Annie Darwin's death, the evolution of tuberculosis and the need for systems epidemiology

When Charles Darwin’s daughter Anne Elizabeth (‘Annie’, Photograph 1 ) died at the age of 10 years on April 23, 1851 her parents were devastated. Charles Darwin was a devoted father and constantly concerned about the health of his 10 children. His concerns were also motivated by fear of the consequences of marriage between relatives: Emma Wedgewood, his wife, was also his first cousin. 1 The possible adverse effects of consanguineous marriage, which was not uncommon in England at that time, were a matter of debate. Annie’s death, and self-fertilization experiments in plants, made him suspect that ‘marriage between near relations is likewise injurious’. 2 In 1870, Darwin motivated his mathematician son George to study the prevalence of close-kin marriages in patients in asylums in comparison with the prevalence of the general population. The study, which is reprinted in this issue of the journal, 3 with several commentaries, 1 , 2 , 4 , 5 was first published in 1875 and concluded that ‘the evil of marriages between cousins has been often much exaggerated’ and that ‘under favourable conditions of life, the apparent ill-effects were frequently almost nil’...