Humboldt died at age 89 from a stroke. He never slowed down in his age, and continued to publish works right up until his death. His multi-volume opus Kosmos, detailing his discoveries and scientific philosophy, was still being revised and was only "completed" posthumously. It was, at the time, an international bestseller. He was never married. When Humboldt's letters to friends and acquaintances were discovered by biographers it was revealed that he had been amorously corresponding with men. Childhood friends and travelling companions received these letters. He may have even lost friends over his amorousness, driving away Francisco Jose de Caldas, the Colombian naturalist and revolutionary. Four years before his death, Humboldt amended his will and left his entire estate to his valet, a man by the name of Johann Seifert. Seifert had served him since 1827 and accompanied Humboldt's ill-fated 1829 Russian expedition. According to some biographers, sneaking same-sex partners into the home as servants was relatively common. While it's impossible to determine if any of these relationships were sexual or just intense friendships, the lack of marriage and the willing of the Humboldt estate to Seifert indicates that Humboldt was possibly gay or bisexual.

I don't bring the matter of Humboldt's sexual orientation lightly or out of some kind tabloid-esq desire to unmask a great figure. I mean, the man is centuries dead and largely forgotten. There's no mask to take off. The man's mystique and fame were destroyed in English-speaking world by two World Wars and a backlash against Germans. The topic of Humboldt's sexuality is important in that this month is Pride Month. There are scarce examples of LGBT scientists, mathematicians or engineers (name one aside from Alan Turing, I'll wait). That one of the greatest scientific thinkers of the 18th century was probably gay should be celebrated.

It's important that we recognize the impact of Humboldt's work and life because we've never been more in need of Humboldtian thinking. Glaciers are melting at an alarming pace. The oceans are warming and acidifying, bleaching The Great Barrier Reef. Drought has gripped California for four years and parts of the west have not seen rain in twelve. Invasive pests threaten our forests and our waterways. We need the kind of broad-spectrum, holistic, precise and cross-disciplinary science that Humboldt was famous for to address these complicated, multinational problems. We need Humboldtian humanism, to recognize the injustices perpetuated against native peoples, many of whom are losing their islands to sea-level rise. We need to acknowledge his sexuality to show LGBT youth that there is a path for them in science, that they can achieve great things.

Humboldt, in many ways, was a man before his time. and of his time. He developed such a thoroughly-modern understanding of the way that living things interact with each other and the environment that we forgot that it had to be developed in the first place. He was a strict empirical, scientist at a time when it was appropriate to cite God when discussing nature. He disagreed and railed against American and Spanish slavery and treatment of native peoples at a time when racial caste systems were "scientific". Humboldt, from beyond the grave, from two centuries ago is relevant. This month, for Pride Month, I urge you to rediscover Humboldt and connect with one of the foundations of the environmental movement.