香港——二十年前，在中国的西北部地区发掘出一具距今三千六百年的年轻女子棺木时，考古学家在她的颈部发现了一件像珠宝般的神秘物质。那是一块乳酪，而科学家们现在表示这是有史以来找到的最古老的乳酪。“通常的乳酪是柔软的，但这块却不如此，它已变成十分干燥、紧致和坚硬的尘土。”中国科学院北京的一位古遗传学家傅晓梅说。她和团队在周二发表于《细胞》杂志上的研究报告中透露了对这块乳酪样本进行DNA分析的结果，这些结果讲述了现在被称为新疆地区的小河人生活的方式以及他们与哺乳动物之间的互动。同时，这也有助于了解亚洲东部畜牧养殖业的演变。
这座青铜时代的棺木是在2003年挖掘新疆小河墓地时发现的。由于该女子的棺木在塔里木盆地沙漠干燥气候下被覆盖并埋葬，因此它以及她的靴子、帽子和包裹着她身体的乳酪都保存完好。古时候，与死者的葬礼物品往往包含对死者具有重要意义的东西。事实证明，那些物品中包含了一块硬奶菌乳酪，这表明“对于他们来说，乳酪非常重要。”傅晓梅补充道。
人们对乳酪的喜爱可以追溯到数千年前。在公元前2000年的古埃及墓室壁画上就描绘了其制作过程，而欧洲的这种做法至少可追溯7000年历史，但科学家们说塔里木盆地样本是实际找到的最古老乳酪样品。傅晓梅及其团队从墓地中的三个坟墓中取样，并对这些DNA进行了处理以追踪数千年间细菌的演变。他们认定此乳酪为硬奶菌乳酪，它是通过使用硬奶菌颗粒发酵牛奶制成的。他们还发现有羊奶和牛奶使用的证据。
此研究揭示了乳酪的旅行路径及其对最终乳酪生产影响的历史线索，同时表明了小河人在过去没有巴氏杀菌与冷藏的时代如何摄入乳制品——而奶酪生产能降低乳糖含量。此前的研究曾提出硬奶菌从现代俄罗斯北部高加索地区传播至欧洲及其他地方这一观点，但这项研究揭示其传播路径还包括向亚洲内地的另一条路线：经过西藏从当今的新疆出发，这提供了关键证据显示了青铜时代人群间的互动。
傅晓梅团队分析的DNA还表明，随着抗生素的普及，细菌菌株获得了对抗生素的耐药性。“如今它们对药物非常有抵抗力。”傅晓梅说。同时，研究也揭示了细菌适应过程——这些原本可能引发人体免疫系统反应的细菌也进行了自我调整，显示这对人类的免疫系统有益并有助于抗体产生。“我们可以看到，在某个点上它与人类相互适应。”
数千年人类活动的演变也在影响着微生物进化的进程，这项研究发现了一种细菌亚种的分化正是由硬奶菌跨人群传播推动的。
被问及是否认为这块乳酪依然可食且她是否会尝试时，傅晓梅表示：“绝对不可能。”
新闻来源：www.nbcnews.com
原文地址：World’s oldest cheese found on ancient Chinese mummies
新闻日期：2024-09-26
原文摘要：
HONG KONG — When the 3,600-year-old coffin of a young woman was excavated in northwestern China two decades ago, archeologists discovered a mysterious substance laid out along her neck like a piece of jewelry. It was made of cheese, and scientists now say it’s the oldest cheese ever found. “Regular cheese is soft. This is not. It has now become really dry, dense and hard dust,” said Fu Qiaomei, a paleogeneticist at the Chinese Academy of Sciences in Beijing and the co-author of a study published Tuesday in the journal Cell. A DNA analysis of the cheese samples, she told NBC News in a phone interview Thursday, tells the story of how the Xiaohe people — from what’s now known as Xinjiang — lived and the mammals they interacted with. It also shows how animal husbandry evolved throughout East Asia. The Bronze Age coffin was discovered during the excavation of the Xiaohe Cemetery in 2003. Since the woman’s coffin was covered and buried in the dry climate of the Tarim Basin desert, Fu said, it was well preserved, as were her boots, hat and the cheese that laced her body. Ancient burial practices often included items of significance to the person buried alongside them. The fact that those items included chunks of kefir cheese alongside the body showed that “cheese was important for their life,” she added. A fondness for cheese dates back thousands of years. Its production was depicted on wall murals in ancient Egyptian tombs in 2000 BC, and traces of the practice in Europe date back almost 7,000 years, but scientists say the Tarim Basin samples are the oldest samples of cheese actually found. Fu and her team took samples from three tombs in the cemetery, and the team then processed the DNA to trace the evolution of the bacteria across thousands of years. They identified the cheese as kefir cheese, which is made by fermenting milk using kefir grains. Fu said they also found evidence of goat and cow milk being used. The journey of the cheese took them to tracing the journey of the kefir culture, which is used to make the final cheese. The study also shows how Xiaohe people, who were known to be genetically lactose intolerant, consumed dairy before the era of pasteurization and refrigeration, as cheese production lowers lactose content. While previous research has suggested kefir spread from the northern Caucasus in modern Russia to Europe and beyond, the study shows the spread also took another route toward inland Asia: from present-day Xinjiang via Tibet, giving crucial evidence of how the Bronze Age populations interacted. The DNA analyzed by Fu’s team also suggested that the bacteria strains gained resistance to antibiotics as they became more prevalent throughout the years. “Today they’re actually very resistant to medicine,” Fu said. But it also showed how the bacteria, which would have earlier triggered immune system responses in humans, also adapted. “They are also good for the immune system and for producing antibodies. We can see at some point it adapted to humans.” The evolution of human activities spanning thousands of years also affected microbial evolution, the study found, citing the divergence of a bacterial subspecies that was found to have been facilitated by the spread of kefir across different populations. Asked if the kefir cheese was still edible and if she would try it, Fu was less enthusiastic. “No way,” she said.
