User:Brandon McIntosh/sandbox

Niche Construction Theory in Anthropology allows researchers to understand the evolutionary consequences of human tendencies to alter their natural and cultural environments to meet their biological and social needs. The application of this theory to understanding human evolution provides opportunity to understand how human behavior has become an active ingredient in the biological and cultural evolution of humans. According to Niche Construction Theory, by constructing environmental and cultural niches, humans have wittingly and unwittingly influenced the direction and pace of their own evolution.

=Theoretical Background=

Niche Construction Theory states that in addition to the ability of organisms to adapt to their local environments, some also actively construct their environments to better suit their needs. By altering their local environment, organisms, or populations of organisms, create feedback in the evolutionary process by changing the degree, or even the kind of natural selection forces operating on the population. By changing the degree and nature of the selective forces operating on a population, organisms influence the evolutionary inertia within their species. Once altered, the constructed environment favors individuals within the population that are best fit for the newly constructed environmental niche, while the constructed environment also creates constraints on previously available alternative design. This means that the newly constructed environment may limit alternative evolutionary trajectories. Some researchers have suggested that the newly altered environments become the source of ecological inheritance as the original niche constructing generation alters the environmental selective pressures that operate on their descendants. Because niche-constructing behavior can influence both cultural and biological evolution, Niche Construction Theory can also provide further insight into Gene-Culture Coevolutionary Theory.

According to Darwinian Evolution, both the biological, and the behavioral components of the human species are dynamic. Both components change through evolutionary processes, and natural selection is at least in part responsible for changes to both human genetic diversity, and variation in human behavior across space and throughout time. Darwinian evolutionary theory has allowed for evermore sophisticated interpretations for biological change in living organisms, including human beings. Darwinian evolution also provides insight into variation in human behavior; therefore, both components of the human species can be examined in Darwinian terms.

Niche Construction Theory adds a level of complexity to the idea of evolutionary change as a result of natural selection. Evolutionary change in human culture may not only be a result of isolated incidents of adaptive innovation as a response to forces of natural selection exclusively, but may also be influenced by the behavior of social participants who, through evolution, have developed the capacity and propensity for altering their natural and social environment to meet their biological and social needs. As a result, niche-constructing behavior may change the immediate social environment sufficiently enough to alter the nature of the selective forces that encourage cultural evolution, and may even become selective forces themselves. It is possible that variation in cultural or behavioral traits can be incorporated by cultural niche construction. If so, according to some theorists, such as F. John Odling-Smee, Kevin Leland, Marcus E. Feldman, and others, niche construction theory is useful in the social sciences such as economics, sociology, and anthropology.

=Documenting Cultural Evolution=

The use of evolutionary theory to understand cultural change requires the identification of cultural entities that can be measured over time. In other words, there have to be some components of culture or behavior that can be quantified so that measured change can highlight cultural evolution through time. As cultural entities are measured across time, an understanding of cultural change becomes historical, and evolution can be observed empirically. An ecological approach to understanding human culture assumes that the natural environment at least partly influences human behavior. As the stage upon which human behavior is played out, the environment provides both opportunity for, and constraint on behavior that will result in survival. The challenge is to identify the link between human culture and the environmental influences identified as potential selective agents.

Human evolutionary ecology was developed to understand adaptive design in human morphology, life history, and behavior. Human behavioral ecology was developed specifically to understand the adaptiveness of human behavior in relation to the natural environment. Some human behavior, such as food acquisition, is directly related to the natural environment. Because of this, human behavioral ecology can highlight the natural selective forces in the environment that influence change in human behavior related to acquiring food resources. As a result, understanding evolutionary change in human behavior and culture becomes integrative, allowing observed change in behavior to be directly correlated to selective pressures found in varying environmental contexts, if these types of functional correlations indeed exist.

=Components of Darwinian Evolution in Cultural Terms=

Once measurable cultural entities have been identified, and can be appropriately measured through time, these data can be tested against the components of Darwinian evolution and Niche Construction theory in cultural terms.

Variation
Whether on a continuous or discrete scale, cultural variation must be observable and quantifiable.

Often cultural variation is thought as the result of innovation, however, variation also comes in the form of copy error when individuals fail in their attempt to adopt cultural knowledge or traits accurately during cultural transmission. These copy errors may also have a profound feedback effect on populations potentially resulting in maladaptive loss of cultural traits.

Transmission
In contrast to biological transmission, which takes place genetically through asexual or sexual reproduction, cultural transmission can take multiple forms.

i. Vertical – parent to offspring, analogous to genetic transmission.

ii. Oblique – non-parental members of one generation to individuals of a subsequent generation.

iii. Horizontal – among members of the same generation.

iv. Group transmission – partly from parent, partly from the average trait value in the parental generation.

An important component of cultural transmission is that it can take place between two individuals or groups of individuals more than once. Genetic transmission takes place only once between parent and offspring. If transmission is repetitive and prolific enough, the rate of spread of an innovation increases.

Selection
If a variant of a cultural trait increases the reproductive success of an individual, then the variant will be selected for in much the same way natural selection operates on the physical expression of genotypes (phenotypes). However, successful biological reproduction is not the only measure of a cultural traits success. Reproduction may also be measured in the proliferation of a cultural trait, or behavior, through a population. In other words, if the cultural trait is reproduced in the behaviors of other cultural participants.

=Examples of the Use of Niche Construction Theory in Anthropology=

Cultural Anthropology
Some critics of the use of Darwinian Evolution in anthropology, such as Patty Jo Watson, have suggested that evolution does not explain the role of the individual in cultural change. In other words, Darwinian evolution does not explain how human agency operates in the process of cultural change. If Niche Construction Theory is included in an attempt to explain cultural change in evolutionary terms, the behavior of cultural participants becomes a significant variable in understanding the forces of change.

Game Theory is often cited as a source of examples of how the behavior of one or some can and does influence how people will behave in the future. Under this theory it is assumed that humans have evolved cognitive mechanisms to adjust their behavior to the conditions created by the behavior of others. This is often expressed in terms of:

If X, then do α; or if Y, then do β.

Because the behavior of cultural participants are influenced by the behavior of others in the population, any change in behavior that becomes a part of the normal suite of culturally accepted behaviors can be understood in evolutionary terms through Niche Construction Theory. In short, the behavior of individuals and groups of individuals can influence evolutionary change in the accepted cultural behavior of a population. Thus cultural evolution takes place in response to behavioral feedback in the evolutionary process. This feedback can create new or novel behaviors, or it can limit the range of behavioral alternatives available as a response to the behaviors of others.

Archaeology
Because archaeology deals directly with the material remains of past human culture and behavior, and because the material remains of culture can be measured in a variety of ways, the evolution of material culture over time can be quantified. Because of the empirical nature of much of archaeological data, it is applicable to models developed under Darwinian evolutionary and niche construction theories.

An empirical example of cultural change as a response to human niche construction is how technology changes in response to changing environmental conditions. Niche Construction Theory provides theoretical framework for understanding how human induced change to local environmental conditions can influence change in hunting and food production strategies and related technology. As the local environment changed throughout prehistory, human populations would have had to alter their subsistence strategies to exploit available food resources. As humans alter their environment, the food sources available would have subsequently changed. If, for example, Archaic hunters in North America subsisted primarily on large game such as deer, as a primary protein source, related site assemblages would reflect a higher proportion of stone tool technology (e.g. specific types of projectile point technology) for successfully harvesting these large animals. If the local environment change sufficiently enough to discourage an abundance of deer, human subsistence strategies would have been forced to shift to another, potentially smaller, protein source, such as rabbits, if human settlements remained in the same location. This shift may be evident in the measurable change in size and form of stone tool technology, or in a change to different technology more appropriate for smaller game (e.g. nets and snares).

Broughton et al. provide material evidence for resource depression due to human hunting pressure among hunter-gatherers in prehistoric California. As prehistoric hunter-gatherers harvested larger fish resources in the Sacramento Valley, fish populations became depressed, or reduced in numbers, to the extent that human settlements were forced to shift their subsistence strategies from a focus on larger anadromous fish, such as salmon and sturgeon, to smaller resident fish, and even low return plant resources such as acorns. The authors of this study suggest that changes in salmon and sturgeon availability was at least in part due to heavy human exploitation and human induced changes to the local environment because changes in species representation in the archaeological record over time in the Sacramento Valley do not correlate with general environmental trends during the Late Holocene. If these authors are correct, initial tendencies to over exploit some fish resources created a need to change subsistence strategies during later periods of site occupation in the valley, and provide an archaeological example of how human niche construction creates feedback in the evolution of cultural behavior in the Sacramento Valley during the Late Holocene.

Biological Anthropology
Biological Anthropology primarily deals with the biological evolution of humans. Modern research in human evolution continues to utilize the fossil record of extinct hominin species that represent our closest primate relatives over at least the last five million years to understand our evolution as a species, but it has also benefited from the continued development genetic research. Genetic research has allowed biological anthropologists to better understand genetic traits that are positively selected for during the historical process of human evolution, including those that may be explained by Niche Construction Theory. A classic example of how human niche constructing behavior has influenced biological evolution among humans is the proliferation of lactase persistence found in the descendants of Neolithic pastoralists.

During the formative years of a mammalian life history, the enzyme lactase-phlorizin hydrolase is found in the lower intestine, which aids in metabolism of milk, or disaccharide lactose carbohydrate hydrolysis. During hydrolysis, these carbohydrates are converted into sugars that can be metabolized in the human digestive system. Like most mammals, humans lose the ability to produce the lactase-phlorizin hydrolase enzyme once weaned from their mother’s milk. However, pastoralist populations tend to show an extended period of lactase-phlorizin hydrolase enzyme production that can, and usually does, persist well into their adult years. This allows for the continuation of disaccharide lactose carbohydrate hydrolysis. Swallow has hypothesized that lactase persistence in humans has been a direct genetic response to the increase reliance on cattle milk into adulthood, a trait that originated among Neolithic Pastoralists. This knowledge alters perspective on what was thought to be the normal ability of adult humans to metabolize milk. Lactose intolerant individuals were once thought to have been exceptions to the norm, but it turns out that lactase persistence is a relatively new development in the human past, and that those who are lactase non-persistent are much more inline with historical metabolic normality.

According to Niche Construction Theory, as human took more control of their subsistence by adopting a pastoralist lifestyle and depending on disaccharide lactose carbohydrates in animal milk as opposed to other sources of carbohydrates, they created a subsistence niche that effectively introduced feedback into the evolutionary process that resulted in human genetic evolution.

= Notes and References =