Initially behind the paywall because I am profoundly dissatisfied with it. Birdbrains & human gains: intelligence, culture, & deep biocultural evolutionary roots of economic history. But I have not managed to find the time or the smarts to fix it, so here it is out in the world...
The story of economic history begins with the evolution of minds, not markets. And not with the evolution of individual minds either. The story properly begins with the biocultural evolution of the time- and space-binding Mind that is humanity considered as an anthology intelligence. It is the peculiar, contingent evolution of that and its capacity for cumulative culture that sets off the possibility of the process. The “market” is merely a latecomer, a surface ripple atop the vast ocean of social learning, language, and trust that made Homo sapiens the protagonist of the coming of the Anthropocene.
The last time I taught my global economic history course, I found myself wishing that I had spent a full two weeks on humanity the coming of agriculture: one class on the jump to our intelligence, one class on our sociability and the jump to our being a cultural-evolution environment-transforming animal, one class on the jump to language as we know it and the the difference we think that made, and one class on the gatherer-hunter lifestyle, the last out-of-Africa migration, and the runup to agriculture and herding. But I do not know when I will.
So it is time to see if there is stuff in my notes that I should get out there, in the hope that somebody in the future (maybe me) will run across it and use it in some way. As Niccolo Machiavelli says, “if [my] poor talent, little experience… and weak knowledge… makes this… not of much utility, it will at least show the path to someone who with more virtue, more discourse and judgment”.
Do birds do it much better? “It” begin intelligence?
In terms of bang for the buck, that is. As Yasemin Saplakoglu reports:
Yasemin Saplakoglu: Intelligence Evolved at Least Twice in Vertebrate Animals <https://www.quantamagazine.org/intelligence-evolved-at-least-twice-in-vertebrate-animals-20250407/>: ‘Complex neural circuits likely arose independently in birds and mammals, suggesting that vertebrates evolved intelligence multiple times…. . Ravens plan for the future, crows count and use tools, cockatoos open and pillage booby-trapped garbage cans, and chickadees keep track of tens of thousands of seeds cached across a landscape… with brains… smaller [that]… lack the highly organized structures that scientists associate with mammalian intelligence. “A bird with a 10-gram brain is doing pretty much the same as a chimp with a 400-gram brain…. How is it possible?”… The mature circuits looked remarkably alike… but they were built differently…. The mammalian neocortex and the avian [pallium and within it the] d[orsal ]v[entricular ]r[idge] developed at different times, in different orders and in different regions of the brain…. Birds and mammals independently evolved brain regions for complex cognition…. Octopuses… “evolved intelligence in a way that’s completely independent.” Their cognitive structures look nothing like ours…. Yet octopuses have been caught performing incredible feats such as escaping aquarium tanks, solving puzzles, unscrewing jar lids and carrying shells as shields…
The crow and the veined octopus are about 1 kg each, the domesticated dog about 20 kg; chimp is about 50 kg, the human 70 kg, the ostrich 110, the elephant 4000, and the blue whale 120,000 kg.
The brain of the crow is about 10g, of the veined octopus 30, of the dog 60, of the chimp 400, of the human 1300, of the ostrich 35, of the elephant 5000, and of the blue whale 8000 g.
The veined octopus has about 0.5 billion neurons—most of them in the arms—the crow 2 billion, the dog 2 billion; the chimp 28 billion, the human 80, the ostrich 2, the elephant 250, and the blue whale 15.
We also have: octopus 0.4 billion cortex neurons (kinda-sorta); crow 1.5; dog 0.5; chimp 6; human 16; ostrich 0.5; elephant 5; blue whale 4 billion cortex neurons.
It seems pretty clear what the elephant is doing with all those neurons: they are for its incredibly flexible trunk. As Suzana Herculano-Houzel writes:
Suzana Herculano-Houzel: The Human Advantage <https://archive.org/details/humanadvantagene0000herc: ‘Why so many neurons in the elephant cerebellum?… [What] is both unique to elephants and requires great numbers of cerebellar neurons[?]…. [Most likely] the highly sensory elephant trunk, a 100-kilogram muscular organ capable of precise, delicate movements, as the most likely source of selective pressure for a much larger number of neurons…. A directly sensorimotor function of the cerebellum, without involving the cerebral cortex, would also explain the break away from the tight linear relationship between numbers of neurons in the cerebral cortex and cerebellum in other species… to deal with both the parallel processing of information from the cerebral cortex and from the trigeminal nerve related to the trunk…
It is also pretty clear why ostriches are not smart: their bigger brains than crows have no more neurons and only 1/3 as many cortical neurons. Their neurons are bigger than crows’ neurons. And a much larger number of neurons is needed to control the much larger ostrich body.
Suzana Herculano-Houzel makes a very good case that it is cortical neuron number that counts for what we think of as “intelligence”. If she is right, than if an ostrich had neurons the size of crows’ and the same cortex-total ratio, it would have as many cortical neurons as a chimp. Given that we have only three times as many cortical neurons as chimps, and that crows appear to bat even cognitively with chimps with only 1/4 as many cortical neurons, we might then be in serious trouble:
Or maybe not.
Perhaps—and here I have been much more than half-convinced by Joseph Henrich—we are not that much smarter than chimps, blue whales, and elephants. Perhaps we only have a slight edge over them on an individual one-for-one level. But we are astonishingly social, have hands, and can talk and listenn. Perhaps those are our key edges. Perhaps it is our ability to learn from others, first by watching and then by listening and speaking, and our highly prosocial nature, and our ability to use are opposable thumbs to do things other than hang from branches. Perhaps those factors make us think that we are uniquely smart, because those are the factors that have allowed us to both (a) transform the environment in which we operate so that its affordances have enormous synergies with the kind of intelligence we have, and (b) effectively become a group organism, an anthology intelligence, now some 8.4 billion strong.
That anthology intelligence has 700 quadrillion cortical neurons, after all.
The next natural question is: how is it that birdbrains punch so much above not just their weight but their neuron count?
We start crow’s pallium can have as many neurons as a macaque’s cortex, despite the crow’s brain being 10x smaller by mass. Continue by noting that bird brains are more compact, with an average distance between neurons is shorter, and that potential for faster signal transmission potentially gives birdbrains a faster clock speed. With neurons 1/3 the size and 1/3 the distance, we have gotten the crow brain up to 0.75 chimp-equivalent neural processing capacity, and that is without taking account of the possibility that fewer neuron working and intercommunicating quicker are better than more with less frequent intercommunication. So perhaps we should not be surprised at all how well crows and parrots can plan, use tools, understand cause and effect, and even pass the mirror test. Their brains are not, along the relevant dimensions, small and slow at processing at all.
I think that the big lesson that would be gained from looking at human intelligence and its evolution would be one of humility: that what we have, even before agriculture, is some explosive increasing-returns runaway which cannot simply be seen as a natural consequence of our individual intelligence alone, which when you look closely does not seem to involve such a huge gulf relative to the elephant, the chimp, and the crow.
Thus I think I want to set a stake that there are a number of fundamental substrates upon which all subsequent economic history is built: the peculiar, contingent, and—dare I say—miraculous evolution more-or-less simultaneously of the human animal’s intelligence, its hypersocial nature, its capacity for cumulative culture, and its emergence as a listening-and-speaking animal.
The evolutionary biologists, from Darwin to Mayr to the more recent work of Joseph Henrich (see The Secret of Our Success, 2016), have made it very clear, to me at least, that the story of Homo sapiens’ intelligence is not the story of a solitary, calculating brain, but of a collective, chattering, imitative, and—crucially—teachable species. The “Machiavellian intelligence” hypothesis, advanced by Richard Byrne and Andrew Whiten in the 1980s, posited that the complexity of human cognition was driven by the demands of navigating ever-more-intricate social relationships: alliances, rivalries, kinship, reputation, and the subtle art of not getting eaten or exiled. The size and density of our neocortex is necessary but far from sufficient. It must, also, be the structure of our social learning that sets us apart.
Consider, for a moment, the “ratchet effect”—that is, the process by which each generation builds upon the innovations of the last, such that cumulative culture becomes possible. This is not mere imitation (the crow can bend a wire into a hook, but her daughter will not necessarily do so unless she, too, discovers the trick). Rather, it is teaching, language, and the capacity for “overimitation” (see Tomasello, 1999), that allows Homo sapiens to maintain, transmit, and elaborate upon the complex toolkits, social norms, and symbolic systems that define human societies. This is not a trivial point: the difference between a chimpanzee’s termite stick and a Hadza bow is not just a matter of degree, but of kind—a difference rooted in the cognitive ecology of teaching, joint attention, and the recursive mind.
In human history, this is present long before language. I have long been struck by Joseph Henrich’s description of human life at Gesher Benot Ya'aqov three-quarters of a million years ago:
Joseph Henrich: The Secret of Our Success <https://archive.org/details/secretofoursucce0000heni>: ‘Stone-tool manufacturing… food processing… controlled fire… hand axes, cleavers, blades, knives, awls, scrapers, and choppers… from flint, basalt, and limestone, tool manufacture… on-site, often from giant slabs carried in from a distant quarry…. Freshwater crabs, turtles, reptiles, and at least nine types of fish… [plus] seeds, acorns, olives, grapes, nuts, water chestnuts… the submerged prickly water lily…. There’s little doubt that we are dealing with a cultural species who hunts large game, catches big fish, maintains hearths, cooks, manufactures complex tools, cooperates in moving giant slabs, and gathers and processes diverse plants. The bottom line: cumulative cultural evolution is old in our species’ lineage, dating back at least hundreds of thousands of years, but probably millions of years…
But why should this matter for global economic history?
Because, I would argue, the entire edifice of “economic growth”—from the first sickle to the silicon chip—is, at bottom, a story of the acceleration of cumulative culture: the harnessing of ever-larger pools of knowledge, the coordination of ever-more-complex forms of cooperation, and the ever-finer division of labor. Adam Smith, in his Wealth of Nations (1776), famously began with the pin factory, but the precondition for the pin factory is not the market, nor the state, nor even the surplus of the agricultural revolution—it is the prior evolution of a species capable of listening, speaking, and, above all, learning from one another.
Economic historians to do their jobs must grapple with the following facts:
The Human Brain as an Expensive Organ: At rest, the adult human brain consumes about 20–25% of the body’s energy, yet comprises only 2% of its mass. Why did natural selection favor such a costly organ? The answer, increasingly, appears to be that the brain’s primary function is not solitary reasoning, but social navigation and cultural learning.
Hypersociality and the Evolution of Trust: Homo sapiens is the “ultrasocial” animal. Our evolutionary success is not the product of individual genius, but of collective intentionality: the ability to form shared goals, coordinate action, and enforce social norms. The biocultural evolution of societal-scale preferences—altruism, fairness, punishment—was a precondition for the emergence of markets, states, and all the other machinery of economic history.
Language as a Cognitive Technology: The emergence of language—whether gradual or sudden, whether as a byproduct of social grooming or as an adaptation for storytelling—transformed the cognitive ecology of our ancestors. Language is not merely a vehicle for information transfer; it is a technology for the coordination of minds, the transmission of norms, and the creation of shared fictions. Consider, for a moment, the economic historian’s dependence on the written record: without language, there is no history.
Cultural Evolution and the “Collective Brain”: Thus the true driver of human progress is not individual intelligence, but the size and connectivity of the “collective brain”—the network of minds linked by social learning. The larger and more interconnected the network, the faster the rate of innovation. This is why, for example, Tasmanian toolkits regressed after isolation (Henrich, 2004), and why the “Great Divergence” may owe as much to the density of social networks as to the “spirit of capitalism.”
Listening and Speaking as Economic Infrastructure: It is easy, in the age of the internet, to forget that the infrastructure of listening and speaking—of face-to-face conversation, of gossip, of oral tradition—was, for most of history, the primary medium of economic coordination. The market, as Hayek (1945) observed, is a mechanism for the transmission of information, but that mechanism presupposes a species capable of encoding, decoding, and acting upon signals—verbal, gestural, symbolic.
From these premises, I think we can draw several conclusions of direct relevance:
First, the “jump” to human intelligence was not a single leap, but a protracted coevolution of brain, sociality, language, and culture. The archaeological record, from Blombos Cave to Göbekli Tepe, is replete with evidence of incremental advances—symbolic art, complex tools, ritual burial—that speak to the gradual ratcheting-up of cognitive and social complexity. The economic historian must resist the temptation to see the Neolithic Revolution as a sharp break; rather, it was the culmination of tens of thousands of years of cumulative culture.
Second, the “hypersocial” nature of Homo sapiens is not merely a background condition, but the engine of economic history. The division of labor, the emergence of markets, the rise of cities—all depend on the capacity for trust, coordination, and norm enforcement.
Third, the evolution of cumulative culture—of the capacity to transmit, store, and improve upon knowledge—renders possible the exponential growth dynamics that define the modern era. Joel Mokyr (2002, The Gifts of Athena) has shown that the “industrial enlightenment” was as much a product of new institutions for knowledge sharing (the Royal Society, the Encyclopédie, the patent system) as of technological invention per se. The economic historian must, therefore, treat the evolution of cultural transmission not as a prelude, but as a central act.
Fourth, the “listening and speaking animal” is the foundation of all subsequent economic infrastructure. The market, the firm, the state—these are, at bottom, systems for the coordination of human action, and thus depend on the evolved capacities for communication, empathy, and normativity. The historian who marvels at the efficiency of the price system should recall that prices are, in the end, just another language—a code for the coordination of plans.
Finally, I think we would do well to remember that the evolution of human intelligence is not a story of unalloyed progress. The same capacities for social learning and norm enforcement that undergird economic growth also enable the spread of misinformation, the entrenchment of inequality, and the perpetuation of violence. To spend a week or two on the biocultural evolution of humanity’s intelligence, hypersociality, cumulative cultural evolution, and linguistic capacities is not to indulge in prehistory for its own sake. It is to lay bare the deep roots of the economic processes that have shaped our world. To understand why Homo sapiens, and not some other clever animal, became the protagonist of global economic history is to understand why history took the path it did—and why, perhaps, it need not have done so.
Thus the economic historian who neglects these origins is like the physicist who neglects the Big Bang. The universe of economic history is, in the end, a human universe—and to understand its laws, we must first understand the animal that made them.
It also has implications for the Fermi Paradox. The fact that when we look at at the universe we do not see—indeed, have not long ago been absorbed by—interstellar civilizations is not because stars don’t have planets, is not because planets are rarely rocky bodies with liquid water, does not seem likely to be because self-replication and variation with natural selection are extraordinary difficult, does not seem likely to be because the replicators have a difficult time developing useful protein-or-analogous coats, and does not seem likely because it is hard to develop complex-cell, sexually reproducing, multicellular life.
And now—looking at octopuses, chimps, and crows—the “tool-using intelligence” hurdle seems unlikely to be the Great Filter.
That leaves many fewer candidates than back when Enrico Fermi was thinking about the problem.
References:
Byrne, Richard W., & Andrew Whiten, eds. 1988. Machiavellian Intelligence: Social Expertise and the Evolution of Intellect in Monkeys, Apes, and Humans. Oxford: Clarendon Press. <https://archive.org/details/machiavellianint00byr>.
Henrich, Joseph. 2016. The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, & Making Us Smarter. Princeton, NJ: Princeton University Press. <https://archive.org/details/secretofoursucce0000heni>.
Herculano-Houzel, Suzana. 2016. The Human Advantage: A New Understanding of How Our Brain Became Remarkable. Cambridge, MA: MIT Press. <https://archive.org/details/humanadvantagene0000herc>.
Herculano-Houzel, Suzana, & Ilari Mäkelä. 2023. “Is the Human Brain Special?” On Humans Podcast, October 3. <https://onhumans.substack.com/p/is-the-human-brain-special-a-conversation>.
Machiavelli, Niccolò. 1996. Discourses on Livy. Ed. & trans. Harvey C. Mansfield & Nathan Tarcov. Chicago: University of Chicago Press. <https://archive.org/details/discoursesonlivy00mac>.
Mokyr, Joel. 2002. The Gifts of Athena: Historical Origins of the Knowledge Economy. Princeton, NJ: Princeton University Press.<https://archive.org/details/giftsofathenahis00moky>.
Sandberg, Anders, Eric Drexler, & Toby Ord. 2018. “Dissolving the Fermi Paradox.” arXiv. <https://arxiv.org/abs/1806.02404>.
Saplakoglu, Yasemin. 2025. “Intelligence Evolved at Least Twice in Vertebrate Animals.” Quanta Magazine, April 7. <https://www.quantamagazine.org/intelligence-evolved-at-least-twice-in-vertebrate-animals-20250407/>.
Smith, Adam. 1776. An Inquiry into the Nature and Causes of the Wealth of Nations. London: W. Strahan & T. Cadell. <https://archive.org/details/wealthofnationsa00adam>.
Tomasello, Michael. 1999. “The Human Adaptation for Culture.” Annual Review of Anthropology 28: 509–529. <https://doi.org/10.1146/annurev.anthro.28.1.509>.
You have the elements of very good and very important teaching here. If you're not satisfied, by all means keep working on it. But I think it's worth a shot to introduce this to your students.
Dear Brad Delong,
You wrote:
"Dp [Do] birds do it much better? “It” begin [being] intelligence?"
Kinda like it better as: "Did Dodo birds do it much better? "It" being living in harmony with our environment."
The stupidity of humans in over harvesting and bringing in predators to the Dodo bird ended their existence. It ain't how many neurons you have, it's how you use them.
I would love to see you expound on a deep consideration about how economics has mostly been shaped by power relationships.
Access to trading routes, roads, aqueducts, water lines, power lines, canals, telegraph lines, radio frequencies, broadband frequencies, and international trade agreements have all been mostly shaped by power relationships. Imperialism, colonialism, globalization, and financialization have been the primary forces driving economic history. Brawn has dominated over brains. China's cutting off the world in general, and America's military in particular, of heavy earth materials and magnets is an example of how the power of vertically integrated monopolistic control of a critical good can completely change the power dynamics of the world order.
It's great to imagine a world where rational thought guided our economic decisions but as Trump said: ‘Real power is … I even don’t like to use the word … but real power is fear,’”