The split between the lineages leading to fungi and animals happened at a measured pace over deep time. A study published in nature revisits how those early branches unfolded.
Around 550 million years ago, during the Cambrian period, animal life diversified dramatically and new lineages formed. Just before this burst, the earliest multicellular organisms emerged, laying the groundwork for complex life as we know it.
Researchers led by Denis Tikhonenkov, based at the Institute of Inland Waters Biology in Borok, joined forces with colleagues to sequence the genomes of more than 80 species spanning animals and fungi. Their aim was to map how the earliest multicellular animals evolved by comparing the genetic material across these kingdoms. By aligning genomes and pinpointing which DNA segments underwent the most dramatic changes, the team tracked how gene content shifted during early diversification. They then grouped mutation patterns in representative species from each kingdom, revealing which gene families stood out as the major players during independent trajectories of animal and fungal evolution.
The results show that the ancestors of fungi and animals followed distinct evolutionary paths long before the first living representatives of the two kingdoms appeared. In broad terms, lineages that would become animals show a trend toward greater mobility and the emergence of new cell types, while fungal ancestors gradually shed genes tied to those very features of early eukaryotes, which are organisms with a defined nucleus.
These findings challenge older theories that emphasized rapid, punctuated leaps in the major milestones of multicellular evolution. Instead, the research paints a picture of protracted, lineage-specific changes accumulating over vast timescales. To deepen this evolving narrative, scientists plan to incorporate amoebae into their comparative framework, aiming to fill gaps and sharpen the timeline of early life on Earth.
In sum, the study offers a nuanced view of how early multicellular life diversified, highlighting that fungi and animals did not follow a single, shared course. Their separate genetic journeys reveal a landscape where complexity grew through parallel yet divergent routes, shaped by the distinct pressures and opportunities each kingdom faced during the deep past. While mysteries remain, these insights mark a meaningful step toward a clearer account of early eukaryotic evolution, clarifying when and how the foundational features of modern fungi and animals began to take shape.
As research progresses, scientists expect a richer understanding of the genetic architecture that enabled multicellularity. The ongoing work promises to illuminate how simple cells coalesced into complex organisms and how different life forms negotiated the tradeoffs between flexibility, mobility, and specialization. In this unfolding story, the fate of early life hangs on the delicate balance between shared ancestry and unique evolutionary experiments that eventually gave rise to the diverse kingdoms seen today.