Building a Better Egg Timer?

制作一个更好的煮蛋计时器？

• 批准号: NE/G005338/2
• 负责人: Julia Lee-Thorp
• 金额: $ 3.89万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG005338%2F2
• 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，出现在近20万年前的非洲，但直到最近，似乎我们所认为的“现代行为”的许多迹象直到5万年前才变得明显。这一关键时期的考古学证据非常稀少，而且日期也不明确。在这一时期发生的剧烈气候和环境变化可能是关键的影响，但在缺乏可靠的测年方法的情况下，很难将零散的人类记录与现有的连续全球气候记录或区域记录联系起来。随着新的测年方法的发展和现代行为早期发生的证据的积累，例如海洋资源开发和在几个地点出现装饰或装饰性物品，情况开始发生变化。后者包括鸵鸟蛋被用作容器和装饰珠子的迹象。然而，目前这些人工制品都不能直接和精确地确定年代。一种可以直接用来测定贝壳和蛋壳年代的方法是氨基酸消旋（AAR）地质年代学，它测量蛋白质的衰变。由于衰变率受时间和温度的驱动，因此可以通过与其他样品的比较来推断相对年龄。确定绝对日期更具挑战性。为了提供可靠而精确的年龄估计，必须了解驱动衰变反应的机制。我们一直在开发一种改进的氨基酸地质年代学，称为“晶内蛋白质分解”（ICPD），只分离和分析来自特定部分的蛋白质，其中蛋白质被困在壳晶体中。这有效地形成了一个蛋白质的“时间胶囊”，在这个胶囊中，蛋白质衰变的产物和反应物的浓度变化应该使我们能够分辨出反应途径。在过去，我们一直受到衰变的粗略测量的限制，但是技术的进步，特别是质谱法，现在使我们能够相当详细地观察产物和反应物。我们计划探索鸵鸟蛋壳碎片中的反应途径，这是最终的“蛋计时器”。初步结果揭示了第一个证据，即在古代贝壳中捕获的主要蛋白质中存在衰变途径，称为struthiocalcin。蛋白质首先分裂成三块，每一块都从一端被“蚕食”。通过使用模型系统（合成肽，加热的外壳和外壳蛋白质）和从南非伊兰湾洞穴的分层和日期明确的考古序列中恢复的外壳碎片的组合，我们可以探索这种初始模式是如何发展的。一旦对衰变有了更完整的了解，我们将建立一个衰变路径模型（确定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品尼高角丰富的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。但是鸵鸟蛋壳不仅仅是蛋计时器-如果我们看看蛋壳的同位素组成，这也揭示了气候和环境的信息。因此，我们可以建立一个强大的，直接日期的植被变化记录，重要的是，在干旱，为该地区。这些数据可以与较长的气候记录联系起来，以便更全面地了解人类行为变化与环境变化之间的关系。

项目成果

A palaeoprecipitation sequence from stable isotopes in ostrich eggshell at Pinnacle Point, Mossel Bay.

莫塞尔湾 Pinnacle Point 鸵鸟蛋壳中稳定同位素的古沉淀序列。

• 发表时间: 2014
• 作者: Lee-Thorp, JA

Holocene Environmental Change at Wonderwerk Cave, South Africa: Insights from Stable Light Isotopes in Ostrich Eggshell

南非 Wonderwerk 洞穴全新世环境变化：来自鸵鸟蛋壳中稳定轻同位素的见解

• DOI: 10.1007/s10437-015-9202-y
• 发表时间: 2015
• 期刊: African Archaeological Review
• 影响因子: 1.6
• 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