The Origin and Early Evolution of Fungi: Challenges, Inferences, and Principles

Fungi are widespread on our planet and essential for life as we know it, but how did they come about? Their last common ancestor lived hundreds of millions of years ago, but its characteristics, and the contours of early fungal evolution, remain mysterious. This review synthesizes information from fungal and eukaryotic microbial diversity, geology, fossils, and evolutionary genomics to infer the early evolution of fungi, identify challenges and major gaps in our knowledge, dispel misconceptions, and propose general evolutionary principles exemplified by the fungal lineage. Even though fungi likely emerged earlier than animals or land plants, their origins and early evolution are the least studied. Reconstruction of the evolutionary and ecological portrait of the first fungi is key for deciphering life in ancient ecosystems, for understanding how fungi eventually facilitated the advent of life on land, and for inferring principles that govern fungal evolution.