Book Summary: “Not by Genes Alone: How Culture Transformed Human Evolution” by Richerson & Boyd


Book Review

Title: Not by Genes Alone: How Culture Transformed Human Evolution (add link to Amazon)
Author: Peter J. Richerson and Robert Boyd
Scope: 5 stars
Readability: 3.5 stars
My personal rating: 5 stars
See more on my book rating system (add link to this page).

Topic of Book

The authors explore the role of biology and culture in human development.

My Comments

This book is a must-read for anyone interested in the topics of this blog.

Key Take-aways

  • Contrary to the famous “nature-vs-nurture” debate, culture is part of human biology.
  • Culture is neither nature nor nurture, but some of both.
  • Natural selection acting on culture is the ultimate cause of human behavior.
  • Culture enables human beings to learn from other humans quickly by copying them rather than spending the time to investigate their environment.
  • This enables humans to adapt to a changing environment far faster than genetic evolution in animals.
  • Technology is culture, not environment.
  • Culture and genes co-evolve, i.e. a change in one puts pressure on the other to adapt.

Important Quotes from Book

Culture is crucial for understanding human behavior. People acquire beliefs and values from the people around them, and you can’t explain human behavior without taking this reality into account.

Culture is part of biology.

However, the most fundamental questions of how humans came to be the kind of animal we are can only be answered by a theory in which culture has its proper role and in which it is intimately intertwined with other aspects of human biology. In this book we outline such a theory.

The heart of this book is an account of how the population-level consequences of imitation and teaching work.

We also believe that the evolution of culture has led to fundamental changes in the way that our species responds to natural selection.

Natural selection shapes the way that developmental processes respond to environmental variation. Environment plays only a proximate role. Differences in the environment may cause genetically identical individuals to behave differently, and in this sense environmental differences are immediate causes of behavior. However, if we want to know

why the organism develops one way in one environment and a different way in a different environment, we have to find out how natural selection has shaped the developmental process of the organism so that it responds to the environment as it does. Or, as biologists put it, the ultimate determinant of behavior is natural selection on genes.

Our concern is that lumping culture with other environmental influences leads people to ignore the novel evolutionary processes that are created by culture. Selection shapes individual learning mechanisms so that interaction with the environment produces adaptive behavior.

Culture is neither nature nor nurture, but some of both.

Odd as it may seem, in many kinds of variable environments, the best strategy is to rely mostly on imitation, not your own individual learning. Some individuals may discover ways to cope with the new situation, and if the not-so-smart and not-so-lucky can imitate them, then the lucky or clever of the next generation can add other tricks. In this way the ability to imitate can generate the cumulative cultural evolution of new adaptations at blinding speed compared with organic evolution. A population of purely individual learners would be stuck with what little they can learn by themselves; they can’t bootstrap a whole new adaptation based on cumulatively improving cultural traditions. This design for human behavior depends on people adopting beliefs and technologies largely because other people in their group share those beliefs or use these technologies.

Culture is an ultimate cause of human behavior.

Natural selection acting on culture is an ultimate cause of human behavior, just like natural selection acting on genes.

The human species is a spectacular evolutionary anomaly, so we ought to expect that the evolutionary system behind it is pretty anomalous as well. Our quest is for the evolutionary motors that drove our divergence from our ancestors, and we believe that the best place to hunt is among the anomalies of cultural evolution.

In this book, we follow Darwin’s path not taken. Beginning with psychologist Donald T. Campbell’s work in the 1960s, we, and a few compatriots, have sought to give cultural evolution its due weight without divorcing culture from biology.

The diversity of the human species is striking especially when you think about peoples in other parts of the world.

Three things could act as proximate causes of this variation. First, people may vary because they inherited different genes from their parents. Second, genetically similar individuals may differ because they have lived in different environments. Finally, people may differ because they have acquired different beliefs, values, and skills through teaching and observational learning.

Technology is culture, not environment.

We think that typical academics’ beliefs about the heredity issue are barely better informed than folk psychology.

Most children adopted into another culture before the age of ten or so, even with a history of traumatic capture or indifferent orphanage upbringing, will fully assimilate emotionally into another culture and become fully functional members of it. This result is not surprising to most people. Nonetheless, it is an extremely strong test of the theories under consideration here. If the behavioral differences between groups were substantially due to genetic differences, adoptees should show significant departures from norms of behavior of their foster culture.

Culture usually evolves by the accumulation of small variations.

Most readers, we are sure, come to this book with the intuition that individual humans are pretty smart, and that this is mainly what is responsible for most of the spectacular accomplishments of our societies. However, there is much evidence that suggests that this view is wrong. Psychological studies of human decision making indicate that human rationality is narrowly bounded.

Culture is (mostly) information stored in human brains and gets transmitted from brain to brain by way of a variety of social learning processes.

The two central facts about cultural variation: traditions exist, and traditions change.

We are advocating that social scientists change the way they do business, supplementing their usual tool kit with ideas imported from biology.

While researchers debate culture in nonhuman animals, one thing is fairly clear: only humans show much evidence of cumulative cultural evolution. By cumulative cultural evolution, we mean behaviors or artifacts that are transmitted and modified over many generations.

Considerable evidence suggests that the ability to acquire novel behaviors by observation is essential for cumulative cultural change. Students of animal social learning distinguish observational learning or true imitation (hereafter, plain imitation) from other kinds of social transmission. Imitation occurs when animals learn a novel behavior by observing the behavior of more-experienced animals. Simpler kinds of social transmission are much more common.

To the extent that observers can rapidly and accurately use the behavior of models as a starting point, imitation leads to the cumulative evolution of behaviors that no single individual could invent on its own.

Thus, we don’t claim that imitation is unique to humans. However, the current evidence suggests that (1) cumulative cultural evolution is rare, and perhaps absent, in other species; and (2) even our closest relatives, the chimpanzees, rely on different modes of social learning than humans.

In fact, there is no evidence that humans made tools as complex as a stone-tipped spear until about four hundred thousand years ago.

By becoming a selective learner, an individual gains most of the advantages of both learning and imitation.

Imitation allows cumulative improvement

Organisms that cannot imitate must start with whatever initial guess is provided by their genotype. They can then learn and improve their behavior. However, when they die, these improvements die with them, and their offspring must begin again at the genetically inherited initial guess.

Imitators can acquire their parents’ behavior after it has been improved by learning. Therefore, imitators will start their search closer to the best prevailing design than purely individual learners, and can invest the information production efforts efficiently in further improvements. Then they can transmit those improvements to the grandkids, and so on down the generations until quite sophisticated artifacts evolve (and re-evolve to meet

the needs of changing environments).

 “When in Rome, do as the Romans do.” This strategy makes good evolutionary sense under a broad range of conditions.

People often imitate the successful.

Determining who is a success is much easier than to determining how to be a success. By imitating the successful, you have a chance of acquiring the behaviors that cause success, even if you do not know anything about which characteristics of the successful are responsible for their success. If you can accurately imitate everything they do, you ought to be a success too, at least insofar as success is based on culturally transmissible characters.

In most animals, this knowledge is stored in the genes, including of course the genes that control individual learning.

Human culture allows learning mechanisms to be both more accurate and more general, because cumulative cultural adaptation provides accurate and more-detailed information about the local environment.

The reason the information contained in this pool is adaptive is that a combination of learning and cultural transmission leads to relatively rapid, cumulative adaptation. Even if most individuals blindly imitate with only the occasional application of some simple heuristic, many individuals will be giving traditions a nudge in an adaptive direction, on average..

People are endowed with two sets of innate predispositions, or “social instincts.”  The first is a set of ancient instincts that we share with our primate ancestors. The second is a set of “tribal” instincts that allow us to interact cooperatively with a larger, symbolically marked set of people, or tribe. The tribal social instincts result from the gene-culture coevolution of tribal-scale societies.

There is a great deal of behavioral variation among human groups. Such variation is the reason why we have culture— to allow different groups to accumulate different adaptations to a wide range of environments.

Human societies are crude superorganisms. One of the human species’ main social adaptations is the ability to organize cooperation, coordination, and a division of labor on a much larger scale than the typical primate kin group.

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