Dementia, heart failure and cancer are now the leading causes of death in industrialised nations, where life expectancy is mostly above 80. A century ago, life expectancy was about 50 and people died mainly from infectious diseases. In the Middle Ages, death was mostly caused by famine, plague, childbirth and war. In the Palaeolithic period, where our species spent 95 percent of its time, we frequently died from violence and accidents.

Causes of death have changed irrevocably across time. In the course of a few centuries we have gone from a world where disease or violence were likely to strike anyone at any age and where famine could be just one bad harvest away, to one where excess food is more of a problem than a lack of it. Why is this? Why don’t we die from plague, scurvy or smallpox anymore? And why are heart attacks, Alzheimer’s and cancer so prevalent today?