Books and Reviews


Not Genes Alone: How Culture Transformed Human Evolution

Richard Nelson reviews (April 27, 2005) Richerson and Boyd's Not by Genes Alone, a new book on the evolution of culture. The authors accepted our invitation to respond to Nelson's review. Registered users can post their own comments on the book at the end of the review. Table of Contents. Read an excerpt from the introductory chapter here.

Review by Richard R. Nelson

This is a splendid book, sophisticated and persuasive in the theoretical argument it puts forth, and erudite in its appreciation of the arguments and issues at stake. Not by Genes Alone comes twenty years after Boyd and Richerson’s Culture and the Evolutionary Process (1985, University of Chicago Press), their first major contribution to theoretic discussion in this area. This new book elaborates and significantly extends their earlier argument.

Their broad argument goes this way.
Human cultures, as bodies of belief and practice broadly shared within a society at any time, are the fruit of a society–wide cross–generational learning process.  They are unique to humans, and in the large extremely adaptive. Living creatures can be adapted to their environment either through hard wired instinct which is effective in that environment, or through learning, which while based on underlying biological capabilities, permits adapting to the environment on a basis of experience. There are significant advantages for having limited hardwiring of behavior and considerable capability for learning, for species that find themselves in a variety of different environments or whose environments can change significantly over time. In such a context, there is a trade–off between an individual in a species learning on his or her own and learning through imitating (in the broad sense of that term) the behaviors of selected others within his or her community. Learning from one’s peers is adaptive when individual learning is slow and difficult, and established practice within the group is relatively effective. The latter is especially likely to be so when the beliefs and practices of the community at any time are the result of a process of effective cumulative learning. The uniqueness of modern human societies is that their cultures are the result of cross–generational learning. That cultural learning process needs to be understood as an evolutionary process in its own right, similar in some respects to biological evolution, but profoundly different in others.

This, in a nutshell, is the basic argument put forth in this book. I find it completely persuasive. And while the argument scarcely is unique to the authors, Richerson and Boyd make it extremely well.

In the first two chapters of the book, the authors state and document the points that human culture, in the sense above, is a very real phenomenon – one can’t explain the diversity of the beliefs and behaviors of different human groups without invoking the concept of culture – and that it is culture and cultural evolution that permits human beings to reside successfully in such a wide range of physical environments. Arguments to the effect that different human groups, over space or over time, differ in their beliefs and behaviors simply because their environments are different are clearly not compelling.  Differences in cultures, which are not uniquely determined by differences in natural environments, are an essential part of any plausible explanation for differences in behaviors and beliefs. The examples used by the authors to document this point are persuasive. The authors make their point about the necessity of powerful cultural learning for human survival in many circumstances by considering what is required for human groups to live in hostile places like deserts. They argue convincingly that a human group without the advantages of such an adaptive cultural tradition would have to leave such environments or perish. The same argument, of course, could be made regarding surviving in modern New York. For those, like myself, who already believe these arguments, the Richerson–Boyd discussion still is useful and interesting because of its sharpness and the examples they use to back it up.

Human cultural evolution is made possible by the particular properties of the human genome. On this basic point, Richerson and Boyd have no trouble with the arguments of the socio–biologists. However, their argument is that the biological ’leash’ (to use the term of Edward Wilson) is long and flexible, not short and binding. The authors highlight that their position on this differs from Wilson’s brand of socio–biology, and from many of the positions articulated by the new group of ’evolutionary psychologists.’ The authors also take the position, with which I am in full accord, that the notions that culture can be neatly divided into things that one can call ’memes,’ or that units of culture can be considered as ’replicators,’ are unhelpful to understanding cultural evolution. Culture doesn’t divide neatly that way, at least not all parts do. And ’imitation,’ or learning more generally what others have learned, tends to be highly imperfect. Nonetheless, one can understand and model cultural change as an evolutionary process.

As I said at the outset, this is a splendid book. But from the point of view of an evolutionary economist, or a social scientist who studies the evolution of modern technologies, science, business organizations or modern political institutions, the book stops surprisingly short of connecting with the modern literatures on these subjects. When Boyd and Richerson wrote their first book twenty years ago, these literatures were somewhat thin. But since that time they have progressed greatly. The puzzle is why Richerson and Boyd have not made contact with this other body of scholarship about the evolution of various aspects of human culture.

The basic reason, I believe, is that these authors take an anthropological approach to human cultures and to the societies that hold these cultures. Boyd is, after all, an anthropologist. Modern anthropology and the social sciences concerned with the nature of modern high–income societies have little contact with each other. Thus in Richerson and Boyd, there is hardly any discussion of formal organizations like business firms, modern hospitals, universities and scientific societies –– entities that are essential to consider when one discusses the evolution of modern science, modern technology, business organization, industrial structure, political systems, etc.  While the view of culture in Richerson and Boyd is ’evolutionary,’ in that today’s body of beliefs and practices are the result of cumulative changes that have occurred over many generations, and which have to some extent been winnowed for adaptiveness, there is no sense in this book of the rapidity of change in modern societies. The elements of culture on which the authors focus change over time, but there is nothing in their treatment that recognizes adequately the tremendous pace of change of modern technologies, scientific understanding, and modern economies.

The authors have a brief reference to Nelson and Winter, and cite Hodgson and Petroski (who writes about the ’evolution’ of modern technologies).  Yet there are no references to Vincenti, Constant, Mokyr or other historians and social scientists writing on the evolution of modern technologies.  There is no reference to Hull, Popper, or Kuhn on the evolution of modern science, and nothing on Chandler and his work on the evolution of the modern corporate form. Likewise there is no reference on Schumpeter and his influence on thinking in evolutionary economics.

This is not a complaint about the book. However, I find it interesting and worth commenting upon the fact that there seems to be very little communication between scholars like Boyd, Richerson, Cavalli–Sforza, Feldman and others who are developing a serious theory of the evolution of culture from the point of view of anthropologists, and scholars in several other disciplines who are developing an evolutionary theory through understanding rapid change in modern societies. And the latter seldom cite the anthropologists. I think this disconnect is unfortunate for both camps. Helping to bridge it is high on my personal agenda.

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Response to Reviewers’ Comments by Peter J. Richerson and Robert Boyd

The Golden Age of the Discipline Still Lies Ahead

We are of course grateful to Professor Nelson for his generous comments on our book. We agree that that he highlights an important gap between our work and that of evolutionary economists, technologists, and others that focus on contemporary cultural evolution in complex societies. We do have a few things to say about these issues, but they are more in the way of hints and promissory notes than any fully developed analysis. Part of this inattention is due to our concern for anthropological topics as Nelson notes. Another reason is our choice of theoretical tools. We make individuals our basic unit of analysis and use a population genetics style formalism to develop the theory that stands behind the analysis in Not By Genes Alone. In this formalism, the simple population level properties of the evolving system are relatively easy to deduce. Hence the models fit simple cultural systems to a useful approximation. The complex societies that began to evolve with urban civilization 5,000 years ago, and which began to explode in complexity about 500 years ago, present major difficulties given our starting point. In these societies, the population is richly structured into castes, classes, occupational groups, ethnic sub-cultures and so forth. These sub-populations interact economically and culturally in ways that the population genetics style models treat in only the sketchiest abstract terms. Nelson and Winter’s own classic contribution to evolutionary economics abstracted away from individuals and treated firms as the basic unit of analysis and deduced the resulting properties of the industry that the firms comprise, an entirely appropriate choice given the importance of firms and industries in modern societies. Our models say something about the basic mechanisms by which such complexity can arise. For example we have modeled how the symbolic boundaries that demarcate such groups can arise. But the population genetics style model cannot, unaided, address the problems of evolution in complex societies. Like Nelson we would love to see this theoretical void filled!

We think that one way forward is to employ another formalism from biology, the one used by community ecologists. Ecologists model the interactions of multiple interacting populations of predators and prey, competitors, and mutualists using what are called the Lotka-Volterra equations. Intra-societal interactions between human subgroups are typically mutualistic but with varying elements of competitive and exploitative relationships. Inter-societal relations tend to be competitive but are leavened with doses of mutualism via trade and predation via conquest. We have written a short programmatic essay sketching how a project using the Lotka-Volterra framework to model the ecology of complex societies might work (Richerson and Boyd 1998). In principle, integrating the population genetics style models with the ecological models is straightforward. Peter Turchin (2003) has quite independently undertaken some real work using the Lotka-Volterra style of analysis applied to the fluctuating cycles of prosperity and recession in pre-modern agrarian states. Likewise, integrating economic models, such as growth theory, with the ecological and population genetics style models is fairly straightforward (Charles Efferson, personal communication). We like to think that we pioneers of evolutionary social science have cleared some useful paths into a wonderfully interesting and diverse wilderness of scientific problems. But no doubt the Golden Age of our discipline is in the future.

Literature Cited

Richerson, Peter J., and Robert Boyd. 1998. Homage to Malthus, Ricardo, and Boserup: toward a general theory of population, economic growth, environmental deterioration, wealth, and poverty. Human Ecology Review 4 (85-90).

Turchin, Peter. 2003. Historical Dynamics. Princeton: Princeton University Press.

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Reader comments

EVOLUTIONARY LEARNING:  imitative, or innovative?       

This exchange of views illuminates, in a flash, a surprising aspect of current work on evolutionary learning.  We are told that the Richerson–Boyd model of cultural evolution has little to offer to those studying the problems of most societies of the past 5,000 years, that is those seeking to understand the basic processes on the agendas of contemporary social science (such as social change, economic development, or war).  That is because this model, whose basic unit of analysis is the individual, “cannot address the problems of evolution of complex societies.”

Central to the Richerson–Boyd model, as succinctly summarized by Richard Nelson, is a concept of evolutionary learning.  The uniqueness of human culture lies in being the result of cross–generational learning.  Learning from one’s peers is adaptive when individual learning is slow, and established practices within the community relatively effective.  Such learning occurs “through imitating (in a broad sense of the term) the behaviors of selected others. ”  That is how imitation becomes the basis of evolutionary learning — evolutionary, it is claimed, because it is adaptive.  But is evolutionary learning?  In school systems that is the conception that underlies ‘rote learning’.

There can be no quarrel with the contention that intergenerational learning is basic to reproducing social organization, hence ‘adaptive’.  It may be as necessary a condition of social existence as some form of economic cooperation, or order maintenance.  Its institution (was it tens of thousand years ago ?) must indeed have been innovative.  But to–day, viewed as imitation, intergenerational learning is a routine process. What is surprising is that that Nelson, co–author of the well–known Evolutionary Theory of Economic Change, finds the Richerson–Boyd claim that this is “evolutionary learning” “completely persuasive.”  Do we need to recall that the distinction basic to that work was one between a firm’s routines, on the one hand, and innovative search and selection behavior, on the other. It is only in the latter that we find the kernel of evolutionary learning. 

If ‘complex society’ is our unit of analysis, then evolutionary learning viewed as innovative search and selection naturally falls into place, and opens new vistas.  Complex society is not just a transmission belt for the intergenerational transfer of established behavior patterns; it is a long–standing and finely tuned innovative problem–solving mechanism.  Human culture functions as ever–reconfiguring memory bank and repository of such cumulative learning.  At the limit, humankind (the human species) is the most inclusive complex society of them all, and we need to know more about what makes it work, and how it learns to solve its problems.

As complex system, human society has evolutionary potential: the capacity to respond to environmental change, and also the ability to shape it. If we dare to conjecture that humankind encodes a learning algorithm for innovative search and selection, then prospects open widely for an array of explanatory projects, some of which are now underway.  For instance, waves of economic–technological innovation have been modeled as manifestations of global economic evolution (1).  World politics has been shown to be an instance of evolutionary learning (2).  And the emergence of social organization of planetary scope has been depicted as a cascade of evolutionary learning processes governed by a power law (3).  Each such case models not imitation but search and selection, in other words, innovative evolutionary learning.

1.  G. Modelski and W.R. Thompson (1996)  Leading Sectors and World Powers:  The Coevolution of Global Economics and Politics.  South Carolina U.P

2.  The “Evolutionary World Politics” Home Page,    G. Modelski (1990)  “Is world politics evolutionary learning?”  International Organization;  Winter; 

3.  T. Devezas and G. Modelski (2003)  “Power Law Behavior and World System Evolution: A Millennial Learning Process”  Technological Forecasting and Social Change,  November..

By GModelski on 2005 06 20

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