Building a Better Egg Timer?

制作一个更好的煮蛋计时器？

• 批准号: NE/G005338/1
• 负责人: Julia Lee-Thorp
• 金额: $ 5.53万
• 依托单位: University of Bradford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG005338%2F1
• 关键词: Building; Better; Egg; Timer

Fossil and DNA evidence suggests that our species, Homo sapiens, emerged nearly 200,000 years ago in Africa, but until recently it seemed that many of the signs of what we would consider 'modern behaviour' were not evident until after 50,000 years ago. The archaeological evidence for this crucial period is exceedingly sparse and poorly dated. The dramatic climate and environmental changes that occurred during this period were likely to be critical influences, but in the absence of reliable dating methods it is difficult to link the patchy human record with existing continuous global climate records, or regional records where they exist. The picture has begun to change with the development of new dating methods and accumulating evidence for the early occurrence of modern behaviours, such as marine resource exploitation and the appearance of decorated or decorative objects in several sites. The latter include indications that ostrich eggs were used as containers and as decorative beads. However, at present none of these artefacts can be dated directly and precisely. One method that can be used to date shells and eggshells directly is amino acid racemization (AAR) geochronology, which measures the decay of proteins. Because the decay rate is driven by time and temperature, the relative age can be deduced by comparison with other samples. Determination of an absolute date is more challenging. In order to provide a robust and precise age estimate, the mechanisms that drive the decay reaction must be understood. We have been developing a refinement of amino acid geochronology, called 'Intra-crystalline Protein Decomposition' (IcPD), isolating and analysing only the protein from a particular fraction of shells, where the proteins have been trapped within the shell crystals. This effectively forms a protein 'time capsule', within which changing concentrations of the products and reactants of protein decay should enable us to pick apart the reaction pathways. In the past we have been limited by crude measurements of decay, but technological advances, notably in mass spectrometry, now enable us to observe both products and reactants in considerable detail. We plan to explore the reaction pathways in ostrich eggshell fragments, the ultimate 'egg-timer'. Preliminary results reveal the first evidence of a decay pathway in the main protein entrapped in ancient shell, called struthiocalcin. The protein first appears to split into three pieces and each piece is 'nibbled away' from one end. By using a combination of model systems (synthetic peptides, heated shells and shell proteins) and shell fragments recovered from the stratified and well-dated archaeological sequence in Elands Bay Cave, South Africa, we can explore how this initial pattern develops. Once a more complete picture of decay is understood, we will put together a model of the decay path (which identifies the temperature sensitivity of key reactions). We will then apply this model to estimate the age of eggshell fragments found in a rich archaeological sequence at Pinnacle Point, South Africa, to refine the chronological framework of these early modern human sites. But the ostrich eggshells are more than just egg-timers - if we look at the isotopic composition of the eggshells, this also reveals information about climate and environment. Thus we can establish a robust, directly dated record of changes in vegetation and importantly, in aridity, for the region. This data can be linked to longer climate records to build up a more complete picture of the relationships between changing human behaviour and changing environments.

化石和DNA证据表明，我们的物种智人在近20万年前出现在非洲，但直到最近，许多我们认为的“现代行为”的迹象直到5万年后才显现出来。这一关键时期的考古证据极其稀少，年代也很糟糕。在此期间发生的巨大气候和环境变化可能会产生重大影响，但在缺乏可靠的年代测定方法的情况下，很难将零散的人类记录与现有的连续全球气候记录或存在的区域记录联系起来。随着新的年代测定方法的发展和现代行为早期发生的证据的积累，情况开始发生变化，例如海洋资源开发和几个地点出现装饰性或装饰性物体。后者包括鸵鸟蛋被用作容器和装饰珠的迹象。然而，目前这些文物都不能直接和准确地确定年代。一种可以直接测定蛋壳和蛋壳的年代的方法是氨基酸外消旋(AAR)地质年代学，它测量蛋白质的腐烂程度。由于衰变速率由时间和温度驱动，因此可以通过与其他样品的比较来推断相对年龄。确定一个绝对日期更具挑战性。为了提供可靠和准确的年龄估计，必须了解驱动衰变反应的机制。我们一直在开发一种氨基酸地质年代学的改进方法，称为“晶体内蛋白质分解”(ICPD)，只从贝壳的特定部分分离和分析蛋白质，在那里蛋白质被困在贝壳晶体中。这实际上形成了一个蛋白质“时间胶囊”，在这个胶囊内，蛋白质腐烂的产物和反应物的浓度变化应该使我们能够拆分反应路径。在过去，我们受到对衰变的粗略测量的限制，但技术进步，特别是在质谱学方面的进步，现在使我们能够相当详细地观察产品和反应物。我们计划探索鸵鸟蛋壳碎片中的反应路径，这是终极的“鸡蛋计时器”。初步结果首次揭示了古壳中的主要蛋白质存在一条衰变途径的证据，这种蛋白质被称为结构硫钙素。这种蛋白质首先会分裂成三块，每一块都会从一端被“啃掉”。通过使用模型系统(合成肽、加热的贝壳和贝壳蛋白)和从南非埃兰德湾洞穴考古层序中发现的贝壳碎片，我们可以探索这种初始模式是如何发展的。一旦了解了更完整的衰变图景，我们将建立一个衰变路径的模型(它确定了关键反应的温度敏感性)。然后，我们将应用这个模型来估计在南非顶峰点发现的丰富考古序列中发现的蛋壳碎片的年龄，以完善这些早期现代人类遗址的年代框架。但鸵鸟蛋壳不仅仅是鸡蛋计时器--如果我们观察蛋壳的同位素组成，这也揭示了气候和环境的信息。因此，我们可以建立一个强有力的、直接注明日期的植被变化记录，更重要的是，记录该地区的干旱变化。这些数据可以与更长的气候记录相联系，以建立起人类行为变化和环境变化之间关系的更完整的图景。

项目成果

Climate, Environment and Early Human Innovation: Stable Isotope and Faunal Proxy Evidence from Archaeological Sites (98-59ka) in the Southern Cape, South Africa.

• DOI: 10.1371/journal.pone.0157408
• 发表时间: 2016
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Roberts P;Henshilwood CS;van Niekerk KL;Keene P;Gledhill A;Reynard J;Badenhorst S;Lee-Thorp J
• 通讯作者: Lee-Thorp J

Ostrich eggshell provides an environmental proxy directly associated with cultural change in the Late Pleistocene of the southern Cape coast, South Africa.

鸵鸟蛋壳提供了与南非开普省南部海岸更新世晚期文化变迁直接相关的环境代理。

• 作者: Lee-Thorp JA