Deep in the mountains of southern China, scientists have uncovered fossils of a tiny partnership between fungi and algae that lived an astonishing 600 million years ago — long before dinosaurs, before even the first animals with backbones swam in the oceans.
The fossils, found in the Weng'an biota in Guizhou province, reveal a lichen-like organism that researchers have named Wenganomyces primitivus. Lichens are those familiar crusty patches you might see on rocks or tree bark — but they're actually two organisms living as one, a fungus paired with an algae or cyanobacterium that uses sunlight to make food.
"These interactions are comparable to modern fungal-algal symbiosis, suggesting the early development of symbiosis in fungi and algae," said Ke Pang, a researcher at Nanjing Institute of Geology and Paleontology who led the study.
The team didn't just stumble upon these fossils — they've been sitting in museum collections for over 20 years. What unlocked their secrets was newer technology: a microscopy technique called confocal laser scanning microscopy, or CLSM, which can build detailed three-dimensional images of microscopic structures. Combined with another tool that reads the chemical fingerprints of ancient materials, the researchers could finally see how the fungal threads and photosynthetic cells interacted inside the fossil.
They discovered that the fungal filaments wrapped around the algae cells in ways strikingly similar to lichens alive today. Some filaments curved to closely surround the cells, a behavior called encirclement. Others lay parallel to cell clusters, touching along their sides.
This pushes back the known history of fungal-algal partnerships by a significant margin. Until now, the oldest clear evidence of lichen-like organisms dated to around 400 million years ago. This discovery suggests that fungi learned to cooperate with photosynthetic partners at least 200 million years earlier.
Symbiosis — two different organisms working together — is everywhere in nature, from the bacteria in our guts to the roots of trees sharing water with fungi underground. Understanding when these partnerships first emerged helps scientists piece together how life on Earth gradually became the interconnected web it is today.