Book Summary: “The Secret of Our Success” by Joseph Henrich

Book Review

Title: The Secret of Our Success: How Culture is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter
Author: Joseph Henrich
Scope: 5 stars
Readability: 4.5 stars
My personal rating: 5 stars
See more on my book rating system.

If you enjoy this summary, please support the author by buying the book.

Key Take-aways

  • The secret of human success has been our ability to form collective brains that store far greater amounts of information and skills than one person can possibly understand.
  • Humans are a cultural species and that characteristic is firmly rooted in our genes
  • Culture and genes work together in an evolutionary process that is unique to humanity and is the root cause of changes and innovation.

Other books/articles by the same author:

Important Quotes

We humans are not like other animals… The key to understanding how humans evolved and why we are so different from other animals is to recognize that we are a cultural species… recognizing that we are a cultural species only makes an evolutionary approach even more important… our capacities for learning from others are themselves finely honed products of natural selection. We are adaptive learners who, even as infants, carefully select when, what, and from whom to learn.

The secret of our species’ success resides not in the power of our individual minds, but in the collective brains of our communities. Our collective brains arise from the synthesis of our cultural and social natures—from the fact that we readily learn from others (are cultural) and can, with the right norms, live in large and widely interconnected groups (are social). The striking technologies that characterize our species emerge not from singular geniuses but from the flow and recombination of ideas, practices, lucky errors, and chance insights among interconnected minds and across generations.

Other species have also spread widely and achieved immense ecological success; however, this success has generally occurred by speciation.

Humans survive neither by our instinctual abilities to find food and shelter, nor by our individual capacities to improvise solutions “on the fly” to local environmental challenges. We can survive because, across generations, the selective processes of cultural evolution have assembled packages of cultural adaptations—including tools, practices, and techniques—that cannot be devised in a few years, even by a group of highly motivated and cooperative individuals. Moreover, the bearers of these cultural adaptations themselves often don’t understand much of how or why they work, beyond the understanding necessary for effectively using them.

This brings us to a central insight. Rather than opposing “cultural” with “evolutionary” or “biological” explanations, researchers have now developed a rich body of work showing how natural selection, acting on genes, has shaped our psychology in a manner that generates non-genetic evolutionary processes capable of producing complex cultural adaptations. Culture, and cultural evolution, are then a consequence of genetically evolved psychological adaptations for learning from other people. That is, natural selection favored genes for building brains with abilities to learn from others… With this intellectual move, “cultural explanations” become but one type of “evolutionary explanation.”

If humans are a cultural species, then one of our most crucial adaptations is our ability to keenly observe and learn from other people. Central to our cultural learning is our ability to make inferences about the goals, preferences, motivations, intentions, beliefs, and strategies in the minds of others

The central argument in this book is that relatively early in our species’ evolutionary history, perhaps around the origins of our genus (Homo) about 2 million years ago, we first crossed this evolutionary Rubicon, at which point cultural evolution became the primary driver of our species’ genetic evolution… Once cultural information began to accumulate and produce cultural adaptations, the main selection pressure on genes revolved around improving our psychological abilities to acquire, store, process, and organize the array of fitness-enhancing skills and practices that became increasingly available in the minds of the others in one’s group. I call the threshold between typical genetic evolution and the regime of autocatalytic culture-driven genetic evolution the Rubicon.

As the process continues over generations, the selection pressures only increase: the more selection pressures only increase: the more culture accumulates… This culture-gene coevolutionary ratchet made us human.

Once a new norm emerges in one group, intergroup competition can grab hold of it and spread it widely through a number of related processes:

Over time, history suggests that all prosocial institutions age and eventually collapse at the hands of self-interest, unless they are renewed by the dynamics of intergroup competition.

In more recent millennia, especially since the origins of plant and animal domestication some 12,000 years ago, the intensity of intergroup competition has dramatically escalated, driving the rise of increasingly large and complex societies.

As both Adam Smith and Friedrich Hayek argued long before Erik and me, it’s our automatic norm following—not our self-interest or our cool rational calculation of future consequences—that often makes us do the “right thing” and allows our societies to work. This means that how well a society functions depends on its package of social norms.

Thus, the world that cultural evolution often creates is one in which different groups possess different social norms and where norm boundaries are often marked by language, dialect, dress, or other markers.

The reason why other species haven’t experienced this may lie in a kind of start-up problem… in the beginning, there won’t be much out there to culturally acquire, and what is there will be simple enough that it will still be learnable by one’s own individual learning efforts (without social learning), by trial and error for example. Thus, natural selection may not favor larger brain size or complexity, because brains are costly to develop and program.

Our species’ dependence on cumulative culture for survival, on living in cooperative groups, on alloparenting and a division of labor and information, and on our communicative repertoires mean that humans have begun to satisfy all the requirements for a major biological transition. Thus, we are literally the beginnings of a new kind of animal.

Recognizing that we are a cultural species means that, even in the short run (when genes don’t have enough time to change), institutions, technologies, and languages are coevolving with psychological biases, cognitive abilities, emotional responses, and preferences. In the longer run, genes are evolving to adapt to these culturally constructed worlds, and this has been, and is now, the primary driver of human genetic evolution.

The answer to why humans are different is that we crossed the Rubicon. Cultural evolution became cumulative, and then both this accumulating body of information and its cultural products, like fire and food-sharing norms, developed as the central driving forces in human genetic evolution. We seem so unique because no other living animal has gone down this road, and those that did, such as Neanderthals, were replaced during one of our species’ many expansions.

The impact of this transition is underlined by the fact that, despite our long evolutionary history as foragers, we generally can’t survive by hunting and gathering when we have been stripped of that relevant culturally acquired know-how.

This culture-gene coevolutionary process… not only accounts for why our species is so much more cooperative than others, but it also explains why human cooperation (1) varies so much across societies and behavioral domains (e.g., food sharing, community defense, ritual participation, etc.), (2) has increased so dramatically in the last 10,000 years, (3) is so readily influenced by cultural learning, (4) relies on the same reputational enforcement mechanisms operating in many noncooperative domains like ritual practices and food taboos, and (5) is sustained by quite different systems of incentives across societies, variously involving rewards, punishments, signals of quality, and selective exploitation of norm violators.

By this view, the ability to construct mini-causal models didn’t cause fancy tools and practices. The cultural evolution of increasingly sophisticated tools and practices first drove the emergence of this cognitive ability, and then the two entered into a culture-gene coevolutionary duet.

Once we understand the importance of collective brains, we begin to see why modern societies vary in their innovativeness. It’s not the smartness of individuals or the formal incentives. It’s the willingness and ability of large numbers of individuals at the knowledge frontier to freely interact, exchange views, disagree, learn from each other, build collaborations, trust strangers, and be wrong. Innovation does not take a genius or a village; it takes a big network of freely interacting minds.

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