Science is sometimes caricatured as a wholly objective pursuit that allows us to understand the world through the lens of neutral empiricism. But the conclusions that scientists draw from their data, and the very questions they choose to ask, depend on their assumptions about the world, the culture in which they work, and the vocabulary they use. The scientist Toby Spribille once said to me, “We can only ask questions that we have imagination for.” And he should know, because no group of organisms better exemplifies this principle than the one Spribille is obsessed with: lichens.
Lichens can be found growing on bark, rocks, or walls; in woodlands, deserts, or tundra; as coralline branches, tiny cups, or leaflike fronds. They look like plants or fungi, and for the longest time, biologists thought that they were. But 150 years ago, a Swiss botanist named Simon Schwendener suggested the radical hypothesis that lichens are composite organisms—fungi, living together with microscopic algae.
It was the right hypothesis at the wrong time. The very notion of different organisms living so closely with—or within—each other was unheard of. That they should coexist to their mutual benefit was more ludicrous still. This was a mere decade after Charles Darwin had published his masterpiece, On the Origin of Species, and many biologists were gripped by the idea of nature as a gladiatorial arena, shaped by conflict. Against this zeitgeist, the concept of cohabiting, cooperative organisms found little purchase. Lichenologists spent decades rejecting and ridiculing Schwendener’s “dual hypothesis.” And he himself wrongly argued that the fungus enslaved or imprisoned the alga, robbing it of nutrients. As others later showed, that’s not the case: Both partners provide nutrients to each other.