Эрдэмтэд 60,000 гаруй ясны хэлтэрхийг шинжилж, денисовын хүн төрөлхтөнд хамаарах шууны ясны анхны баттай нотолгоог олж илрүүлжээ.
Хятадын Юньнань мужийн Бианьфү агуйгаас олдсон 60,000 гаруй ясны хэлтэрхийг судлаачид масс-спектрометрийн аргаар (ZooMS) шинжилж, денисовын хүн төрөлхтөнд хамаарах таван олдворыг ялгаж авчээ. Хятадын Шинжлэх ухааны академийн профессор Цяомэй Фү-гээр удирдуулсан судалгааны баг ясны хэлбэр дүрсээр урьдчилсан сонголт хийх болон уургийн шинжилгээг хослуулах замаар судалгааны үр ашгийг эрс нэмэгдүүлсэн байна. Энэхүү аргачлалын үр дүнд денисовын хүнд хамаарах шууны яс, хоёр гавлын ясны хэлтэрхий болон хоёр шүдийг баталгаажуулсан бөгөөд судалгааны үр дүнг Nature сэтгүүлд есдүгээр сарын 9-нд нийтэлжээ.
Олдворуудаас илэрсэн уургийн бүтэц, тухайлбал денисовын хүнд өвөрмөц COL1A2 R996K уургийн хувилбар нь тэдгээрийг бусад эртний хүн төрөлхтнөөс ялгах гол түлхүүр болсон байна. Шүдний паалан дахь уургийн шинжилгээгээр хоёр шүд нь эрэгтэй хүнийх болохыг тогтоосон бол хувьслын холбоог тогтоосон шинжилгээгээр бүх таван олдвор денисовын хүн төрөлхтөнтэй 100 хувийн магадлалтайгаар холбогджээ. Олдворууд нь дундад плейстоцений сүүл үе буюу ойролцоогоор 167,000-аас 134,000 жилийн өмнөх үед хамаарч байна.
Шууны ясны (BFD771) хэлбэр нь неандерталь хүний ястай төстэй том хэмжээтэй боловч ерөнхий гадаад төрх, хүзүүний хэсгийн геометрийн хувьд орчин үеийн хүнтэй илүү төстэй байгаа нь денисовын хүмүүсийн механик ачаалал болон дасан зохицлын өвөрмөц шинжийг харуулж байна. Бианьфү агуй нь Денисова агуйгаас гаднах денисовын олдвор хамгийн олноор олдсон газар болж байгаа бөгөөд тухайн бүс нутгийн уур амьсгал, хүнсний нөөц нь тэдний амьдрахад таатай орчин байсныг илтгэж байна. Энэхүү нээлт нь денисовын хүн төрөлхтний Ази дахь тархалт болон бие бялдрын онцлогийг ойлгоход чухал хувь нэмэр оруулж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
A forearm fragment from a cave in southwest China is the first confirmed Denisovan radius. Proteins preserved in the bone, and in four other remains from Bianfu Cave, identify their owner as a member of this ancient human group.
Denisovans are thought to have lived across much of Asia, but their fossil record is sparse, particularly for bones below the skull. That scarcity has left researchers with little evidence of the physical traits that helped them adapt to different environments.
Five remains from Bianfu Cave in Yunnan Province now begin to fill that gap. They date to the late Middle Pleistocene and cover a longstanding hole in the group’s known distribution in southwest China. According to the Chinese Academy of Sciences, Professor Qiaomei Fu of the Institute of Vertebrate Paleontology and Paleoanthropology led the research with multiple institutions, and the findings were published in Nature on September 9.
Finding a Few Bones Among 60,000
The cave held more than 60,000 bone fragments, so the first problem was simply where to look. Researchers increasingly use Zooarchaeology by Mass Spectrometry, or ZooMS, to screen large fossil collections through protein signatures. It requires minimally invasive sampling and is simple, fast, and relatively inexpensive. Even so, hominin fossil recovery rates at Denisova Cave and Baishiya Karst Cave have been just 0.1%, and running ZooMS on every Bianfu fragment would have been costly and inefficient.
So the team tried something different. Their “morphological pre-screening + ZooMS identification” strategy started with bone shapes, which yielded 22 potential hominin remains. ZooMS then confirmed that the two parietal fragments and the radius fragment were hominin.
The combined approach substantially improved screening efficiency, and the researchers describe it as “a repeatable method for searching other Paleolithic sites with abundant bone fragments,” as quoted by SciTechDaily.
What the Proteins Revealed?
Knowing a bone is hominin doesn’t say which group it belongs to. The researchers therefore analyzed proteins preserved in three bones and two teeth, recovering 6 to 16 proteins from each specimen. Protein fragments in the tooth enamel also indicated that both teeth belonged to males.
All five fossils carried the Denisovan-specific protein variant COL1A2 R996K. Additional variants in the teeth supported the identification and helped distinguish the fossils from other ancient human groups, including Homo erectus. Evolutionary trees built from the recovered sequences clustered all five specimens with the Denisovan specimen Denisova 3, with 100% posterior probability.
The layers matter too. The radius (BFD771) and one skull fragment (BFD767) came from Layer 7, dated to approximately 148,000 to 134,000 years ago. That layer also contained four hominin teeth, two of which the researchers included in the study: a lower fourth premolar (YHB3518) and a lower second molar (YHB3075). The other skull fragment, BFD769, came from the older Layer 9, dated to approximately 167,000 to 150,000 years ago.
A Forearm That Mixes Old And New
The radius fragment preserves the end nearest the elbow. Its large dimensions there resemble Neanderthal radii, as does the likely inward orientation of its radial tuberosity, the bony projection where the biceps muscle attaches. Its overall external shape, however, is closer to that of modern humans, and so is the geometry of a cross section through the middle of its neck, the narrowed region near the elbow end.
As explained by the researchers, this combination reflects distinctive mechanical demands and behavioral adaptations in Denisovans, differing from those inferred for Neanderthals and modern humans.
The two skull fragments, both pieces of parietal bones, offer another comparison. Their skull vault thickness patterns most closely resemble those of Homo heidelbergensis and late Middle Pleistocene archaic Homo from East Asia.
These findings make Bianfu Cave the richest known source of Denisovan fossils outside Denisova Cave. The remains date to a glacial period known as Marine Isotope Stage 6, and they suggest that the Yunnan-Guizhou Plateau’s relatively warm climate and abundant food resources may have provided a favorable habitat for Denisovans.
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