Last year, I argued that fungi are often excluded from conversations about the evolution of multicellularity (“Fungi are weird“):
Whenever we’re looking for commonalities among the various origins of complex multicellularity, commonalities that might suggest general principles for the transition to multicellular life, the fungi tend to either buck the pattern or provide an ambiguous fit. I have to admit that when fungi come up in these discussions, I have an unfortunate tendency to say “Who knows? Fungi are weird.” However, if László Nagy is right that complex multicellularity has arisen 8-11 times within the fungi, we might fairly say that the fungi include most origins of complex multicellularity. If so, maybe it’s not the fungi who are weird. If fungi truly include the majority of origins of complex multicellularity, fungi are the norm. Maybe it’s the rest of us that are weird.
I have finally gotten around to reading Maureen O’Malley’s Philosophy of Microbiology, which argues that any comprehensive theory of evolution needs to account for microbial life, life that often evolves in fundamentally different ways from the plants and animals on which most of the theory has been based. She makes a related, but broader, point:
No special account of evolution need be given exclusively for microbes, but any general theory of evolution needs to accommodate the greater range of evolutionarily relevant activities in which microbes participate. Perhaps this is also the place to make a plea for other organisms that have so far been invisible to the philosophy of biology, such as the enigmatic fungi. Although more closely related to animals than any other major clade, fungi have not featured prominently in either mainstream evolutionary theory or philosophical analyses of such theory. Looking at gaps and neglect is not an exercise for its own sake, but a constructive project: to work out how the current framework stands when confronted with apparently anomalous and wayward organisms. –p. 129
I couldn’t agree more. Animals and plants are special cases, with features such as an alternation of haploid and diploid generations, (usually) obligate sexual reproduction, and (in some cases) early germline segregation that have major implications for the way they evolve. Much of evolutionary theory, the standard models of population genetics and quantitative genetics for example, has taken these lineage-specific features as starting assumptions. A truly general theory should apply to all of life, with animals, plants, fungi, microbes, and even viruses treated as particular cases within the larger framework of the theory as a whole.