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

人们是如何、何时以及为什么第一次到达并定居在美洲的？这个谜题已经引起了科学界和公众的想象力，并且是持续辩论的主题。“克洛维斯第一”的传统模式断言，克洛维斯文化，以他们在20世纪20年代和30年代在新墨西哥州的克洛维斯附近发现的独特的石器命名，大约在13,500 BP到达大陆。这些人可能是在最后一个冰河时期海平面下降的时候，穿越西伯利亚的白令吉亚陆桥，最终在落基山脉的东侧向南行进。最近，越来越多的证据表明这是一个更为复杂的过程，可能有几波不同文化群体的移民。这导致了一种情况，即人们对人类最初如何来到美洲没有共识。解决这一争论的主要障碍是缺乏保存完好的遗址和容易确定年代的材料，在那里我们可以确定我们所确定的年代确实代表了人类的存在。这一时期的人类骨骼遗骸特别罕见，而且由于1990年美国原住民坟墓保护和遣返法案（NAGPRA）的限制，研究起来也非常困难。然而，一种更不寻常的考古证据形式在洞穴中保存完好：化石化的人类粪便，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，其年代为公元前14,300年，比克洛维斯文化的证据早了1000年。这些粪化石是“前克洛维斯”占领北美的有力证据。根据古DNA鉴定，该粪化石属于人类化石，但其地层完整性一直存在争议。这是一个继续成为这一领域许多研究的基础的问题。我们只是不知道这些分子在洞穴沉积物中移动的程度。这是一个缺失的科学环节，它阻止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解决这些问题，通过使用一种新的整合地球化学和沉积物微形态-一种由PI和Co-I成功开发的方法。沉积物的微形态可以被认为是显微镜下的一次挖掘。考古沉积物的完整块被固定在树脂中，并在显微镜下观察。通过这种方式，我们可以直观地检查沉积物沉积的过程，以及它们随后是否被改变。将其与粪便脂质的生物化学分析相结合，将使我们能够量化这些分子从沉积点移动的程度。我们将结合特定化学成分的放射性碳测年进行这种分析-而不是测年样品中的所有有机物质，我们将测年粪化石中的单个化学成分。这样，我们就可以提供一个坚定的物种鉴定，同时明确的日期，当粪化石沉积。无论这些早期定居者是谁，他们留下的这些不太可能的证据来源包含了丰富的信息，我们现在可以使用本研究项目中提出的新技术访问这些信息。一旦我们能够证明洞穴中发现的粪化石材料的完整性，并因此对我们从中获得的科学数据有信心，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人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相结合，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的关系，以及他们如何利用可用的资源？

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?