Dear reader. This article is really long; probably about twice as long as anything else I’ve written. Rather than post the whole thing below, instead here is the introduction and an outline. A link to the rest of the article is above. Treat this forum post as a way to comment and provide feedback on the essay!



In a 1989 book, the biologist Stephen Jay Gould posed a thought experiment:

I call this experiment “replaying life’s tape.” You press the rewind button and, making sure you thoroughly erase everything that actually happened, go back to any time and place in the past… then let the tape run again and see if the repetition looks at all like the original.”[1]

Gould’s main argument is:

…any replay of the tape would lead evolution down a pathway radically different from the road actually taken… Alter any early event, ever so slightly and without apparent importance at the time, and evolution cascades into a radically different channel.[2]

Gould is interested in the role of contingency in the history of life. But we can ask the same question about technology. Suppose in some parallel universe history proceeded down a quite different path from our own, shortly after Homo sapiens evolved. If we fast forward to 2022 of that universe, how different would the technological stratum of that parallel universe be from our own? Would they have invented the wheel? Steam engines? Railroads? Cars? Computers? Internet? Social media? Or would their technologies rely on principles entirely alien to us? In other words, once humans find themselves in a place where technological improvement is the rule (hardly a given!), is the form of the technology they create inevitable? Or is it the stuff of contingency and accident?

In academic lingo, this is a question about path dependency. How much path dependency is there in technology? If path dependency is strong, where you start has a big effect on where you end up: contingency is also strong. But if path dependency is weak, all roads lead to the same place, so to speak. Contingency is weak.

Some people find this kind of thing inherently fun to speculate about. It’s also an interesting way to think through the drivers of innovation more generally. But at the same time, I don’t think this is a purely speculative exercise. My original motivation for writing it was actually related to a policy question. How well should we expect policies that try to affect the direction of innovation to work? How much can we really direct and steer technological progress?

As we’ll see, the question of contingency in our technological history is also related to the question of how much remains to be discovered. Do we have much scope to increase the space of scientific and technological ideas we explore? Or do we just about have everything covered, and further investigation would mostly be duplicating work that is already underway?

I’ll argue in the following that path dependency is probably quite strong, but not without limits. We can probably have a big impact on the timing, sequence, and details of technologies, but I suspect major technological paradigms will tend to show up eventually, in one way or another. Rerun history and I doubt you’ll find the technological stratum operating on principles entirely foreign to us. But that still leaves enormous scope for technology policy to matter; policies to steer technology probably can exert a big influence on the direction of our society’s technological substrate.

The rest of the post is divided into two main parts. First, I present a set of arguments that cumulatively make the case for very strong path dependency. By the end of this section, readers may be close to adopting a view close to Gould’s: any change in our history might lead to radically different trajectories. I think this actually goes too far. In the second part of the essay, I rein things in a bit by presenting a few arguments for limits to strong path dependency.

The rest of the piece goes on to make the following argument:


Part One: The Case for Strong Path Dependency

Small scale versions of replaying the technology tape point to path dependency being at least big enough to notice

The landscape of possible technologies is probably very big because

Combinatorial landscapes are very big

Technology seems to have an important combinatorial element

Our exploration of this space seems a bit haphazard and incomplete

From the constrained set of research and invention options actually discovered, an even smaller set get an early lead, often for highly contingent reasons, and then enjoy persistent rich-get-richer effects


Part Two: The Limits of Path Dependence

It may not matter that the landscape of technological possibility is large, if the useful bits of it are small. This may be plausible because

This might be the case for biology

It is probably possible to discover the small set of universal regularities in nature via many paths

Human inventors can survey the space of technological possibility to a much greater degree than in biological evolution

A shrinking share of better technologies combined with our ability to survey the growing combinatorial landscape can yield exponential growth in some models


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