The authors argue in this paper that technological innovations are the collective result of our cultural brains. The main novelty in this assertion is the implication that technological evolution often occurs outside of people's awareness or understanding. In the authors' words, "just as thoughts are an emergent property of neurons firing in our neural networks, innovations arise as an emergent consequence of our species' psychology applied within our societies and social networks... [Societies] can produce complex designs without the need for a designer—just as natural selection does in genetic evolution". 

Preceding this conclusion are the recent studies in human evolutionary biology that show that humans are remarkable imitators. This unique psychological trait, unmatched by any other primate species, enables innovations to diffuse and transmit across generations without deterioration. As a consequence, this unique skill for learning from our peers and copying their behaviors, has allowed societies to accumulate an ever increasing repertoire of practices, norms, tools and know-how. 

An important result from mathematical models of cultural evolution is that the population size and interconnectedness between individuals determine the diversity and complexity of a social group’s cultural repertoire. Social institutions that prevent the degree to which individuals can connect with each other will have a negative effect on innovation rates. Conversely, institutions that enable the inflow of people and ideas from outgroups will foster innovation.

In particular, the authors argue that three factors influence the speed of cultural evolution and the rate of innovation: “sociality” (i.e., population size and interconnectedness), transmission fidelity (how accurate individuals are at imitating), and transmission variance (the variety of errors that arise when imitating others).

Aside from citing a large body of experimental and empirical literature supporting their hypotheses, Muthukrishna and Henrich test their ideas on data of language use. Languages can be seen as a specific cultural technology that has facilitated coordination problems and the transmission of ideas. Their study of languages reveals that larger populations of speakers have larger vocabularies, larger grammatical tools, and consequently, more efficient languages. Moreover, they cite evidence that shows that languages with more speakers are easier to learn. Therefore, their results stand as an example in which a cultural dimension (language) fosters its own evolution. 

Accordingly, they argue that culture can affect its own evolution. This has to do with two opposing forces: on the one hand, a group of social learners act as a collective brain that can accumulate a large body of knowledge, and on the other hand, as knowledge accumulates, learning becomes harder.

Therefore, keeping up with the growing body of technological knowledge as a culture evolves and increases its complexity becomes more difficult. Muthukrishna and Henrich hypothesize that culture, as it evolves and grows, imposes certain evolutionary pressures which may be tuning sociality, transmission fidelity, and transmission variance in such a way to cope with the increase in the complexity of tools, practices, beliefs and behaviors. Consistent with this hypothesis, the authors cite evidence that large-scale societies, with more complex technologies, engage in more teaching. This turns out to be a key insight for thinking about economic development and its relation to theories of human capital. Muthukrishna and Henrich’s evolutionary approach suggests that developed countries have higher rates of education because their economies are complex, not the other way around. 

As this paper exemplifies, studies of cultural evolution are helping bridge the fields of economics and human evolutionary biology. The connections are still unexplored, but new insights have already emerged, for example, from the theory of economic complexity. In models of economic complexity, there is a difference between a skillful society and a society of skilled individuals. In line with Muthukrishna and Henrich, this theory puts an emphasis on the tacit aspects of knowledge (i.e., know-how), and how it gets coordinated in a society. From this perspective, the wealth of a society is determined by its collective know-how, which arises from coordinating complementary skills in such a way that the whole achieves more than any of its parts.

As a concluding remark, Muthukrishna and Henrich’s emphasis is on the psychological features exhibited by humans that enable the collective emergence of culture, and the specific mechanisms by which culture evolves and accumulates through a series of innovations. This approach offers a refreshing complement to traditional economic analysis where economic incentives and the efficiency of markets are invoked as the channels for technological evolution.

Innovation in the collective brain, by Michael Muthukrishna, Joseph Henrich. Phil. Trans. R. Soc. B 2016 371 20150192; DOI: 10.1098/rstb.2015.0192. Published 29 February 2016