标题：
千年乳酪重现历史：我国西北古墓惊现古代人类食品
正文：
中国西北地区，考古学家们在一处被称为小何公墓的地点，发现了数千年前埋葬在荒漠中的青铜时代居民遗迹。这些死者被以奇异方式安葬——在头部和颈部散落着奶酪，或许是为他们通往另一个世界的旅程准备的美味零食。
经过十年的研究，科学家从这些古老的乳酪中提取并进行了测序，这是迄今为止人类考古发现中最古老的一块乳酪。这一突破揭示了小何人制作乳酪的方式，并揭示了古代人类如何利用微生物改善食物以及通过微生动态追踪文化影响的历史长河。
研究发表在《细胞》杂志上，“这开启了古代DNA研究的新领域。”哈佛大学社会科学与人类学教授克里斯蒂娜·沃内尔森说，她未参与此研究。她说：“当今发酵食品大多仅使用少量人工培育的商业细菌和酵母制造，很少有人知道过去人们如何利用多样化的传统微生物生产今天的标志性食品。”
科学家姜秋梅领导的研究小组在样品乳酪中识别出了山羊和牛的DNA，证实了其为基夫乳酪——现今广泛制作并食用的一种奶酪。她是北京古脊椎动物与人类研究所的古代DNA实验室主任。
千年之前的小何人如何制作基夫乳酪
1990年代，在中国的新疆地区发现了一片荒凉的沙漠地带，小何墓地中的自然风干条件保存了大约4000年历史的数百具木乃伊。面部特征和发色依然清晰可见，他们的服装以羊毛制品和编织物为主，并被安葬在不寻常的船只型坟墓中。
这些所谓的塔里木盆地木乃伊及其多种文化影响长期以来一直困扰着考古学家。尽管他们属于一个基因隔离的群体，但仍然接受新思想和技术。
研究显示，小何人可能没有将不同类型的动物奶混合用于制作基夫乳酪——这是传统中东和希腊奶酪制造中常见的做法，目前不明确原因是什么。
“小何人在做基夫乳酪时使用的是一种家庭、朋友和其他社会联系传递的先前制备的基夫颗粒（类似于康普茶菌种或面包发面团）的方式。”阿肯色大学人类学副教授泰勒·赫姆斯说，“这是研究如此重要的部分——我们能看见这些微生物商品如何流传并在亚洲传播。”
进化中的益生菌
姜秋梅团队发现，墓地中发现的三份乳酪样本含有细菌和真菌种类，包括一种常见的现今基夫颗粒中的乳酸杆菌-科非坦种（Lactobacillus kefiranofaciens）和皮奇亚-库德里亚泽维希亚种(Pichia kudriavzevii)，这些通常都包含在基夫乳酪中。这种颗粒结合了益生菌细菌与酵母，将奶发酵成基夫乳酪。
姜秋梅及其同事也对古代基夫乳酪中的细菌基因进行了测序，揭示了在过去3600年中益生菌细菌的进化过程。目前有两类主要的Lactobacillus细菌——一种源自俄罗斯，另一种来自中国西藏的一个自主行政区，根据研究显示，这两类细菌在全球范围内广泛使用。
当姜秋梅及同事将古代基夫乳酪中的乳酸杆菌-科非坦种与现代物种进行比较时，发现它与起源于西藏的不常见Lactobacillus群落密切相关。这一细菌起源挑战了基夫乳酪仅在高加索山脉地区起源的传统观点。
“这是一项前所未有的研究，使我们能够观察到一个细菌在过去3000年中的进化过程。”姜秋梅说，“通过分析奶制品，我们对古代人类生活及其与世界互动有了更清晰的了解。这只是开始。”
令人惊叹的是，在如此古老的历史中保存了乳酪，并且有可能从食品中提取DNA。
“微生物的古代DNA分析通常面临技术难题，主要是由于现代细菌的污染。”阿肯色大学人类学助理教授赫姆斯补充道，“在没有冷藏的情况下储存牛奶几乎是不可能的，因此发酵过程不可避免地在几分钟内开始。”
“小何人会用与当今传统生产者相同的方式制作基夫乳酪——通过使用先前通过家庭、朋友和其他社交联系传递的基夫颗粒。”
这些发现揭示了奶酪和其它乳制品是古代社会生活方式的基础，对人类文明影响深远，并且至今仍构成我们生活的重要部分。
新闻来源：www.cnn.com
原文地址：DNA from 3,600-year-old cheese sequenced by scientists
新闻日期：2024-09-25
原文摘要：
Bronze Age desert dwellers unearthed from graves in what’s now northwest China were buried with cheese scattered on their heads and necks — perhaps as a snack packed for the afterlife. A decade after the dairy discovery on strikingly intact remains mummified by the Taklamakan Desert’s arid conditions, scientists have extracted and sequenced DNA from the 3,600-year-old cheese, the oldest in the archaeological record. The analysis revealed how the Xiaohe people made cheese, showing the way humans harnessed microbes to improve their food and how microbes can be used to track cultural influences through the ages. The findings, published Wednesday in the journal Cell, open a “new frontier in ancient DNA studies,” with this “type of research unthinkable even a decade ago,” said Christina Warinner, John L. Loeb Associate Professor of the Social Sciences and Anthropology at Harvard University. Warinner wasn’t involved in the research. “Fermented foods today are overwhelmingly produced using only a handful of mostly lab-grown commercial strains of bacteria and yeasts,” she said. “Little is known about the once diverse range of heirloom microbes that people used in the past to produce today’s most iconic foods — ranging from bread to cheese and from beer to wine.” A team led by Chinese paleogeneticist Qiaomei Fu identified goat and cattle DNA in samples of the cheese. The researchers were was also able to sequence DNA of microbes contained in the cheese, confirming it was kefir, a type of cheese that’s still widely made and eaten today. Fu is director of the ancient DNA laboratory at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. How an enigmatic desert people made kefir Hundreds of mummified individuals were found in the 1990s in what’s known as the Xiaohe cemetery in the Tarim Basin, an inhospitable desert area in China’s Xinjiang region. Naturally preserved by the dry desert air, their facial features and hair color are clearly discernible despite being up to 4,000 years old. Buried with felted and woven clothing in unusual boat graves, the so-called Tarim Basin mummies and their assortment of cultural influences have long puzzled archaeologists. Despite belonging to a genetically isolated group, the individuals nevertheless embraced new ideas and technologies, according to an October 2021 study. The new research suggested that the Xiaohe people did not mix different types of animal milk when making kefir, a practice common in traditional Middle Eastern and Greek cheesemaking, although it’s not clear why. “The Xiaohe people would have made cheese in the same manner that traditional producers make kefir cheese today, by using previously made kefir grains (similar to kombucha mother or bread starter) that was passed on through family, friends and other social contact,” said Taylor Hermes, an assistant professor in the department of anthropology at the University of Arkansas, who was not involved in the research. “This is what makes the study so important — we can see how these microbial commodities were handed down and spread throughout Asia,” Hermes said. Evolution of probiotic bacteria Fu’s team discovered that the three cheese samples from the graves contained bacterial and fungal species, including Lactobacillus kefiranofaciens and Pichia kudriavzevii, respectively, both commonly found in present-day kefir grains. The grains are a mix of probiotic bacteria and yeast that ferment milk into kefir cheese. Fu and her colleagues also sequenced the bacterial genes in the ancient kefir cheese, revealing insights into how probiotic bacteria evolved over the past 3,600 years. Today, there are two major groups of Lactobacillus bacteria — one that originated in Russia and another from Tibet, an autonomous region of China, according to the study. The Russian type is widely used globally, including in the United States, Japan and European countries, for making yogurt and cheese. When Fu and her colleagues compared Lactobacillus kefiranofaciens from the ancient kefir cheese with the modern-day species, they found that it was closely related to a less common group of Lactobacillus that originated in Tibet. The bacterium’s origins challenge a long-held belief that kefir began solely in the Caucasus Mountains region, Fu said. “This is an unprecedented study, allowing us to observe how a bacterium evolved over the past 3,000 years. Moreover, by examining dairy products, we’ve gained a clearer picture of ancient human life and their interactions with the world,” Fu said in a statement. “This is just the beginning.” It was remarkable that not only had the cheese survived but that it was possible to sequence DNA from the foodstuff, Hermes said. “Ancient DNA analysis, especially on microbes, is fraught with technical problems, mostly stemming from contamination by modern bacteria,” he added. When did cheesemaking really start? It wasn’t surprising that the Xiaohe people fermented cheese, Warinner said. The process made milk more easily digestible, with microbes producing lactic acid that causes milk to curdle and form the basis of cheese. “In the absence of refrigeration, it is essentially impossible to store milk for more than a few hours with spontaneous fermentation setting in so there was probably never a time when milk and dairy were used without fermentation,” she said. “However, over time people became better and better at controlling fermentation and selecting for specific microbes that produced the most desirable effects in dairy production,” she added. While the dairy product found with the mummies is the oldest intact cheese in the archaeological record, other evidence such as animal proteins in human dental calculus and milk residues on pottery suggest that cheesemaking originated much earlier, likely more than 9,000 years ago in Anatolia or the Levant, Warinner noted. The genomic analysis that the team performed was truly groundbreaking, said William Taylor, an assistant professor of anthropology at the University of Colorado Boulder and curator of archaeology at the school’s Museum of Natural History. “It’s amazing to see the complexity of the products that folks were making, which normally isn’t preserved in the archaeological record,” said Taylor, who wasn’t involved in the research. “These incredible findings show us that cheese and other dairy products were really the foundation of a whole way of life that would continue to be important for millennia and is still a huge part of life today.”
