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When should we be surprised that an invention took “so long”?

My first highly popular essay was “Why did we wait so long for the bicycle?” I’ve asked the same question of the cotton gin and the threshing machine. Others have asked it of the steam engine and the wheel. Recently Brian Potter asked it about wind power and Anton Howes about semaphore signaling systems. See more examples here.

When asking these questions, we should think about when the question even needs an answer. That is, “why did it take so long” is only interesting if it took an abnormally long amount of time.

Here’s my model for this.

First, an invention is not going to happen at all if (1) it’s not technically possible or (2) there’s no market for it.

Gate (1), technical possibility, could include, for example:

Scientific foundations. No light bulb before electromagnetism, no antibiotics before the germ theory.
Components. Airplanes were not possible before the internal combustion engine.
Materials. Skyscrapers could only be built once cheap steel girders were available.
Manufacturing techniques. Precision machining was necessary to make the gears, sprockets, chains, bearings, and other parts for a wide variety of inventions, probably including the threshing machine and the bicycle.

Gate (2), the market, is whether it can be done commercially at a price that anyone will pay. If someone does make an invention there is no market for, it doesn’t go anywhere, and we might not even hear about it, because it is unlikely to make the history books. In any case, it wouldn’t affect the world, because it wouldn’t get distribution, and so it wouldn’t be historically relevant for our purposes. You see examples of this from time to time, such as the Korean movable-type printing press that predated Gutenberg.

Note that the bar inventions have to meet is not just a proof of concept: they have to be sufficiently powerful, efficient, and reliable to be of practical use. Early computing machines were too slow; early threshing machines broke down too frequently; early light bulbs burned out too quickly. These are technically interesting prototypes, but not true inventions. An invention does not merely demonstrate a concept, it solves a problem—the whole problem, not just a part of it, even if it is the most visible or obvious part. An invention has to be practical. (See more discussion of this here.)

Once something is technically possible and economically viable, then the clock starts ticking on how long we “waited” for it. But invention is a human process, and it’s not instantaneous. There is no perfectly efficient market in which an invention springs to life immediately as soon as it’s viable. It takes time, effort, trial and error. People have to decide to do something—they have to get the idea, and be sufficiently inspired and motivated to devote full-time efforts to something unknown, with an indefinite timeline and uncertain rewards. (Only a minority of people even have the temperament for this; in this sense, I agree with Anton Howes that innovation is not simply “in human nature.”) Then they have to get free to do it: at any given time, most inventors will be busy with projects, and only a subset will be looking for something new to do. They may have to acquire resources or recruit help, which takes time. Once they finally get to work, they have to experiment with approaches, discard failures, get new ideas, iterate.

Given the nature of that process, there are several factors that affect the time that elapses before an invention. I have written about many of them before in the context of “flywheels of progress.” Here are some that I would call out specifically regarding the invention process:

Total amount of R&D effort in the world, or in a specific field. This includes the number of inventors or researchers, the financing available for R&D, and the existence of instutitions such as labs where this work is done.
Speed and frequency of communication among researchers. The printing press sped up innovation, as did the Internet.
Total market size / strength of opportunity. Big, obvious opportunities will attract many parallel efforts.
Social/moral strictures. When something is taboo, relatively few innovators will pursue it. In the 1600s it was still frowned upon to create labor-saving devices. In the 1900s it was controversial to create birth control.

You can think about this by analogy to stochastic processes in thermodynamics: the exact path of any given molecule is random, but in aggregate there are predictable patterns, and they are determined in part by macro-level factors such as temperature and pressure. You could think of total amount of R&D effort as like the temperature of a system, and the market size as a kind of pressure in a particular direction. Or in an electronic analogy, speed of communication is like conductivity in a material, a large market is like a high voltage differential, and social strictures are a kind of resistance. (These are rough analogies, not mathematical isomorphisms.)

Given all that, it’s not surprising to me if we “waited” many years for a recent invention, or several decades in the 18th or 19th centuries, or centuries in the period before that. For instance, all of the following seem normal to me:

The 50+ year gap between the Newcomen and Watt steam engines
The similar gap from Faraday’s electromagnetism to Edison and Westinghouse
The many centuries between the ard and the plow, or the spindle and the spinning wheel
The gap of more than a decade between Fleming’s discovery of penicillin in mold and the the Florey lab making it into a drug
The several years between the first popular smartphones and the first successful ridesharing apps such as Lyft and Uber

That’s just how long these things take.

It’s also not too surprising when we wait a long time for something that doesn’t have a billion-dollar market (or the equivalent in the past). I don’t really think we need to scour for explanations or wrack our brains over why it took “so long” to get wheels on suitcases, or role-playing games. These are niches.

And just for the record, I’m no longer surprised by the bicycle, either. I think that case is fairly well explained by materials and manufacturing techniques, overall market size, and the other general factors listed above.

For a while, I was surprised that flag-based naval messaging systems were not in use until the late 1700s. It’s a very simple technology, with a strong, obvious need not only economically but militarily. But after Anton’s recent essay, I think there is much less to explain: telescopes needed to be carried on ships in order to see the details of flags in the distance, and that starts the clock much later.

In fact, I can’t immediately come up with an invention gap that isn’t explained by this model.

Does this render irrelevant the factor of fundamental philosophical attitudes towards progress—the idea of progress itself, and whether it is possible and desirable? No, quite the contrary: the belief in progress affects most if not all of the factors above. A society that believes in progress will encourage its best and brightest to become scientists and inventors, set up networks of communication for them (from the Republic of Letters to arXiv), establish institutions for them to work in, provide plentiful funding for them, and drop its moral strictures against various forms of progress—indeed, there will be honor and acclaim for progress and those who make it.