Compounding the problem further is the fact that Darwin’s symptoms sometimes rose and fell with his stress levels. As he wrote in 1862, per Butterflies & Wheels, “I suffer severely from an ailment of a very peculiar kind, which prevents me from all mental excitement.” Peculiar indeed. In his lifetime, Darwin did sometimes enjoy some brief relief with “hydropathic” treatments, but Victorian-era medicine, lacking the knowledge of what was really wrong with him, could do little to cure him.

As he suffered from certain characteristic symptoms prior to his Beagle voyage, an illness such as Chagas disease was not the beginning of his ill health, but may have exacerbated it if present. Butterflies & Wheels goes on to suggest that Crohn’s disease may have been present (a study published by The Royal Society in 2006 considers the final diagnosis to be Crohn’s Disease of the small intestine), along with illnesses as they were defined in Darwin’s time (aggravated gout among them). Malaria and typhoid are also possibilities, while his eczema is now defined as atopic dermatitis, and he also had fibromyalgia (rheumatism) and cyclical vomiting syndrome.

The long-suffering naturist’s full list of ailments may never be definitively drafted, but one thing’s for sure: The workaholic didn’t help himself.