A cleverer pathogen
The proximate cause of [typhoid] fever is in all cases a material and specific agent or virus.
William Budd, On the Causes of Fevers, 1839
We should not, for our peace of mind, reflect on the incredible series of accidents down through the millennia that have led to our own arrival on the scene. The number of narrow escapes, near misses, and astounding coincidences that finally result in a particular sperm meeting a particular egg at a particular time is enough to make anybody reassess his or her importance in the grand scheme of things. Things could easily have turned out quite differently. All of us know such stories of accidental survival in our ancestry. Members of my own family provide some particularly striking examples, since many of them spent years on the outer marches of the British Empire, exposed to unusual levels of risk of all kinds.
My maternal grandfather, a vigorous and adventurous man, spent the early I920s as a geological surveyor in India. He travelled widely, often to unexplored regions. My grandmother, frail but determined, would accompany him, sometimes being carried in a sedan chair. But in 1922 she was stricken with severe typhoid fever, from which she nearly died. It took her six months to recover, and on her doctors' advice she returned to England.
It was not long before her husband was forced to join her. One day in the spring of 1924 he was prospecting in the Bokara coalfield west of Calcutta. He jumped into a dry wash and found a black bear with two cubs waiting for him at the mouth of a cave. The mother immediately attacked, and as he turned to flee one of the cubs seized him by the trouser leg, tripping him up. He defended himself stoutly with his