THE CURRENT ROLE OF EVOLUTIONARY THEORY
IN ARCHAEOLOGICAL THOUGHT

John Giacobbe
Environmental Management Group
Stantec Consulting, Inc.
Phoenix, Arizona
jgiacobbe@stantec.com

INTRODUCTION

Evolutionary theory has played a seminal role in archaeological theory since the development of the discipline. Most recent definitions of culture include an evolutionary perspective, such as Binford's view that "Culture is all those means whose forms are not under direct genetic control which serve to adjust individuals and groups within their ecological communities" (Binford 1972:431). Dunnell considers that modern evolutionary biology provides an explanatory framework for the processes of cultural change, but that it cannot "be applied unammended and uncritically to cultural phenomena, be they ethnographic or archaeological" (Dunnell 1982:37). This paper will attempt to synthesize relationships and applications of evolutionary theory and modern archaeological theory and practice.

HISTORICAL OVERVIEW

The following historical review is basically a refinement and synopsis of my first paper on the history of cultural evolutionary theory. This version is tailored to highlight the salient points that concern the present state of cultural evolutionary theory in archaeology. I considered it necessary to briefly review certain issues in the historical background in more depth than was covered in the previous paper as a necessary prelude to the discussion of the current theoretical views. As Santayana said "Progress, far from consisting in change, depends on retentiveness... Those who cannot remember the past are condemned to fulfil it" (or more appropriately, those who cannot remember the past are condemned to reread it.

The seeds of modern evolutionary thought in archaeology were planted at the origins of the discipline itself. In the mid 1800's, Scandinavian antiquarians such as C.J. Thomsen and J.J.A. Worsaae first proposed a three-age system of cultural development and used it, in conjunction with stratigraphic associations, to relatively date archaeological remains (Eddy 1991).

During the latter part of the nineteenth century, Sir John Lubbock further refined cultural stage classifications by using manufacturing technology as well as stratigraphy and raw materials (Eddy 1991). At the same time, new ideas were developing in the social sciences that focused on the processes of change over time in the natural world (Garbarino 1977). One of the major proponents of explanatory frameworks of societal change was the English philosopher, Herbert Spencer (Garbarino 1977).

Spencer was an evolutionary theorist even before the publication of Darwin's Origins had popularized the term. He attempted to relate the evolutionary approach to every field of science. He promoted evolutionist thoughts from a sociological perspective, and generated an organic analogy between the social/behavioral sciences and the biological sciences (Garbarino 1977).

Spencer's ideas are now recognized as being rather Lamarckian in nature (i.e.: acquired characteristics are genetically inherited). Although an attempt at explanation, Spencer's ideas did not give serious consideration to the mechanisms of change. In addition, Spencer strongly implied that a directional and teleological force controls evolutionary events, with developmental stages being virtually ordained (Mayr 1988). These two views are now considered incorrect when applied to a biological evolutionary framework (Mayr 1988). Spencerian ideas prevailed in anthropological thought until the latter half of the twentieth century, even though they were rejected by biological evolutionists by the turn of the century (Dunnell 1982).

This lack of discrimination by anthropologists in adopting biological evolutionary theory is still causing noticeable confusion in modern archaeological literature (Dunnell 1982; Kirch 1982). A dichotomy developed, in which archaeologists would apply Darwinian processes and mechanisms to their analysis of cultural evolution, while at the same time, be considering their interpretations and projections from a Spencerian philosophical viewpoint (Dunnell 1982).

Much of the debate over modern evolutionary thought in archaeological science is due to this initial confusion over which school of thought should be adapted to archaeological applications. A brief discussion of the distinction between Darwinian and Spencerian evolutionary ideas would not be out of place at this point.

Spencerian evolution embodies the concepts of progressive and unilinear evolution. It implies that evolution has a teleological force directing the development of evolving entities (Mayr 1988). Although Spencer coined the term "survival of the fittest" he remained Lamarckian with respect to his evolutionary views until relatively late in his life, and was not able to reduce the impact of his views on the public perception of evolutionary theory, especially his "Social Darwinism" (Strickberger 1990).

Darwinian evolution does not imply that any form of progress is inherent in the evolutionary process. In Darwinian evolution species change, or evolve, over time via changes in expressed gene frequencies. The directing influence of the environment (among other influences) is applied through natural selection acting on the various allelle expressions, tending towards an increase in reproductive fitness. Fitness is determined by how well an organism is adapted to the particular environmental conditions existing at the time (Mayr 1988).

In Darwinian evolutionary theory, neither increased complexity nor any sequential stages of development are implied. There is no evolutionary goal (i.e. civilization) waiting for those taxa (or societies) that manage to survive the game (Darwin 1859; Mayr 1988; and Strickberger 1990). [A more detailed discussion of Darwinian biological evolution will follow, in the section concerning biological evolutionary theory.]

From these foundations, evolutionary thought in archaeology progressed with the work of E.B. Tylor in Great Britain and L.H. Morgan in the United States (Bee 1974). Morgan and Tylor viewed evolutionary theory from a Spencerian perspective. They were primarily concerned with classifying developmental stages of human society (Bee 1974). Morgan and Tylor were apparently more interested in demonstrating that development took place than in discussing how it might have occurred. As Bee states:

... Morgan and Tylor were not primarily
concerned with the mechanisms of change.Their
evolutionary schemes were as much static
categories for the classifications of traits and
institutions as they were dynamic models [Bee 1974:63].

A possible explanation for their failure to do so might be found in the lack of evidence of a temporal/chronological nature that was then available. Most of the data on which their assumptions were based were drawn from ethnographic observations (in Tylor's case, derived secondhand from others). This made it difficult for them to evaluate any mechanisms of change they might have thought were in operation (Bee 1974). Ethnography seldom concerns itself with changes through time, and this resulted in their studies never reaching much beyond grosso modo classifications of evolutionary "progression".

During the beginning of the twentieth century, Classical cultural evolutionism fell under criticism from members of the Historical School, especially anthropologist Franz Boas (Garbarino 1977). Boas recognized the tenuous and nonscientific nature of the Spencerian evolutionary scheme, with its only validation at that time coming from ethnographic accounts (Garbarino 1977).

While Boas' insistence in historical particularism had the temporary effect of pushing cultural evolutionism to the theoretical background, his criticisms and those of his students, forced some theoretical shifts that were necessary for the development of a workable theory. Boas demanded a return to the use of empirically verifiable evidence on which to base our assumptions about cultural processes (Willey and Sabloff 1980).

The reemergence of evolutionary theory in archaeology came about with the neo-evolutionary theories of V. Gordon Childe, Julian H. Steward, and Leslie White (Eddy 1991). Through a synthesis of the original concepts of Classical cultural evolutionism, the Historical school, and the British social anthropologists' Functionalist approach (as represented by the theories of A.R. Radcliffe-Brown and B. Malinowski), neo-evolutionary theory was developed (Eddy 1991; Wolf 1964; Garbarino 1977).

Childe can be credited with contributing the idea of revolutions in human economy, and how this can be met with an evolutionary response coupled with economic determinism (Eddy 1991; Garbarino 1977). Steward was concerned with demonstrating that evolution occurs along parallel lines (multilinear evolution), which are determined by differential environmental adaption (Willey and Sabloff 1980). White added the concept that universal evolution is the consequence of the technical capture of energy (Eddy 1991; Garbarino 1977).

These theories focused thought on the concept of the environment as a deterministic and directing force for cultural evolution. Steward's cultural ecology approach involved observation of the environment and how environmental conditions influence the nature of technological adaptations. He held that this would be reflected in other aspects of culture as well (Willey and Sabloff 1980). These ideas influenced later cultural evolutionary models such as Wittfogel's theory of hydraulic despotism, which he used to explain the origin of large scale irrigation projects and the origin of complex civilizations in Mesoamerica (Willey and Sabloff 1980).

Another aspect of Steward's theories that had a great influence on later evolutionary thought was the concept of multilinear evolution. This concept allowed different explanatory theories for each particular cultural manifestation. It was also a philosophical watershed, in which the observable range of worldwide cultural variations were understood as reasonable adaptive strategies, rather than classified as ranks or stages of a unilinear "progression" to civilization (Willey and Sabloff 1980).

Leslie White considered that the theory of cultural evolution was as valid as that of biological evolution. He believed that the difficulty the Classical evolutionists had met with while implementing their theories was due to the standard of measurement of cultural change (Garbarino 1977). He considered that this measurement should be universal to all societies at all levels of development, as well as scientifically testable. He developed what he called the Basic Law of Cultural Evolution, which states that: "..culture evolves as the amount of energy harnessed per capita per year increased, or as the efficiency of the instrumental means of putting energy to work is increased" [Garbarino 1977:88].

White's position came to be known as neo-evolutionism. He, however, considered his theories to be nothing new, mearly a refinement and codification of cultural evolutionism. This refinement gave cultural evolutionary theory increased scientific rigor through the use of units of measurement and alternative sources of data collection (Garbarino 1977). Several students of Steward and White took up the neo-evolutionist banner, and through reformulation and expansion of their ideas, paved the way for the development of the "New Archaeology", with its foundations in evolutionary thought.

NEO-EVOLUTIONARY THEORY

The "New Archaeology" had its own dichotomy in White's unilinear evolution and Steward's multilinear evolution. White maintained that culture should be studied as a living system. Binford considers that White's work "laid the theoretical framework for a logicodeductive science of culture" (Binford 1972:110), and that this approach allowed for the formulation of general laws concerning cultural systems. Steward's approach considered that given similar initial conditions, cultural systems integrated at similar levels will evolve in predictable ways. Thus, cultural laws are determined within empirically correlatable variations of morphology, function, and temporal sequence (Binford 1972).

An important bridge between Steward and White and the New Archaeology was formed by the work of Elman Service and Marshall D. Sahlins, colleagues at the University of Michigan. Service and Sahlins were the first anthropologists to consider cultural evolution as a direct correlate of biological evolution (Wenke 1981). They developed the concept of `universal evolution which they related the stages of evolution to human culture from a general point of view. Although they argue from a Whitean point of view (unilinear evolution), they do recognize that not all cultures pass through the same stages, or even have stages at all, which can be correlated to other cultures.

Sahlins and Service consider that both biological and cultural evolution move in two directions at the same time. They consider that evolution causes both diversity and progression of characteristic adaptions. Sahlins and Service assert that diversity refers to adaptive changes that cause new forms to evolve out of older forms (Sahlins and Service 1960). Progress refers to those situations in which evolution creates more complex forms (Sahlins and Service 1960). What Sahlins and Service call `General evolution' provides the basis for evolutionary stages of cultural development.

The alternate form of evolution `Specific evolution', is regarded not as a different evolutionary event, but as an integrated part of the evolutionary process (Sahlins and Service 1960). Specific evolution is concerned with the adaptation of a particular culture to its environment, via cultural evolution. According to Sahlins and Service, general evolution is the ways in which cultural development in a specific society allows us to infer that the society is more advanced, and therefore at a higher level of cultural evolution. (Sahlins and Service 1960). As Sahlins and Service themselves put it:

... specific evolution is descent with modification, the adaptive variation of life along its many lines; general evolution is the progressive emergence of higher life stage by stage. The advance or improvement we see in specific evolution is relative to the adaptive problem; it is progress in the sense of progression along a line from one point to another, from less to more adjusted to a given habitat. The progress of general evolution is, in contrast, absolute; it is passage from less to greater all-round adaptability. [Sahlins and Service 1960:436].

Sahlins and Service increased the level of influence modern evolutionary theories had on the development of cultural evolutionary ideas. However, aspects of the sociological (Spencerian) perspective remained more influential in Sahlins and Service's theories than aspects of the biological (Darwinian) perspective. The idea of societal and cultural progression (from lower to higher states), and the idea of evolutionary forces directing increased complexity still is a principal component of their theoretical constructs. In their search for nomothetic principles, Sahlins and Service developed the Law of Cultural Dominance, which embodies the general tone of their theory, as follows:

... a cultural system which more effectively exploits the energy resources of a given environment will tend to spread in that environment at the expense of less effective systems... a cultural system will tend to be found precisely in those environments in which it yields a higher energy return per unit of labor than any alternate system available [Sahlins and Service 1960:444].

Sahlins and Service's theory of specific evolution is purely Darwinian in nature, focusing on adaption as a necessary and immediate result of the occurrence of evolutionary change (Dobzhansky 1950). Their theory of general evolution is, however, clearly Spencerian in nature, focusing on unilinearity and progression, increased complexity and hierarchical rankings of cultural systems.

From the theoretical foundations of Sahlins and Service, cultural evolutionary theory played an integral part in the genesis of the New Archaeology. The Spencerian view of cultural evolution, which emphasizes directionality, teleology, and virtually predestined stages of development, is currently accepted as a theoretically viable construct. The New Archaeologists, and their modern successors, have adopted and retained this view of cultural evolution. Another group of cultural evolutionary theoreticians, including Robert Dunnell and Patrick Kirsh, have adopted a more Darwinian approach to cultural evolution. One of the earlier applications of evolutionary theory in archaeology was done by Robert Adams. He considered the rise and development of civilizations in Central America and Mesopotamia (Willey and Sabloff 1980). Adams emphasized the complexity and interdependence of occurrences leading to the major stage transformations, and called for contextual and functional analysis as an intermediate phase between chronological ordering and processual comprehension (Willey and Sabloff 1980).

Many researchers accepted the Sahlins and Service view of cultural evolution and made attempts to apply it to actual cultural/archaeological situations. Karl A. Wittfogel considered water as an environmental limiting factor (Thomas 1989:563). He observed the complex control mechanisms applied to water utilization in the development of agriculture and applied an evolutionary framework to them.

Wittfogel determined that the resulting pattern was common of evolutionary development, and that the evolution of cultures proceeded through such an increase in societal organization (Thomas 1989:563). He considered that these patterns could be predicted (or postdicted) to occur in a similar fashion in other societies. He states that the mechanisms of large-scale irrigation projects are directly responsible for the development of a state-level society (Thomas 1989:563). This is clearly directional in nature, and implies the necessity of increasing complexity in evolutionary developments.

Another researcher that applied this brand of cultural evolutionary theory was Robert L. Carneiro. Carneiro considered that land was an environmental limiting factor, and that control of circumscribed land represented a struggle for existence and evolutionary success. The cultural adaptive response was the development of large autonomous political units (states), whose formation gave some selective advantage to one culture over another. He determined that increasingly complex warfare patterns inevitably lead to the development of the most efficient mechanism for the maintenance of circumscribed land, the state (Carneiro 1970).

One of the first of the New Archaeologists to articulate evolutionary views was Lewis Binford. Binford is often credited with beginning the New Archaeology (Dunnell 1981). In his article Archaeology as Anthropology (1962), he proposes changes in how we perceive and interpret the archaeological record. He suggests that archaeologists take a systemic approach to explain archaeological events, that the types of explanations themselves need to change to processual accounts that make generalizations about archaeological events (Dunnell 1981).

Binford stresses generalizations about the causative factors of cultural variability (Binford 1972). He believes that the environment acts as the organizational mechanism of evolution, as well as being the contextual field in which cultural evolution occurs (Binford 1972). Binford considers evolutionary views in anthropology from the perspective of general systems theory and ecology. He defines evolutionary processes as "those which operate between a living system and its environmental field" (Binford 1972:106). His ecological approach seeks to investigate the interrelationships that one system maintains with field variables (Binford 1972).

Binford considers that to demonstrate evolution we must observe structural change. He states that when directionality in the patterning of variation can be demonstrated, it is possible that this patterning is indicating aspects about differences occurring between cultural systems (Binford 1972). Binford considers, however, that this patterning is not necessarily indicative of evolutionary change, but that an explanation of it could be functional in nature (Binford 1972).

In Binford's view, the unit of evolutionary relevance is an organizationally integrated biological system, in a holistic fashion (Binford 1972). He considers that what is measurable with the present methodological and theoretical sophistication is "the rate of change of formal attributes of artifacts and certainly not the rates of evolution" (Binford 1972:107). Binford defines the objectives of general evolutionary research as the "determination and explanation of the successive transformations of culture through its several stages of overall progress" (Binford 1972:108). He states that:

The locus of evolutionary change is between a system and its environment, and the outcome of the operation of evolutionary process could be extinction, a decrease in complexity, reorganization of the system without any major increase or decrease in complexity, or the emergence of higher forms [Binford 1972:108-109].

While appearing to adhere to modern biological evolutionary precepts, Binford fostered evolutionary ideas of an outdated nature. As a student of White's, he accepted the Spencerian view that evolution has a teleological and directional aspect to its force of development.

The Darwinian view holds that evolution occurs, and is influenced, through adaptionary responses only. In Darwinian terms, there is no preset or desirable goal to either biological or cultural evolution, other than continuation of the line. Evolution is caused by changes in the frequency or the expression of a characteristic, but this new expression need not be either of increased complexity or a `higher form', but simply a form (of organism or culture) that is best adapted to the particular environment it occupies.

Spencerian cultural evolution, however, was the primary basis for the integration of evolutionary archaeology into the New Archaeology paradigm (Wenke 1981). With the evolution of processual archaeology, researchers have taken the Spencerian view and adapted it to modern archaeological constructs.

SPENCER AND DARWIN - THE STATE OF THE DICHOTOMY

Current evolutionary theory in archaeology has reached a point just short of what Kuhn might consider a paradigm state. A majority of archaeological theorists consider some sort of evolutionary processes to be the overriding mechanism of cultural change. These can be classified under two major cultural evolutionary theoretical constructs, both based on traditional evolutionary views. The Spencerian evolutionary view (with proponents such as Binford, Wenke, Sahlins, Service and others) considers cultural evolution to be directional, teleological and stage organized. The Darwinian view (whose proponents shall be discussed later) rejects these principles, and considers that evolution proceeds through adaption. This adaption is necessitated primarily by environmental stresses, and is guided by natural and other selective forces.

THE SPENCERIAN SCHOOL

Robert J. Wenke is one of the current researchers that have taken the cultural evolutionary perspective from the New Archaeology and developed it for application in the post-New Archaeology world. Some of the significant concepts that were incorporated from the New Archaeology into current evolutionary theories, include, as Wenke states:

..(a) a commitment to materialistic determinism, (b) confidence in the eventual formulation of cultural laws, and (c) adoption of some (but not all) concepts of the Darwinian evolutionary theory [Wenke 1981:85].

Wenke, in this author's opinion, has taken the Spencerian cultural evolutionary view to an extreme. He has rejected biological evolutionary models almost entirely, and does not appear to consider it likely that models of cultural complexity taken directly from Darwinian evolutionary theory might be archaeologically useful (Wenke 1981).

Wenke considers that there are four main reasons for the rejection of modern biological evolutionary theory as an analogy useful to archaeology. They are:

(a) the vastly different systems of character transmission in biological and cultural evolution;
(b)the relatively modest time scale of cultural processes;
(c) the absence of nontautological, empirically testable concepts of natural selection and "fitness" in the cultural sphere; and
(d) the lingering suspicion that cultural phenomena are different from all others and can usefully be examined only within cultural terms [Wenke 1981:111; after White 1959; and Rappaport 1967].

Archaeologist Norman Yoffee has used case studies of Mesopotamian civilization to illustrate the deficiencies he perceives in the modern biological-to -cultural evolutionary analogy (Yoffee 1979). Yoffee considers that the analogy between social change and biological evolution is not a valid one (Yoffee 1979). He states that archaeologists have simply adopted the precepts of the biological-cultural analogy as "revealed truth through which data must be interpreted" (Yoffee 1979:6). He suggests that biological evolution can be used to elucidate cultural change in a reductionist scenario only. In his words:

...this `paradigm' has contributed little to the development of cross-cultural tools for measuring the differences between simpler and more complex cultures and for appraising the internal dynamics of change [Yoffee 1979:6].

Yoffee states that the Darwinian view of culture has merely transformed cultural evolution into an extrapolated form of functionalism (Yoffee 1979). He considers that cultural change is not limited to adaption as a response to external conditions (Yoffee 1979). He criticizes the biolgical-cultural analogy because it has not been made operational in the field, but has only been used as a theoretical construct from which to interpret the archaeologically derived data (Yoffee 1979).

In Yoffee's Mesopotamian case studies, he observed clear developmental progression from simple to complex societies and levels of organizations (Yoffee 1979). He noted that not all the societies responded to environmental conditions in exactly the same manner and at the same rate of change (Yoffee 1979). He then uses these two observations to invalidate the Darwinian perspective of cultural evolution. Yoffee suggests that as Darwinian cultural evolution has failed to predict the exact sequence and type of developmental processes in Mesopotamia, we should scrap the theory. He offers as an alternative, the use of a more Spencerian model of cultural evolution coupled with middle range models designed for each specific case, and based on exchange networks and economic developmental patterns (Yoffee 1979). In his new text Archaeology: A Cultural-Evolutionary Approach, Frank W. Eddy describes cultural evolutionary theory from a completely Spencerian viewpoint, entirely omitting alternative views (Eddy 1991). Eddy considers several evolutionary principles as long-term trends in prehistory:

(1) Evolutionary change is directional rather than random or cyclical. This pattern is illustrated by the fact that society has evolved from simple to complex.
(2) Evolutionary change is adaptive because it involves an increasingly closer fit with the environment for the extraction of materials and energy, and increasingly more structured relations among human members of society.
(3) Change progresses toward survival of the human species as measured by increasing numbers of people and their ever wider geographical spread over the face of the earth.
(4) And finally, the rate and pace of evolutionary change has accelerated through time [Eddy 1991:39-41, emphasis in the original].

These four principles comprise the main tenets of the Spencerian school, and are some of the points of divergence between the two schools of modern cultural evolutionary thought.

THE DARWINIAN SCHOOL Robert C. Dunnell is one of the principal proponents of the use of Darwinian biological evolutionary theory as an analogy for cultural evolution. Through a functionalist and adaptionist approach, Dunnell has outlined what he considers to be the effective limitations of an evolutionary framework, one that is scientific and particular as to what aspects of the cultural and archaeological record it might apply (Dunnell 1978, 1981, 1985).

Dunnell seeks to utilize evolutionary approaches to generate historical explanations. He states that cultural evolution is not directly equatable with Darwinian biological evolution, but that as culture is adaptive and functions within environmental parameters, a suitable analogy can be derived from it (Dunnell 1981).

Dunnell considers evolution as a framework for explaining cultural change as the differential persistence of variation in cultural characteristics (Dunnell 1981). He states that the role of stochastic components, as well as environmental constraints, play a part in evolutionary development (Dunnell 1981). Cultural continuity can be observed through the fact that all cultural phenomena within a society are historically and empirically interrelated (Dunnell 1981).

Dunnell believes that the subject of cultural evolution is change. He states that similarity and differences between adaptive strategies are not important, other that as a cultural-specific explanations for adaptive strategies (Dunnell 1981). With application of the concept of equifinality, a wide variety of possible adaptions to the same environmental constraints must be considered. While this may weaken the predictive (or postdictive) ability of cultural evolutionary theory, it vastly increases its explanatory abilities (Dunnell 1981).

Dunnell considers evolution as a selective process, its accomplishments observed as the alteration of the frequency of discrete variables. Selection acts on three components of evolution: empirical variation, the transmission of this variation, and the resulting differential representation of the variables in subsequent cultural states (Dunnell 1981).

Dunnell takes exception to the propensity of Spencerian cultural evolutionists to equate change with progress (Dunnell 1981). He states that progress has no place in cultural evolution (nor in biological evolution), and that it is clearly not the inevitable result of evolution. Cultural evolution causes changes in adaptive strategies. Often these changes involve an increase in cultural complexity, but this is not mandated.

Many cultures have been observed to exhibit decreases in complexity as an adaptive response. In Spencerian terminology, this would be labeled devolution, or characterized as an anomalous condition. From the Darwinian perspective this is no different from any other adaptive strategy developed to deal with an environmental shift.

Spencerian theory does not appear to be a suitable model for postdicting and explaining any change in culture that did not involve an increase in complexity. Darwinian theory allows for plenty of room within its theoretical bounds to deal with any shift in complexity, and has the means to explain it, such as through adaptive shifts towards homeostasis. The primary reason for this is the Darwinian focus on natural selection as the influencing factor for cultural change. Naturally selective pressures function to favor those adaptionary choices which offer better survival benefits for a culture (Dobzhansky 1982).

Dunnell does note that increases in complexity do often occur, but he interprets this increase in complexity as a likely response to population size increases. He describes this as analogous with Stephen Jay Gould and Niles Eldredge's theory of punctuated equilibrium (Gould and Eldredge 1977). Dunnell postulates that the population explosion which occurred at the end of the Cambrian era [which Gould attributes to a log increase causing a phase change in population ecologies (Gould 1976)], might be considered analogous to a perceived "Holocene Explosion" for human cultural diversity at the Pleistocene/Holocene boundary (Dunnell 1978).

Carl Renfrew proposed a similar idea in his analysis of the collapse of the Maya (Renfrew 1978). He developed a model based on Catastrophe Theory to explain too-rapid changes in sociopolitical and environmental structures. Renfrew considers that the Maya had reached a homeostatic equilibrium between their cultural system and their environmental system (Renfrew 1978). The population reached the environmental carrying capacity and went beyond, buoyed by highly efficient cultural institutions.

Eventually, after a period of environmental degradation, the environmental situation changed, and was no longer as predictably bountiful. The cultural institutions did not react (adapt) quickly enough, resulting in a collapse of the entire cultural system (Renfrew 1978). In terms of punctuated equilibrium, the cultural organism underwent a prolonged period of homeostasis, punctuated by a rapid period of shift in adaptive strategy. The Mayan cultural system still exists now, in another period of homeostasis, having reached an adaptive plateau.

The Dunnellian view holds that the processes of biological evolution require some redefinition for use in cultural definition (Dunnell 1981). He does however, consider that sufficient analogy exists to transpose one theory for another in many aspects of archaeological investigations (Dunnell 1981).

Dunnell considers that the processes of natural selection, gene flow, gene drift, and mutation all have clearly analogous processes in both biological and cultural evolution (Dunnell 1978). He considers that the specific origin or invention of new elements is not important, and equates mutation with the act of invention and innovation (Dunnell 1978).

Presumably, Dunnell would take this analogy further. Gene flow and gene drift exhibit a clearly analogous relationship with diffusionary processes. Natural selection appears to have the same adaptionary stimulation within both cultural and biological evolutionary models. Dunnell sums up his position by stating that:

... evolutionary processes do have considerable potential in explaining cultural phenomena and the laws unique to cultural phenomena are possible and necessary. It is also apparent that not all phenomena traditionally considered cultural can be explained with such processes [Dunnell 1978:200].

An important aspect of evolutionary theory is the role of adaptation. Almost all theories of cultural evolution incorporate adaptive responses into their explanatory frameworks. Adaptive responses are those "..features of organisms that have come about by natural selection because they serve certain functions and thus increase the reproductive success of their carriers" (Dobzhansky et al. 1977:498). O'Brien and Holland cite Futuyma's definition of cultural adaptation, "...a process whereby the members of a population become suited over the generations to survive and reproduce" (O'Brien and Holland 1992:38; after Futuyma 1979:308).

O'Brien and Holland note that adaptation has been too often used as a post-facto explanation of the expression of a cultural trait (O'Brien and Holland 1992). They suggest that simply the occurrence of a new expression of a cultural trait (such as in innovation, invention or diffusion) is not enough. It is only after that trait is replicated and subsequently influences and is accepted by selective processes that an adaptation exists as a cultural element (O'Brien and Holland 1992). Following this definition, all functional variations are classified as adaptations, but only those influenced by selection are considered adaptive components of a cultural system (O'Brien and Holland 1992). Conversely, stylistic traits are considered those that neither affect adaptedness nor are under selective control (O'Brien and Holland 1992).

To mention an alternative position, Phillip Shelley has noted that even those expressions of a trait that would typically be labelled stylistic, and therefore non-adaptive, may in reality possess some adaptive significance (Shelley, personal communication 1992). Shelley notes that stylistic variation may perform some emblematic function, and that in a cultural system, emblematic identification could certainly have some selective, survival, and reproductive value (Shelley,personal communication 1992).

O'Brien and Holland note that there are two basic steps in the analysis of the adaptive significance of a trait's expression. The authors state:

... it is necessary to identify which archaeological features contributed to the adaptedness of the human group(s) under study. This procedure is linked directly to an analytical separation of potential adaptedness from realized adaptedness. Second, archaeologists are obliged to chart the evolutionary history of a particular feature in order to decide whether it has been shaped by selection, since then and only then can a trait be considered an adaption [O'Brien and Holland 1992:55].

Patrick V. Kirch suggests that adaptation is the key to the integration of many disparate methodological orientations into an analysis of the central theme of cultural change as it is related to the environment (Kirch 1981). Adaptation, according to Kirch "...lies at an intersection point between evolutionary and ecological theory.. (and) offers a contextual perspective on change" (Kirch 1981:121). Kirch considers adaptation the fitting of an organism or culture to the environment.

Kirch considers culture as a special kind of adaption and that cultural adaptions are transmitted via learned, nongenetic and extrasomatic behavioral patterns (Kirch 1981). He considers that cultural transmission of adaptive fitness is clearly Lamarkian in nature, with ontogeny rather than phylogeny the vector of transmission (Kirch 1981).

Kirch suggests that the emergence of the concept of culture as an adaptive system linking biological human populations with their environment has served to place culture in an evolutionary meaningful context. Kirch has attempted an integration of adaptation to archaeologically meaningful evolutionary principles (Kirch 1981).

This systemic-adaptive paradigm has generated certain major points of agreement. Kirch concludes that: 1) culture be analyzed in terms of the relations between elements, particularly feedback, and of the function of relations as channels for information flow; and 2) culture is an open system, coupled with environment as well as with the physical population and its somatic-genetic system, with feedback occurring internally between elements of the system and between the environment, culture and the somatic systems themselves (Kirch 1981). From these assumptions, he derives a definition for cultural adaptation as "a process of alteration of a cultural system in response to change in its coupled environmental and/or somatic systems" (Kirch 1981:134). Those types of behavior that have proven selective advantage will be selected for and retained, while those that cease to be advantageous will be selected against, and dropped from the `cultural pool" of behavioral patterns (Kirch 1981).

Kirch cites three features of culture as an adaptive system paradigm, these include: 1) the importance of a source of variation within a cultural system in order to have available options to respond to the adaptive challenges posed by the environment; 2) a set of selective criteria that evaluate this behavioral variation based upon selective advantage; and 3) a mechanism for the transmission of those behavioral strategies that gave a selective advantage to their carriers (Kirch 1981).

Kirch notes that the main difference between cultural and biological models lies in the nature of each's mechanism of transmission (Kirch 1981). Biological transmission of trait expression occurs in the reproductive act and resides in genetic material stored and translated through DNA (Mayr 1988). Cultural transmission of trait expression occurs through an interaction between the central nervous system and the environment, with trait expression information residing in the collective consciousness of the population, in the form of accumulated experience (Kirch 1981; O'Brien and Holland 1992).

Kirch recognizes four contributing components involved in the process of changing adaptive strategies. These components are the available variation itself, the processes of selection acting on the available variation, the environmental conditions which determine selective advantage, and the demographic situation of the population acted upon (Kirch 1981).

Variation is the basis for all possible change. A major issue of archaeological research is the relation of observed variation to the probable selective pressures of the environment. The amount of variation in a population can be used as a measure of the potential adaptedness of a population. Although behavioral variants originate with the individual, variation must be disseminated for it to have an adaptive effect on the population (Kirch 1981).

Selection is primarily manifest as natural selection. Some sexual selection, however, clearly has an influence on character transmission (Strickberger 1990). This is the factor that decides how much influence a particular expression of a trait will have on the overall adaptive strategy (Mayr 1988). Selection acts on the group rather than the individual, as far as cultural evolution is concerned. The criteria for selective value are manifold, including the efficiency of energy capture, survival and reproductive success, and even perceived satisfaction of needs and wants. In the long run, however, the most important aspect of selection is its benefit to the survivability of a culture group (Kirch 1981).

Kirch outlines three types of selection. Stabilizing selection tends to promote maintenance of the status quo, and functions as long as the environment and cultural adaptions remain in equilibrium (Kirch 1981). Directional selection acts to guide adaptionary changes to fit an environmental constraint. It is through this type of selection that most evolutionary events occur (Kirch 1981). Diversifying selection acts to favor extremes of trait expression. It would tend to favor alternate forms of an expression, and tend to not favor a median form (Kirch 1981).

The environment is the primary source of selective pressure. It is also the ultimate test by which adaptions are measured for their selective value (Kirch 1981). Demographic conditions, such as population size, geographical distribution, and life table dispersions are a source of adaptionary influence. As mentioned previously (see Gould and Dunnell), population parameters and interactions with the environment are the principal influencing factors towards adaptive success (Kirch 1981).

CONCLUSION

The obvious problems of interpretation and explanation of the Spencerian approach to cultural evolution lead this author to favor Darwinian theory as more applicable to archaeological investigations. Darwinian evolutionary theory can be incorporated into an explanatory framework, possibly even as a paradigm, for cultural processes, and it is eminently qualified to give empirical significance to the archaeological record. To conclude, I return to the wisdom of Dunnell, the development of an evolutionary paradigm "... may place us in the novel position of making genuine contributions to Western thought that go beyond what happened when" (Dunnell 1981:89).

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