很多关于古代战争的研究的主要目标是确定敌对行为的原因。研究人员在最终和大致的原因之间进行仔细的区分，但是如长期干旱等环境因素通常需要考虑，在古代世界范围内，环境因素被看作族群间冲突的开端。很少有关于这种因素对日常生活影响的研究，如狩猎者和农户如何在缺水和社会冲突中重建他们的生计，或在由冲突所导致的争议性环境下的性别和其他社会角色如何重新协调。

北美东部林地史前时代晚期的考古学研究已经显示出族群之间的紧张冲突，如房屋、村庄甚至是整个区域的放弃。篱笆、被焚毁的村庄，以及与暴力冲突相关的骨骼创伤，这些都是最明显的古代敌对行为的考古学证据。虽然一些证据反映了冲突的规模和程度，但是它们并不能告诉我们古代人群如何生活在战争之中。长期的战争是否会危害和限制与家庭和社群的社会经济再生产有关的生存资料？农牧者如何调整食物的收集和生产策略以抵消战争所带来的危险？

我们的研究对象是位于美国中西部、伊利诺伊中心西部的伊利诺伊河谷中部（CIRV）13世纪的密西西比群体，主要关注长期激烈的战争对他们生存的影响。除了长时间的冲突，生活于此时此地的村民还需要对抗长时间的干旱。而这种气候条件无疑导致了大规模紧张的战争。我们的研究检视了农牧者做出一些决定的原因，即减少暴露于冲突之中，同时试图在缺水的环境中生产出足够的粮食。我们还探究了人们如何调整他们每天、每季和每年的农猎活动，以维持社群和他们自身的生活。在研究过程中，我们将重点放在了三个证据之上：古代植物数据、动物遗存和从玉米籽粒中提取的碳氮同位素，以探讨冲突和干旱对于当地农业社群的影响。我们用这些证据来解读对于长期暴力冲突和干旱的主要应对措施：饮食上的历时性变化、食物生产与获取的季节性和习惯性变化，以及农业策略的改变。

背景介绍

史前时代晚期的美国东南部和中西部见证了大范围文化传统的发展，即始于公元1000年左右的密西西比文化。密西西比文化社会通常有几个特征：区域政治等级、平台土丘和象征及仪式用具在地区之间的交换。大多数社群还有农业经济和世袭的领导权力。然而，从地理范围和政治复杂化的角度来看，不同密西西比社会之间存在着巨大的差异。如一些在伊利诺伊西南部的大型政体，像卡霍基亚包含了许多居住了大量人口的大规模聚落。大多数其他密西西比文化群体，如那些伊利诺伊河谷中部的聚落，与卡霍基亚相比无论在规模或者复杂化程度上都显得更弱一些。

总体而言，虽然从玉米的重要性和集约种植的程度来看，区域之间的差异十分明显，但密西西比文化阶段仍被认作从狩猎和小规模食物生产到集中玉米农业转变的开端。除了相对重要的作物种植，密西西比人还广泛采集坚果、水果和新鲜绿叶菜。采集的植物从主要或次要的主食（如山核桃）到补充性资源（如应季的新鲜蔬菜）均有。广泛多样的可食植物为基于玉米的日常饮食提供了更均衡的营养，因为玉米为基础的饮食缺乏烟酸、基本的氨基酸和异亮氨酸等。当时除了狗之外没有其他本地家养动物，人们通过渔猎来摄取蛋白质。虽然陆地与水生动物的相对比例（以及目标物种）因地区而不同并且与定居地有关，但是仍有一些普遍而常见的猎物，如白尾鹿、野生火鸡、迁徙水禽、乌龟和各种鱼类。

密西西比河谷中部的密西西比文化始于公元1100年左右，到约公元1450年遭到废弃。这一区域早期密西西比文化的聚落通常由小而分散的居址组成。不同地点的聚落似乎在仪式和政治层面与一些小型庙宇和墓葬群相关。到公元1200年，这种分散的早期密西西比聚落模式被一些与外围小型聚落连接的核心城镇所取代。大多数城镇都建在伊利诺伊河西侧的可防御的悬崖边缘地带。这些悬崖一般高38米到45米不等，可供人们监视广阔的洪积平原，以防敌方发动突然袭击。尽管防线坚固，在经历大规模的直接进攻或突然的战略性放弃之后，一些村庄还是被敌方付之一炬。

战争和干旱的共同出现使伊利诺伊河谷中部相比于其他史前时代晚期东部林地的地区更为紧张。残留人骨的分析揭示出了与整个东部林地其他密西西比文化遗址相比，这里有更高的因暴力冲突所致的骨骼创伤。与暴力有关的墓葬模式，包括一座至少埋有15人的合葬墓，以及大量身上插有箭镞、头皮被剥或头骨遭受钝击的个体。到公元1300年，大部分地区的居民已经迁移到了戒备森严的城镇中，这表明在围墙保护范围之外的区域已经不再安全。除了与战争有关的风险，最近基于帕尔默干旱强度指数（PDSI）所得出的降水模型显示出该区域在公元1100至1245年间遭受了长时间的干旱，包括之前的湿润期和之后的极端缺水。因此，在公元1200至1250年间，村民必须同以下两种情形相抗争：（1）当他们离开村庄去打猎、捕鱼和觅食时，所面临的暴力袭击和死亡威胁；（2）玉米等谷物的种植条件恶化，很可能导致他们到围墙之外去种植，而那里的农民多为女人，可被城墙上的弓箭手所保护。这种靠近村庄的集中耕种使得作物无法轮种，也降低了土壤的肥力。公元1250年之后，干旱终结，但是区域的暴力冲突持续摧残本地的人口。

我们通过对4个区域冲突开始到干旱结束之地点食物遗存进行的历时性分析，评估了人们如何处理战争和干旱。最早的拉姆（Lamb）遗址是一处可以追溯到公元1100-1150年间的农庄，也标志着密西西比文化在此地的开端。拉姆的定居发生在干旱来袭之初，预示着地区冲突的爆发。卡铂（Copper）为一处小型村庄，存在于公元1200到1235年的持续干旱之中，也发生了最早的地区冲突。带有栅栏的村庄欧伦多夫（Orendorf）在公元1200年前后建立，到1250年被焚毁，与此同时山谷也再次变得潮湿起来。最后一处遗址迈尔-狄克森（Myer-Dickson），大致存在于公元1250年至1300年之间，它代表了一种社区的流动。居民们仍旧面临着同样的敌对环境，但干旱早已不再是问题。

生存方面历时性的改变

通过对4个遗址中浮选样品的分析，揭示出了一种从野生采集食物的转变。很明显的统计数据显示坚果（在数量上与玉米存在竞争关系一种主食）、水果、野生种子和新鲜绿叶菜的减少。伴随而来的是其他植物的饮食总体上变得不再那么多样化，玉米成为了主要的食物。这一发现表明，当时的生业形态大大缩短了寻觅和采集植物者（主要为女性）远离村庄保护而去外出收集食物的时间和路途。然而，在这一过程中，玉米的产量并没有增加，这表明村民不能够通过种植玉米来抵消野生植物性食物的减少。

动物骨骼的分析，揭示了在战争开始后鱼的急剧下降，同时伴随着哺乳动物在饮食中的增加。对鱼脊椎骨的分析表明，人们不再获取不同尺寸的鱼，而是强调更大的鱼，这表明网捕鱼技术的下降。关于哺乳动物，出现了一个向猎捕更大动物（鹿和麋鹿），而不是向可以通过陷阱捕捉的更小猎物的转变。同时相关证据还指出，小鱼和哺乳动物往往不会被渔网和诱捕器所捕获，它们通常是被妇女或儿童在他们寻找植物性食物的时候发现。因此，这种从鱼类和小型哺乳动物转向大型猎物的转变表明妇女和儿童对蛋白质寻觅活动变得更加有限，而更倾向于与成年男性的合作狩猎。虽然更大的鹿和麋鹿成为主要的肉食资源，但是它们的骨骼碎片在尺寸上却在减小。这种情况表明油脂和骨髓的处理更为彻底，通常这种现象可能与食物短缺或营养不足有关。

季节性和产地的历时性改变

对野生植物生长地偏好的分析，揭示了从湿地的开发向主要集中在林地（坚果）和散布的植物上的明显转变。对野生植物收集的季节性评估也表明，人们从春季和初夏的采集性活动转变为在夏末秋初的时候进行觅食活动。这时人们将注意力主要集中在坚果上，而其他植物的收集则是在大范围开发活动中附带进行。动物数据显示这种季节性的觅食转变主要是在秋季。鹿和麋鹿的狩猎季节主要在秋天，并且此时野生动物群也变得偏向于这些猎物。捕鱼策略的转变也支持了向秋季捕猎的季节性转变。我们可以清楚地从序列上看到从大到小的鱼。在一年的大多数时间中，这些大鱼生活在河湖深处且难以捕捞。每年春天和夏天，湖泊和河流都会泛滥，从而形成新的溪流，以连接河流、湖泊等。在秋天洪水泛滥结束时，湖底和泥沼被主要河流切断，留下浅滩，而在其中则有很多大鱼被困住，并轻易可为人捕捞。因此，即使本地居民将捕鱼作为一种主要的生存手段，但他们把注意力集中在了秋季这样一个短暂的季节中，因为在这期间可以迅速捕捉大型鱼类。这个季节性捕猎的转变暗示了这些地区的居民在春天和夏天的时候都在种植和保护他们的玉米作物。

农业模式的变化

从该地区战争开始以来，野生植物种类和数量急剧下降，动物骨骼破碎程度升高，所以我们认为当时的人们更倾向于从农业生产中获得更多的食物资料。但实际情况却并非如此。所以我们便通过观察大量的玉米粒的度量数据和从每个遗址中获得的15-20个碳、氮同位素获取信息。玉米粒的度量数据显示，在公元1250年之前，当地玉米粒个体偏小且大小差异明显，这表明密西西比文化晚期的农民种植玉米的间距较之前的时期更密集，导致了土壤肥力衰减。不出意外，密集的种植方式和衰减的土壤肥力使得农业产量并无增长，尽管当地在海拔较高处也有丰富的肥沃土壤可供人们迁移耕地，但在公元1250年之前，耕种高处分散的田地可能遭受武力攻击的风险超过了食物短缺、粮食减产的严重性，因此农民选择在居住地附近的田地上耕种更长的一段时间。

值得庆幸的是，在公元1250年，困扰本地区长达150年的干旱得到缓解。玉米籽粒中的碳和氮同位素支持帕默干旱严重程度指数模型，为地区干旱条件的时间提供支持。同时，碳、氮同位素还能追踪谷物的水量吸收与利用的效率，这种技术目前仅在旧大陆的遗址中有运用。另外，氮元素还能够提供关于土壤肥力的信息。测年显示早于公元1250年的玉米粒遗存整体比晚于1250年的玉米粒包含更多的碳和氮，所以可以说：公元1250年之后碳、氮同位素值下降的情况表明了当地玉米粒吸收了比之前更充足的水分。氮同位素值下降也说明当地土壤变得贫瘠。

尽管旱情在1250年结束，但生活在Myer-Dickson遗址的居民依旧需要继续应对当地贫瘠的土壤，由于之前的过度耕种，这些土地的肥力极大衰减，我们从密集的耕种间距和玉米颗粒大小差别显著这两点上可以清晰地了解这一情况。但是，这些Myer-Dickson居民非常精明且善于变通，他们在传统的豆类植物之外，引入了一系列新的玉米品种。这些新的颗粒更小的玉米，发芽和生长速度较以往的主要玉米品种更快，可以在一季耕种中更早被收获。另外，豆类植物的引入也提高了土壤中的氮含量，从而使得玉米的产量在土壤肥力衰减的情况下仍能够保持稳定。

结论。在本文中，通过解读各种综合利用的经济模式，我们揭示出了生活在中央河谷地带的人们生存危机逐渐深化，这一地区变得危机四伏、气候干旱和并充斥着武力冲突。毫无疑问，发生在这里的旱情与之后地区内的冲突加剧密不可分。在一定的时间里，生业经济转变的时间和地理位置表明当地的居民从比较局限的觅食行为逐渐向更广泛的食物资源利用模式发展。对补充性食物资源的开发也越来越与高产出的生业经济密切结合，例如农耕、橡果、鱼类资源的获取以及鹿、麋鹿的狩猎。资料显示大型哺乳类动物骨骼破损程度提升、同时可辨认标本量也在减少，两者结合，从而我们知道：麋鹿和鱼类资源的利用可能并不均衡，导致了当地人口蛋白质摄取量整体减少。

同样的，野生植物资源和农耕产品的获取也不均衡。尽管当地在海拔较高处也有丰富的肥沃土壤可供人们迁移耕地。但在公元1250年之前，耕种高处分散的田地可能遭受武力攻击的风险超过了食物短缺、粮食减产的严重性，因此农民选择在居住地附近的田地上耕种更长的一段时间。此外，干旱对农业周期造成的影响十分清晰：玉米颗粒整体变小、土壤肥力下降。然后，当地的农民及时适应并积极应对这些富有挑战的情况：他们引入新的生长周期更短的玉米品种并发展豆科植物-根瘤菌共生固氮体系。整体上看，这些考古材料清晰地显示出当时的人们如何在战争/和平的间隔时期内应对干旱的气候条件，为我们提供了一个微妙的视角来审视那些生活在关键历史变迁时期的人群。通过将历史记载中生活在战争前与战争中的人们与高分辨率的气候资料结合在一起，我们可以更好地揭示古代人群是如何适应环境、调整生业模式来应对危机状况，并且当遇到生存瓶颈时人们如何做出关键决择，甚至牺牲物质资源和过去的意识价值体系，来保存自己和家人生命和安全。

Much of the research on ancient warfare has focused primarily on identifying the causes of ancient hostilities. While researchers are careful to discern between ultimate and proximate causes, it is often the case that environmental causes, such as prolonged droughts, are credited with heralding the onset of inter-group violence across the ancient world. Less examined are the effects that such conditions have on the practices of everyday life, such as how foragers and farmers reconstitute their subsistence practices in the wake of water deficit and social conflict, or how gender and other social roles are renegotiated in a contentious climate mediated by conflict.

Archaeological research in the Late Prehistoric Eastern Woodlands of North America has revealed situations where the intensity of inter-group violence resulted in the abandonment of homesteads, villages, and even entire regions. Palisade walls, catastrophically burned villages, and violence-related skeletal trauma are the most obvious archaeological indicators of these ancient hostilities.  And although such evidence informs us about the scale and intensity of these conflicts, it tells us little about what it was like for ancient people to live with war on a daily basis. Did chronic warfare compromise or constrain subsistence pursuits and other basic practices related to the social and economic reproduction of households and communities? How did farmer-foragers alter food collection and production strategies to contend with warfare-associated risks?

Our research focuses on the impacts of chronic and intensive warfare on the subsistence pursuits of 13^th century Mississippian groups in the Central Illinois River Valley (CIRV) of west-central Illinois, located in the midwestern portion of the USA. In addition to chronic violence, villagers living in this region and at this time were contending with a long period of drought, which undoubtedly contributed to the scale and intensity of warfare. Our investigation of these issues examines the decisions that farmer-foragers made in order to limit their exposure to violence while attempting to produce and procure sufficient foods in a water-deficient environment. We examine how people altered their daily, seasonal, and annual foraging and farming practices to sustain their communities and their very lives. In doing so, we focus on three lines of evidence to address the effects of conflict and drought on local farming communities—ancient plant data, faunal remains, and Carbon and Nitrogen isotopic data extracted from maize kernels. These lines of evidence are used to address three primary issues that we interpret as responses to chronic violence and drought: diachronic changes in diet, seasonal/habitat changes in food production/procurement activities, and changes in agricultural strategies.

Background

The late Prehistoric Southeastern and Midwestern United States witnessed the pan-regional development of a cultural tradition known as Mississippian, beginning around AD 1000. Mississippian societies are generally characterized by their regional political hierarchies, earthen platform mounds, and the interregional exchange of symbolic and ritual paraphernalia; most had agricultural economies and hereditary leadership positions of some form.  However, Mississippian societies varied considerably in terms of geographic scale and political complexity. Some large polities like Cahokia in southwestern Illinois were comprised of multiple large settlements inhabited by thousands of people. Most other Mississippian groups such as those in the Central Illinois River Valley (CIRV) were smaller in scale and less complexly organized than Cahokia with towns and villages inhabited by hundreds not thousands of people.

In general, the Mississippian period is credited with heralding the transition from foraging and small-scale food production to intensive maize agriculture, although there is a great deal of regional variation throughout the broader region in terms of the relative importance of maize and the degree of cultivation intensity. Regardless of the relative importance of plant cultivation, Mississippian people foraged extensively for myriad nuts, fruits, and fresh greens. Foraged plants ran the t from primary/secondary staples (e.g., hickory nuts) to supplementary resources (e.g., fresh seasonal greens). A diverse range of wild edible plants would have been necessary to provide nutritional balance to a diet based on maize, which is deficient in niacin and essential amino acids lysine and isoleucine. Protein was procured through hunting and fishing, activities that were important throughout the prehistory of the region as there were no native animal domesticates except for the dog.  While the relative proportion of terrestrial versus aquatic fauna (and the species targeted) varied by region and in relation to settlement location, the most common animal prey included white-tailed deer, wild turkey, migratory waterfowl, turtles, and various species of fish.

The Mississippian period occupation of the CIRV dates from around AD 1100 and ends with the abandonment of the region around AD 1450. Early Mississippian settlements in the region consisted primarily of small and widely dispersed homesteads. Different localized settlements appear to have been ceremonially and politically associated with a number of small temple and mortuary complexes. By AD 1200 this early Mississippian settlement pattern of dispersed communities was replaced by fortified and nucleated towns linked with smaller outlying settlements. Most towns were built on defensible bluff-edge locations on the western side of the Illinois River. These bluffs generally range from 38 to 45 meters in height, and would have allowed a broad expanse of the floodplains to be visually monitored, providing views that would have hindered attempts by enemy forces to launch surprise offensives. Despite the high risks associated with attacking fortified villages situated in these locales, several such villages met their ends as a result of enemy attacks in which they were set ablaze either during large-scale direct assaults or after sudden, strategic abandonments.

Both warfare and drought appear to have been particularly intense in the CIRV in comparison to many other portions of the late Prehistoric Eastern Woodlands. In terms of violence, analyses of the human skeletal remains have revealed a higher adult rate of violence-related skeletal trauma than any other Mississippian site in the entire Eastern Woodlands. Violence-related mortuary patterns include a mass grave with 15 plus interments and numerous other individuals with embedded arrow points, scalp marks, and blunt force cranial trauma. By AD 1300 much of the regional populace had relocated to fortified towns, indicating that it was no longer safe to live outside the protective boundaries of palisade walls. In addition to the risks associated with warfare, recent models of rainfall patterns based on the Palmer Drought Severity Index (PDSI) reveal that this region also suffered a prolonged period of drought between AD 1100 and 1245, bracketed by wet periods before and after this extreme water deficit. Thus, between AD 1200 and 1250, villagers had to contend with both: (1) the risks of violent attack and death when leaving their palisaded villages to hunt, fish, and forage; and (2) deteriorating growing conditions for their maize crops, which they likely planted directly outside the palisade where the farmers, which were women, could be protected by archers stationed on the walls. This focus on infields situated close to the village would leave little space for crop rotation, with negative consequences for soil fertility. After AD 1250, drought conditions ended but regional violence continued to plague the populace.

We assess how people dealt with problems of warfare and drought through a diachronic analysis of food remains at four consecutively occupied sites which span both the onset of regional hostilities and the cessation of drought conditions.  The earliest site, Lamb, is a small farmstead that dates to AD 1100-1150 and marks the beginning of the Mississippian occupation in the region. The Lamb occupation was settled around the onset of drought conditions but it predates the outbreak of regional hostilities. Cooper, a small village, was occupied between AD 1200 and 1235, a time of continued drought, and brackets the earliest outbreak of regional hostilities. The palisaded Orendorf village was settled around AD 1200 until the incineration of its final occupation around AD 1250, the same time when wet conditions returned to the valley. The final site, Myer-Dickson, was occupied from AD 1250 to 1300, and represents a community in flux—residents were still faced with the same hostile environment, but drought had ceased to be an issue.

Diachronic Changes in Subsistence

Analysis of the plant remains from flotation samples from these four sites reveal a clear shift away from wild, foraged plants.  There are clear, statistical declines in nuts (a staple food that rivals maize in its abundance), fruits, wild seeds, and fresh greens. The plant diet also became less diverse in general, with maize as the primary foodstuff. This finding suggests that plant foragers, which were women, significantly curtailed food collection excursions that would have taken them away from the protected limits of their villages. However, maize abundance did not increase at all during the sequence, suggesting that villagers were unable to offset the decline in wild plant foods by growing more maize.

Analysis of the animal bones reveal a sharp decline in fish with the onset of warfare, accompanied by an increase in mammals in the diet. Metric analysis of fish vertebrae indicate that people stopped procuring fish of variable sizes and instead emphasized larger-bodied fish, suggesting a decline in net-based fishing techniques. With respect to mammals, there was a clear shift towards larger prey (deer and elk) over smaller prey that can be caught in traps and snares. It bears noting that smaller fish and mammals tend to be taken with nets and traps/snares, respectively, which are often checked and maintained by women and children as they forage for plant foods. Thus, this shift away from fish and small mammals and towards large prey suggest that women and children’s protein foraging activities became more limited in favor of cooperative male hunts. Although larger deer and elk became the primary meats, there was nevertheless a decrease in the size of their bone fragments; this pattern indicates more intensive processing for grease and marrow, which is often associated with food shortages and/or nutrient deficiencies.

Diachronic Changes in Seasonality and Habitat

Analysis of habitat preferences of the wild plants reveals a clear shift away from wetlands exploitation, with a primary focus on woodlands (nuts) and disturbance plants. A seasonal assessment of wild plant collection also demonstrates a shift away from spring and early summer foraging towards a concentration on the late summer and fall seasons—foragers focused primarily on nuts, with incidental collection of other plants in the context of mast exploitation. This seasonal shift towards foraging primarily in the fall is bolstered by the faunal data. Deer and elk hunting season occurs in the fall months, and the faunal assemblage becomes heavily skewed towards these prey. The change in fishing strategies also supports a seasonal change towards fall-based animal foraging. We see a clear increase in large-to-small fish over the sequence. During most of the year, these larger fish species live in deep lake or river waters and are difficult to capture. Lakes and rivers flood annually in the spring and summer, creating new streams and connecting the rivers, lakes, and sloughs. Following floodwater recession in the fall, bottomland lakes and sloughs are cut off from the main river channels, leaving shallow pockets in which large fishes get trapped and are easily captured by humans. Thus, although regional residents deemphasized fishing as a primary subsistence pursuit, they narrowed their focus towards large species that could be quickly exploited during a narrow seasonal window in the fall. This shift away from spring and summer foraging suggests that the regional inhabitants oriented their spring and summer months around planting and protecting their maize crops.

Changes in the Agricultural regime

Given the indicators of dietary insufficiency (decline in abundance and diversity of wild plants, increased bone fragmentation) that followed the onset of warfare in the region, one might expect an increase in agricultural yields. But this is not the case, despite multiple measure of abundance. We thus assess changes in agricultural strategies using metric data on hundreds of maize kernels and Carbon/Nitrogen isotopes on a sample of 15-20 kernels from each site. Metric data reveal that, by AD 1250, maize kernels were smaller and more variable in size, suggesting that Late Mississippian farmers planted denser stands than previously, which leads to more soil nutrient loss. Not surprisingly, the combination of denser stands (signaled by more size variability) and declining soil fertility (signaled by smaller kernels) did not increase yields. While there was plenty of rich upland soil to permit extensive shifting cultivation, by AD 1250, the risks of attack while overseeing scattered plots outweighed the risks of possible food shortage and crop loss, leading farmers to intensify cultivation in infield plots for longer periods of time.

Luckily, the drought conditions that had plagued the region for 150 years had finally come to an end by AD 1250. Carbon and Nitrogen isotopes on maize kernels support the Palmer Drought Severity Index model for the timing of regional drought conditions. Together, Carbon and Nitrogen isotopes track water uptake and water use efficiency in crops, a technique that until now has only been employed in Old World case studies. In addition, Nitrogen can also provide information on relative soil fertility. Maize kernels dating prior to AD 1250 have higher Carbon and Nitrogen values than the kernels post-dating AD 1250; the decline in both Carbon and Nitrogen isotope values in the post-AD 1250 maize kernels signal a clear increase in water uptake into the maize plants. The Nitrogen decrease is also suggestive of poor soil fertility.

While the drought may have ended by AD 1250, farmers living at the Myer-Dickson site still had to contend with deteriorating soil conditions from over-cropping the same plots, which is signaled by the smaller kernels with greater size variability that they were planting. But these Myer-Dickson farmers were canny and resilient; they incorporated a completely new variety of maize into their cropping system, in addition to common beans. This smaller kerneled-maize (smaller even than the dominant variety which had shrunk over the last 150 years) could germinate faster than the dominant maize variety, producing a crop earlier in the season. Moreover, the introduction of beans would have improved the nitrogen economy of the soil, thus maintaining maize yields despite deteriorating soil conditions.

Conclusions

We interpret this combination of patterns as reflecting an intensification of peoples’ concerns over safety as the Central Valley became a more uncertain, dry, and violent place. The correlation of regional drought conditions and the subsequent onset of regional hostilities is undoubtedly linked. Shifts in the timing and location of subsistence pursuits through time suggest that people narrowed foraging forays to target a suite of resources in a manner consistent with large group excursions. The exploitation of supplemental foods became increasingly embedded within higher-yielding subsistence pursuits, such as farming, mast and fish collection, and deer/elk hunting. Evidence of increased fragmentation and decreased identifiability of large mammal bones suggest that the trade-off between deer and fish may have not have been a perfect one, resulting in a lower overall protein yield for villagers.

Likewise, the trade-off between wild plant foods and farmed produce was not a perfect one either. While there was plenty of rich upland soil to permit extensive shifting cultivation, by the Late Mississippian period, the risks of attack while overseeing scattered plots outweighed the risks of possible food shortage and crop loss, leading farmers to intensify cultivation in infield plots for longer periods of time. Moreover, the impact of drought on the farming cycle is clear in the reduction of maize kernel size and the decline in soil fertility. Nevertheless, farmers adapted to these challenging conditions by introducing a new maize variety with a shorter growing cycle and inter-cropping with nitrogen-fixing legumes. Collectively, these data provide clarity on human decision-making in a drought-plagued peace-time/war-time transition, providing a nuanced look at the people straddling a critical historical period of change. By linking the connected histories of people living in the pre-warfare and warfare periods to high resolution environmental data, we can better illuminate how practices are altered in crisis situations and determine when people reach thresholds at which they are willing to sacrifice both material resources and close-held ideologies to keep themselves and their families safe.