German geographer and explorer Alexander von Humboldt was BOTD in 1769. Born in Berlin to a prominent military family, he showed an early interest in the natural world, undertaking a range of studies in botany, geology, anatomy, astronomy and modern languages to prepare himself for foreign travel and scientific exploration. He travelled extensively through Europe, befriending Captain Cook’s botanist Joseph Banks. In 1799, the Spanish crown granted him permission to travel through South America. He spent five years exploring Venezuela, Cuba, Colombia, Ecuador, Peru, Mexico and Cuba, before being invited to North America by Thomas Jefferson. Humboldt’s research and subsequent publications made him a scientific celebrity. His research made major contributions the studies of ecology, geography, meteorology and geology. He also popularised the use of the word “cosmos” to describe the universe as a single interacting entity, and made early studies into the human effect on climate change. Unusually for his times, he expressed sympathy in his writing towards indigenous peoples and advocated for the abolition of slavery, though contemporary critics have also accused him of racist and imperialist attitudes. Humboldt never married, claiming to be too busy to have a family. His private letters reveal his numerous romantic attractions to men, and he had a number of live-in companions throughout his life. He died in 1859 aged 89, leaving his fortune to his live-in valet and travel companion Johann Seifert, a working-class man 30 years his junior. Biographers and historians continue to debate whether Humboldt’s male friendships were sexual, with many conservative critics still insisting that the great man of science was a life-long celibate.