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2.9-million-year-old butchery site reopens case of who made first stone tools

Discovery of stone tools and cut-marked animal bones in Kenya offers window into the dawn of stone technology.


Along the shores of Africa’s Lake Victoria in Kenya roughly 2.9 million years ago, early human ancestors used some of the oldest stone tools ever found to butcher hippos and pound plant material, according to new research led by scientists with the Smithsonian’s National Museum of Natural History and Queens College, CUNY, as well as the National Museums of Kenya, Liverpool John Moores University and the Cleveland Museum of Natural History.


The study, published today, Feb. 9, in the journal Science, presents what are likely to be the oldest examples of a hugely important stone-age innovation known to scientists as the Oldowan toolkit, as well as the oldest evidence of hominins consuming very large animals. Though multiple lines of evidence suggest the artifacts are likely to be about 2.9 million years old, the artifacts can be more conservatively dated to between 2.6 and 3 million years old, said lead study author Thomas Plummer of Queens College, research associate in the scientific team of the Smithsonian’s Human Origins Program.

这项研究发表在2月9日的《科学》杂志上,展示了可能是最古老的石器时代创新的例子,科学家们将其称为奥尔多安工具组(Oldowan toolkit),以及人类食用大型动物的最古老证据。该研究的主要作者、史密森尼人类起源项目科学团队的助理研究员、皇后学院的托马斯·普卢默说,尽管多条证据表明这些文物可能有290万年的历史,但这些文物可以更保守地追溯到260万年到300万年之间。

Excavations at the site, named Nyayanga and located on the Homa Peninsula in western Kenya, also produced a pair of massive molars belonging to the human species’ close evolutionary relative Paranthropus. The teeth are the oldest fossilized Paranthropus remains yet found, and their presence at a site loaded with stone tools raises intriguing questions about which human ancestor made those tools, said Rick Potts, senior author of the study and the National Museum of Natural History’s Peter Buck Chair of Human Origins.

该遗址位于肯尼亚西部的霍马半岛,名为尼亚扬加(Nyayanga)。在该遗址的挖掘工作中,还发现了一对巨大的臼齿,属于人类进化上的近亲——副人类。该研究的资深作者、国家自然历史博物馆人类起源的彼得·巴克主席里克·波茨(Rick Potts)说,这些牙齿是迄今为止发现的最古老的类人猿化石,它们出现在一个堆满石器的地方,引发了一个有趣的问题,那就是人类的祖先是谁制造了这些工具。

“The assumption among researchers has long been that only the genus Homo, to which humans belong, was capable of making stone tools,” Potts said. “But finding Paranthropus alongside these stone tools opens up a fascinating whodunnit.”


Whichever hominin lineage was responsible for the tools, they were found more than 800 miles from the previously known oldest examples of Oldowan stone tools — 2.6-million-year-old tools unearthed in Ledi-Geraru, Ethiopia. This greatly expands the area associated with Oldowan technology’s earliest origins. Further, the stone tools from the site in Ethiopia could not be tied to any particular function or use, leading to speculation about what the Oldowan toolkit’s earliest uses might have been.


Through analysis of the wear patterns on the stone tools and animal bones discovered at Nyayanga, Kenya, the team behind this latest discovery shows that these stone tools were used by early human ancestors to process a wide range of materials and foods, including plants, meat and even bone marrow.


The Oldowan toolkit includes three types of stone tools: hammerstones, cores and flakes. Hammerstones can be used for hitting other rocks to create tools or for pounding other materials. Cores typically have an angular or oval shape, and when struck at an angle with a hammerstone, the core splits off a piece, or flake, that can be used as a cutting or scraping edge or further refined using a hammerstone.


“With these tools you can crush better than an elephant’s molar can and cut better than a lion’s canine can,” Potts said. “Oldowan technology was like suddenly evolving a brand-new set of teeth outside your body, and it opened up a new variety of foods on the African savannah to our ancestors.”


Potts and Plummer were first drawn to the Homa Peninsula in Kenya by reports of large numbers of fossilized baboon-like monkeys named Theropithecus oswaldi, which are often found alongside evidence of human ancestors. After many visits to the peninsula, a local man named Peter Onyango working with the team suggested they check out fossils and stone tools eroding from a nearby site that was ultimately named Nyayanga after an adjacent beach.

波茨和普卢默第一次来到肯尼亚的霍马半岛,是因为有报道称有大量名为奥氏狮尾狒的类似狒狒的猴子化石,它们经常与人类祖先的证据一起被发现。在对半岛进行了多次访问后,一位名叫彼得·奥尼扬戈(Peter Onyango)的当地人与该团队合作,建议他们检查一下附近一处遗址的化石和石器,该遗址最终以邻近的海滩命名为尼亚扬加(Nyayanga)。

Beginning in 2015, a series of excavations at Nyayanga returned a trove of 330 artifacts, 1,776 animal bones and the two hominin molars identified as belonging to Paranthropus. The artifacts, Plummer said, were clearly part of the stone-age technological breakthrough that was the Oldowan toolkit.


Compared to the only other stone tools known to have preceded them — a set of 3.3-million-year-old artifacts unearthed at a site called Lomekwi 3, just west of Lake Turkana in Kenya — Oldowan tools were a significant upgrade in sophistication. Oldowan tools were systematically produced and often fashioned using what is known as “freehand percussion,” meaning the core was held in one hand and then struck with a hammerstone being wielded by the opposing hand at just the right angle to produce a flake — a technique that requires significant dexterity and skill.


By contrast, most of the artifacts from Lomekwi 3 were created by using large stationary rocks as anvils, with the toolmaker either banging a core against the flat anvil stone to create flakes or by setting the core down on the anvil and striking it with a hammerstone. These more rudimentary modes of fabrication resulted in larger, cruder and more haphazard-looking tools.


Over time, the Oldowan toolkit spread all the way across Africa and even as far as modern-day Georgia and China, and it was not meaningfully replaced or amended until some 1.7 million years ago when the hand-axes of the Acheulean first appeared.


As part of their study, the researchers conducted microscopic analysis of wear patterns on the stone tools to determine how they were used, and they examined any bones seen to exhibit potential cut marks or other kinds of damage that might have come from stone tools.


The site featured at least three individual hippos. Two of these incomplete skeletons included bones that showed signs of butchery. The team found a deep cut mark on one hippo’s rib fragment and a series of four short, parallel cuts on the shin bone of another. Plummer said they also found antelope bones that showed evidence of hominins slicing away flesh with stone flakes or of having been crushed by hammerstones to extract marrow.


The analysis of wear patterns on 30 of the stone tools found at the site showed that they had been used to cut, scrape and pound both animals and plants. Because fire would not be harnessed by hominins for another 2 million years or so, these stone toolmakers would have eaten everything raw, perhaps pounding the meat into something like a hippo tartare to make it easier to chew.


Using a combination of dating techniques, including the rate of decay of radioactive elements, reversals of Earth’s magnetic field and the presence of certain fossil animals whose timing in the fossil record is well established, the research team was able to date the items recovered from Nyayanga to between 2.58 and 3 million years old.


“This is one of the oldest if not the oldest example of Oldowan technology,” Plummer said. “This shows the toolkit was more widely distributed at an earlier date than people realized, and that it was used to process a wide variety of plant and animal tissues. We don’t know for sure what the adaptive significance was but the variety of uses suggests it was important to these hominins.”


The discovery of teeth from the muscular-jawed Paranthropus alongside these stone tools begs the question of whether it might have been that lineage rather than the Homo genus that was the architect of the earliest Oldowan stone tools, or perhaps even that multiple lineages were making these tools at roughly the same time.