming proportionately fatter than other species of the tropical savannah. Humans also evolved under selective pressures imposed by the necessity of eating wild animals and plants and being physically active. The human genotype was ‘thrifty’, making effective use of scarce resources.