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INVESTIGATING THE NATURE AND TIMING OF THE EARLIEST HUMAN OCCUPATION OF NORTH AMERICA USING A NOVEL INTEGRATION OF BIOGEOCHEMISTRY AND MICROMORPHOLOGY

利用生物化学和微观形态学的新颖整合研究北美最早人类占领的性质和时间

基本信息

批准号：
NE/P003001/1
负责人：
Lisa-Marie Shillito
金额：
$ 73.73万
依托单位：
Newcastle University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2016
资助国家：
英国
起止时间：
2016 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FP003001%2F1
关键词：
INVESTIGATING NATURE TIMING EARLIEST HUMAN

项目摘要

How, when and why did people first arrive and settle in the Americas? This puzzle is one that has captured scientific and public imagination, and is the subject of continued debate. The traditional model of 'Clovis First' asserts that the Clovis culture, named after their distinctive stone tools found near Clovis, New Mexico, in the 1920s and 1930s, arrived on the continent around 13,500 BP. These people would have travelled across the Beringia land bridge in Siberia, during a time when sea levels were lowered during the last ice age, and eventually made their way south on the east side of the Rocky Mountains. Recently a growing body of evidence points to a more complex process, with perhaps several waves of migration of different cultural groups. This has led to a situation where there is no consensus on how humans first came to the Americas. The main barrier to addressing this debate, is the scarcity of well-preserved sites and easily datable materials, where we can be sure that what we are dating really does represent human presence. Human skeletal remains from this period are especially rare, and also incredibly difficult to study due to restrictions of the Native American Graves Protection and Repatriation Act 1990 (NAGPRA). However, a more unusual form of archaeological evidence are well preserved in caves: fossilized human faeces, or coprolites. One of the most famous prehistoric coprolites, is a specimen from Paisley Caves, Oregon, dated 14,300 BP; one thousand years earlier than evidence from the Clovis culture. This coprolite is strong evidence for the 'Pre-Clovis' occupation of North America. The coprolite was identified as human on the basis of ancient DNA, but there have been debates over the stratigraphic integrity. This is a problem which continues to underlie much research in this area. We simply do not know the extent to which these molecules are mobile within cave sediments. This is the missing scientific link which prevents the coprolites from being used, unambiguously, to confirm the pre-Clovis hypothesis and solve this long running debate. Our research will make a first attempt to address these problems, by using a novel integration of biogeochemistry and sediment micromorphology - a method successfully developed by the PI and Co-I. Sediment micromorphology can be thought of as an excavation under the microscope. Intact blocks of archaeological sediments are set in resin and turned into slides for viewing under a microscope. This way we can visually examine the processes by which sediments have been deposited, and whether they have been subsequently altered. Combining this with biogeochemical analysis of faecal lipids will enable us to quantify the extent to which these molecules move from their point of deposition . We will conduct this analysis in conjunction with radiocarbon dating of specific chemical fractions - rather than dating all the organic material in a sample, we will date individual chemical fractions within the coprolites. This way we can provide a firm species identification, and simultaneously an unambiguous date for when the coprolite was deposited. Whoever these early settlers were, these unlikely sources of evidence that they left behind contain a wealth of information which we can now access using the novel techniques proposed in this research project. Once we can demonstrate the integrity of the coprolite materials found in the cave and therefore have confidence in the scientific data we obtain from them, we can use the molecules and fossils preserved with the coprolites to reconstruct the diets of these individuals, and the environment they inhabited. By linking this with high resolution radiocarbon dating, we can begin to extend the research potential to look at other questions of scientific and archaeological interest such as the seasonality of cave use; what relationship did these early settlers have with the environment, and how did they utilise the resources available to them?

人们如何、何时以及为何首次抵达美洲并定居？这个谜题激发了科学界和公众的想象力，并且是持续争论的主题。 “克洛维斯优先”的传统模型认为，克洛维斯文化以其独特的石器命名，于 1920 年代和 1930 年代在新墨西哥州克洛维斯附近发现，大约在距今 13,500 年左右抵达该大陆。这些人可能在最后一个冰河时期海平面下降的时期穿过西伯利亚的白令海峡陆桥，最终在落基山脉东侧向南行进。最近，越来越多的证据表明了一个更为复杂的过程，可能还伴随着几波不同文化群体的移民浪潮。这导致了人类最初如何来到美洲尚未达成共识的情况。解决这一争论的主要障碍是缺乏保存完好的遗址和易于确定日期的材料，我们可以确定我们所约会的东西确实代表了人类的存在。这一时期的人类骨骼遗骸尤其罕见，而且由于 1990 年美国原住民坟墓保护和归还法案 (NAGPRA) 的限制，研究起来也极其困难。然而，一种更不寻常的考古证据在洞穴中保存完好：人类粪便化石，或粪化石。最著名的史前粪化石之一是来自俄勒冈州佩斯利洞穴的标本，距今 14,300 年；比克洛维斯文化的证据早一千年。这种粪化石是“前克洛维人”占领北美的有力证据。根据古代DNA，该粪化石被鉴定为人类，但地层完整性一直存在争议。这个问题仍然是该领域许多研究的基础。我们根本不知道这些分子在洞穴沉积物中的移动程度。这就是缺失的科学环节，它阻碍了粪化石被明确地用来证实前克洛维斯假说并解决这一长期争论。我们的研究将首次尝试通过生物地球化学和沉积物微形态学的新颖整合来解决这些问题——这是 PI 和 Co-I 成功开发的方法。沉积物微形态可以被认为是显微镜下的挖掘。完整的考古沉积物块被放置在树脂中并制成载玻片以在显微镜下观察。通过这种方式，我们可以直观地检查沉积物沉积的过程，以及它们随后是否发生了改变。将此与粪便脂质的生物地球化学分析相结合将使我们能够量化这些分子从其沉积点移动的程度。我们将结合特定化学成分的放射性碳测年来进行这种分析，而不是对样品中的所有有机材料进行测年，而是对粪化石中的各个化学成分进行测年。通过这种方式，我们可以提供可靠的物种鉴定，同时提供粪化石沉积的明确日期。无论这些早期定居者是谁，他们留下的这些看似不可能的证据来源都包含了大量信息，我们现在可以使用本研究项目中提出的新技术来获取这些信息。一旦我们能够证明在洞穴中发现的粪化石材料的完整性，从而对我们从其中获得的科学数据充满信心，我们就可以使用与粪化石一起保存的分子和化石来重建这些个体的饮食以及他们居住的环境。通过将其与高分辨率放射性碳测年联系起来，我们可以开始扩展研究潜力，以研究其他具有科学和考古意义的问题，例如洞穴使用的季节性；这些早期定居者与环境有什么关系？他们如何利用可用的资源？