Spoilers ahead, but if you haven’t read Seveneves by now they probably don’t matter.

Seveneves is an unusual and great novel, and it’s great as long as you attribute some of its less plausible elements to an author building a world. One plausible element is the way humanity comes together and keeps the social, political, and economic systems functional enough to launch large numbers of spacecraft in the face of imminent collective death. If we collectively had two years to live, I suspect total breakdown would follow, leaving us with no Cloud Ark (and no story—thus we go along with the premise).

But that’s not the main thing I want to write about. Instead, consider the loss of knowledge that inherently comes with population decline. In Seveneves humanity declines to seven women living in space on a massive iron remnant of the moon. They slowly repopulate, with their descendants living in space for five thousand years. But a population of seven would probably not be able to retain and transmit the specialized knowledge necessary for survival on most parts of Earth, let alone space.

That isn’t a speculative claim. We have pretty good evidence for the way small populations lose knowledge. Something drew me to re-reading Joseph Henrich’s excellent book The Secret of Our Success, and maybe the sections about technological loss are part of it. He writes about many examples of European explorers getting lost and dying in relatively fecund environments because they don’t have the local knowledge and customs necessary to survive. He writes about indigenous groups too, including the Polar Intuit, who “live in an isolated region of northwestern Greenland [. . . .] They are the northernmost human population that has ever existed” (211). But

Sometime in the 1820s an epidemic hit this population and selectively killed off many of its oldest and most knowledgable members. With the sudden disappearance of the know-how carried by these individuals, the group collectively lost its ability to make some of its most crucial and complex tools, including leisters, bows and arrows, the heat-trapping long entry ways for snow houses, and most important, kayaks.

As a result, “The population declined until 1862, when another group of Intuit from around Baffin Island ran across them while traveling along the Greenland coast. The subsequent cultural reconnection led the Polar Intuit to rapidly reacquire what they had lost.” Which is essential:

Though crucial to survival in the Arctic, the lost technologies were not things that the Polar Intuit could easily recreate Even having seen these technologies in operation as children, and with their population crashing, neither the older generation nor an entirely new generation responded to Mother Necessity by devising kayaks, leisters, compound bows, or long tunnel entrances.

Innovation is hard and relatively rare. We’re all part of a network that transmits knowledge horizontally, from peer to peer, and vertically, from older person to younger person. Today, people in first-world countries are used to innovation because we’re part of a vast network of billions of people who are constantly learning from each and transmitting the innovations that do arise. We’re used to seemingly automatic innovation, because so many people are working on so many problems. Unless we’re employed as researchers, we’re often not cognizant of how much effort goes into both discovery and then transmission.

Without that dense network of people, though, much of what we know would be lost. Maybe the best-known example of technology loss happened when the Roman Empire fell, followed by the way ancient Egyptians lost the know-how necessary to build pyramids and other epic engineering works.

In a Seveneves scenario, it’s highly unlikely that the novel’s protagonists would be able to sustain and transmit the knowledge necessary to live somewhere on earth, let alone somewhere as hostile as space. Quick: how helpful would you be in designing and manufacturing microchips, solar panels, nuclear reactors, plant biology, or oxygen systems? Yeah, me too. Those complex technologies have research, design, and manufacture facets that are embodied in the heads of thousands if not millions of individuals. The level of specialization our society has achieved is incredible, but we rarely think about how incredible it really is.

This is not so much a criticism of the novel—I consider the fact that they do survive part of granting the author his due—but it is a contextualization of the novel’s ideas. The evidence that knowledge is fragile is more pervasive and available than I’d thought when I was younger. We like stories of individual agency, but in actuality we’re better conceived of as parts in a massive system. We can see our susceptibility to conspiracy theories as beliefs in the excessive power of the individual. In an essay from Distrust That Particular Flavor, William Gibson writes: “Conspiracy theories and the occult comfort us because they present models of the world that more easily make sense than the world itself, and, regardless of how dark or threatening, are inherently less frightening.” The world itself is big, densely interconnected, and our ability to change it is real but often smaller than we imagine.

Henrich writes:

Once individuals evolve to learn from one another with sufficient accuracy (fidelity), social groups of individuals develop what might be called collective brains. The power of these collective brains to develop increasingly effective tools and technologies, as well as other forms of nonmaterial culture (e.g., know-how), depends in part on the size of the group of individuals engaged and on their social connectedness. (212)

The Secret of Our Success also cites laboratory recreations of similar principles; those experiments are too long to describe here, but they are clever. If there are good critiques of the chapter and idea, I haven’t found them (and if you know any, let’s use our collective brain by posting links in the comments). Henrich emphasizes:

If a population suddenly shrinks or gets socially disconnected, it can actually lose adaptive cultural information, resulting in a loss of technical skills and the disappearance of complex technologies. [. . . ] A population’s size and social interconnectedness sets a maximum on the size of a group’s collective brain. (218-9)

That size cap means that small populations in space, even if they are composed of highly skilled and competent individuals, are unlikely to survive over generations. They are unlikely to survive even if they have the rest of humanity’s explicit knowledge recorded on disk. There is too much tacit knowledge for explicit knowledge in and of itself to be useful, as anyone who has ever tried to learn from a book and then from a good teacher knows. Someday we may be able to survive indefinitely in space, but today we’re far from that stage.

Almost all post-apocalyptic novels face the small-population dilemma to some extent (I’d argue that Seveneves can be seen as a post-apocalyptic novel with a novel apocalypse). Think of the role played by the nuclear reactor in Steven King’s The Stand: the characters in the immediate aftermath must decide if they’re going to live in the dark and regress to hunter-gatherer times, at best, or if they’re going to save and use the reactor to live in the light (the metaphoric implications are not hard to perceive here). In one of the earliest post-apocalyptic novels, Earth Abides, two generations after the disaster, descendants of technologically sophisticated people are reduced to using melted-down coins as tips for spears and arrows. In Threads, the movie (and my nominee for scariest movie ever made), the descendants of survivors of nuclear war lose most of their vocabulary and are reduced to what is by modern standards an impoverished language that is a sort of inadvertent 1984 newspeak.* Let’s hope we don’t find out what actually happens after nuclear war.

In short, kill enough neurons in the collective brain and the brain itself stops working. Which has happened before. And it could happen again.

* Check out the cars in Britain in Threads: that reminds us of the possibilities of technological progress and advancement.