Snakes and Singularities

A new paper asks the provocative question: why were snakes so talented at exploring the adjacent possible?

Scrolling through Twitter the other night, my eyes landed on this image, the cover from an issue of Science from late last month:

Snakes induce the mix of intrigue and repulsion in me that seems to be fairly common in the general population, but in this case it was something else that caught my eye: the cover copy promoting a new paper that examined an unsolved mystery about the evolutionary history of snakes, using a mix of natural history observations and genomic data. The mystery is this: snakes display far more phenotypic diversity than lizards, their close relatives in the Squamata order, a subset of the larger class of Reptilia. Their diets, skull shapes, forms of locomotion, body size are all far more varied than those of the lizards. As the authors of the science paper put it, “The 4,000 extant snake species include shovel-snouted burrowers that hunt desert scorpions, slender arboreal predators that prey on tree snails, and paddle-tailed marine forms that probe reef crevices for fish eggs and eels.” And then of course there are the chemical innovations of snake venom, which are found in over 400 species of snakes, but rare among lizards.

Put in lay terms, lizards are all mostly in the same line of work, but snakes figured out a whole host of ways to make a living. The major finding announced in the Science paper is that it appears that this “adaptive radiation”—all those diverse traits in the snake order—did not emerge through an incremental process, but instead resulted from a sudden phase shift, or at least “sudden” on the time scale of evolution. At some early point in their history, a switch was flipped, and overnight (or over a few million years, technically) something in the evolutionary landscape enabled snakes to generate hundreds of new strategies for surviving long enough to pass their genes onto the next generation, while the lizards mostly kept to their traditional patterns. “These phase shifts,” the researchers write, “can be conceptualized as macroevolutionary ‘singularities’: patterns of rapid change across multiple organismic and ecological axes that, when viewed retrospectively through the prism of geological time, are sufficiently clustered together so as to seem virtually instantaneous.” 

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That caught my attention because I've been thinking a lot lately about periods of rapid cultural and technological evolution. Singularity is maybe too charged a word, given the current obsession with the so-called singularity of artificial general intelligence, but there are many similar patterns in the fossil record of human culture. We used to call them paradigm shifts: some new complex of ideas emerges, and it unlocks a whole new set of possibilities that weren't directly available before. You can see this pattern play out in the history of science, like the sudden explosion in chemistry in the late 18th century when many of the elemental gases (including, famously, oxygen) were first identified. It happens in the realm of art as well, like the explosion in formal experimentation that happened in popular music during the second half of the 1960s. Sometimes the cultural-scientific revolutions play off each other. There's a lovely sequence in Oppenheimer where Christopher Nolan tries to capture this phenomenon with a montage of his protagonist in Europe as a young man, musing on the ideas that would become the Born-Oppenheimer Approximation, with relativity, quantum mechanics, and cubism all swirling together in the cultural ether.

The other way of describing this pattern, of course, is Stuart Kauffman's idea of the adjacent possible, an idea that is obviously very dear to my heart. What happens during the snake "singularity" is that the snakes are able to explore the adjacent possible—new forms of venom, new body types, new strategies for burrowing into the sand to hunt desert scorpions (which sounds pretty horrifying, if you ask me)—more effectively than the lizards. When I first wrote about the concept in Where Good Ideas Come From, I quoted Kauffman describing the long-term tendency of the adjacent possible to expand. “The biosphere has expanded, indeed, more or less persistently exploded, into the ever-expanding adjacent possible,” Kauffman wrote. “It is more than slightly interesting that this fact is clearly true, that it is rarely remarked upon, and that we have no particular theory for this expansion.” The same was clearly true for the possibility space of culture: we have far more technological platforms now than we did two hundred years ago, which means we have far more new doors to open in the adjacent possible technologically.

But what I hadn't really thought about—or at least I don't remember thinking about—is not the idea that the adjacent possible expands over the long term, in biology and culture; that was clear from the very first sentences I read in Kauffman's book almost twenty-five years ago. What I hadn't thought about was this: on shorter-time scales -- millions of years for biological evolution, years or decades for cultural evolution -- there are periods where the adjacent possible widens and then narrows. It's not a linear, incremental expansion. There are singularities where suddenly a whole new set of approaches appear on the table. And then there are periods where it gets more challenging to experiment, where it's just easier to stay in your lane. In the tech world, we lived through one of those periods between roughly 2010 and 2022: we had transitioned to a mobile- and social-first era, and so most of the innovations during that period were small variations on existing templates: Instagram to Snapchat to TikTok; iPhone 4 to iPhone 14. The one new wing of the adjacent possible that seemed to be opening during that period—the blockchain—ended up not leading anywhere. (Or at least not yet—that's a whole other conversation.)

In the tech sector, the periods where the adjacent possible suddenly widens are often described as “platform shifts,” for understandable reasons. When a new platform consolidates—the Web in the mid-90s, or touch UI-based mobile phones in the late aughts—there's invariably a huge amount of uncharted space on the map to explore, either adapting old forms for the new platform (a bookstore on the Web!) or inventing entirely new forms. In evolutionary terms, platform shifts are the equivalent of a species stumbling into a new habitat, with entirely new sources of food or protection—or predators. The underlying environment has changed, which opens up the door for new experiments.

But the Science paper on snakes suggests another potential driver for these singularities. In evolutionary history, sometimes the key change is not in the underlying habitat, but rather the evolution of a single new trait that turns out to have enormous consequences. The authors do not propose a specific change behind the snake singularity, but one possible explanation they suggest is the evolution of extreme “cranial kinesis” in snakes, where their skull bones are loosely connected and can move independently. Cranial kinesis allows them to devour prey much larger than their own head, despite the fact that most snakes swallow their prey whole. (Pythons, for instance, are known to feast on mammals as large as deer and antelopes.) The ability to expand their jaws much wider than the lizards expanded the range of creatures that the snakes could use as a source of energy, which then opened up whole new ecological niches for the snakes to explore.

I'll leave it to another edition of Adjacent Possible to discuss how single-trait singularities like this might apply to technological or cultural history. (And perhaps our present moment.) For now, though, I just want to focus on this idea of the possibility space expanding and contracting over time (not unlike the jaws of that python, I suppose.) Part of the lesson here is the importance of gauging which mode you're currently in the middle of: is it the right time to set out for uncharted new territory, or is it time to polish or upgrade your existing home base? In general, I like the idea that the adjacent possible would be cyclical in this way—even if the long-run story is all about expansion. It would be exhausting to forever live on the cusp of a paradigm shift. Much better to have seasons of change: time to invent, and time to refine.