The Concept of Evolution as Applied to the Development of Human Cultures
This short paper recognizes the aspiration that the story of human cultural development over the past 100,000 years, and more especially over the past 10,000 years, be encompassed within the broad explanatory framework of Darwinian evolution. It recognizes progress towards this aspiration, exemplified by the work of Leslie White (1959) or of Cavalli Sforza and Feldman (1981), and more recently of Stephen Shennan (2002). But while considerable work has been undertaken in expressing or translating potential explanations of culture process into a broadly Darwinian terminology (e.g. Durham 1991), few insights have yet emerged that are helpful to the archaeologist or cultural anthropologist. The notion of adaptive advantage over the several million years duration of the Palaeolithic era, when evolutionary processes led from Australopithecus to Homo sapiens has been well explored (Boyd and Richerson 1985; Mithen 1996). But such arguments have been less successful when applied to the much more stroking changes visible in the human story over the past ten to fifteen thousand years (Renfrew 2007). My critique is not of the aspiration: I share the wish to deal with the human story within a broadly “scientific” framework, and admire the success of the Darwinian approach in placing the emergence of humankind within the broader framework of the evolution of species. My concern is that this approach has so far been less rewarding than one might have expected with the human story since the emergence of our species.
The “speciation” and “tectonic” phases of human evolution
It is now widely recognized that the emergence of our species, Homo sapiens, had been accomplished, in Africa, more than 100,000 years ago. The molecular genetic record supports this conclusion, and offers quite a detailed scenario for the out of Africa dispersal of our species around 60,000 years ago (Forster 2004).
The interesting observation which follows is that in evolutionary terms, thinking specifically about the genetic basis for humankind, namely the sequence of bases composing the human genome, this was established by that time. Certainly the basic Darwinian processes of variation and natural selection did not end 100,000 years ago and are still operational today. However a baby born today is not very different genetically from one born 100,000 years ago. The variation between now and then is not significantly different in scale from the variation between living members of our species today.
It is certainly the case that we do not yet understand very well the evolutionary processes which led over the past 5 million years or so from Australopithecus to Homo sapiens. That they involved the participation of human material culture —man the toolmaker— with adaptive advantages operating selectively upon the genome, is altogether likely. That is what is sometimes implied by the term coevolution. But the process was in some senses accomplished well before the out-of Africa dispersal episode of 60,000 years ago. This is what may be termed the speciation phase in the development of our species, and it was accomplished 100,000 years ago.
From then on the human story is one primarily of cultural development. Of course the processes of mutation and genetic drift did not cease. But the differences which were visible in the different cultures of the globe some 500 years ago, before the colonization processes of the second millennium AD, are not to be ascribed to differences in the DNA of their bearers.
With the human dispersal of some 60,000 years ago the picture changes. The momentum we see in cultural evolution after that point, and in particular after the agricultural and sedentary revolutions in different parts of the world, is no longer genetically based. Cultural innovation and cultural transmission have now become the dominant mechanisms. We may refer to this phase of development, where change in the genome is no longer significant, as the tectonic phase, laying the emphasis upon the notion of the construction of human culture (Renfrew 2007, 97). The Oxford English Dictionary defines tectonics as “the constructive arts in general”. This phase is characterized by new forms of engagement with the material world, and the name refers to the construction of the cultural world in which we live. The distinction now is that in the tectonic phase the genotype is broadly fixed. Within the tectonic phase the evolution that is taking place is essentially cultural evolution.
Evolution and culture
It is worth returning for a moment at this point to reconsider what is implied by the term “evolution”. Darwin’s position, at its most concise, has been summarized (Szthamáry 2006):
Units of evolution must multiply, have heredity and possess variability: and among the heritable traits, some must affect survival and/or reproduction. If these criteria are met, evolution by natural selection is possible in a population of such entities.
When we are talking of the human speciation phase, that long period of hominin development over perhaps 5 million years leading to the emergence in Africa between 200,000 and 100,000 years ago of our own species Homo sapiens, the processes involved may be subsumed under the term “natural selection”, as so defined. It is, however, necessary to observe that “horizontal transmission” — the borrowing of cultural features between contemporaries who may not be closely related genetically — becomes increasingly important (Cavalli-Sforza and Feldman 1981). The term coevolution, commonly used in biology to refer to the interaction of competing species, predators and prey, hosts and parasites etc. (Slatkin and Maynard Smith 1979), has been appropriated in discussions of human evolution to refer to the interacting evolutionary processes of human genes and human culture (Lumsden and Wilson 1981, 237; Mace 2005, 4). But while it is an attractive term it may carry with it problems at the more detailed explanatory level. For the mechanisms of genetic evolution are increasingly well understood, following the elucidation of the structure of DNA, and it is not clear how the horizontal transmission process implicit in this use of the term “coevolution” operates within such a framework. At the same time, however, the insights of Darwin and of Mendel have in general been upheld in the light of molecular genetics, although they could have no detailed knowledge of its mechanisms at the molecular level.
The same might be claimed for the term “meme”, conceived as the cultural equivalent of the gene, and introduced into the discussion by Richard Dawkins (1976). It has been enthusiastically adopted by several authors (e.g. Mace 2005, 4). However it carries with it implications about mechanism, indeed mechanistic implications, which may be highly dubious. It is a term which Shennan (2002) generally avoids, despite the title of his book.
One criticism of the term “meme” is that it regards the units of cultural information as single atomistic particles, perhaps traveling independently. It is the case, however, that most major innovations involve complexes of related innovations, for which the structure of the recipient society must be “ready”, or “pre-adapted”. Single units or members do not seem an appropriate mechanism. This being said, however, the validity of the term in some cases must be respected. It is notable, for instance, how the innovation of alphabetic script was readily adopted, after its inception in the Levant of Egypt, on a widespread basis. In some areas it replaced pre-existing (usually syllabic) systems of writing. In other areas it proved apt for the introduction of writing as a novel recording system. The inception of the alphabetic, as single, coherent system, can perhaps be modelled in this way.
That human learned behavior, or “culture” frequently does behave in a gradual way, aptly described by the term “evolution”, was noted by several archaeologists in the years following the publication of Darwin’s On the Origins of Species. Among them were General Pitt Rivers and Oscar Montelius. The evolution of languages, following Darwin’s insights, was modelled in tree-like form by Augustus Schleicher (1863) and has since continued to prove amenable to phylogenetic analysis (Forster and Renfrew 2006; Gray, Drummond and Greenhill 2009). That this is so may perhaps be explained by the considerable degree to which language transfer is indeed by inheritance between generations, indeed usually from the parents. It is in those cases where horizontal transfer by “borrowing” is particularly marked that the reconstruction of linguistic trees by standard phylogenetic methods becomes more dubious (Heggarty 2006).
Emergent properties in human culture and society
Following the out-of-Africa dispersals of Homo sapiens some 60,000 years ago, human populations gradually became dispersed about the various continents. It is easy to characterize the subsequent histories of regional populations on these various continents as trajectories through time of the different cultures or culture systems. And it is tempting to make a comparison or analogy between the emerging cultural diversities of these groups and the emerging differences between plant or animal species as studied by Darwin. Splitting of populations, isolation, and genetic drift are processes which can lead to the differentiation into new species. So, at a very general level the differentiation into different cultures (as defined archaeologically) of the human populations along their trajectories of development might be compared with the development of new varieties and species among plant and animal populations.
These patterns, however, are not simply those of increasing diversity. There are emergent features, which might be described as of increasing complexity (Flannery 1972). Moreover, analogous events may be noted along different and apparently independent cultural trajectories. Among these may be noted:
- The use of the bow and arrow
- The construction of boats for marine travel
- The development of formalized burial practices for the ritual disposal of the Dead
- The sedentary revolution, implying also the development of farming to sustain the settled villages which developed, along with a series of cultural traits including the making of pottery, the practice of weaving etc.
- The development of figurative representation (or art)
- The development of pyrotechnolgical skills (cooking, pottery, metallurgy, glass)
- The development of systems of trade and exchange
- The development of ritual practices which often involved the veneration of postulated beings or deities
- The emergence of urban centers or cities
- The development of systems of ownership and inheritance of property
- The emergence of commodities esteemed to be of high value (gold, feathers, jade etc.)
- The emergence of writing systems
- The emergence of formalized exchange systems involving units of value (money)
Most of these are innovations which occurred independently along several trajectories of development, on several continents. And it is major developments such as these which one would like to see developed in evolutionary terms. They can of course be described in what approximate to evolutionary terms, and most narratives in the relatively new discipline of world prehistory take such a form (Clark 1961; Renfrew 2007).
Several problems arise in their analysis. And of course it must be recognized that several in the list are relatively simple technical innovations (bow and arrow, sea-going boat) while others are much more complex. In the first place, it must be questioned in what sense the different instances in various locations, as listed, may be regarded as the “same” innovation. Agriculture in different parts of the world relies upon different species, and the domestication of one plant food is not the same as that of another.
It is tempting, however, to see an analogy here with Darwinian evolution among animal species. A major cultural development, such as the inception of metallurgy or the phenomenon of urbanization might be compared with a major innovation, archived independently by some species along different lineages. Such, for instance, would be the phenomenon of flight. The flight of birds may first have been achieved by an ancestor of all bird species today. But the flight of a mammal, such as the bat, is believed to have a different ancestry. And that of flying insects is different again. The archaeologist and anthropologist may have much to learn from the evolutionary analysis of evolutionary advances along different trajectories which may in some sense be considered comparable.
The cognitive dimension
Many of the advances exemplified above, and others like them are firmly rooted in the cognitive dimension. They are, moreover, the result of the experience of humans with the material world. They are emergent properties which involve the simultaneous engagement of the brain and the body (Malafouris 2004; Renfrew 2004). In this respect they cannot be modelled in molecular genetic terms, and a different approach is needed which involves certain fundamental concepts.
Among these are notions of measurement, for instance the concept of weight. There is also the notion of value, as ascribed to a commodity. These come together in a nexus which is the basis of the commercial systems which form the basis for much of the social and economic life of the modern world. The notion of the “meme” here seems, at any right at first sight, too atomistic to model the phenomenon.
For many of the properties involved are examples of what the philosopher John Searle would call “institutional facts” (Searle 1995). They depend upon a consensus in understanding among humans in a group. They are not “brute facts” about properties of the material world, but rather accepted conventions operating within the social world of the society in question. It is these novel and emergent features which are difficult to model using the available tools of evolutionary theory.
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