Mogollon Manos, Metates andAgricultural Dependence:Pithouse Villages, A.D. 200-1000Michael W. Diehl

SFI WORKING PAPER: 1993-06-034

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Mogollon Manos, Metates and Agricultural Dependence:Pithouse Villages, A.D. 200-1000.

by

Michael W. DieW

AbstractComparative analyses of the morphological attributes of maize processing tools areused to estimate relative differences in the agricultural dependence of prehistoricMogollon pithouse dwellers. The interval from AD. 200-650/700 was a period ofsubsistence stability. Beginning around AD. 650/700, dependence on maizeagriculture began to increase. By AD. 1000 Mogollones were producing at least20% more maize per grinder than in AD. 650/700. The introduction or indigenousdevelopment of a new strain of maize (with larger cobs, larger kernels, and higheryields) instigated this increase in agricultural dependence. I close with a discussionof the potentially destabilizing effect of reliance on the new maize.

A caveat: This is a preliminary report on research in-progress. It includes approximately 80% ofthe data that will be used in the final version.

IntroductionThe adoption of agricultural domesticants and the subsequent intensification of their use by

prehistoric peoples is a subject of paramount interest to archaeologists. The agricultural orhorticultural lifestyle represents a fundamental change in human subsistence strategies from ageneralized hunting, gathering, fishing and collecting strategy that reacts to the spatiotemporalavailability of resources, to a strategy in which humans target specific resources and control thetiming, quantity and location of their availability.

In turn, the agricultural revolution seems to many archaeologists to be an event that enabledother sociocultural processes such as high reproduction rates, the formation of large populationaggregates, and the emergence of political and social complexity (hierarchical stratification) (Foroverviews of these issues in the North American Southwest, see Cordell 1984, Cordell andGumerman 1989; Crown and Judge 1991; Kohler 1993).

Since agricultural dependence entails more work than generalized hunting and gatheringlifestyles, and is often (along with increased population) accompanied by serious social problems,archaeologists are naturally curious as to why, when, where and how agriculture becameimportant. Apart from these basic issues Southwestern archaeologists also wonder whetherprehistoric agriculture was a "stable" adaptation.

Our concern with the stability of agricultural systems is at least in part a consequence of theobservation that various parts of the Southwest were abandoned at different times, and that theseabandonments may have been predicated by climatic events such as droughts, or human ecologicaldevastation such as soil nutrient depletion or deforestation.

The Study AreaThe Mogollon region of the southwest encompasses approximately the southern third of

New Mexico, southeastern Arizona, and northern Chihuahua (Mexico) (see Cordell 1984).Mogollon area researchers offer a variety of hypotheses regarding the timing and degree of

dependence on maize. Most accept the fact that maize first appeared in the region by 1200-2000B.C. (e.g. Wills 1985). There is little agreement about events that transpired over the next three

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thousand years, particularly for the interval from A.D. 200-1000, when the fIrst populationaggregations with highly visible architecture made their appearance.

Gilman (1987), Wills (1991, 1985), and Lekson (1992) suggest that Mogollon Pithouseperiod occupations are best described as heavily oriented towards hunting and gathering withcasual dietary supplements provided by maize. They argue for stability in this adaptation until A.D.1000 when another spurt of change saw revolutions in the kinds of architecture and the size ofvillages in the region. In contrast, LeBlanc and Whalen (1980) and others (Martin 1979;Woodbury and Zubrow 1979), have argued that the appearance of pithouse villages around A.D.200-300 coincided with diets that were primarily dependent on maize.

The present research indicates that the degree of dependence on maize remained relativelyconstant from A.D. 200-700. However, around A.D. 700 prehistoric Mogollones began to dependmore heavily on maize as a dietary staple. By A.D. 1000, proportions of dietary may haveincreased by at least 19% over levels established in A.D. 700..

This research uses changes in the morphology of manos and metates to assess differencesin agricultural production among prehistoric Mogollon pithouse dwellers, A.D. 200-1000. Itbuilds, in part, on previous analyses of Mogollon manos by Lancaster (1984), Hard (1988), andMauldin (1991), but addresses some concerns raised by J. Adams' (1988, 1993).Prior Research: Manos

Paul Martin suggested that the variety and frequency of "types" of ground stone artifactscould be used to determine, in a general sense, a prehistoric group's relative dependence on wildrather than domesticated foods (Martin 1941:177; Martin and Rinaldo 1946). Mauldin (1991)credits Bartlett with the same observation as early as 1933. However, formal theories linking manomorphology with agricultural dependence are a recent introduction.

Lancaster (1984) measured the lengths and widths of manos from the Galaz site (LA635),and found that manos clustered into two categories (Type I and Type IT). These categories are therough equivalent of the "one hand" and "two hand" manos of common archaeological parlance.Lancaster also found differences in surface striations on Type I and Type IT manos. Type I manosfrom the Galaz site were typically used in a rotary motion, and may represent a "generalizedgrinding tool." Type IT manos were most often used in a linear motion, with striations runningparallel to the short axis, and probably were used to grind corn (Lancaster 1984:251).

More recently, Adams (1993) conducted experimental studies to examine the humanmotions and grinding effIciency involved in the use of different mano and metate pairs. The use oftwo hands on a large mano in a "trough type" metate was more efficient than the use of one handon a small mano in a "basin type" metate. The use of flat metates was yet more effIcient than troughtype metates because flat metates avoid some of the problems associated with the "fIt" between themano and trough metate pair.

Hard (1988) and Mauldin (1991) emphasized the importance of time stress to develop aformal theory linking mano morphology with agricultural dependence. As households becomemore dependent on maize, the time required to prepare maize should increase until, ultimately, itbegins to conflict with other tasks. Time stress could promote technological innovations that wouldincrease grinding effIciency, thereby reducing the amount oftime required to prepare maize (Hard1988; Mauldin 1991).

Mauldin's study of maize grinding in a modern Bolivian village demonstrated that grindingeffIciency positively correlates with mano surface area (Mauldin 1991:63). Mauldin also foundsome evidence in support of the I-hand vs. 2-hand mano dichotomy based on the surface areas ofmanos. Small manos, typically used to process chile and salt, had a mean surface area of 75 cm.2Larger manos that were used to mill grain had a mean surface area of 375 cm.2

Mauldin applied the ethnoarchaeological observations to the analysis of Mogollon manosfrom the Pine Lawn through Tularosa phases, in the Pinelawn Valley sites excavated by PaulMartin. Data used by Mauldin somewhat overlap data used in the present study since both studiesused manos from SU, Promontory, and Turkey Foot Ridge.

This research therefore builds on Mauldin's, but differs in three aspects. First, Mauldinused measurements listed in Paul Martin's published reports (Martin 1943, 1940; Martin andRinaldo 1950, 1947; Martin, Rinaldo and Antevs 1949). Martin described the "typical" size of

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manos of various "types" rather than presenting the actual dimensions of individual artifacts. It isnot apparent that Martin's "typical" sizes represent statistical means rather than subjective clusters.To obtain information on the grinding stones recovered by Martin, the present study usedexcavation notes, and direct measurement of manos stored at the Field Museum of Natural History,Chicago.

Second, this study uses mano data from 14 Mogollon Pithouse period villages, whereMauldin used samples from four. (Mauldin was interested in a broader temporal picture andexamined several hundred manos that postdate the pithouse periods.)

Finally, this study uses a finer-grained temporal scale. Mauldin grouped Pithouse periodmanos into Early (AD. 200-550) and Late (AD.550-lOoo) occupations. In this paper I assignartifacts to more specific occupation phases within the Early and Late Pithouse periods: EarlyPithouse period (AD.200-550) (also referred to as the Cumbre phase), and the Georgetown (550­6501700), San Francisco (700-800/850), and Three Circle phases (AD.800/850-1000). (Anyon,Gilman, and LeBlanc [1981], and Lekson [1992] discuss the chronology ofthe Mogollon Pithouseperiod phases). The determination was made by assigning each mano to the occupation phase ofthe pithouse from which it was excavated.

Manos from extramural or other undated contexts are not used in this research. Manos fromSU pithouse D were excluded because pithouse D contained a small Three-Circle phase pithouse(D-l) superimposed on a larger Early pithouse period pithouse (D). Martin did not distinguishbetween manos obtained from pithouse D and D-l.

Prior Research: MetatesThis research uses the ratio of basin to trough metates to infer changes in subsistence.

Specifically, this research assumes that changes in the ratio of trough metates to basin metatesreflect relative changes in the dependence on plants that have large achenes (maize and possiblypinyon) vs. other plants. This argument rests on two observations.

1) Metates are associated with plant processing and other grinding tasks. This is anestablished historical fact. Further, Adams (1988) conducted use wear studies that suggest thathistorically observed uses of metates are consistent with microscopic wear on prehistoric metates.

2) Trough metates are more efficient for maize processing than are basin metates. Adams(1993) conducted experiments with the use of basin and trough metates and found that it waspossible to grind twice as much maize with trough metates than with basin metates, in the sameamount of time. According to Adams, metates may be ordered hierarchically from highest to lowestefficiency, in the following order: slab metate-and-mealing-bin (set), full-trough metates, closed­trough metates, and basin metates (Adams 1993).

As maize processing becomes more important, grinders should use metates that are moreefficient. The ratio of efficient vs. less efficient metates should increase as the need to processmaize efficiently increases. Ifwe assume that the time stress that drives the need for increasedefficiency is related to increased agricultural output, then we may conclude that changes in theproportion of efficient metates are driven by changes in agricultural dependence.

Adams' research also suggests that, in the absence of selective pressure, metate users mightprefer to use basin metates rather than trough metates. A disadvantage associated with the use oftrough metates is that the user cannot vary the grinding stroke to relieve muscle tension. Basinmetates offer more freedom of motion, and the grinding stroke can be varied to relieve tension(Adams 1993).

In this research I assume that changes in the ratio of trough metates to basin metatesprovide a useful indirect measure of changes in agricultural productivity.

An aside: slab metates considered and discardedAdams also observed that the use of the slab-metate-and-mealing-bin tool kit induces less

fatigue than the use of trough metates, and is more efficient than basin metates. Adams does notoffer estimates of differences in the grinding rates that can be accomplished with trough and basinmetates. However, she does note that relief from muscle strain may enhance maize processing byallowing grinders to work longer (Adams 1993).

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However, the issue of performance differences between slab and basin metates is not aconsideration in this study. since mealing bins are not found in Mogollon pithouse villages.Moreover, Martin is apparently the only person ever to find a slab metate in a Mogollon pithouse.Inventories from the SU and Turkey Foot Ridge sites contain a large number of "slab metates,"however published photographs (e.g., Martin 1941:43 Figure 15) indicate Martin's "slab type"metates are probably basin metates. They have obvious ovoid surface depressions that are notconsistent with Adams' (1993 Figure 2) slab metates.

Mano Analyses: Results and InterpretationsThe following analyses are based on a sample of whole manos, and whole and broken

metates, from 14 Mogollon Pithouse period villages. For the purposes of this study, a "mano"includes any hand-held grinding stone that the excavators described as a mano, or Paul Martin's"rubbing stones." The latter are large enough to warrant description as small manos in theimprecise mental templates used by different researchers.

Data on mano length, width, shape and wear marks were obtained by direct inspection ofmanos in extant collections, and by examining detailed field notes and archived artifact descriptioncards. Information on Winn Canyon site manos was obtained by measuring to-scale illustrations inFitting (1973). Information on LA5407 manos was obtained from an unpublished manuscript inpossession of the Office of Archaeological Studies (Museum of New Mexico, Santa Fe).Information on the morphology, shape, and use of manos from Crooked Ridge Village weregenerously supplied by Jenny Adams (Arizona State Museum).

For manos that were available for examination, use wear was observed with a 7x handlens. Under bright illumination, faint striations could be observed on the surfaces of some of themanos.

Many manos were not directly available for study. However, index cards or recordingsheets that describe discarded ground stones frequently include sketch illustrations that depict theprevailing direction of use, in addition to measurements, and raw material. Such documents wereavailable for most of the manos excavated by Paul Martin, and many of the manos and metatesexcavated by Emil Haury at Harris Village and Mogollon Viilage.

Preliminary AnalysisThe purpose of the preliminary analysis is to identify different categories of manos, similar,

possibly, to the familiar" I-hand vs. 2-hand" mano dichotomy. Since different types of manos maybe used for grinding different substances (J. Adams 1993, 1989; Mauldin 1991), it is obviouslyimportant to identify manos that were most likely restricted to maize processing.

The histogram for all manos used in the present study (Figure 1) reveals a hiatus around110-115 cm.2, rather than at 75 square centimeters (as observed by Mauldin [1991:67]).Differences between Mauldin's distribution and Figure 1 in this research may be a consequence ofthe inclusion of post Pithouse period manos in Mauldin's sample. Perhaps late manos haddeveloped into two specialized and distinct forms.

The observed distributional break is never a complete hiatus. "Noise" may have beenintroduced to the distribution by factors such as the mean size of locally available raw materials, thereduction of "large" manos into "small" ones by extensive use (Adams 1992) and tool scavengingand reuse (Nelson 1991). Prehistoric mano selection and use may have been a probabilistic event,with soft, or tolerant upper limit size-performance thresholds for small manos.

To determine whether the observed distributional hiatus in mano size reflects realdifferences in mano use, I compared wear patterns, cross-sectional shape, and surface area withsize categories. It is easy to imagine two classes of manos diverging, over time, from one categoryof generalized hand grinding tools, so I analyzed manos from each occupation phase separately.

Analyses of variance of means (ANOVA) tests indicated that there were no significantdifferences of the mean mano areas of flat and convex manos for the Georgetown, San Franciscoand Three-Circle phases, although flat manos are smaller than convex manos during the Cumbrephase (this test is not shown).

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PhasePine LawnGeorgetownSan FranciscoThree Circle

However, mean mano area strongly differed by wear pattern for all occupation phases;these results are presented in Table I.

Table I: Mean Mano Area by Wear Pattern

-- Mean Surface Area (cm.2)-------- Wear Pattern ----------

Linear Multilinear Curvilinear N168 105 62 21146 112 79 20170 n.d. 98 40214 137 89 69

Although the cross-sectional shape of the grinding surface is not strongly associated withmano size, the surface wear pattern is strongly associated with mano size. Manos that haveunidirectional, linear wear have sample means greater than 146 cm.2 Manos that have curvilinearwear produce sample means less than 112 cm.2 These tests suggest that there are real functionaldifferences between large and small manos, and that the 115 cm.2 intermode observed in Figure 1is a reasonable, if fuzzy, boundary between the two groups.

Summary of Determination of Mano FunctionAnalyses of mano use wear, grinding surface morphology, and grinding surface area

strongly suggest that at least two classes of manos occur in Mogollon Pithouse village manoassemblages. Small manos tend to have surface areas less than or equal to 115 cm.2 and havemacroscopic wear patterns that suggest that their use is not restricted to maize grinding. Largemanos tend to be larger than 115 cm.2 and are relatively specialized tools that are associated withmaize grinding.

It is possible to examine diachronic changes in mean mano area for those manos that aremost likely to be exclusively associated with maize processing, in light of the two-categoryfunctional classification derived in the analyses.

Diachronic Changes in Mean Surface Area of Large ManosThis final mano analysis of those with surface areas greater than 115 cm.2 since

preliminary analyses suggest that the larger manos are maize processing tools.This research asks whether there were diachronic changes in the efficiency of maize

processing tools. I assume that changes in processing efficiency are a consequence of changes inagricultural dependence. The question may be framed formally as follows:HO: Mean mano areas for agricultural manos from different occupations do not have significantlydifferent means. (Agricultural dependence did not change diachronically).

HI: There are statistically significant differences in the mean areas of manos from differentoccupation phases. (Agricultural dependence changed).

The Cumbre, Georgetown, and Three Circle phases, were each represented by 140randomly selected manos, and their sample mean areas were compared. ANOVA tests mandateequal sample sizes and random selection (Levin and Fox 1983).Forty-five San Francisco phase manos were available, and I did not wish to constrain the ANOVAtest with small sample sizes; therefore San Francisco phase manos were omitted from the ANOVAtest.

The ANOVA test indicated that mean mano areas differ significantly by occupation phase(Table 2) and that the means increase through time. While there is no difference of means betweenthe earliest phase (Cumbre and Georgetown) there is a large difference of means between theGeorgetown and Three Circle phase manos.

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The mean area for San Francisco phase manos is listed in Table 2 (see also Figure 3)although they were not included in the ANOVA test. San Francisco phase manos are larger thanCumbre and Georgetown phase means.

Figure 2 presents histograms of mano areas, categorized by occupation phase. Figure 3presents plots of mean mano area, standard error and standard deviation, by occupation phase (formanos larger than 115 cm.2) Figures 2 and 3 include San Francisco phase manos that are not usedin the ANOVA test.

Table 2: Analysis of Variance of Means Test (ANOVA)Mean Mano Area by Occupation Phase(Sample Restricted to Large Maize-Processing Manos)

PhaseCumbreGeorgetownThree Circle

ManoAreaMean (cm.2)

183184219

F=16.32 P<O.OOO N=140San Francisco 194 N=45

Analyses (Table 2; Figures 2 and 3) presented here clearly suggest that mean mano areasincreased substantially between the Cumbre and Three Circle Phases. Again, no differencebetween the Cumbre and Georgetown phases was observed. A difference is observed between theGeorgetown and San Francisco phases. The largest increase occurs between the San Francisco andThree Circle phases.

Between the Georgetown and Three Circle phases, mano areas increased by 35 cm.2 Thechange in mano area, from a Georgetown phase mean of 185 cm.2 to a Three Circle phase mean219 cm.2 represents a relative increase of 20%. Based on this result, I suggest that prehistoricMogollones experienced a real agricultural intensification of at least 20% between AD. 650 andAD. 1000. In other words, by AD 1000 maize grinders processed at least 20% more maize thantheir AD. 650 counterparts, in the same amount of time.

Metate Analysis: Results and InterpretationsWere there changes in agricultural productivity between the Early and Late Pithouse

periods? The question is reframed in the form of hypotheses regarding changes in the intensity ofuse of different kinds of metates.

HO: There are no significant temporal differences in the distributions of different metate types.(There is no evidence for diachronic changes in the dependence on maize.)

HI: There exist significant temporal differences in the distributions of metate types. (There existsevidence for diachronic changes in the relative dependence on maize).

Pearson's chi-square (X2) test is an appropriate statistic for determining whetherdistributions across categorical variables may be explained as a consequence of chance (Levin andFox 1983).

AnalysisThis analysis of metate data is rendered complex by the presence of both whole and

fragmentary metates in the sample. As a general trend, ignoring whether the artifacts are wholemetates or partial fragments, the ratio of basin metates vs. trough metates decreases through time.That is, in early occupations (Cumbre phase), basin metates outnumber trough metates. Insubsequent phases, trough metates outnumber basin metates. The trend is statistically significant

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(X2=35.88, df=6, P=O.OOO), with a proportional reduction of error (Guttman's coefficient ofpredictability or I) PRE=0.26. (See Levin and Fox 1988:354 for a discussion of the I coefficient).

Unfortunately, a separate analysis of the ratios of fragments vs. intact metates of differenttypes is not supported by the low frequencies of intact metates in this data set. If samples werelarge enough, we could arrive at some estimate of the intensity of the use of different kinds ofmetates. For example, we could generate preliminary estimates of use-lives based on the ratio offragments vs. intact metates (with corrections for differences in the lengths of differentarchaeologically-defined phases, and the effects of scavenging).

Samples of fragmentary metates are somewhat larger. Given that at present there exists noway to account for scavenging of intact metates from abandoned sites or rooms, the prudent courseof action is to eliminate whole metates from the analysis. Figure 4 illustrates the diachronic trend inthe ratio of broken trough metates to broken basin metates. Again, the trend suggests that troughmetates become increasingly important relative to basin metates. Associated chi-square tests of thedistributions of broken trough and basin metates, by phase, are statistically significant (X2=34.52,df=6, P=O.OOO, PRE=0.23).

The trend in the ratio of fragments of trough metates to fragments of basin metates, and theassociated chi-square test, suggests that there were statistically significant increases in the use oftrough metates (as compared to basin metates) from the Cumbre through the Three Circle phases.From this increase it is inferred that agricultural productivity generally increased from A.D. 200 to1000.

Further, the greatest rate of increase seems to have occurred "between" the Georgetownand San Francisco phases. As with the mano analyses, the metate data indicate that maizeprocessing technology changed substantially beginning between A.D. 550 and 700.

Confounding factors considered and dismissedOther factors may have contributed to this diachronic change in the ratios of different kinds

of metates, or to the increase in mean mano areas. Constructive preliminary comments on thisresearch questioned whether differences in the uses of sites, or in the formation of specificdepositional contexts, could have biased the results. For example, diachronic changes in theoccupation length of sites may differentially affect the frequency distributions of different artifactclasses. Also, context-dependent differences in the deposition of different types of manos andmetates could bias this research.

Schlanger studied frequency distributions of one-hand manos, two-hand manos, andtrough metates, from the Dolores area of southwestern Colorado (Schlanger 1991). Schlangercompared sites that were occupied for long periods against short term sites and found evidence fordifferences in the content of extramural-fill and intramural-floor assemblages.

However, close inspection of Schlanger's data indicates that the relative proportions ofone-hand to two-hand manos, ignoring depositional contexts, is not affected by the duration of siteoccupation. For short occupation sites the ratio of one hand to two hand manos is 0.25. For longeroccupations the ratio is 0.27. The associated chi-square test (mano type crosstabulated by siteoccupation length) is not significant (X2=1.16, df=l, p=.28). In any case, analyses that are notcentral to this research suggest that the patterns of long-term site use did not differ from the Earlypithouse through San Francisco phases. Three Circle phase villages may have been the loci ofslightly more intense use in the form of longer occupations or more reoccupations.

Since the present study uses manos from fill and floor contexts, if Schlanger's research hasany application to Mogollon pithouses, then her data suggest that differences in the long term useof sites would not bias my results. The analyses presented in this paper are not derived from datathat were restricted to one kind of depositional context.

Is the current study biased by the exclusion of extramural assemblages? Adams (l992b)examined the groundstone assemblages from pithouses at Crooked Ridge Village. Adamscalculated Brainerd-Robinson coefficients of similarity for floor and fill assemblages by artifacttype.

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The variation in ground stone artifact types, however, seems to be equally represented in theassemblages from the fill and floor, from structures that filled with trash and those that were fillednaturally, and from pitstructures that were burned and unburned. How structures were abandonedand post-occupationally ftlled impacts some aspects of the ground stone assemblage and theseimpacts must be considered in any discussion of the development of grinding technology. (J.Adams 1992b).

In other words, Adams' analysis of the Crooked Ridge Village assemblage indicates thatthere are no differences in the kinds of ground stone artifacts deposited in floor and fillassemblages at Crooked Ridge. Adams' results are consistent with my close inspection ofSchlanger's data from the Dolores area. My use of ground stones from floor and fill contextsreduces the risk of the introduction of systemic bias... a risk that seems quite small to begin with inlight of Schlanger's and Adams' research.

A curious coincidence of eventsParticularly interesting is the rough temporal coincidence between the advent of the

development of increasingly efficient grinding tools, and the introduction of larger kerneled, higheryield varieties of "maize de ocho" around AD. 700 (Adams 1993; Galinat 1987; Upham,MacNeish, and Galinat 1987).

Analyses in the present study suggest that tool efficiency did not change from the EarlyPithouse period to the Georgetown phase (AD 200-650), but began to increase rapidly during theGeorgetown phase (AD.550-650) through the Three Circle phase (AD. 800-1000).

These dates are obviously coarse estimates, and critics of this research will be able to picktheir flavor of interpretation. A skeptic might argue that the mean Georgetown phase mano area of184 cm.2 represents early Georgetown phase manos, and that the San Francisco or Three Circlephase means represent late manos from those occupations. With effort we could extend the rangefor the probable advent of changes in groundstone morphology to AD.550-1000... which makesthe "smoking gun" (temporally speaking, anyhow) of the new maize seem relatively unimportantfor changes in the maize grinding technology.

Extraordinary efforts to skepticism are not warranted, may not even be helpful, andcertainly offend the sensibilities of anyone concerned with parsimony. To argue that manos fromthe Georgetown phase were biased towards AD. 550 (as opposed to AD. 650), or that manosfrom other phases are somehow biased towards later dates, would add layers of assumptions tothis research. In any case, to paraphrase Lekson (1992), in the absence of a scalpel, we might aswell use a mallet. Perhaps future excavations will provide groundstones with finer temporalassociations. In that event, we may eventually be able to reexamine how closely the advent ofchanges in the ground stone morphology coincides with the introduction of high yield maize.

Possible Impact of the "New" MaizeTo understand the potential impact of the new maize you must consider the history of the

"old" maize. Maize was available to prehistoric Mogollones by 1300 B.C. or perhaps earlier (Wills1985). Minnis has described the introduction of domesticated plants as a "monumental nonevent"in Southwestern prehistory (Minnis 1985b). Wills views the early use of maize as a means ofenhancing an essentially wild foods diet (Wills 1985). As mentioned earlier, many researchersview the Mogollon Pithouse periods as predominantly hunting-and-gathering oriented. Their viewseems to suggest that subsistence strategies in the region did not change remarkably over a periodof 2300 years (B.C. 1300 to AD. 1000). This research shortens the span to an interval from B.c.1300 to AD. 700 (2000 years).

Even so, a two thousand year interval of subsistence stability is remarkable in light of whathappened after AD. 700. Most suggest that by AD. 1000 agriculture was the dietary mainstay ofthe Mogollones, supplemented by some hunting and gathering. The Classic Mimbres phase (AD.1000-1130/1150) Mogollones lived in large population aggregates; large villages typically haveseveral roomblocks with hundreds of rooms in each (e.g. Swartz, Galaz).

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From AD. 1000 onward, Mimbreno subsistence and settlement patterns seem remarkablyunstable. Minnis (1985a) suggested that agriculture was so intensively parcticed that Classic phaseMogollones may have destroyed most of the riparian woods growing in the vicinity of theirvillages. By AD 1030/l050, the core of the Mimbres Mogollon was either abandoned, or all oflarge villages had fragmented into smaller communities. Ben Nelson (Nelson and LeBlanc 1986)describes subsequent reoccupations of the Mimbres area as episodes of "short term sedentism."People move in, build settlements, grow maize for a few years, and move on to new settlements.

Could the use of the new maize pushed the Mogollones into a fundamentally unstablepattern of resource use? Little enough is known of early or late varieties of maize, and moreresearch into the growth habits, caloric yield, and nutrient requirments is urgently needed.However, Galinat (1988) suggests that the earlier variety of eight row maizeproduced relatively small (short and narrow) cobs with small kernels.

In contrast, the later variant was considerably larger and had larger kernels. The largerkernels required larger cobs. Large cobs would of course require larger stems (cornstalks) tosupport the increased mass. The entire anatomical infrastructure of the plant would have had toincrease proportionally, to support the larger cobs produced by the new, post- AD. 700 maize.The nutritional demands that this plant would place on local soils must have been remarkably high,by comparison with the older, small-cobbed ancestor. In this context, it seems quite possible thatthe new maize caused very high soil depletion rates... forcing Mogollones to move fairlyfrequently except in locations with exceptional fertility.

ConclusionThis research used changes in the morphology of prehistoric manos and metates to track

changes in the dependence on agricultural domesticates in the Mogollon region of SouthwesternNorth America from AD. 200-AD.1000. Analyses indicate that there was a 20% increase in theproduction of maize from the Georgetown phase through the Three Circle phase. This increase wasmost likely driven by the availability of a higher yield variety of maize introduced around 700 AD.

Surface Area (Square centimeters)

ReferencesAdams, Jenny L.1992 Technological Development of Manos and Metates on the

Hopi Mesas. Kiva, 58(3):331-344.

1988 Methods for Improving Ground Stone Artifact Analysis:Experiments in Mano Wear Patterns. In Experiments inLithic Technology, edited by Daniel S. Amick andRaymond P. Mauldin, pp.259-296. BAR InternationalSeries 528, Oxford, England.

Adams, Karen R.1993 A Regional Synthesis of Zea Mays in the Prehistoric

American Southwest. In Corn and Culture in thePrehistoric New World, edited by Christine A Hastorfand Sissel Johannesson. Westview Press, Boulder.

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Synthesis of South-Central and Southwestern New Mexico,by Steven A. LeBlanc and Michael E. Whalen, pp.l42-204.Manuscript on fIle with the Bureau of Land Management,Albuquerque.

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Sequence. Kiva, 46(4):209-225.

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Cordell, Linda S. and George J. Gumerman (eds.)1989 Dynamics of Southwest Prehistory. School of American

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the Winn Canyon Site. The Artifact, 11(1&2): 1-94.

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12

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