Evolutionary Approaches In Archaeology Research Paper

1. Evolution

‘Cultural evolution’ is often used by archaeologists to refer to a progressive historical trend, with progress defined in ethnocentric terms, such as greater social and political complexity. Anthropologists of the midtwentieth century, including Leslie White and Julian Steward, brought such progressive evolutionism into the anthropological mainstream, and the ‘New Archaeology’ of the 1960s and 1970s was influenced by these efforts. Dunnell (1980) has argued, however, that ‘cultural evolution’ of the progressive variety, which can be traced back to the nineteenth-century writings of Spencer, Tylor, and Morgan, has little in common with scientific evolution, which was developed within biology following publication of Darwin’s Origin of Species in 1859. According to Dunnell (1980, p. 44), ‘cultural evolution’ is not scientific because it provides no mechanisms to explain history, instead positing plausible empirical generalizations that summarize certain ethnographic observations recorded during European expansion across the globe.

Dunnell (1982) and others (Lyman and O’Brien 1997, Schennan 1991) find antecedents of a scientific evolutionary archaeology not in ‘cultural evolution’ of the progressive variety but rather in culture historical studies of the early through mid-twentieth century. What culture history had going for it that cultural evolution did not was a ‘decidedly materialist feel’ (Lyman and O’Brien 1997, p. 43). ‘Materialism,’ which is used in this context as a synonym for ‘population thinking’ (Mayr 1959), is the view that historical change arises out of individual variation. This was Darwin’s great insight (Lewontin 1974). Before Darwin, explanations of change were bound by an essentialist worldview. With habits of thought derived ultimately from Aristotelian essentialism, early evolutionists could only conceive of change as taking place when things are transformed into other things through individual striving or the unfolding of potentials inherent in the individual’s underlying essence. Cater-pillars are transformed into butterflies; monarchies are transformed into parliamentary democracies. Darwin freed evolution from the bounds of essentialism when he argued that ‘descent with modification’ could arise as a purely mechanistic consequence of variants being reproduced and dropping out of populations at different rates. Inasmuch as they purport to be Darwinian, all of the evolutionary approaches summarized below adhere at least implicitly to this fundamental understanding of the mechanism that produces change through history.

2. Evolutionary Approaches In Archaeology

Taking inspiration from Darwin’s phrase ‘descent with modification,’ Durham (1992) distinguishes between cultural evolutionary studies focusing on descent and those focusing on modification. Out of favor during the heyday of the ‘New Archaeology,’ studies of cultural descent were revived during the 1980s in works such as Renfrew’s (1987) study of Indo-European origins, Kirch and Green’s (1987) study of cultural phylogeny in Polynesia, and Flannery and Marcus’s (1983) study of Zapotec prehistory. Other historical sciences, such as historical linguistics and biological anthropology contribute along with archaeology toward the common goal of reconstructing cultural phylogenies.

When biological, linguistic, and material similarities are summarized in the form of a cultural phylogeny, an underlying assumption is that the pattern was created by the mechanisms outlined by Darwin (which Durham (1992) subsumes under ‘modification’). But how would Darwinian mechanisms work to generate the material remains that make up the archaeological record? The ways that archaeologists have answered this question can be conveniently grouped under five headings, which provide a framework for the following survey of evolutionary approaches in archaeology.

2.1 Evolutionary Archaeology

The approach instigated by Dunnell (e.g., 1978, 1980) is often called evolutionary archaeology (EA) by both its proponents and its critics (e.g., Boone and Smith 1998). Evolutionary archaeologists contend that culture constitutes an inheritance system that parallels genetic inheritance. Moreover, culturally transmitted traits, like genetic traits, may affect an organism’s probability of survival and reproduction, which leads to frequency change over time in cultural traits just as it does for genetic traits. The complete human phenotype is encoded by both genetic and cultural instructions, and artifacts and other cultural manifestations therefore owe their existence and diversity to the same evolutionary processes (selection and drift) that create biological diversity (e.g., Dunnell 1989). Humans perceive and solve problems, but the importance of these intentional efforts is that they generate variation, which then becomes available for selection (Rindos 1989).

David Rindos’ (1984) work on the origins of agriculture incorporated many aspects of the EA approach first articulated by Dunnell (1980). Rindos viewed the emergence of domesticates as a Darwinian evolutionary process in which selective pressures shaped genetic evolution of the plants at the same time they were shaping cultural characteristics in coevolving human populations. Rindos argued that the same coevolutionary processes govern the mutualistic relationships between humans and their domesticated plants as those which govern other animal-plant relationships, such as that between ants and acacia trees that they harvest for food. A distinctive (though perhaps not unique) feature of the human-plant coevolutionary relationship is that two distinct modes of inheritance, one cultural and one genetic, are responsible for transmission of the human behavioral traits that are being shaped by selection. Nonetheless, Rindos subsumed frequency change in both genetic and cultural traits within the same set of coevolutionary models. Hart (1999) has recently applied and extended Rindos’ framework in a study of the evidence for maize agriculture in the Eastern Woodlands.

Theoretical works in the EA tradition have elaborated themes originally introduced by Dunnell, such as the style-function dichotomy. According to Dunnell (1978), functional traits can be understood in an evolutionary context to be those traits that are fixed by selection (i.e., they have positive fitness values), where-as stylistic traits are those for which frequency change can be attributed to drift. Dunnell contends that archaeological frequency seriation requires neutral traits, and this has been borne out by mathematical models and simulation (Neiman 1995, Lipo et al. 1997). Results of this research have been used to develop a series of inferences regarding intergroup interaction in the Woodland period Midwest (Neiman 1995) and lower Mississippi Valley (Lipo et al. 1997).

Left unanswered in Dunnell’s original works is the question of whether biological reproductive success is necessary for a cultural trait to exhibit positive fitness and thus be favored by selection. Leonard and Jones (1987) introduce the term ‘replicative success’ to refer to any trait that increases in frequency relative to alternative traits, but they maintain that cultural traits that do not affect biological reproductive success cannot be termed functional (i.e., subject to selection). Barton and Clark (1997, pp. 12–13) summarize the conflicting positions of evolutionary archaeologists on this issue.

A theoretical issue dealt with at greater length in EA (e.g., O’Brien and Holland 1990, Neff and Larson 1997) is the supposed circularity of ‘fitness’ when more fit individuals are identified as such only because they enjoy greater success at passing on genetic or cultural information. As in evolutionary biology, the ‘propensity definition’ of fitness backed up by engineering analysis of artifact design are seen as means to circumvent this circularity (O’Brien and Holland 1990). These arguments lead to one of the major methodological prescriptions of EA, namely that investigation of evolutionary history should focus on concrete phenomena (artifacts at various scales) and proceed by advancing and testing hypotheses about the forces that shaped observed artifact design. A focus on concrete phenomena, such as artifacts, is also suggested by Dunnell’s (1980) discussion of empirical sufficiency.

Substantive applications within EA, not surprisingly, have tended to emphasize the explanation of variation at the level of the artifact. Examples are found in a volume edited by Teltser (1995), where the case studies include one on ceramic source-usage variation through time, one on the design of agricultural fields, one on artifactual change following the arrival of Europeans in the New World, and one on ceremonial architecture in Polynesia. In these studies, the history of artifact design changes is explained by reference to constraints and opportunities posed by the environment. The models of neutral trait distributions developed by Neiman (1995) and Lipo et al. (1997) have also emphasized variation at the level of the artifact.

2.2 Evolutionary Ecology

The evolutionary ecology (EE) approach to the analysis of archaeological remains emerged in the early 1970s (citations in Broughton and O’Connell 1999). Archaeologists identifying themselves with this approach (e.g., Boone and Smith 1998) stress the fact that human organisms have been designed by past selection of genetic variation to seek fitness-enhancing ways of responding to environmental conditions. Thus, cultural change and diversity are explained primarily by phenotypic adjustment to variable opportunities and constraints posed by the environment. More specifically, ‘adaptive phenotypic variation involves the interaction between genetically or culturally evolved cognitive mechanisms and variable environmental conditions’ (Boone and Smith 1998, p. S144). To take a now paradigmatic example, snowmobiles replaced snowshoes among the Cree in less than one human generation, a change that evolutionary ecologists explain by reference to Cree calculation of energy return rates under various transportation options and subsequent decisions to adopt the most efficient one.

The premise that humans have been designed by natural selection to seek fitness-enhancing behaviors warrants the use of optimization models, which is a key defining feature of the EE approach to archaeology. That is, given a set of alternative behavioral strategies, evolutionary ecologists assume that humans will follow the strategy that tends to maximize biological fitness in a given environment. Broughton and O’Connell (1999) point out that this underlying premise leads most naturally in archaeology to an emphasis on subsistence and settlement. For instance, usage of prey species, about which the optimal foraging models of EE make clear predictions, can be inferred more or less directly from archaeological data. Winterhalder and Goland (1997) have used the prey-choice framework to explore how different plants, including eventual domesticates, might have been brought into the diet of hunter-gatherers. This account converges with and complements the EA account of agricultural origins offered by Rindos (1984). In some cases, predictions about prey choice can also be extended to predictions about change in tools used to obtain various prey species, thus extending the applicability of EE into the realm of technology (Broughton and O’Connell 1999). Winterhalder (1997) shows how optimization models of evolutionary ecology apply to another key area of archaeological interest, exchange.

Although the inference of behavior from archaeological remains is quite direct when the focus is on subsistence, EE models, by definition, are always stated in behavioral terms, and this means that methods for reconstructing behavior from archaeological remains are crucial components of the EE program. EE proponents recognize that this constraint ties their research to other programs aimed at pro- viding a rigorous basis for behavioral inference in archaeology. Thus, it is argued that ethnoarchaeology (O’Connell 1995) and behavioral archaeology (Boone and Smith 1998, Broughton and O’Connell 1999) can render the archaeological record interpretable in behavioral terms, while EE furnishes the theory to explain why particular behaviors have appeared when and where they have in human history. Schiffer (1999), the main architect of behavioral archaeology, approves of the EE focus on behavior, but considers the optimization models of EE useful for explaining only a small part of the range of human behavioral variability.

A somewhat polemical debate between proponents of EE and proponents of EA emerged in the late 1990s. Evolutionary archaeologists contend that diversity and change observed in the archaeological record can be explained by reference to the effects of selection and drift on cultural inheritance. They reject the EE reliance on phenotypic adjustment on the grounds that it ties explanation to individual intent rather than mechanisms (Dunnell 1989, Lyman and O’Brien 1998). EE proponents contend, on the contrary, that many if not most instances of historical change happen too fast to be explainable by reference to the long-term process of natural selection working on culturally inherited traits. They cite the Cree snowmobile case in support of the necessity to consider phenotypic adjustment: the long-term criterion of differential biological success, they argue, simply cannot explain the adoption of snowmobiles in less than one human generation (Boone and Smith 1998, Sects. 146–7).

The EE and EA camps also dispute whether behavior should constitute the object of evolutionary explanation in archaeology. Evolutionary ecologists advocate a hypothetico-deductive approach in which optimization models are the basis for predictions about prehistoric human behavior, and they argue that, with methods of behioral archaeology and ethnoarchaeology, these predictions are testable. From this point of view, the preoccupation with artifacts and their distributions in time and space is a serious limitation of the EA approach (e.g., Boone and Smith 1998, pp. S154–6, Broughton and O’Connell 1999, pp. 158). EA proponents (e.g., Dunnell 1989, Lyman and O’Brien 1998), however, argue that evolutionary models stated in behavioral terms are inherently untestable because the behaviors about which they make predictions are unobservable and can only be inferred from the archaeological record with a leap of faith.

2.3 Approaches Based On Dual Inheritance Theory

Dual inheritance theory (DIT) (Boyd and Richerson 1985, Durham 1992) addresses the ways in which the principle of selective retention coupled with the special properties of cultural transmission lead to expectations about the evolution of adaptive and not so adaptive cultural practices, artifacts, and institutions. The theory explicitly incorporates complexities of cultural transmission that are suggested by social learning research. Boyd and Richerson (1985) construct models of how various forms of bias in the transmission process lead to different evolutionary results; Durham (1992) prefers to call the forces of bias ‘cultural selection.’

Two main predictions emerge from DIT. First, cultural evolution, which is aided by guided variation and biased transmission (Durham’s (1992) ‘primary value selection’), can converge on solutions that are adaptive for the human organism faster than evolution that depends exclusively on natural selection of genetic variation. In this case, fitness maximization adequately predicts human behavior. Second, DIT predicts that differential survival of cultural variants may also generate inherited behavior patterns that run counter to the predictions of genetic fitness maximization (Bettinger 1991, Shennan 1991). Indirect bias and frequency-dependent bias (which Durham (1992) calls ‘secondary value selection’) further enhance the potential for cultural manifestations to be maladaptive in a biological sense.

DIT shares with EA the view that culture constitutes an inheritance system evolving with some degree of independence. However, the EA conviction that variation must be independent of the force of selection for a true Darwinian process to work is violated by guided variation and biased transmission, which are central to DIT. For their part, dual inheritance theorists argue that natural selection is inadequate, on its own, to explain cultural change and diversity (Richerson et al. 1998). Instead, decision making—the ways in which cultural transmission interacts with learning to pro- duce variation that can then be shaped by selection— has to be modeled explicitly if the archaeological record is to be understood in evolutionary terms.

DIT is thus aligned with EE regarding the importance of decision making in cultural evolution. Moreover, the optimality models of EE are regarded as valuable sources of hypotheses that can serve as starting points for archaeological investigation (Bettinger and Richerson 1996). At the same time, however, the independent dynamics of an evolutionary process based on cultural transmission leads to skepticism regarding simple optimality interpretations of human behaviors (Bettinger 1991, Richerson and Boyd 1992, Shennan 1991). People may tend to acquire beliefs, values, practices, and artifacts that are adaptive in the biological sense, but this assumption is limited in its potential to account for the full range of human variation.

Efforts to put DIT to work in the service of archaeology have tended to emphasize means for recognizing archaeologically the various modes of cultural transmission. Bettinger (1991, pp. 203–7), for instance, suggests that the complex of changes associated with the European Upper Paleolithic transition may be explainable as indicators that indirect bias and frequency-dependent bias for the first time came to play important roles in human cultural evolution. Bettinger argues that climatic change and population growth would have favored local subsistence specialization, which in turn would have favored mechanisms (like indirect and frequency dependent bias) for efficiently acquiring locally adaptive behavioral traits as a complex.

2.4 Approaches Based On Evolutionary Psychology

Like dual inheritance theorists, Mithen (1989, 1997a, 1997b) believes that simple adaptive models of human behavior such as those that make up EE are insufficient to account for human behavioral variation. However, rather than exploring the implications of cultural transmission mechanisms, Mithen explains departures from adaptive expectations largely by reference to the fact that humans now and in the recent past have lived in environments very different from those in which human cognitive capacities evolved. This viewpoint has been explored most thoroughly within evolutionary psychology. A major implication of this research, accepted by Mithen (1997a, 1997b), is that the human brain consists of various specialized devices designed by evolution to solve specific problems faced by hominids in the past. Mithen (1997a) contends that this modular view invalidates models, such as Boyd and Richerson’s, that only indirectly consider the content of cultural transmission.

Mithen’s methodological prescriptions converge with those of many other brands of archaeology, especially behavioral archaeology (see Sect. 2.2). The archaeological record is conceived as the aggregate result of active individuals endowed with common psychological propensities making decisions in unique historical contexts, and archaeology’s task is to relate the short-term individual behavior to the gross character of the archaeological record (Mithen 1989, pp. 491–2). Evolution enters the picture to the extent that behavioral patterns inferred from the record are eventually interpreted as adaptations, or as the expression of human propensities that are no longer adaptive due to their existence in novel, inappropriate environments, or as the unintended consequences of pleiotropic adaptive traits.

Mithen(1997a, 1997b) also believes that archaeology can contribute to evolutionary psychology by providing better understanding of the evolution of human cognitive capacities. As an example of the mutualistic relationship of cognitive archaeology and evolutionary psychology, Mithen (1997a) interprets religious ideas as evolutionary byproducts of increased ‘cognitive fluidity’ (i.e., increased integration of the brain’s modular cognitive capacities) that characterizes the brains of modern humans. Since religious ideas are not in themselves adaptive and may often be maladaptive, the brain has no specific cognitive capacity for trans- mitting religious ideas. Early modern humans there-fore had to develop techniques, including ritual and art, to ensure religious transmission. Thus, the flowering of Upper Paleolithic art is interpreted as the archaeological expression of evolutionary changes in cognitive architecture associated with the emergence of modern humans.

Proponents of other evolutionary approaches in archaeology have mainly ignored the cognitive archaeology work, despite some severe critiques launched by Mithen (1997a) in the other direction. From the EA perspective, inference of cognitive processes from artifacts would probably be considered informed speculation at best. Evolutionary ecologists, for their part, might observe that optimization models that lie at the core of EE are preferable to antiquated functionalist arguments used to attribute adaptive significance to behavioral patterns inferred model-free from the archaeological record.

2.5 ‘Memes’ And Cultural Virus Theory

In the evolutionary approaches considered so far, artifacts are viewed either as reflections of human behavior (EE, DIT, and evolutionary psychology) or as phenotypic characteristics of individuals (EA). An alternative perspective, considered by some ‘the most extreme variant of cultural selectionism’ (Maschner and Mithen 1996, p. 7), builds on the meme concept introduced by Dawkins (1976). Memes are cultural replicators, analogous to genes. The only purpose of any replicator, whether it is a gene or a meme, is to make copies of itself. Memes cannot self-replicate, but, like the genetic instructions in viruses, they can harness the capacities of other organisms to get themselves replicated. The last characteristic has led Ben Cullen (1993, 1996), the main proponent of this perspective in archaeology, to propose naming it ‘cultural virus theory’ (CVT).

To the extent that opportunities for memes to be replicated are limited by the amount of brain space available in a human population, memes ‘compete,’ just as other replicators (i.e., genes) compete. But the differential persistence of memes need have little to do with the biological reproductive success of human organisms in which they reside. Instead, differential persistence of memes arises purely out of differential success at replicating from brain to brain. The reasons why some memes enjoy relative success at replication can be found in the differential physical effects they have upon the world: under some circumstances, a cooking pot in which water boils in five minutes will have its design memes copied more often than one that requires 10 minutes. Evolutionary ecologists might argue that selection of memes in this case arises in the human cognitive capacity (which was designed by natural selection of genetic variation) to recognize more optimal solutions to problems such as how to boil water. From the meme perspective, however, artifacts, not humans, are the ‘interactors’ in the evolutionary process. Artifacts are packages of the physical effects of memes, and the success or failure of artifacts determines frequency change in their design memes. Archaeological assemblages, from this point of view, represent ecological assemblages of artifacts as interactors.

Although CVT has been largely ignored by less ‘extreme’ advocates of evolutionary approaches in archaeology, the artifact-oriented approach of EA can be considered consistent with this perspective. The engineering design approach of O’Brien and Holland (1990) evaluates the fitness of artifacts, thus implying that artifacts are the interactors in the evolutionary process. Likewise, models for predicting the pattern of trait distributions in the archaeological record (e.g., Lipo et al. 1998; Neiman 1995) necessarily ignore the biological reproductive cycles of humans and lead to predictions about the distributions of traits counted on artifacts.

Like DIT and approaches based on evolutionary psychology, memetics (or CVT) predicts the existence of cultural manifestations that are irrelevant to bio-logical success or even patently maladaptive from the perspective of human survival and biological reproduction. However, as the example of the cooking pot mentioned above illustrates, expectations about artifactual evolution can converge with predictions of an optimality argument. More generally, human proclivities and decision-making capacities, fashioned by natural selection in the past, provide selective criteria that help determine the fate of culturally encoded designs.

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