Contemporary Darwinian medicine is a still-expanding new discipline, one of whose principal aims is to arrive at an evolutionary understanding of those aspects of the body that leave it vulnerable to disease. Historically, there was a precedent for this research; between 1880 and 1940, several scientists tried to develop some general evolutionary theories of disease as arising from deleterious traits that escape elimination by natural selection. In contrast, contemporary Darwinian medicine uses evolutionary theory to consider all the possible reasons why selection has left humans vulnerable to disease.