The Impact of Fluctuating Agricultural Potential
on Coosa's Sociopolitical and Settlement Systems
William W. Baden
Coosa: Variation in Population Trends and Traditions
52nd Annual SEAC
I want to shift the focus of our discussions from Coosa, in particular, to
Mississippian in general. Non-coastal Mississippian Period cultures
(A.D. 900 to 1700?) have traditionally been seen as ranked societies
supported by intensive maize agriculture. While considerable research
has produced lengthy statements on the proposed sociopolitical aspects
of these precontact populations, little attention has been focused on
generating models of the economic system which served to support
these societies. Yet, some archaeologists associate changes in the
prehistoric record with cultural adjustments precipitated by intensive
The settlement pattern of Mississippian populations in some flood-
plain situations might also change through time if soil depletion
necessitated shifting the location of homesteads, and perhaps even
local centers [Smith 1978],
The reasons for the abandonment of hamlets were probably varied
but may have centered on both the depletion of natural food
resources and on soil fatigue by unrestricted crop-growing [Harn
Yet, others correlate the distribution of Mississippian centers with
"inexhaustible soil resources that annually are refreshed by flooding".
Both of these assumptions cannot be true. I think, minimally, we can
agree that archaeologists probably would make interesting farmers. If
we examine the ethnohistoric accounts dealing with aboriginal
agricultural systems we get a real-world view of the impact of soil
depletion and firewood exhaustion:
Sagard, ca. 1632, on the Huron states:
The chief town formerly contained two hundred large lodges, each
filled with many households; but of late, on account of lack of
wood and because the land began to be exhausted, it has been
reduced in size, divided in two, and rebuilt in another more
convenient locality . . . . There are certain districts where they
move their towns and villages every ten, fifteen, or thirty years,
more or less, and they do so only when they find themselves too
far away from wood . . . . They move their town or village [also]
when in course of time the land is so exhausted that their corn can
no longer be grown on it in the usual perfection for lack of
manure; because they do not understand cultivating the ground
nor putting the seed anywhere else than in the usual holes [Sagard
Francois du Peron, ca. 1639, writes of the Huron:
The land, as they do not cultivate it, produces for only ten or
twelve years at most; and when the ten years have expired, they
are obliged to remove their village to another place [Thwaites
In 1724 Lafitau, after ten years in Canada, writes:
As the Indians never manure their ground and do not even let it lie
fallow, it is soon exhausted (and worn out). Then they are forced to
move their villages elsewhere and make new fields in new lands.
They are also reduced to this necessity, at least in North American
and cold countries, by another more pressing reason for, as the
women have to carry firewood to their lodges every day, the longer
a village stays in the same place, the farther the distant the wood
is so that, after a certain number of years, they can no longer keep
up the work of carrying the wood on their shoulders from so far
William Bartram, ca. 1773, received this answer from a trader in the
Creek town of Apalachucha when asked why the Indians "frequently"
broke up their towns and settled new ones:
. . . the necessity they were under of having fresh or new strong
land for their plantations, and new, convenient and extensive
range or hunting ground, which unavoidably forces them into
contentions and wars with their confederates and neighboring
tribes; to avoid which they had rather move and seek a plentiful
and peaceable retreat, even at a distance, than contend with
friends and relatives or embroil themselves in destructive wars
with their neighbors . . .[1928:315].
All of this supports a model of shifting aboriginal agriculture correlated
with depletion of firewood and the necessity of incorporating it into our
definition of the Mississippian system. If we can model this process,
we should be able to test a wide range of hypotheses, not the least of
which would be the condition of the Coosa hegemony at the time of the
I would like to show you the results of a study I completed about ten
years ago (Baden 1987) that redefined aboriginal agriculture in terms of
stability theory. Namely, I developed a measure of agricultural potential
that, when plotted over time, reveals periods of stability and instability.
Most of the details and proofs behind this study go beyond the time
constraints (and maybe attention spans) of this session. For that reason,
I have provided a handout that details useful references and a graphic
representation of the study's results.
There are 3 major components to any model of agriculture: population
demands, technological options, and environmental constraints. My
approach involves looking through ethnohistoric accounts to define
behavior and technology. Unless there was some lost art to farming
known only to the Mississippian elites, contact experiences should
approximate these potentials. Environmental potential can be
approximated from soil surveys at the county level. When my original
study was completed, I lacked climate data that, today, is available with
the bald cypress studies of Stahle and Cleaveland (1994). However,
my examination of this data correlated with known crop yields does not
present a clear, predictable pattern. Estimates of rainfall amounts are
not sufficient to predict crop yields the way we would like. Although I
am continuing to examine the potential of including this information into
my model, the complexities of this undertaking will not be attempted
here. Botanical discussions can help define the varietal component of
prehistoric maize's yield potential. Finally, I look at agronomic studies
on growing maize to determine the impact of these "choices" on the
sustainability of prehistoric agriculture. Again, I will have to summarize
my findings and hope that you will accept the intermediate arguments as
"magically derived", at least for today. I can only assure you that the
magic is strong!
Summarizing the behavioral component, the Eastern North American
Indian's agricultural tradition involved the following generalized
1. Fields were cleared using fire one or more years in advance of
the first planting;
2. Fire was also used to clear old fields prior to planting;
3. Planting was undertaken after the first sufficient thaw;
4. Three to ten kernels were placed in hills spaced two to three feet
apart in rows up to six feet apart;
5. No recognized soil fertilization procedure was practiced;
6. Cultivation involved two minimal hoeings when the plants were
roughly six inches and two feet high, respectively;
7. Harvesting was undertaken in two phases: the first in middle-to-
late summer when the kernels were in the milky stage and the last
in the fall after the grain had completely ripened;
8. Yield estimates ranged between 10 and 20 bu/acre;
9. Field sizes ranged between 0.3 and 1.5 acres/person.
Population dynamics include some estimate of initial, Emergent
Mississippian size and a rate of increase over time. Both are difficult to
calculate. For rate of increase, the Coale-Demeny life table models
(Coale et al. 1983) provide long term analysis of worldwide
populations over the last century. Using their population classification
scheme and burial population summaries, I would assume an annual rate
of increase ( r ) lying between [3 to 17 per 10,000] (0.003 and 0.017),
which agrees with their West Level 1 tables. Applying this value of r to:
P = P e
creates an exponentially increasing population function. Defining P0
becomes problematic. How many people does it take to "start" a
Mississippian social structure? I don't think we have this answer, but
we can make estimates and test them against the rest of the model. We
can also assume a fixed population size that, by definition, can be set to
the largest, most stable value possible (under the other constraints of the
model). That is what will be done here, pending better estimates of
Mississippian population sizes.
Population demand for maize can be estimated using isotopic assays of
skeletal remains. It has been reported that a cline between 35% and
72% caloric dependence existed for Mississippian populations (Lynott
et al. 1986:61). Using 3600 calories/kg of maize (Minnis 1985:11),
each person would require 6.47 bu/year or 1.64 quintals/year for a
65% dependence (that's 0.025 quintals/percentage dependence).
Most demand curves take the form of a sigmoid and this can be used to
estimate dependence across time with strong correlation with skeletal
data. [SLIDE 1: DEPENDENCE CURVE]
Turning to the maize varieties or races, we can assume that early
Mississippian populations grew a form of Basketmaker maize. This
variety would be capable of producing yields in the range of 7.5 bu/acre
(4.7 quintals/ha). Later races of Northern Flints would have achieved
maximum yields between 18 and 30 bu/acre (11.3 to 18.8 quintals/ha).
These yields are consistent with early 19th century farming records (it
wasn't until the mid 19th century that hybridization practices developed
more productive varieties like today's southern dents). Turning yield
potential into field size requires matching varietal capabilities with
dependence. A 35% dependence on Basketmaker maize would
require 0.47 acres/person (0.19 ha/person). A 65% dependence on
Northern Flints would require closer to 0.9 acres/person (0.4
ha/person). It is unlikely that more than an acre of ground would have
been planted per person under any circumstances.
The potential environment for aboriginal agriculture consisted of rich,
easily tilled bottomlands. Proximity to a lower water table enhances
survival during drought years and the friable soils would be encourage
root growth and be the easiest to work with wood, bone, shell, and
lithic tools. To estimate the maximum field potential in any area, I use
the Capability Class I soils as the most likely candidates for prehistoric
fields. Capability IIw class soils might also be useful, although by
today's standards they would be considered prone to flooding and
waterlogging. Tabulating these soils and adjusting modern yield
potentials to estimate prehistoric yields, gives us an initial reservoir of
agricultural soils for any region. This "reservoir" will be used to define
stability. Here the reservoir of soils is defined at the county level.
This is a macroscopic approach. As soils become mapped at the field level,
a more specific geographically defined reservoir will be possible.
Finally we need to examine the critical and least understood component
of this model: the nitrogen cycle. Without belittling the importance of
other nutrients, like potassium and phosphorus, we must recognize that
prehistoricly as well as today, nitrogen is the key nutrient for maize
production. Its incorporation into useable, mineralized inorganic forms
(i.e. nitrate and ammonium) depends on a number of conditions
including the presence of organic matter and nitrogen-fixing microbes.
Only about 1-3% of the predominant organic N is mineralized each
year. Studies in the late 19th century (Hall 1917), designed to
encourage the use of fertilizers, can be used to demonstrate the effects
of not supplementing nitrogen in maize fields as well as generate curves
for predicting nitrogen loss over time. [SLIDE 2: DEPLETED
YIELDS] Nitrogen is further depleted each year when fields were
burned prior to planting (killing microbes and releasing 95% of available
N). Fields that have become depleted have been shown to require as
much as 100 to 150 years to naturally replenish their organic nitrification
potentials (Russell 1973:324).
Before I provide examples of this model, I need to address some
commonly held misconceptions about the sustainability of Mississippian
agriculture (indeed, these same points apply to all agriculture). First,
flooding supplies needed nutrients to refresh fields. Not true when it
comes to nitrogen, the critical element. Flood waters do not hold
nitrogen (that is, not until 20th century synthetic nitrates entered the
environment!). Flood waters create denitrifying environments and leach
nitrates out of the upper soil horizons. Waterlooging can rapidly release
iron and magnesium cations that are highly toxic to rhizobia bacteria &
plants (like Phaseolus vulgaris). Floods are detrimental to the nitrogen
capacity of soils.
Second, beans planted with maize add nitrogen to the soil. Again,
not true unless the beans are plowed in as a green manure. Studies
have shown that seldom is there a direct transfer of nitrogen between
legumes and maize. In the few experiments where a transfer was
measured it never exceeded 5% and then it was more a result of
drought conditions causing the legume to produce a surplus of nitrogen
which it released to the surrounding soil (Giller and Wilson 1991:118-
136). Of all the grain legumes, Phaseolus vulgaris has been shown to
be the worst nitrogen-fixing plant (due to poor nodulation); in fact even
with inoculation it generally fails to fix nitrogen into the soil.
Lastly, maize can be stored indefinitely. Naturally, this is not true and
although surpluses could be used to minimize subsequent crop failures,
the long term storage potential of maize, in the southeast, would
probably not exceed one year. Beyond that, the nutritional viability
would be diminished and the planting potential of the stored grain would
be equally jeopardized.
A summary of the models parameters would now be appropriate:
1. Population will be expected to increase at a rate between 0.003
and 0.017 per year.
2. Individual maize consumption per year is expected to be on the
order of 0.025 quintals (0.1 bu) per percent dependence, e.g. an
average 65% dependence implies a 1.63 quintals/year (6.5
bu/year) requirement per person. As a function of time,
consumption for the Mississippian Period will approximately
follow a sigmoidal trend.
3. Maximum potential yield under optimal conditions is not expected
to greatly exceed 18.8 quintals/ha (30 bu/acre) during the period.
Emergent Mississippian yields would not be expected to exceed
4.7 quintals/ha (7.5 bu/acre).
4. Maximum labor output will not exceed 0.4 ha (1.0 acre) per
5. The expected non-depleted average yield will be 9.99 quintals/ha
(sd = 3.31) (15.92/5.28 bu/acre). Fluctuations will follow a
normal distribution based on observed, crop yields.
6. Yields are expected to be annually reduced and, allowing for
depletion, maximum potential yield follows. [SLIDE 2].
7. To account for heavy weed growth, all yield equations will use 2t
for t (i.e. twice the consumption of maize alone).
8. The recovery or fallow period will be on the order of 100 to 150
[5 SLIDES of MY EXPERIMENTAL PLOT]
Let's go through a quick 300 year simulation using the above
parameters on an example in the literature. Jon Muller, in 1978
(1978:287-288), briefly described the agricultural conditions for the
Kincaid site in southern Illinois. At the time, he concluded that Kincaid
was composed of 400 individuals supported by 621ha. The population
was seen as requiring 0.4 ha/person. He concluded that Kincaid could
have supported 1500 people. Strictly as an example application, if we
define demand to be 1.64 quintals/person (65% dependence) minimal
required yield would be 4.1 quintals/ha (6.5 bu/acre). Let's arbitrarily
say that 3 sequential failures will result in field abandonment. (In
reality, an aboriginal farmer would know when certain weeds begin to appear
that the field should be abandoned). Let's further use a value of 0.01
for r, the rate of population increase. The results follow from the
[SLIDE 3: POPULATION CURVE]
[SLIDE 4: HARVESTS]
[SLIDE 5: AVAILABLE LAND].
After 51 years all available land would be in a depleted state. At t =
176 the site could be repopulated (in this case by 400 people).
Because of the periodic nature of site repopulation, total depletion
would again occur at t = 227. Population adjustments occurred at t =
41 and 215. During the 300 year period the average planting duration
was 12.6 years per field. The average surplus per person was 0.72
quintals. Although highly generalized, this example demonstrates that
soil depletion could seriously inhibit growth at Kincaid. Such a level of
population density could not be supported for more than a few
generations without major adjustments.
Carneiro (1960:82) would argue that the maximum sustainable
population (carrying capacity) of such a site should be :
--------------- 12.6 yr
(125 + 12.6) yr
--------------------------- = 142.2 people
If we re-simulate the above conditions, maintaining a zero population
growth at P0 = 142, the fluctuating amount of available land (R ) is
shown in [SLIDE 6: AVAILABLE LAND USING CARNEIRO].
Because of soil depletion, population reductions would occur at t = 126
(Pt drops to 133). Total abandonment would occur at t = 134. Failure
to recognize the negative environmental impact of agriculture invalidates
the usefulness of carrying capacity, so defined.
Moving to a larger example, I want to examine the expected results of
Mississippian agriculture in east Tennessee's Little Tennessee River
Valley. The study area includes three counties: Monroe, Blount, and
Loudon. [SLIDE 7: STUDY AREA SLIDE] Total Class I soils
acreage equals 19,559.2 ha. The expected maximum yield for
Northern Flint varieties is 17.2 quintals/ha. Using this example we can
further examine the impact of behavioral choices. First we can examine
the selection of field size [SLIDE 8: 13 0.1ha/person]. Larger field
sizes serve to minimize failures by assuring sufficient maize can be
harvested each year. [SLIDE 9: 0.4ha/person] A population of
1000 with an r value of 0.008 produces the following dynamic
fluctuations in population levels [SLIDE 10: POPULATION
GROWTH]. To remove the population constraints, we can consider
stationary population levels and use the rest of the model's constraints
to provide us with estimates of the maximum population size that never
requires fissioning or totally depletes the valley's land reservoir [SLIDE
11: ZERO GROWTH CURVES]. Further, we can allow for
adjusted field sizes over time [SLIDE 12: ADJUSTED FIELD
SIZES] [SLIDE 13: HARVESTS WITH ADJUSTED FIELD
SIZES]. Note the relatively large field size increases in A.D. 950,
1200, 1325, and 1550. These dates suggest times of strategic decision
making shifts (critical points?). Using these adjustments, we can
calculate a stationary population size of 4010 (twice that of the historic
Overhill Cherokee in 1760). We now can produce one last simulation
for 4010 people with an r of 0.0 between A.D. 900 and 1700. The
field statistics for this run reveal a mean harvest of 5.8 quintals/ha,
mean surplus of 0.431 quintals/ha, and mean field life of 9.87 years.
Now, returning to the original purpose of all this: stability measures.
If we can define a potential variable (here it is available land), we can
examine the graph of its fluctuations over time and see clear areas of
rapid change, stability, and instabilities [SLIDE 14: Stability Curve].
Note the rapid decrease in land potential between A.D. 900-1000
(Emergent Mississippian); this is an unstable time. This occurs again
between A.D. 1300-1400. Each instability is separated by a fairly
stable period (A.D. 1000-1300). The points of change (discontinuities)
mark transition points (phase shifts) that correlate well with Martin
Farm, Hiwassee Island, Dallas, and Historic Cherokee.
Now back to Coosa. If we look at the Coosa River drainage in
northwest Georgia [SLIDE 15: COOSA DRAINAGE] and apply the
same techniques to its 25,981.4 ha of Class I soils, we can produce a
similar curve. The stationary population size for this area would be
5668. The maximum yield potential would be 17.89 quintals/ha.
[SLIDE 16: COOSA STABILITY CURVE] What are the implications?
Certainly the concept of "permanent village" needs to be re-examined.
"Contemporaneous" villages may also be questioned. Social
organization and information processing structures, on a wide
geographical scale, would have been encouraged. Stress induced by
reduced agricultural potential would force cultural changes and
ultimately, for the archaeological record, create recognizable phase
changes. This study presents an alternative perception of cultural
change. Change is here seen as the inevitable result of a system, far
from equilibrium, adapting to fluctuating conditions. Such a system
displays a dissipative structure (Nicolis and Prigogine 1977) in that,
while maintaining local stability at some material/energy cost, it
eventually reaches a threshold where it evolves into an unstable order
in response to fluctuations. It is under these conditions that new
cultural phases are produced (morphogenesis).
The Spanish arrived at the second critical period in Mississippian
morphogenesis and it is difficult to say whether their impact pushed a
marginally stable population beyond the edge or, through disease,
reduced the population demands to levels capable of being supported
with smaller land reservoirs. We will never know what transition would
have occurred had the Spanish never appeared, but using model
building techniques like this, with the addition of other cultural
components, we may someday be able to extrapolate Mississippian
trajectories. With better spatial control of soils, we should be able to
simulate the entire shifting settlement system. At least we should now
have a better appreciation for the impact of nitrogen depletion on
EXTENDED LIST OF REFERENCES
Baden, William W.
1987 A Dynamic Model of Stability and Change in Mississippian
Agricultural Systems. Unpublished Ph.D. dissertation, Department of
Anthropology, The University of Tennessee, Knoxville.
1853 Observations on the Creek and Cherokee Indians. Edited by E.
G. Squier. Transactions of the American Ethnological Society 3(1).
1928 Travels of William Bartram. Edited by M. Van Doren. Dover
Publications, New York. Originally published 1791 as Travels Through
North and South Carolina, Georgia, East and West Florida.
1960 Slash and Burn Agriculture: A Closer Look at its Implications
for Settlement Patterns. In Men and Cultures, edited by A. F. C.
Wallace, pp. 229-234. University of Pennsylvania Press, Philadelphia.
Coale, Ansely J., Paul Demeny, and Barbara Vaughan
1983 Regional Model Life Tables and Stable Populations. Academic
Press, New York.
Giller, Ken E. and Kate J. Wilson
1991 Nitrogen Fixation in Tropical Cropping Systems. CAB
Hall, A. D.
1905 The Accumulation of Fertility by Land Allowed to Run Wild.
Journal of Agricultural Science 1:241.
1917 The Rothamsted Experiments. Revised by E. J. Russell. Murray,
Harn, Alan D.
1978 Mississippian Settlement Patterns in the Central Illinois River
Valley. In Mississippian Settlement Patterns, edited by B.D. Smith, pp.
233-268. Academic Press, New York.
Lafitau, Joseph F.
1977 Customs of the American Indians Compared with the Customs
of Primitive Times, vol. II. Edited and translated by W. N. Fenton and
E. Moore. The Champlain Society, Toronto. Originally published 1724.
Lynott, Mark J., Thomas W. Boutton, James E. Price, and Dwight E. Nelson
1986 Stable Carbon Isotopic Evidence for Maize Agriculture in
Southeast Missouri and Northeast Arkansas. American Antiquity
Minnis, Paul E.
1985 Social Adaptation to Food Stress: A Prehistoric Southwestern
Example. University of Chicago Press, Chicago.
1978 The Kincaid System. In Mississippian Settlement Patterns, edited
by B. D. Smith, pp. 269-292. Academic Press, New York.
Myrick, Herbert (editor)
1903 The Book of Corn. Orange Judd Co., New York.
Nicolis, G. and I. Prigogine
1977 Self-Organization in Nonequilibrium Systems. John Wiley
and Sons, New York.
Russell, E. Walter
1973 Soil Conditions and Plant Growth. Longman, London.
1939 The Long Journey to the Country of the Hurons. Translated by
H. H. Langton and edited by G. M. Wrong. The Champlain Society,
Toronto. Originally published 1632.
Smith, Bruce D.
1978 Variation in Mississippian Settlement Patterns. In Mississippian
Settlement Patterns, edited by B. D. Smith, pp. 479-503. Academic
Press, New York.
Stahle, David W. and Malcom K. Cleaveland
1994 Tree-ring Reconstructed Rainfall over the Southeastern U.S.A.
During the Medieval Warm Period and Little Ice Age. Climatic Change
Thwaites, Rueben J. (editor)
1896-1901 The Jesuit Relations and Allied Documents. 73 vols.
Burrows Brothers, Cleveland.
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