Hmm, I think I disagree with the premise that we've gotten that much better at making guesstimates. My guess is that for most people, their ability to take systematic action in their environment in a way that has direct positive consequences has gotten a lot worse, but the ability of a small group of people to leverage systematic action for really large consequences has gotten a lot better.

My interpretation of Scott's recent posts, in combination with some of the quotes from Vaniver's "Steelmanning Divination" is something like the following:

• A lot of people need to follow cultural rituals to succeed at their goals, in particular in domains that they don't have time to think about a lot
• Most of the rituals were created by individuals that did actually understand the real reasons for why certain things had to happen, but the complicated true explanations often couldn't compete with the much simpler but wrong explanations that nevertheless allowed for the derivation of the correct instructions
• On a societal level guesstimates have worked for a long time and are the source of a lot of our most valuable cultural institutions, and didn't get particularly more effective recently

Very interesting question - the sort that makes me swing between thinking it's brilliant and thinking it's nonsense. I do think you overstate your premise. In almost all of the examples given in The Secret of our Success, the relevant knowledge is either non-arbitrary (e.g. the whole passage about hunting seals makes sense, it's just difficult to acquire all that knowledge), or there's a low cost to failure (try a different wood for your arrows; if they don't fly well, go back to basics).

If I engage with the question as posed, though, my primary answer is simply that over time we became wealthy and technologically capable enough that we were able to replace all the natural things that might kill us with whatever we're confident won't kill us. Which is why you can improvise while cooking - all of the ingredients have been screened very hard for safety. This is closely related to your first hypothesis.

However, this still leaves open a slightly different question. The modern world is far too complicated for anyone to understand, and so we might wonder why incomprehensible emergent effects don't render our daily lives haphazard and illegible. One partial answer is that even large-scale components of the world (like countries and companies) were designed by humans. A second partial answer, though, is that even incomprehensible patterns and mechanisms in the modern world still interact with you via other people.

This has a couple of effects. Firstly, other people try to be legible, it's just part of human interaction. (If the manioc could bargain with you, it'd be much easier to figure out how to process it properly.)

Secondly, there's an illusion of transparency because we're so good at and so used to understanding other people. Social interactions are objectively very complicated: in fact, they're "cultural norms and processes which appear arbitrary, yet could have fatal consequences if departed from". Yet it doesn't feel like the reason I refrain from spitting on strangers is arbitrary (even though I couldn't explain the causal pathway by which people started considering it rude). Note also that the space of ideas that startups explore is heavily constrained by social norms and laws.

Thirdly, facts about other humans serve as semantic stop signs. Suppose your boss fires you, because you don't get along. There's a nearly unlimited amount of complexity which shaped your personality, and your boss' personality, and the fact that you ended up in your respective positions. But once you've factored it out into "I'm this sort of person, they're that sort of person", it feels pretty legible - much more than "some foods are eat-raw sorts of foods, other foods are eat-cooked sorts of foods". (Or at least, it feels much more legible to us today - maybe people used to find the latter explanation just as compelling). A related stop sign is the idea that "somebody knows" why each step of a complex causal chain happened, which nudges us away from thinking of the chain as a whole as illegible.

So I've given two reasons for increased legibility (humans building things, and humans explaining things), and two for the illusion of legibility (illusion of transparency, and semantic stop signs). I think on small scales, the former effects predominate. But on large scales, the latter predominate - the world seems more legible than it actually is. For example:

The world seems legible -- I can roughly predict how many planes fly every day by multiplying a handful rough numbers.

Roughly predicting the number of planes which fly every day is a very low bar! You can also predict the number of trees in a forest by multiplying a handful of numbers. This doesn't help you survive in that forest. What helps you survive in the forest is being able to predict the timing of storms and the local tiger population. In the modern world, what helps you thrive is being able to predict the timing of recessions and crime rate trends. I don't think we're any better at the latter two than our ancestors were at the former. In fact, the large-scale arcs of our lives are now governed to a much greater extent by very unpredictable and difficult-to-understand events, such as scientific discoveries, technological innovation and international relations.

In summary, technology has helped us replace individual objects in our environments with safer and more legible alternatives, and the emergent complexity which persists in our modern environments is now either mediated by people, or still very tricky to predict (or both).

We just have better medical and welfare systems which allow people to take more risks.

I would think it's something like this, though I would put it differently: we're not at subsistence anymore. If you're at subsistence, then probably most of what you're doing is just to get by, and if you deviate too much from it, you die and/or fail to reproduce.

Now that we have slack, we can take on bigger risks, speculate, and be creative and enterprising.

Human civilizations have survivorship bias such that you're seeing the iterated output of those that found parameter insensitive parts of critical distributions. Exogenous shocks are common, and civs that weren't metastable disappeared. This happened on both the cultural and genetic level (you are already a civilization of trillions of cells). As the pace of change accelerates things might get more dangerous as people push farther/harder within the span of a single lifetime before natural self corrections kick in (four horsemen). The current trend could be seen as the human race essentially tinkering with cancer (runaway, uncontrollable growth) to see if it will grant us immortality before it kills us.

Hypothesis: Guesstimates have always worked on transparent and opaque domains. As communication and reasoning tools have become better over time, more domains have become transparent and opaque. What used to have been encoded by culture can now be encoded in big data.

Hypothesis:

As communication and reasoning tools have gotten better, things have become more intertwined in complex, complicated, and unexpected ways. This means that the things we do can have unexpected consequences, and that distributions we're shutting up and multiplying in can be effected at unexpected times in unexpected ways. This makes more domains Knightian.

In other words, we have the illusion of more transparency, but we actually have more Knightian environments.

Hypothesis: Smoothing out knightian environments to make them more predictable in the short term makes them more suspectible to large black swans. The smoothing behavior you noted above may actually contribute to this illusion of transparency.

I think it's some mix of genuine improvement and legibility bias.

We really have learned more about the world and made many aspects we care about more legible. On the other hand, we also tend to focus on what we see and ignore what we don't, so improved legibility in some areas may make us more likely to pay attention to those at the expense of others.

Things get extra tricky if we optimize too hard on legible metrics. To the extent illegible things matter, we can goodhart and incur illegible technical debt that's masked in the short run by legible improvements.