31 October 1969, Volunmc 166, Number 3905

Settlement, Farming Technology, aniEnvironment in the Nochixtlan VallcA valley of Oaxaca provided the geographical base fdevelopment of Mixtec culture: 700 B.C. to A.D. 1 6C

Ronald Spo

Six decades of intenisive reseairchhave produced numerous studies on ther-ise of civilization in Mesoamerica.Conventional archeological and ethno-historical investigations of the prehis-toric developments in central Mexicoand in the Maya area hCave been auLg-menited in recent years hy several morerigorously defined problem-orientedstudies. Multidimensional reseairch onthe cultuLral ecology of the valleys ofNtexico, Tehuacan, and Oaxac(a halsVielded substantial, knowledge of cul-turIal evoluLtion in Mesoamerica aLnd atthe saim.e time has served to refine thetheoretical framework for observingand explaining devclopmiiental processesthat were operative in the rise of civili-zation here and elsewher-e (1, 2).

During the past 3 years these studieshave been extended into still anotherarea, the Mixteca Alta of northwesternO1axac,a (Fig. ). Abundant archeologi-cal and docunmentary resouLrces and theexistence in the larea of the moderndescendants of ancient peoples affordan exceptional opportunity to employwhat Strong callled the "direct historicallapproach" for studying the long-rangecultural change from prehistoric andprotohistoric time.s to the historic pe-riod (3). Starting with living peoplesand the early historic aIccounts of peo-The aUthor is associate profcssor of anthli-opol-

oev, Vanderbilt Uniicrsit\, Nashvillc. Tennicssce372'03.

ple who haid lived inpLished our inquiry farthe prehistoric past to itural origins, for patterment and change, and f(of these developments wmicrogeographical contchixtlaln Valley of north

This article examines Iof populltion growth, Icand cultural developnmechixtlan Valley. Our partion has been set forthby Cook and Fletchetreated relationships betion and cultural develValley of Mexico durirtoric, and modern timestaites that "the Valleya long historv ot overpOne way of relieving psure wias by maintenanctrade and tribute whiclagricultural specialists tthe agricultural produtareas." Another responssures, in both ancientti mes, has been temnpoInent emigration. Thesehave heen of particulcaaInd economilc significaning the course and di.tural developmnent, notMexico hut throughoutica.

In accdition to the iml

SCIENCE:

oration, trade. and tribute in allowingthe maiintenance of populations toolarge to be supported by local agricul-tulral production, I believe that theretlre two additional alternative responses:territorial expansion by political means(possibly, hut not necessarily. relatedto tributary expansion) and technologi-cal innovation. These five alternativeshave heen available to expanding civil-izations in both hemispheres since farm-for ing, village life, the accumulation of

0. exploitable surpluses, and higher levelsol social and political integration be-came possible in Neolithic and Formna-

res tive timiecs. While all variables are worthyof consideration, we will be concernedwith only one-technological innova-tion and its relationship to population-rowth. Archeological, historical. and

the area, we ethnological stuLdies in the Nochixtlanther back into Valley suggest that there is a causalsearch for CaIl- relationship between demographic pres-ns of develop- sure and certain technological innova-or explanations tions that have taken place in the Val-ithin a specific lev dtLiring anicietnt, protohistoric, andtext-the No- historic times.west Oalxacal.the relationishipcall adaptation, The iXlixteca and the Xlixtecsnt in the No-rticulaLr orienlta- The Nfixteca is the geographicallyto soniec extenit diversified area which comprises ther who hrietly western third of the modern state oftween populal- Oaxaca. Parts of the region are high,lopment in the cool, and moderately moist (the Alta):ig ancient, his- other atreas are low, hot. and semiiarids (4). Fletcher (the Baja); and still other areas are low.of Mexico has hot. and humid (the Costa alnd portions)opulation. . of the Baja). These three mnajor zonessopulation pres- were occupied by closely related Mlix-e of systems of tec-speaking peoples at the time of theh allowed non- Spanish conquest, and more than 250,--o be fed f'rom 000 of their descendants continue toction of other reside in the area (5). Their most nota-e to these pres- ble cultural achievements, however,t and modern were centered in the Mixteca Altarary or permia- (Fig. 2).related factors When the Spaniards arrived in the

tr sociopolitical 1 520('s, the Mixtec people were orga-.ce in determin- nized into many small kingdonms whichrection of caIl- were governed by powerful rLuling lin-only in central eages that controlled the most produc-Middle Amer- tive lands in the Nochixtlan Vallley and

elsewhere in the Mixteca. In return forportance otf mi- political, social, and ceremoniial leader-

55731 OCTOBERZ 1969

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Fig. 1. Map of Mexico, indicating the locthe Mixteca.

ship, economic security, and protectionwhich were provided by the rulingelites, the citizens of a kingdom wererequired to pay tribute, to provide laborfor the fields and houses of the rulers,

cation of Oaxaca and the three subareas of

to support the religious cult, and toserve in war. The institution of theMixtec regional or community king-dom (termed "cacicazgo" by the Span-iards) was firmly established long be-

Fig. 2. Map of central and western Oaxaca, indicating locations of the three Mixtecas,the valleys of Nochixtlan and Oaxaca, and several of the principal towns in the area.

558

red clays of the Yanhuitlan-Huajuapanseries of deposits. The well-developedsoils which have formed on the Yan-huitlan beds consist of up to 60 centi-

SCIENCE, VOL. 166

Mixteca AJitCosts

fore the Europeans colonized the area,and continued in gradually alteredform for many decades after the Span-ish conquest. Much is known of theMixtec community and the cacicazgobecause of the existence of abundantdocumentation as a result of litigationover royal lands and titles in the 16thcentury and because of the preservationof pictographic historical documents,several of them dating to pre-Hispanictimes. This corpus, still only partiallyutilized, serves as the basis for directhistorical inferences about the ancientculture of the Nochixtlan Valley (6).The Nochixtlajd Valley, about 450

kilometers southeast of Mexico City onthe Pan American Highway, is the larg-est area of relatively open and levelland between the Valley of Oaxaca 100kilometers to the south and the NexapaValley at Izucar and the TehuacanValley, more than 200 kilometers tothe north. It was probably the singlemost important area in the Mixtecathroughout its occupational history andcontinues to be the most fertile, pro-ductive, and intensively settled of theseveral valleys of the region (Fig. 3).The Valley is composed of four ma-

jor sectors: Yanhuitlan in the north-west, Yucuita in the north, Nochixtlanin the east, and the Jaltepec sector inthe southeast below the confluence ofrivers flowing from the other three sec-tors. From the northern and northwest-ern extremities to the southeast margin,the Valley measures apppoximately 25kilometers. It varies from 5 to 10kilometers across and consists of aseries of narrow valleys situated be-tween and among high mountainranges and is punctuated by numeroushills, buttes, and piedmont spurs. Levellands are found only in the central por-tions of the large and small valleysand in areas where artificial terracinghas altered the natural contours of theland.

Preliminary geomorphological in-vestigations conducted by Michael andAnne Kirkby during the summer of1968 indicate -that the basic under-stratum of the Valley is a fairly re-sistant rock formation composed ofsome deposits- of Jurassic and Cretace-ous age, others of Cenozoic volcanics;with gneiss outcrops appearing particu-larly in the southeastern end of theValley. Interbedded with and overlyingthese formations were the buff to deep

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meters of dark grtav to gray-hrow n claysoil, overlying a 50- to 250-centimeter1Iale gray to xshitish lime accumulationlayer, which itself usually overlies little-weathered Yanhuitlan beds contaliningsonie lime nodLules. The lime aCCumIlu-lation lalyer has a tough claylike con-sistency in the soil, but hardens on ex-PosuIc to a tOugh catliche niaterial(locally tcrimned "endceque") which hasb-een uLsed in the VLilley s a huildingstoIne sinic Fornaitive timiles. Prohablythis caliche cover extended over miostof the Valley in presettlemcint tinies; itcertainly precdiates the extensive visibleer-osion in the area and nmuLst havefornimed ulndlel conditionsi which did notCecourage gullving; this sLIggests aheallthyr veta,ition cover proablynatura11-.l oalik and pine forest appropriateto the 21(100- to 2500-meter elevation ofthe Vallcy. When analyzed, pollen saln-p1cs taken. 1tromm stratiti-raphic tests willhelp greatly in estaLblishing the nItTreof enxvironmentail conditions dLI-iurinj0Formait ve and( later tilmlcs.

Fo)rmaiative Stage: lie Criuz hlase

fIthouIgh remiltins ot ossifiedl maml-mioth were dliscovered duirinm thesite sUrvev of the Vailleyv no evidenceof contemporaineous hunian life c Uldhe lfound in excavaltions carried out atthe point of discovery (7). At the siteof YuLzalnIuu near Y.anhuitlaIn, I oretizorecovered a very cruide asseniblage ofchipped stone tools fromii deep ailluviIImin aIssociation with a hearth that datedto approximately 2000 B.C. (8). Suir-VeVs of 130 sites failed to produice ain-other precerianmic site. In fact. no sitecoulld definitely be said to predate the1--ate Formitive, set at around 700 B.C.I his contrasts mairkedly with the situLal-tion in the vailleys of Oaxaca antdI ehulacan. in Chialipas, aind on the coalst( (juatitelil"11a where sedentarx villagesfretound in Early Formaztive times

()). P'resenit indicaLtions are thait theNochixtlan Valley was peripherall tocarliest devclopmaents in aigriCuLltuLre andscttled village life, and th.at it becamie.In iiportainit occuLpationail zone afterthis pattern Wlas well estalbflished inother regiolns.

I-he eairliest substantial occupationin the Nochixtlan Valley is assigned bycerlillic crossties with the ValCle\ of()a\aca and by rellatixve stratigraphicplacement to a period extending fr:om.iro.nd 700 B.C. to aLhout 20t) B.(( 10). Ceramic inclicators of the LalteFormaitiv.e CruL7 pha;se are presenit in 2 131 OCTOBER 1969

of the 1 30 sites surveyed, bLit onlv Sof these sites were intensively occupiedlor Lttilized (2). Most sites were locatedon low-lying piedmont spurs that pro-jected inlto the vldley from hills, buttes.and peripheral mountain ranges. Thechoice of locacition for settletiietit, justabove hittadjacent to fertilc and lcvelhottomllands, conforms to a patternobserx ed in contemporaneous aind Clear-lier mnlifestations in the Vallev ofO.ax.axca (11).The (ruLz phIlase Nwas cncounlitercd

stratigraphical ly in excaivations atYucUita. hbUt at present very little iskinowtn of the totall material culture otarchitecture of these eatrly vallev farm-ers. Sotmne otf the structures foLnd intest trenches were hbilt of cuit o1rroLugThlN shaped stone and formled intostraliht-sided malsonrv walls which in-tersected to tfor-mi contigluoLsaISpartment-like cells of indetermina,te tise. Asso-

ciated shallow pits were dug for cook-ing, rubbish disposal. or for other pur-poses and were found to contain animalhones, ash, pottery griddles, large pot-tery fragments. manos, and metates.Very few chipped stone implementshave beeti encountered in Cruz phasecontexts.

Large Tan jars, usuLally painted onthe sides .and rims with red or darkorange paint, were produced and uti-lizedt b\v the thous.ands. These are asso-ci.ated with severail decorated Grav andRed-and-White wares and distinctivefigurines which serve to link the No-chixtlan Valley with Oaxaca, Tehua-caln, and Chiapas (hiring the LateF-ormatlie perivodL.

Settlemielnts were locatedL otl the pro-jecting sptirs of land which are invari-a1by area,Is oft diark brown soils overly-ing(y red clav soils. While two yNpes ofland verc axvailahle to the first farm-

'i.:Yucunudahui ..

Chachoapan. S I tY~~~~ucuita },....,.

N..

. . .....-. '.. /Nochixtian

:::Etlaton go:

Nochixtlan ValleyModern communities

Major classic sites .......

| > ~~~Piedmont ,@-.% iI- ggiThi< Mountains ,,.,,& alec. Ja itepec.-'.-0 5 10 km

Fig. 3. aptof the Nochixtia.n \alle, indkicating the fouLr major geographic zindsurvey sectors of Yanhluitlarl. YucUit;,. Nochixtlitn,inmd .Ialtepec: six import,ant Valleytouns; and the location (if five of the I.troeTcst nmd most important Classic Period(Lazs Flores ph;asee) sites.

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Fig. 4. Four Ramos phase figurine frag-ments from YUcUita.

ers-valley bottom and hillside-thelevel, generally more fertile, black soilsof the valley floor and margins wouldhave been preferred. At that time, priorto the massive alluviation of the valleyfloor, seasonal flooding and relativelyeasy diversion of streanm waters wouldhave rendered the valley floor and itsperipheries more fertile and productivethan the irregular contours of the oak-covered slopes and mountaintops. Withso few sites being intensively occupiedin the valley, vast areas of flat, low,fertile, and easily tillable land wouLldhave been available with little or nopressuLre on land resources.

Early Classic Stage: The Ramos Phase

A marked increase in the number ofsites is noted for the Ramos phasewhich is believed to have begtun around

560

-~-~

200 B.C. and to have lasted until A.D.250 or 300. Ramos sites and levels aredefined by the presence of a ceramiccomplex dominated by three varietiesof plain Tan bowls and jars. Relativefrequencies of Red-on-Tan jars andplain or decorated Gray wares are muchlower than in the preceding phase, butexcellent modeled figurines continuedto be made (Fig. 4).To date, 56 Ramos phase sites have

been found, and 24 of them seem tohave been intensively used. Settlementswere in the same areas as before, onthe piedmont spurs. Experimentationwith a new occupational niche is sug-gested by the appearance of a few siteson mountain- and hilltops, but no ap-precia,ble shift in the location of sitesis observed. There is, however, a sub-stantial change in the size and elabo-rateness of settlements. They are morenumerous, larger, and architecturallymuch more complex than Cruz phasesettlements. One cluster of mounds,plazas, and buildings at Yucuita islinked by an extensive systenm of sub-terranean tunnels and covers more thana square kilometer (Fig. 5). It is of suf-ficient dimension to suggest that therehad been a concentration of economicresources and political power sufficientto command the creative participationof a large number of people. Cere-monialism is clearly important and thisis reflected in the massive architectureand evidence of ritual (including can-nibalism) in and around Ramos phasestrLIctures.

Population was at least double thatof earlier times, and it can be assumedthat increased pressure was being ex-erted against the productive potentialof the Valley. Farming strategy, never-theless, did not vary greatly from thepreceding phase. There is no indicationof appreciable alluviation at this time,nor is there any significant disconform-ity between Cruz and Ramiios depositsthat would suggest substantial altera-

tion in settlement-environmental rela-tionships. There is no indication of hill-side erosion, steep slopes apparentlynot being utilized for agriculture at thistime. Settlements continued to hug thespurs and low-lying ridges, and valleylands were farmed as before.

Later Classic: The Las Flores Phase

No less than five major ceremonialaLnd civic centers were developed dur-ing the period which began aroundA.D. 300 and gradually phased outsometime between 900 and 1 100. Yu-cuita remained extremely important.as evidenced by massive extensionsand relocations which took place dur-ing this phase. Of equal, or perhapseven greater, importance was Yu-cLfiudahui which sits astride a high,steep-sided mountain ridge just north-west of the modern town of Chachoa-pan (Fig. 6) and directly across theYucuita arm of the Valley from Yu-cuita (12). Similar civic-religious cen-ters were developed at Cerro Jasminnear Yanhuitlan, at Etlatongo in thecentral region of the Valley, and atJaltepec in the far southeastern ex-treiiity of the Valley. These sites wereeither clustered on and around highbuttes rising from the valley floor, onhigh ridges, or on mountaintops. Doz-ens of smaller sites are found in analo-gOUS locations in all parts of the Valley,but most notably in the Nochixtlansector. These lesser sites consisted offrom one to three central mounds, aplaza area that was paved or plastered.usually several stone alignments of un-determined function, stepped terraces,stelae, and sometimes one or two sub-sidiary plaza-mound complexes.The ceramic inventory associated

with Las Flores sites is simple, rela-tively drab, and undistinguished. PlainGray wares reemerge, and togetherwith a fine tempered variety of orangepainted Orange or Tan-Cream ware, amedium to coarse tempered Orange-Rust ware, and coarse Brown jars,dominate the ceramic complex (13).

Ninety-two sites were occupied, andthis, coupled with the fact that unusu-ally heavy and extensive deposits ofLas Flores ceramics are found on 36of these sites, would indicate an up-surge in population (14). Not only aremore sites being occupied but there isalso a new emphasis on larger centers,probably increased clustering of popu-lation, and a shift from earlier timesin the choice of site location. The val-

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ley floor continued to be intensivelyfarmed, but many settlements weremoved above the low-lying ridges andspurs onto higher elevations. The de-sire to open additional farmland alongthe formerly occupied lomas and pied-mont may well have furnished theimpetuLs for the shift in settlement. Thenumber and size of sites and the heavyconcentrations of ceramics suggest atleast a doubling of population sinceRamos times. The inferred intensity ofoccupation and the number of largequasi-urban centers (five covering atleast 1 square kilometer) indicate thata 150 percent increase in populationwould not be out of reason.

Examination of alluvial deposits re-

veals the existence of a medium layerof black soil which contained LasFlores and earlier materials that weredeposited during Las Flores times. Theblack layer can still be found in un-disturbed areas on the mountaintopsand on certain steep slopes. The exist-ence of a black stratum in the valleyalluvium is proof that the mountainsand slope6 were being intensively util-ized in response to increasing demo-graphic pressure. Hillside terraces,many of which are presumed to beagricultural, are found adjacent to ma-jor Las Flores centers.

External ties, as reflected by ceramicinventories, architecture, and locationof sites, are very strong with the north,

manifestations being found in theTamazulapan Valley in the MixtecaAlta, at Huajuapan and Tequixtepec inthe heart of the Mixteca Baja, and pos-sibly as far away as Xochicalco andTeotihuLacan. There are certain affilia-tions with Monte Alban III A-B sitesin the Valley of Oaxaca, but these havenot yet been clearly defined (15).

Postclassic Stage: The Natividad Phase

From around A.D. 1000 to the Span-ish conquest, the number and size ofsites greatly increased. At least 111 ofthe 130 sites show definite signs ofoccupation, and 78 of them were in-

Fig. 5. The ancient archeological site and modern community center of Yucuita, shown in the lower portion of the photograph.Remains from all major phases of cultural development-Cruz. Ramos, Las Flores, Natividad, Convento, and Modern-are repre-sented in the site which measures more than 2 kilometers north to south and 1 kilometer east to west. Across the river fromYucuita, to the west, is the ancient site of La Pefia, and to the northwest, in the upper right, is the modern town of Chachoapan.[Mexicana Aereofoto]31 OCTOBER 1969 561

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tensively used. Many mlounitain top set-tlements of the Las Flores phase. in-cluding several large centers, wereabandoned or only partiallVy utilized.reflecting the pronounced tendency forsettlements to once again cluster alongthe piedmont, piedmonit spurs, and low-lying ridges (16). The surviving Nati-vidad architecture pales beside theimpressive Las Flores strUctural com-plexes, but the very extensive aCCUImIU-lations of pottery and scattered stonemlake it apparent that a massive ex-pansion did occur. Distributions ofsherds are frequenitly found to extendcontinuously ftrom 1 to 3 squLare kilo-meters, and persisting nucleationi of set-tlement is quite evident. The northernend of the Valley around Yanhuitlanseems to h.ave been filled to near capa-city, with 52 of 58 sites in the sectorshowing signs of moderate to heavyoccupation. A descending ridge sy,stemrunning fronm Yanhuitlan to Sayultepec

and Etlatongo, some 1 to 2 kilometerswide and 10 kilometers long, shows analmost continuous concentration ofNatividad phase ceramiiics. Even a fewof the alluvial lands, so valuable foragTriculture, reveal limited occupation:this is particularly noticeable in theYanhuitlan sector and in the vicinityof Nochixtlan.A number of new cultural fealtures

appear in the Nochixtlan Valley. Themlost prominenit feature of this emerg-in*g pattern is the Mixtec ceramic comIl-plex xvhich wNe know to have been car-ried hy the Mixtec-speaking people ofthe Valley in 1520 and later. AlthouLghpositive dating on the initial appear-anice of the various components of thecomplex is lacking. it preceded theSpanish conquest by several hundredvears and continued to be a featuLre ofthe culture long after.The basic Natividad wares reflect the

same kind of slow persistent change

thalt had characterized the total mate-rial culture of the Vallev for many cen-turies. Continuities in vessel fornis,paste texture, and modeling techniquLesare, however, associated with the ap-pe,arance of several additional formiisand some impressive new decorativetechniques. Instead of having an overallcoaLting of thin orange paint as in eair-lier times, the dominanit Creami orOrange bowls were decorated withvariable combinations of' well-execuLtedportraits, lines, dots, and geomletr-icforms applied with red or brown paint(Fig. 7). Identical design elements werealso combined to decorate a beaultil'ulnew polychrome ware ("Mixtec Polv-chronme") which appears in the area f'orthe first time, although not f'requenitly.Three varieties of incense bulrlners,trough-handled ladles, pottery graters,mold-made figurines, fine Gray vesselswith effigy tripod legs, and sonme dis-tinctive incised and punctuated minia-

Fig. 6. At left is the modern community of Chachoapan. At center right, northeast of Chachoapan, is the community of Coyotepec.The ancient Classic (Las Flores phase) site of Yucufiudahui extends along the summit and uipper slopes of the mountains north-west of Chachoapan and can be seen in the uipper-right corner of the photograph. [Me\xicna Aereofoto]

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ture vessels. called 'ollitas." ar-e comn-monlv found together (17). Niany ofthe svmbols used in decoriating potterywer-e also found in picture manuscripts,in murals, and in stone, bone, andwood carvings.

Few traces of intact architecturehave survived more than 400 years ofstone robhing and reuse, but mlassiveacCUMUlations of sherds, bone, scat-tered building stones, and stone toolsmake it clear that unprecedented pres-sure had been exerted on the produc-tive resources of the Valley. It is prob-able that normal population gro\vthwas augmented by movements of otherNM ixtec-speaking groups into the areafrom the north, that there was more orless continuous social and econom iccontact and interaction with the Puebla-Tehuacan areas, and that these contactsand migrations were responsible formi.any of the cultural modifications inthe Nochixtlan Valley dLuring the Post-classic period (18). It is also likely, ofcourse, that customs, techniques, andgoods evolving in the Valley were "fedback" to the north, and that this cul-tural interchange existed for many cen-turies before and after the Spanish con-quest. Many of the specific designelements found on materials pertainingto the Cholula phase at Cholula and tothe Venta Salada phase in the Tehua-can Valley are repeated in Nochixtlan,hut, with the exception of Polychromeand rather distinctive Gray tripod ves-sels, these tend to be absent in areasfarther to the south.

Unusual demographic pressures inthe Nochixtlan Valley made it neces-sary to use all available bottomlandthat was not occupied. However, eventhis appears to have been inadequateto meet the needs of a rapidly expand-ing population. But without substantialimprovement in an agricultural tech-nology based on hand labor, the useof the digging stick, and apparently al-most total dependency on rainfall andsome diversion irrigation, no substan-tilal increase in productivity could heexpected.

Purposive Erosion

The Mixtecs of the Valley respondedto these needs by constructing stoneand rubble dikes designed to trap waterand eroding soils as they descended thenatural drainage channels that extendedfrom the mountain to the valley floorduring the period of heavy summerrunoff. These dikes, built of coursed31 OCTOBER 1969

Fig. 7. A "Red-on-Cream' vessel of the Natividad phase from the Nochixtlan Valley.[Courtesy C. Moser]

stone and rubble, were I to 4 metershigh aind from 10 to 200 meters long.Modern farmers, who continue to con-struct these terrace systems, find thatin 2 to 3 years sufficient soil (lamza)can be accumulated in a new terrace(ter-raza, triticlierar, or ho)rdo) to formlevel and quite fertile farm plots, andthey produce excellent yields of corn,grain, and vegetables. The plots, whichrange from a few hundred square feetto 10 hectares. can be worked for aslong as the system is maintained, andmany terraces have been worked sinceantiquity (19) (Fig. 8).

Farming strategy in Natividad timeswas (i) to continue to work the valleylands. (ii to till limited areas on moun-tain- and hilltops where the old darksoil overlying the caliche could be re-tained on more or less level plots (iii)to trap the black top soil or underlyingred soils in small V-shaped valleys andat the heads of larger valleys. The newstrategy devised in response to increas-ing need led to appreciable expansionof arable land and productive potential.The Kirkbys' preliminary geomor-

phological investigations indicated that,once the black soils from the slopes

had been removed by ta combinationof use (and erosion, it wals necessary, ifthe laina-bordo system was to be mIain-tained, to intentionally cut downthrough the caliche layer at the edgeof the valley and expose the underlyingsoils of the Yanhuitlan beds. Once aninitial experiment or accident of thissort had occurred, the predictable se-quence must have been clear to everyfarmer in the Valley. Gullying cut backthe red Yanhuitlan beds, progressivelyundercutting the caliche layer upslope.Below the gullied area, farmers couldtrap and farm the red soil which waswashing down and create new farm-land (Figs. 9 and 10). Level and well-watered farm plots could thereby beproduced in areas that had previouslybeen considered unsuitable for agricul-ture, and locall productivity was sub-stantially increased.The conclusion which must be drawn

is that the disastrouls erosion so appar-ent in the Nochixtlan Valley today wasnot simply the result of deforestation,intemperate grazing, or agriculture thatfollowed the Spanish conquest, but thatit was in large part intentionally in-duced and encouraged by pre-Hispanic

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Mixtec farnmers who wanted to expandand improve the lauia-bordo terracesystem (20). It is significant that thiseffective but not always farsightedmanipulation of the environment con-tinues in 1969.

The Spanish Conquest:The Convento Phase

Clear archeological indications ofthe European culture that began topenetrate the Nochixtlan Vatlley in the1 520's are relatively rare, being foundlin trace amounts on 44 sites but inten-sively on only 7 sites. Natividad phase(continuing Postclassic Mixtec) mnate-rial persisted in unadulterated form illmany areas known through documenta-tion to have been occupied both beforeand after Spianish contaict. In fact. it

has not been possible to detect anychange in the cultural remains of many'sites that are known to have been oc-cupied during the early Spanish period.It is only in the important civic centersor around the churches, chapels, andmonastery built by the Dominicans thatEuropean architectural innovations andceramics are well represented. Othersites reveal strongly persistent Nativi-dad technology, material culture, andsettlement patterns, a fact that coin-cides quite well with a documentedpersistence of native art, technology,aInd social and political institutions formatny decades after the Spanish con-luest (21).The continuing needs of a large pop-

LIlItion, coupled with increasing de-ma,nds for goods and services by theFncomenderos, the Spanish crown, theclergy. and the privileged native nobil-

ity. placed (additional strain on the re-sources of the Valley. Although theSpaniards introduced several new cropsto the area, they fostered no substantialtechnological innovation in farmingmethods, and it was probably neces-sary to expand the lama-hor(do systenmto an unprecedented level. It seemslikely that local farmers continued thepralctice of cutting into the Yanhuitlandeposits through most of the 16th cen-Wry. During the last quarter of thecentury, however. depopulaltioni tand acorresponding reduction in demandsfor tribute led to decreasing pressureoin land resources and probably toabandonment of much of the terracesvstem. Grazing and intentional re-moval of plant cover served only toexacerbate the destruction of the slopesthat had been caused by the creationais well as the abandonment of the ter-

Fig. 8. Ancient and moder-n mlama-ordo terrmces radiating fr-oml the commtunity of Amtlaln. [Mexicana Aereofoto]SCIENCE. VOL. 166>64

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2). MoIdlerIn Uama-or tCr r.CC, it Y hli LUI. I cti-t,1-cc -ire formcd lb1, iI;umilcm.Uit ion f behird dIikcs *f 1o0tS, brut-LIsl ((lI [s111 9 ( 9f 56I

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1 1.P)'I C- III,,l ti pict11 (I ;dn)nI.o L tilIc i tll IiTll C iuiO ic ( tiit'; ic t'rItIaiLiIh( I3. ,Ut1 \'-% tC )C OCCLil1tCd ({I Iri 11t- I I11TIIC',ltil1' d11(t Cl Ct>I III.tCd'( 1101)L5I ;I"IIi-ol)II ttIc -1ollllI%c tilm--t o1

ment of the area that there wals a de-cline in population, and it amounts toaround 35 percent in 80 years (24).MIoreover, it is clear th.at there was nosubstantial population recovery here orelsewhere in Mexico until well into thepresent century, most notably since1930 (25). Available data, in fact, sug-gest that the population may havedropped to a low of 8000 around 1745!

With the 16th centuLry as a demo-graphic base line, and proceeding fromlthere to a consideration of the relativenuLmber and intensity of occupation olsites, it is possible to infer a tentativepopulation profile for the NochixtlanValley (Table 1). During the Cruzphase, when population was at its low-est level, there was more than suLffiCientbottomland to support the farmingactivities needed for the subsistence ofthe estimated population of 4000. Thissufficiency continued into Early Classictimnes, but in Late Classic and Post-classic times, expanding population andprobably increased tributary demiandsbl a native nobility, eager to amass andconcentrate wealth, resulted in growingpressure on the available level fieldsfavored by Mixtec farmers. This ledfirst to the clevelopment of hillsidte ter-racing in Las Flores times and latter,in the Natividad phase, to the dliscov-eriy and development of the lamna-bordotechnique. The erosion of higher ele-vations was induced during Natilidadtimles in order to fabricate fertile ter-races in the lower drainage channels.Then, as population declined after theconqu1eSt and Spaniards were forced torIedLice tribute assesstmients, many ter-raced lands were abandooned and lower-slopes were allowed to erode.

Since the 16th century nearly onethird of the productive land ha,.s bIeenremiioved froml the slopes aItnd Irede-posited over already fertile bottomIl-.lands. The destructionl of the land wasdlirectlyr correlated xvith a sharp decliniein populatioll, abandonment of terracesaindc settlemients on slopes and lonms. abreakdown of native polity which hadserved as the coordinating and direct-ing force in the Valley, and a rapideconomiiic decline which heg.an in thelate 16th century with no significantrecovery uLntil the mid-9Oth century.Renewed demands for farmii landcls,

particularl) during the 1930's, 40's,and 50's led to renewed attempts tocheck crosion for the purpose of re-oreating usable terrace fields along thehills and a-rroyos. In many cases, how-ever, the crosional process has out-31 OCTOBER 1969

stripped the ability of modern farmersto respond effectively with ancient tech-niques. placing tertile bottomlands andreclaimiable slope lands aIt a premium.Competition tfor these lands duringthe last fouLr decades trequLently led toviolenit interfamilv feuLding, factionalSplits, and1ti i ntcrcomilmIuLnity warfare.FortuLna,telV. the escLape valve of emi-griation has opetied in recent years and,aIs a resuLlt. a SUbstantial proportion ofthe populaktion has becn siphoned offby the induLIstriaKlized u1rban1M centers and

effectively removed from the explosivecompetition for land. Machinery, fer-tilizers, and more judicious uise of avail-able lands have made it possible forfarrmers who remain in the area tomake better use of the productive re-sources of the Valley. Thus, an in-crease in technology during the lastdecalde has made it possible for theValley to support a sizable popullationbut on considerably less arable landthan was available before the SpalnishconqLuest.

Fig. 11. Unchecked erosion, such as here at Nochixtian, has removed uip to one thirdof the land formerly tinder cultivation in the Valley.

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Conclusion: Nochixtan and the"Nuclear Hypothesis"

These investigations suggest a steadyevolution of culture and growth of pop-ulation in the Nochixtlan Valley fromFormative times to the Spanish con-quest. There has been a long and con-tinuous occupation by Mixtec-speakingpeople who came into the Valley inFormative times and continued to comeand settle there until late Postclassictimes. Contact with groups outside theValley was always maintained, butthese affiliations seem to have beenstrongest during the Formative Cruzphase, then much later in Natividadtimes. Experimentation during theFormative was followed by a periodof internal stability and consolidationduring the Classic and then -by a timeof primarily externally induced elabo-ration of the material culture during thePostclassic.

Conquest-level Mixtec cultureemerged during the Postclassic, prob-ably as a result of the mixing of localtraditions with dramatic new influencesfrom the Cholula-Puebla area. TheNochixtlan Valley did not, however, at-tain the level of influence and urbancomplexity enjoyed by Cholula and inthis respect seems to have lagged be-hind other key areas throughout its his-tory. The Mixteca Alta has been in-cluded with the valleys of Oaxaca,Puebla, Mexico, and Guatemala Cityin Wolf and Palerm's group of fiveMesoamerican "nuclear areas," whichwere hypothesized to have "maintainedtheir key importance from Archaictimes right up to the time of the Span-ish Conquest" (2, 26). Flannery andassociates have demonstrated the con-tinuing "nuclearity" of the Valley ofOaxaca throughout the Formative,Classic, and Postclassic periods, andthere seems little doubt about the sus-tained importance of the other regions.But it must be concluded that theNochixtlan Valley-and by extension,the Mixteca Alta-did not maintain"nuclearity" throughout the three ma-jor periods, but only during the Post-classic period, and even this must bequalified. The importance of the areain Postclassic times is not denied, butit is inappropriate to speak of it as anarea of "massed economic and demo-graphic power" relative to contempo-raneous developments in Puebla, theValley of Mexico, and in the Valley ofOaxaca. When we compare the levelof internal development and probabledegree of social, political, and economic

568

influence attained by the other nuclearareas, it must be concluded that theNochixtlan Valley occupied a decidedlyinferior position of power, possiblyeven during the Postclassic period.

Examination of the long record ofcultural development in the NochixtlanValley has produced no convincing evi-dence of massive displacement of pop-ulation, large-scale warfare, radical po-litical reorientations, depletion of wildplant and animal resources, significantclimatic shift, or any comparable cata-clysm that would account for thechanges in settlement and use of landwhich have been observed. Immigration,emigration, trade, tribute, and territorialexpansion through political means (war-fare, alliance, or royal marriage) playedroles of varying importance in allowingadjustments to the needs of a growingpopulation (27). Clearly, technologicalinnovation has played a highly signifi-cant role in the development of Mixtecculture. It is believed that investigationscurrently under way will serve not onlyto further illustrate the connection be-tween demographic pressure and tech-nological innovation but also that allother variables can be placed in theirproper functional contexts as relatedto the development of culture in theNochixtlan Valley. These demonstra-tions will lead to a greater understand-ing of the processes of cultural devel-opment in the Valley and in all areaswhere similar variables can be shownto be operative.

References and Notes1. W. T. Sanders, "The Cultural Ecology of the

Teotihuacan Valley" (Pennsylvania StateUniv., University Park, 1965); R. S. Mac-Neish, Science 143, 531 (1964).

2. K. Flannery, A. Kirkby, M. Kirkby, A. Wil-liams, Science 158, 445 (1967).

3. W. D. Strong, Smithsonian Inst. Misc. Collec-tions 100, 353 (1940); , in AnthropologyToday, A. Kroeber, Ed. (Univ. of ChicagoPress, Chicago, 1953).

4. S. F. Cook, Amer. Antiquity 13, 45 (1947);C. S. Fletcher, Teotihuacan to Tierra Caliente(mimeographed paper, 1967).

5. Based on the Mexican National Census of1960.

6. J. Paddock, in Ancient Oaxaca, J. Paddock,Ed. (Stanford Univ. Press, Stanford, Calif.,1966); I. Bemal, in ibid.; , in Hand-book of Middle American Indians, vol. 3,Archaeology of Southern Mesoamerica, G. R.Willey, Ed. (Univ. of Texas Press, Austin,1965); A. Caso, in ibid.; , I. Bernal,J. Acosta, La Cerdmica de Monte Albdn (In-stituto Nacional de Antropologia e Historia,Mexico City, 1967). Historical and pictograph-ic manuscripts have served as the basis forseveral ethnohistorical studies, including thefoliowing: A. Caso, Interpretacidn del CddiceBodley (2858) (Sociedad Mexicana de Antro-pologia, Mexico City, 1960); M. E. Smith,Tlalocan 4, 276 (1963); B. Dahlgren, La Mix-teca: Su Cultura e Historia Prehispdnicas(Universidad Nacional de M6xico, MexicoCity, 1954); R. Spores, The Mixtec Kings andTheir People (Univ. of Oklahoma Press,Norman, 1967).

7. In 1966 a mammoth mandible in loose as-sociation with lithic implements was foundembedded in an arroyo bank under 6 to 7

meters of alluvium. Careful excavation of thesite by archeologists from the InstitutoNacional de Antropologia e Historia (underthe direction of J. L. Lorenzo) found thatthe mandible and associated materials werethe result of redeposition. The contemporanei-ty of man and mammoth in the Valley re-mains in doubt.

8. J. L. Lorenzo, Un Sitio Precerdmico en Yan-huitldn, Oaxaca (Instituto Nacional de An-tropologia e Historia, Mexico City, 1958).

9. B. Warren, in VIII Mesa Redonda: LosMayas del Sur y sus Relaciones con losNahuas Meridionales (Sociedad Mexicana deAntropologia, Mexico City, 1961). K. A.Dixon, Pub. New World Archaeol. Found. 5(1959); M. D. Coe, Papers Peabody MuseumArchaeol. Ethnol. Harvard Univ. 53 (1961);

and K. Flannery. SmithsonianContrib. Anthropol. 3 (1967); R. MacNeish,Science 143, 531 (1964); K. Flannery, inDumbarton Oaks Conference on the Olnmec(Trustees for Harvard University, Washing-ton, D.C., 1968).

10. Two runs on radiocarbon samples from Cruzphase context (Geochron Laboratories) areinconclusive. Ceramic ties between the Cruzphase and the late Guadalupe and MonteAlban I phases of the Valley of Oaxaca areso clear, however, that virtually no doubtexists as to the proper temporal placementof the Cruz phase in the last half of theFormative period.

11. Intensity of occupation at each site has beenestimated by rating localities where ceramicswere noted on the surface on a scale from1 (light concentration) to 5 (heavy concentra-tion). Localities rated 3 (medium), 4(medium-heavy), or 5 (heavy) are consideredfor present purposes to have been intensivelyoccupied.

12. A. Caso, Inst. Panamericana Geograf. Hist.Pub. 34 (1938); , in Aetas del 27 Con-greso Internacional de Americanistas (MexicoCity, 1947).

13. Plain Gray does in fact reemerge, but de-tailed study of paste composition and formsuggests that the Gray wares of the LasFlores phase are probably derived from theTan wares so common in Ramos times. Colordifferences are attributed to changes in firingtechniques. In addition, the large Brown jarsseem to evolve from the large Red-on-Tanjars of the preceding phase, and the Orangewares represent a further refinement of theearlier Ramos Tan wares.

14. There are nearly twice as many Las Floressites as Ramos sites, but the former phaseseems to have endured perhaps 200 yearslonger than the latter. The size and in-tensity of occupation of the Las Flores sites,however, are much greater than for Ramossites, and I feel secure in inferring a doublingof population between the end of Ramosand the end of Las Flores.

15. J. Paddock, Ed., "Excavations in the MixtecaAlta," vol. 4 of Mesoamerican Notes (1953);I. Bernal, in Ancient Oaxaca, J. Paddock, Ed.(Stanford Univ. Press, Stanford, Calif., 1966);J. Paddock, in ibid.

16. Extensive survey of the large Las Flores phasesite of Yucufiudahui brought to light only onevery small area in the entire site that showedsigns of utilization during Natividad phasetimes. It is clear from historical documents,however, that hilltop sites were employedfor ceremonial purposes in Colonial andNatividad times.

17. Caso's 1937 excavation at Iglesia Vieja,Chachoapan, produced an estimated 10,000Mixtec Polychrome sherds (never thoroughlystudied and now lost) from a refuse pit.My excavations at this site in 1967 producedless than 100 examples of Polychrome outof a total of more than 7000 Natividadphase sherds. The frequency with which sherdsof this ware are found on, but not beneath,the surface (with the exception of Caso's testpit, which also contained part of a Spanishsword) leads to agreement with Bernal thatMixtec Polychromo, although an importantcomponent of the Mixtec complex, was arelatively late introduction to the area. Inmany cases the ware upon which Polychromedesigns are applied does not seem to arisefrom local Tan, Cream, Gray, or Browntraditions, and we are tempted to derive mostMixtec Polychrome from some point totallyoutside the Nochixtlan Valley, probablyPuebla.

18. Design elements found on Polychrome and

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Cream wares in the Nocihixtian Valley appearin both painted and incised form in theCholula phase at Cholula and in the VentaSalada phase in the Tehuacan Valley andprobably begin earlier here than in Nochixt-lan. E. Noguera, La Cerctmica de Choliula(Editorial Guarania, Mexico City, 1954); R.MacNeish and R. Chadwick, in The Prehis-tori' of the Tehuiacan Valley, D. Byers, Ed.(Univ. of Texas Press, Austin, 1968), vol. 1.There are also strong parallels with the Coyot-latelco tradition of the Valley of Mexico thatrequiire further investigation. E. Rattray inMesoamerican Notes 6 (1967). Historicaldocumentation [for example, Relaci6n deC(holila (1580)] also suggests strong ties be-tween the ruling families of the Mixtec com-mtunities and the city of Cholula.

19. Brief comment on the economic importanceof the Nochixtlan terrace system is providedby M. T. De la Pefia, Metnorias del InstitutoNacional Indigenista, 2 (No. 1), 39 (1950).Strikingly similar terrace structures of ancientdate are reported for the Chihuahua-Sonoraarea of northern Mexico, and modem terracesmtLch like those in the Nochixtlan Valley arefotund in the Valley of Mexico. L. C. Herold,Univ. of Denver Dept. of Geography Techni-cal Paper 65-1 (1967); C. S. Fletcher, Teoti-hitacan to Tierra Caliente (mimeographedpaper, 1967).

20. Present findings strongly support Cook's viewthat mtuch of the erosion of the Valley wasan accomplished fact before the Spanish con-quest; S. F. Cook, Ibero-Amiericana 34, 14(1949).

21. R. Spores, Southws'estern J. Anthropology20, 15 (1964).

22. Based on figures derived from the MexicanNational Census of 1960 with an incrementof 1f) percent for growth between 1960 and1969.

The pace at which radiation effectsin the Japanese survivors of the atomicbombs are being reported has recentlyquickened. In this article I seek to putinto perspective the major findings of theAtomic Bomb Casualty Commission(ABCC).

Immediately after World War II, ajoint commission of the U.S. Army andNavy made observations concerning theimmediate effects of exposure to theatomic bombs in Hiroshima and Naga-saki. Upon completion of its work, thejoint commission recommended that the31 OCTOBER 1969

23. OuLr own census of an average-sized (1041) towni(Yucuita) in 1968 revealed that 284 (27 per-cent) townsfolk still maintaining social tieswith the community and considered "family"by town residents actually lived oitside thephysical community, in such places as OaxacaCity, Puebla City, Mexico City, and in var-ious locations in the United States. Inquiriesand observations made in Yanhuitlan, Sinaxtla,Tecomatlan, Tillo, Chachoapan, and Nochixt-Ian would suggest that the Yucuita figuresare roughly typical for both large and smalltowns in the Valley, but that, in some ofthe smaller towns (Tecomatlan and Tillo)the incidence of emigration would be evenhigher.

24. Derivation of reliable demographic informa-tion for Colonial and modem Mexico is ahighly complex procedure, the difficulties ofwhich cannot be discussed in the presentarticle. Our estimates are based on consulta-tion of numerous primary sources from theArchivo General de la Naci6n (Mexico City);the Papeles de Nueva Espajia (Est. Tipogrhtico"Sticesores de Rivadeneyra," Madrid, 1905-06); Epistolario de Nueva Espaiia (PorruaRobredo, Mexico City, 1939-42); Tasacione.sde la Nuteva Espafia (Archivo General de laNaci6n, Mexico City, 1952); Relacion de losObispados de Tlaxcala, Michoacdn, Oaxaca votros lIugares en el siglo XVI, L. GarciaPimentel, Ed. (published by the author.Mexico, 1904); Theatro Americano (EditoraNacional, Mexico City, 1952); and from the re-cent demographic studies of M. T. De la Pefia,W. Borah, S. F. Cook, G. Simpson, and G.Kubler. It is essential to state that the in-terpretations of the last mentioned writersmight well be at variance with mine, and Ido not pretend to speak for them. Forexample, I believe that Cook's estimate-based on general population trends in Mexico

National Academy of Sciences-NationalResearch Council conduct a study ofthe long-range biomedical effects of theexposures. The Council convened an ad-visory group, whose study of the situa-tion in Japan led to a Presidential di-rective authorizing the National Re-search Council (NRC) to establish anorganization to evaluate the delayed ef-fects of exposure to the bombs. Thusthe Atomic Bomb Casualty Commissioncame into existence (1). Its large-scalestudy, begun in 1948, is a cooperativeventure between the NRC, representing

-of l()(,()()0 for the Valley at the time ofthe Spanish conquest is far out of reasonand not supported by our town-by-town as-sessment [S. F. Cook, Ibero-Americana 34.15 (1949)].

25. W. Borah, Revista Mexicana de EstudiosAntropologicos 16, 159 (1960).

26. A. Palerm and E. R. Wolf, "Ecologicalpotential and cultural development in Meso-america," Pan American Union Soc. Sci.Monograph No. 3 (1957).

27. There is considerable documentary and arche-ological evidence to suggest a Mixtec expan-sion into the Valley of Oaxaca in Postclassictimes [J. Paddock, in Ancient Oaxaca, J.Paddock, Ed. (Stanford Univ. Press, Stan-ford, Calif., 1966); I. Bernal, in ibid.] See R.Spores [The Mixtec Kings and Their People(Univ. of Oklahoma Press, Norman, 1967)]on trade, tribute, and territorial expansion inthe Mixteca Alta in Postclassic and earlyColonial times.

28. This research supported by Vanderbilt Uni-versity Center for Latin American Studies,the Ford Foundation, and the Vanderbilt Uni-versity Research Council. Geomorphologicalstudies were conducted by M. Kirkby and A.Kirkby of Bristol University. J. Broster, C.White, E. Mcintire, R. McIntire, S. Moore,and W. LaFevor, students at Vanderbilt Uni-versity. and M. Winter, graduate student at theUniversity of Arizona, have participated asmembers of the project field staff. K. Flan-ncry. J. Paddock, D. Butterworth, J. VVheeler,A. W. Williams, C. E. Smith, M. E. Smith, T.Charlton, C. Moser, and F. V. Scholes havecontributed direct advice and assistance. I.Bernal, J. L. Lorenzo, and L. Gamio sub-stantiallv aided research through their officeswith the Instittito Nacional de Antropologia eI istoria.

the United States, and the Japanese Na-tional Institute of Health. The Commis-sion's present staff of 725 Japanese and36 foreign nationals, including 18 U.S.professionals, is collecting and analyzingdata from periodic comprehensive medi-cal examinations, from postmortem find-ings. and from a review of vital certifi-cattes as they are generated.

Genetic Effects

It is commonly thought that con-genital anomalies are the only measureof genetic effects among children con-ceived after one or both of the parentshave been exposed to ionizing radiation.The studies conducted at the ABCC,however, concerned six indicators ofgenetic damage in the F1 generation.

Pregnancies were ingeniously ascer-tained (1). In postwar Japan, when foodwas in short supply, pregnant womenwere allowed an extra ration of rice,beginning in the fifth month of preg-nancy. When such women registered forthis supplement in Hiroshima or Naga-saki, they were entered in the ABCCThe author is chief of the Epidemiology

Branch at the National Cancer Institute, NationalInstitutes of Health, Bethesda, Maryland. Thisarticle is based on a presentation made at asympositLm on the biological implications ofthe nuclear age, held in March 1969 to dedicatenew biomedical laboratories at the LawrenceRadiation Laboratories, Livermore, California.

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Delayed Radiation Effectsin Atomic-Bomb SurvivorsMajor observations by the Atomic Bomb

Casualty Commission are evaluated.

Robert W. Miller

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