Why did cahokia decline

We should not automatically assume that deforestation was happening, or that deforestation caused this event. This conclusion is important because the hypothesis at Cahokia — and elsewhere — is sensible on its face. The people who constructed this remarkable site had an effect on their environment. Wood depletion could have been an issue.

By eliminating this possibility, it moves us toward other explanations and requires we pursue other avenues of research. Comments and respectful dialogue are encouraged, but content will be moderated. Please, no personal attacks, obscenity or profanity, selling of commercial products, or endorsements of political candidates or positions.

Website: meilansolly. One of the more than earthen mounds preserved at the Mounds State Historic Site Getty Images At its peak around the turn of the first millennium, Cahokia , a city in what is now Illinois, was home to as many as 20, people.

Archaeologist Caitlin Rankin conducts excavations at Cahokia. Post a Comment. Human activities and the complexity of societies evolve to make use of whatever energy is available Tainter, In the American Bottom, the energy supplied by the plants of the Eastern Agricultural Complex led to the establishment of a metropolis.

The Lohmann phase saw the termination of a system of rural villages, and the transfer of their populations to Cahokia. This coincided with the construction of a planned urban center, including Monk's Mound, the Grand Plaza, and smaller mounds, including Mound All this was done in a period of no more than 50 years.

Cahokia became the home of 10, to 15, people. The sacrifice and burial of dozens of individuals in Mound 72 indicates that the rulers of Cahokia had unprecedented power. In a subsistence economy dependent on solar energy, prosperity and power come from a combination of land and labor. The burial within Mound 72 of 53 females of reproducing age, most likely slaves, means that Cahokia's rulers were sacrificing future prosperity and power, including their own. They did so as a form of conspicuous display.

This act, as much as the other activities undertaken in the Lohmann phase, shows the confidence of Cahokia's elites in their own power and its metabolic basis. It also demonstrates that the institution of slavery existed at Cahokia.

For comparison, among the native Illinois at the historic Grand Village of the Kaskaskia, slavery was common, especially of women Morrissey, , p. The plant food diet seems to have remained unchanged in the Lohmann phase.

Use of fish declined, while mammal use mainly deer increased proportionately. This may reflect a change in the distribution of population. Fewer people resided in bottomland villages, near fishing locations. More people settled in or near the bluffs and uplands the Richland Complex , where more deer were to be found, especially within the bluffzone forests.

As population dispersed outward from Cahokia during the Stirling phase, Cahokia's metabolic basis did not immediately change. A three-tiered settlement hierarchy developed in the countryside as the population of Cahokia declined by half. More of the population was living near their agricultural fields, so that the labor cost of transporting food to Cahokia was increased.

During the thirteenth century, population declined in both Cahokia and the countryside. At the same time, plant food diets shifted away from the Eastern Agricultural Complex crops toward more use of maize Fritz, , p.

The political and demographic stresses that the region was experiencing required a change in diet, a change to a crop that was more productive but less nutritious. Animal use became more localized and the use of fish increased. People consumed more of the less desirable parts of deer carcasses. By the end of the thirteenth century, Cahokia had collapsed as a complex metropolis. More and more people left the American Bottom, and it was largely unused until the nineteenth century. As an experiment in complexity, Cahokia had exceeded its metabolic basis.

When investigating the collapse of a complex society, it is best to look for social, political, and economic changes within the society, and changes in its environment. Notwithstanding the palisade, there is no unequivocal evidence that Cahokia's existence was threatened by other societies. There were, however, changes in its biophysical environment. George Milner notes that Mississippian structures in the American Bottom are rarely found below m.

In historic times land below this elevation was inundated seasonally or year-round, and was valueless unless drained Milner, , p. Mark Mehrer points out that in the Moorehead phase at Cahokia and in the countryside houses were consistently placed at somewhat higher elevations than previously , p.

It has been argued from this that flood levels were increasing and that this would have reduced the area of bottomland suitable for farming and habitation Milner, , p. A high volume of wood went into Cahokia's construction and occupation. Lopinot and Woods ; Woods, argue that in the Stirling phase wood use came to be increasingly localized and diversified. They suggest that intensified local cutting increased runoff and caused floods to become more frequent, severe, and unpredictable.

Milner notes that after the area experienced rapid soil deposition, and suggests that it was caused by increased runoff from cutting bluff-zone forests , p. More recent research questions these evaluations, since the area had been significantly deforested centuries before Munoz et al.

There is much uncertainty about such arguments. Larry Benson, for example, suggests that the region was affected by drought, with severe droughts in of years after Benson et al. This may have led to the abandonment of the Richland Complex sites along with the agriculture that sustained Cahokia Benson et al.

Broxton Bird finds midcontinental droughts after , and also a possibility of increased flooding in this period Bird et al. Munoz notes a prominent floodwater deposit at around A. Kelly , p. Arguing contrariwise, Pompeani asserts that there is no evidence for a large, late Stirling phase flood. The noted flood deposits, rather, represent local erosion Pompeani et al.

Munoz et al. Such a flood would cover a large part of the American Bottom. White et al. Fecol stanols organic molecules that originate in the human gut, and persist for centuries in soils closely track reconstructed population trends in the American Bottom White et al. The frequency of these molecules, argue White et al. Much work needs to be done to understand Cahokia's environment, and whether changes in the environment were connected to the collapse.

The research to date is important, but does not demonstrate that environmental factors caused Cahokia's collapse. If spring flooding was a problem, one solution would be to shift cultivation to the uplands, beyond the reach of flooding. This area was indeed the location of a set of farming villages, the Richland Complex, as discussed above. Yet this is precisely the area that had been abandoned late in Cahokia's history.

As for drought, a society that had experienced years of dry conditions will have adapted to such conditions. Drought lasting nearly a century and a half would become normal. Moreover, an environmental condition extending over years does not fully explain the profound changes beginning in the Stirling Phase, nor does it comprehensively explain the collapse of a powerful polity during the Moorehead Phase.

The labor required for public works peaked in this phase Milner, , p. Neither flooding nor drought can, by themselves , explain the collapse of Cahokia. While Cahokia's environment was of course important, we must turn to social and economic factors to understand the end of Cahokia.

The most enigmatic aspect of early Cahokia is the constellation of rapid changes about A. Over a short time Cahokia was transformed from an important village to a planned metropolis. Its population grew perhaps ten-fold. Cahokia underwent processes common to the early phases of urbanization. These included the planning and construction of its core, and the transfer of populations from rural agriculture to central public works. The countryside was transformed as well. Rural social structure was atomized—reduced to the most basic element, the household.

The horizontal ties of community integration were severed, leaving society to be reconstituted along vertical lines. History may offer few examples of such profound, rapid, system-wide changes. It is a truism, and one of history's most accurate generalizations, that over the past 12, years human societies have shown an almost inexorable tendency to grow more complex. This is puzzling on the surface. Complexity always has a metabolic cost, paid in early societies by human labor Tainter, The cost of supporting complex institutions must always have inhibited the development of cultural complexity.

Thus, explaining the human trend toward greater complexity is more of a challenge than we customarily think. One of the paradoxes of complexity is that it actually simplifies. Elaboration of structure and emergence of organization simplify and channel behavior. An activity formerly distributed among many components of a social system will, with increased complexity, be concentrated in a specialized component or new hierarchical level.

This is the essence of decision-making hierarchies. The benefit of complexity is that it can be deployed as a simplifying, problem-solving strategy, and often is with great success.

It is for this reason that ever since the end of the Pleistocene there have been veritable explosions in the complexity of such areas as technology, economics, settlement, sociopolitical organization, and information processing Tainter, Given that complexity both carries costs and yields benefits, it can be analyzed as an economic process, subject to the same constraints as other economic matters.

One of these constraints is the marginal utility of complexity. Developing greater complexity is suitable for problem-solving as long as the strategy yields stable or increasing returns.

Ultimately and inevitably, though, as economical solutions are progressively exhausted, societies reach the point of declining marginal returns to complexity Figure 8 Tainter, Beyond this point growing more complex yields lower and lower benefits per unit of investment.

This is the realm of diminishing returns to complexity. It can be brought about either by growing more complex, or by remaining at a specific level of complexity while the per capita costs of complexity increase—as seems to have happened late in Cahokia's development Milner, , p. Societies that experience this problem for a protracted time will ultimately encounter three options: impoverish the support population, acquire new energy subsidies to pay for complexity, or collapse.

These options aren't mutually exclusive: the first and second often do no more than delay the third. Figure 8. The marginal product of increasing complexity after Tainter, , p. Diminishing returns to complexity make a society vulnerable to collapse through two processes.

The first is through simple economic weakness, which leaves a society without sufficient reserves to cope with emergencies Tainter, The second is through disaffection of the population, who are called upon to support the higher costs of complexity. Both factors can be seen to have been at work in well-studied cases, such as the collapse of the Western Roman Empire or the Classic Maya Tainter, Several factors are pertinent to understanding the collapse of Cahokia, including the level of public works, the status of the support population, and the extent of vertical differentiation within the elite stratum.

Based on present knowledge we observe that after the initial, massive constructions of the Lohmann phase—Monks Mound and the Grand Plaza—public building continued at a high level during the Stirling phase and into at least early Moorehead. In fact, the labor required for public works peaked in the Moorehead phase Milner, , p.

The palisade and post-and-circle monuments were built, then rebuilt over and over. The ordinary mounds of later periods tended to be more massive than those of the Lohmann phase. There were clearly public labor requirements throughout most of Cahokia's duration.

It is significant that later constructions—the palisade and post-and-circle monuments—would have required higher levels of information in their design and building. This is another societal cost, for it indicates the development and transmission of esoteric knowledge, and suggests expansion of midlevel elites specializing in knowledge production. Throughout the countryside there is evidence for yet more midlevel functionaries in nodal sites. These sites came fully into existence during the Stirling phase, and include diversified structures such as mounds, sweat houses, and temples Emerson, a : — At Cahokia itself the later construction boom in intermediate-sized mounds suggests expansion in intermediate levels of the hierarchy.

This combination of trends indicates both that the hierarchy was differentiating vertically—always a sure way to increase costs—and that the power once consolidated in the paramount was being diffused downward and outward e. Phillips has suggested that one of the factors that often weakens emerging complex societies is the dispersion of income through intermediate hierarchical levels. Expanding the middle levels of a hierarchy increases the overall societal costs to support elite classes, and creates levels of administrators who can block the flow of resources to the top of the hierarchy.

The population trends of the region are probably the most important indicator of all. Population decline is often a correlate of sociopolitical collapse. In some cases population leveled off or actually began to decline generations to centuries before collapse.

In these cases—which include the Roman Empire, the Maya, the Abbasid Caliphate, perhaps the Western Chou Dynasty, and Cahokia—population trends seem to have been a harbinger of collapse Tainter, , Cahokia's population trends become especially significant in this light.

Through the twelfth and thirteenth centuries the population first declined at Cahokia as it increased throughout the American Bottom, then declined in both the center and the hinterland.

Voluntary emigration from the American Bottom was apparently a major component of this decline. Those remaining had to assume a higher labor burden to support the ongoing public works. The population trend indicates both that the metabolism supporting Cahokia was being weakened, and that disaffection of the population was a component of Cahokia's fall.

There are several collapse cases in which the population decline was surprisingly long-lasting. These areas were for several centuries afterwards either unoccupied or settled sparsely. Cahokia was one of these cases, for after its collapse both the site itself and the American Bottom were used for several centuries by no more than a few families at a time Pauketat and Emerson, , p.

For such cases it seems particularly worthwhile to investigate whether there was a component of environmental degradation to the processes of collapse and abandonment, so that these regions became unsuitable for dense occupation. This may have been the case in the American Bottom, although evidence does not yet support such a finding. Cities grow where people have already settled, which is likely to be the best agricultural land.

As noted above, this was the case at Cahokia, which had more of the best land nearby than other locations in the American Bottom Dalan et al. Such optimal land is converted to urban uses. Population aggregation and continued growth must then be sustained by less productive land Barthel et al. This forces cities to undertake the cost of transporting food, and creates pressure to cultivate intensively. Intensive cultivation on less desirable land is likely to lead to degradation of the land.

Thus we see characteristic patterns to the collapse of Cahokia: initial centralization and reorganization of the support population, followed by population dispersal and vertical differentiation, a continued high level of public construction, population decline, and collapse.

As people left the American Bottom those remaining assumed a higher labor burden per capita to support the hierarchy and its public works. The cost to each individual of supporting the hierarchy grew without any commensurate increase in the hierarchy's outputs. It was a characteristic case of diminishing returns to investment in complex institutions and it made the collapse probable or even inevitable.

Any comparison between past and contemporary cities is hampered by the fact that past metropolises were built on solar energy, while contemporary ones depend on fossil fuels. Past cities were constrained ultimately by the cost of land transport.

The energy cost of transporting food and other resources by land is so high Jones, , p. Ancient cities could grow to a large size only if they were close enough to a body of water to allow transport by ship Tainter, Speaking of Black behind bars By Patrick Yeagle Feb 4, Mining decision challenged as illegal By Patrick Yeagle Oct 15, More ».

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