900年前世界上最大的文明之一被遗弃 考古学家现在发现了新线索
One of the World's Largest Civilizations 900 Years Ago Was Abandoned - Archaeologists Now Discover New Clues
卡霍基亚土丘曾是今天圣路易斯附近一个繁荣的定居点，但在 1400 年被遗弃，留下了一个谜。最近的研究对人们长期以来认为干旱导致农作物歉收的观点提出了质疑。相反，有证据表明卡霍基亚人可能拥有缓解这种环境挑战的技能，他们的离开很可能受到社会因素和外部压力的影响。
The Cahokia Mounds, once a thriving settlement near present-day St. Louis, was abandoned in 1400, leaving behind a mystery. Recent research challenges the long-held belief that drought led to crop failure. Instead, evidence suggests that the Cahokians may have possessed skills to mitigate such environmental challenges, and their departure was likely influenced by social factors and external pressures.
900 年前，卡霍基亚丘定居点与现在的圣路易斯市隔密西西比河相望，是一个繁荣的大都会地区，人口约有5万。它是当时世界上最大的社区之一。然而，到了 1400 年，这个曾经热闹非凡的遗址几乎变成了一片荒芜，而大规模迁徙的原因至今仍是一个谜。
Nine hundred years ago, the Cahokia Mounds settlement, located just across the Mississippi River from what is now St. Louis, was a thriving metropolitan area with a population of around 50,000. It was one of the largest communities in the world at the time. However, by 1400, this once-bustling site had become nearly deserted, and the reasons for the mass departure remain a mystery.
一种流行的理论认为，卡霍基亚居民是在长期干旱导致农作物大面积歉收后放弃了定居点。但圣路易斯华盛顿大学艺术与科学考古学助理教授娜塔莉-穆勒（Natalie Mueller）和 20 年博士凯特琳-兰金（Caitlin Rankin）在《全新世》（The Holocene）杂志上发表的一项新研究表明，卡霍基亚人很可能还有其他离开城镇的原因。
One popular theory is that the Cahokia residents abandoned the settlement after a massive crop failure brought on by a prolonged drought. But a new study in the journal The Holocene by Natalie Mueller, assistant professor of archaeology in Arts & Sciences at Washington University in St. Louis, and Caitlin Rankin, PhD ’20, suggests the Cahokians likely had other reasons to leave town.
兰金在历史悠久的卡霍基亚遗址的土壤深处挖掘，收集碳的同位素，这是在人类人口崩溃、整个中西部地区普遍干旱时植物生长留下的原子。
RRankin dug deep into the soil at the historic Cahokia site to collect isotopes of carbon, atoms left behind by the plants growing when the human population collapsed and drought was common across the Midwest.
所有植物都使用碳 12 和碳 13 这两种碳中的一种进行光合作用，但并非所有植物的光合作用方式都相同。适应干燥气候的植物--包括草原草和玉米（卡霍基亚时期重要的新作物）--将碳以植物死亡和腐烂时留下的蛛丝马迹的速度融入体内。
All plants use one of two types of carbon, Carbon 12 and Carbon 13, for photosynthesis, but not all plants do photosynthesis the same way. Plants adapted to dry climates — including prairie grasses and maize, an important new crop during the Cahokia period — incorporate carbon into their bodies at rates that leave behind a tell-tale signature when the plants die and decay.
卡霍克人可能会采摘作为食物的大多数其他植物（包括南瓜、鹅掌楸和闾草等）都会留下不同的特征，它们与湿地和原生森林中的植物有着相同的特征。
Most of the other plants that the Cahokians would have harvested for food — including squash, goosefoot, and sumpweed — will leave a different signature, one they share with plants from wetlands and native forests.
"兰金的样本显示，碳 12 和碳 13 的比率在这一关键时期保持相对稳定，这表明该地区生长的植物类型没有发生根本变化。"穆勒说："我们没有看到草原草被取代的证据，而这正是我们在作物大面积歉收的情况下所期望的。"
Rankin’s samples showed that ratios of Carbon 12 and Carbon 13 stayed relatively consistent during that crucial period — a sign there was no radical shift in the types of plants growing in the area. “We saw no evidence that prairie grasses were taking over, which we would expect in a scenario where widespread crop failure was occurring,” Mueller said.
"卡霍基亚人以他们的聪明才智而闻名，兰金说，他们可能拥有工程和灌溉技能，能够在困难的条件下保持庄稼茂盛。"兰金现在是内华达州土地管理局的考古学家，他说："他们可能并没有真正感受到干旱的影响。
The Cahokians are known for their ingenuity, and Rankin said they may have had the engineering and irrigation skills to keep crops flourishing under difficult conditions. “It’s possible that they weren’t really feeling the impacts of the drought,” said Rankin, now an archaeologist with the Bureau of Land Management in Nevada.
穆勒补充说，卡霍基亚的成熟社会几乎肯定包括谷物和其他食物的储存系统。居民们的饮食也多种多样，包括鱼类、鸟类、鹿、熊以及森林水果和坚果，即使一些食物来源消失了，他们也能保持营养充足。
Mueller added that the sophisticated society that blossomed at Cahokia almost certainly included a storage system for grains and other foods. Residents also enjoyed a varied and diverse diet — including fish, birds, deer, bear, and forest fruits and nuts — that would have kept them nourished even if a few food sources disappeared.
"为了更好地掌握中西部土著人的饮食和农业实践，穆勒希望建立一个数据库，收集整个地区的古植物证据。"她说："收集这些信息将有助于我们了解人们是否因气候变化而改种不同的作物。她还计划在校园内受控条件下种植某些粮食作物，以了解它们是如何应对古代干旱和其他挑战的。"
To get a better grasp of the diets and agricultural practices of Indigenous people of the Midwest, Mueller hopes to build a database that collects paleo-botanical evidence from across the region. “Gathering that information would help us see if people switched to different crops in response to climate change,” she said. She’s also planning to grow certain food crops in controlled conditions on campus to understand how they might have responded to ancient droughts and other challenges.
那么，卡霍克人为什么要离开他们的富饶之地？穆勒怀疑这是一个渐进的过程。她说："我不认为会出现成千上万的人突然涌出城镇的场景。人们可能只是为了靠近亲戚或寻找不同的机会而分散开来。他们为建造这些土丘付出了很多努力，但可能也有外部压力导致他们离开。情况可能很复杂。"
So, why did the Cahokians leave their land of plenty? Mueller suspects it was a gradual process. “I don’t envision a scene where thousands of people were suddenly streaming out of town,” she said. “People probably just spread out to be near kin or to find different opportunities.”