Why your garden mushrooms are actually closer relatives to you than to plants

Gardening · Published 3 October 2026 Swipe more like this →

In short: You might assume fungi belong with plants, but biology tells a different story. Animals and fungi share a common ancestry within a group called opisthokonts. Defined by a unique rear-propelling flagellum, this clade reveals that the line between the animal and fungal kingdoms is thinner than we once imagined.

The term opisthokont originates from the Greek words for rear and pole, describing the single posterior flagellum used by the group's motile cells. While many fungi have lost this feature over time, it remains a defining trait for the clade, which includes both the animal and fungal kingdoms. This classification marks a significant shift from older systems that grouped fungi with plants based on their sessile nature.

Genetic evidence, including a specific triple fusion of enzymes involved in nucleotide synthesis, confirms that animals and fungi share a more recent common ancestor than either does with plants. Plants possess a different set of enzyme fusions, placing them further away on the evolutionary tree. This discovery, supported by phylogenomic studies like those of Guifré Torruella in 2015, divides the opisthokonts into two primary branches: the Holomycota, which contains fungi and their closest relatives, and the Holozoa, which encompasses animals and their nearest kin.

The history of this classification is one of constant refinement. Early researchers like Herbert Copeland identified the group in 1956, but the formal recognition of the animal-fungal link was championed by Thomas Cavalier-Smith in 1987. As genomic data improves, organisms once misidentified as algae or protozoa are being reclassified. For instance, microsporidia, previously thought to be apicomplexa, are now firmly placed within the fungal lineage. Despite these advancements, the search for the earliest opisthokonts continues, as no organisms basal to the split between Holomycota and Holozoa had been identified as of 2020.

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