Rescue Excavation of Large Mammal Skeleton and Associated Stone Tools from Temporarily Exposed Section, Lake Victoria, Kenya

2009年9月，T.布朗陪同L博士。巴塞尔和发现了一个深沟沉积物海岸的维多利亚附近的一个小镇叫奇安达乌尤马半岛，这是积极侵蚀揭示骨骼和文物。他们在寻找维多利亚湖的岩石和前海岸线时，注意到半关节式的大型哺乳动物骨骼和从侵蚀活跃的斜坡上突出的象牙。更仔细的检查发现了来自小型哺乳动物的更多骨碎片，其中一些似乎被切割标记，以及头骨碎片。在被侵蚀的表面上和周围散布着石器，包括熔岩、凝灰岩和石英的薄片和核心。巴塞尔（一位石器专家）认为这些是中石器时代的古物。中石器时代是非洲的一个时期，被认为持续了大约50万至5万年前，与我们物种最早的成员智人的进化有关，但很少有遗址已经过时。同时发现这个时代的化石和岩屑在东非环境中是非常不寻常和重要的，因为土壤条件通常是酸性的，骨头不能很好地保存。然而，研究人员也知道，在20世纪30年代，一位热心的考古学家和路易斯·利基的亲密同事，副主教欧文在奇安达附近进行了调查和收集。他收集化石和石器材料，但没有挖掘。他认为他发现的化石动物群是中新世的，是一系列被称为希威吉组的沉积物的一部分。欧文从基安达东部和南部的其他中新世遗址收集了材料，如鲁辛加岛，那里的希威吉组现在被认为是超过1800万年的。肯尼亚西部以其中新世化石而闻名，在几十年来集中研究的几个地点发现了各种各样的动物和植物遗骸。在Rusinga的某些地方，这些遗址包含令人难以置信的保存完好的树枝，坚果和浆果，尽管在那里进行了80年的研究，但仍继续发现新的动物物种。这些遗址最著名的原因可能是它们发现了一种非常早期的灵长类动物的遗骸，称为Pro Consul，一些研究人员认为它是智人的远祖。动物群和植物群化石的确切年龄仍然存在争议，多年来研究的不同地点如何相互关联，以及特定地点之外的环境条件究竟是什么样的，也存在一些困惑。例如，中新世时这里有湖泊吗？现在的维多利亚湖大约有爱尔兰那么大，但以前的研究表明，这个湖大约在40万年前才形成，而且由于大规模的气候波动，它可能已经完全干涸了好几次。在此之前，人们对该地区的环境知之甚少。无论奇安达遗址是中新世还是更近的，这种情况下的脊椎动物遗骸都是古老而罕见的。它们被侵蚀的沉积物范围有限，椎骨和象牙的位置表明，一些尸体可能已经被侵蚀掉了。这个项目是一个救援挖掘，以保护这个不寻常的发现和任何其他化石或文物发现之前，它被摧毁。古环境专家布朗教授对奇安达的地层序列进行了进一步研究，发现这里有可以确定年代的沉积物，这些沉积物表明是沼泽边缘或浅水河流/湖泊环境。斯图尔特博士、I.布玛儿和艾博士Onjala，他们将尝试找出动物是什么，该网站是多么古老，并采取样本，使我们能够了解以前的环境条件在该地区，以及他们如何与过去的气候变化。

Whilst investigating potential Middle Stone Age sites in Kenya in September 2009 Prof T. Brown accompanied Dr L. Basell and discovered a deep gully in sediments on the shore of Lake Victoria near a town called Chianda on the Uyoma Peninsula which was actively eroding revealing bones and artefacts. They were looking for lithics and former shorelines of Lake Victoria, when they noticed semi-articulated large mammal bones and a tusk protruding from the actively eroding slope. Closer examination revealed further fossilised bone fragments from smaller mammals some of which appeared to be cut marked, and skull fragments. Strewn over and around the eroding face were stone tools including both flakes and cores of lavas, tuffs and quartz. Basell (a stone tool specialist) considers these to be of Middle Stone Age antiquity. The Middle Stone Age is a period in Africa that is thought to last from about 500,000-50,000 years ago and is associated with the evolution of the earliest members of our species, Homo sapiens but there are very few sites which have been well dated. Finding fossils and lithics of this age together is extremely unusual and important in an eastern African setting, as soil conditions are generally acidic and bone of does not preserve well. However, the researchers also knew that during the 1930s Archdeacon Owen, a keen archaeologist and close colleague of Louis Leakey conducted survey and made collections near Chianda. He collected fossil and lithic material but did not excavate. He believed the fossilised fauna he found was Miocene in age and part of a sequence of deposits called the Hiwegi Formation. Owen had collected material from other Miocene sites to the east and south of Chianda in places such as Rusinga Island where the Hiwegi Formation is now thought to be >18 million years old. Western Kenya is well known for its Miocene fossils, and a wide array of animal and plant remains has been found at several sites where research has been concentrated over decades. In certain places on Rusinga, these sites contain incredibly well preserved twigs, nuts and berries, and new faunal species continue to be discovered despite 80 years of research there. These sites are perhaps best known because they have yielded remains of a very early primate called Pro Consul which some researchers think is a distant ancestor of Homo sapiens. The precise age of the faunal and floral fossils is still debated, and there is some confusion about how the different sites researched over the years relate to each other, and exactly what the environmental conditions were like beyond specific sites. For example, was there a lake here during the Miocene? The present Lake Victoria is about the size of Ireland but previous research has suggested that the lake only formed about 400,000 years ago and may have dried up entirely several times since then as a result of large-scale climatic fluctuations. Very little is known about the regional environment prior to this. Whether the Chianda site is Miocene or more recent, the vertebrate remains in this condition are old and rare. The deposits from which they are eroding are limited in extent and the position of the vertebrae and tusk suggests that some of the carcass or carcasses may have already been eroded away. This project is a rescue excavation to preserve this unusual find and any other fossils or artefacts found with it before it is destroyed. Further examination of the stratigraphic sequence at Chianda by Prof. Brown, a palaeoenvironmental specialist, indicated that there were deposits here which could be dated and that the deposits indicate a marsh edge or a shallow river/lake environment. With three further experts Dr J. Stewart, Dr. I. Boomer and Dr I. Onjala, they will try and find out what the animal is, how old the site is and take samples so we can learn about previous environmental conditions in the area and how they relate to past climatic change.