(Roughly) Daily

Lacy M. Johnson argues that there is no hierarchy in the web of life…

… Humans have been lumbering around the planet for only a half million years, the only species young and arrogant enough to name ourselves sapiens in genus Homo. We share a common ancestor with gorillas and whales and sea squirts, marine invertebrates that swim freely in their larval phase before attaching to rocks or shells and later eating their own brain. The kingdom Animalia, in which we reside, is an offshoot of the domain Eukarya, which includes every life-form on Earth with a nucleus—humans and sea squirts, fungi, plants, and slime molds that are ancient by comparison with us—and all these relations occupy the slenderest tendril of a vast and astonishing web that pulsates all around us and beyond our comprehension.

The most recent taxonomies—those based on genetic evidence that evolution is not a single lineage, but multiple lineages, not a branch that culminates in a species at its distant tip, but a network of convergences—have moved away from their histories as trees and chains and ladders. Instead, they now look more like sprawling, networked webs that trace the many points of relation back to ever more ancient origins, beyond our knowledge or capacity for knowing, in pursuit of the “universal ancestors,” life-forms that came before metabolism, before self-replication—the several-billion-year-old plasmodial blobs from which all life on Earth evolved. We haven’t found evidence for them yet, but we know what we’re looking for: they would be simple, small, and strange.

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Slime molds can enter stasis at any stage in their life cycle—as an amoeba, as a plasmodium, as a spore— whenever their environment or the climate does not suit their preferences or needs. The only other species who have this ability are the so-called “living fossils” such as tardigrades and Notostraca (commonly known as water bears and tadpole shrimp, respectively). The ability to become dormant until conditions are more favorable for life might be one of the reasons slime mold has survived as long as it has, through dozens of geologic periods, countless ice ages, and the extinction events that have repeatedly wiped out nearly all life on Earth.

Slime mold might not have evolved much in the past two billion years, but it has learned a few things during that time. In laboratory environments, researchers have cut Physarum polycephalum into pieces and found that it can fuse back together within two minutes. Or, each piece can go off and live separate lives, learn new things, and return later to fuse together, and in the fusing, each individual can teach the other what it knows, and can learn from it in return.

Though, in truth, “individual” is not the right word to use here, because “individuality”—a concept so central to so many humans’ identities—doesn’t apply to the slime mold worldview. A single cell might look to us like a coherent whole, but that cell can divide itself into countless spores, creating countless possible cycles of amoeba to plasmodium to aethalia, which in turn will divide and repeat the cycle again. It can choose to “fruit” or not, to reproduce sexually or asexually or not at all, challenging every traditional concept of “species,” the most basic and fundamental unit of our flawed and imprecise understanding of the biological world. As a consequence, we have no way of knowing whether slime molds, as a broad class of beings, are stable or whether climate change threatens their survival, as it does our own. Without a way to count their population as a species, we can’t measure whether they are endangered or thriving. Should individuals that produce similar fruiting bodies be considered a species? What if two separate slime molds do not mate but share genetic material? The very idea of separateness seems antithetical to slime mold existence. It has so much to teach us…

More at: “What Slime Knows,” from @lacymjohnson in @Orion_Magazine.

See also, “Slime Molds Remember — but Do They Learn?” (from whence the image above) and “Now, in addition to penicillin, we can credit mold with elegant design.”

* Lucretius, On the Nature of Things

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As we contemplate kinship, we might send insightful birthday greetings to Johann Hedwig; he was born on this date in 1730. A botanist noted for his study of mosses, he is considered “the father of bryology” (the study of mosses… cousins of mold).

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