Эрдэмтэд Сибирийн алдарт Денисовын агуйгаас олдсон ясны хэлтэрхийнүүдэд генетикийн шинжилгээ хийж, өмнө нь бүртгэгдээгүй сарлагийн төрөл зүйлийг тогтоожээ.
Алтай уулын бэлд орших Денисовын агуй нь эртний хүн төрөлхтний үлдэгдлээрээ алдартай бөгөөд энд 250,000 гаруй ясны хэлтэрхий хадгалагдаж байдаг. Шинжилгээнд хамрагдсан ясны үлдэгдлийн 95 хувь нь хэт жижиг, бүрэн бус байсан тул судлаачид Current Biology сэтгүүлд нийтлэгдсэн судалгаандаа ДНХ-ийн шинжилгээний аргыг ашиглажээ. Энэхүү судалгаагаар “сарлаг X” хэмээн нэрлэсэн, мөхсөн зүйлийн дор хаяж 20 геномыг илрүүлсэн байна.
Генетикийн судалгаагаар “сарлаг X” нь орчин үеийн Гималайн сарлагтай 400,000 жилийн өмнө нэг өвөг дээдсээс салж, 250,000 жилийн өмнө бүрмөсөн тусгаарлагдсан болохыг тогтоожээ. Стокгольмын их сургуулийн судлаач Лав Дален болон түүний баг эдгээр амьтны гадаад төрх нь орчин үеийн сарлагтай төстэй байсан байж болох ч яг ямар шинж чанартай байсныг тодорхойлох боломжгүй хэвээр байгааг тэмдэглэв. Тэд одоогоор “сарлаг X”-ийн уургийн кодлогч генийг судалж, орчин үеийн сарлагаас ялгаатай талуудыг тогтоохоор ажиллаж байна.
Эрдэмтдийн олсон хамгийн сүүлийн үеийн геном 27,000 жилийн настай бол хамгийн эртнийх нь 247,000 жилийн настай аж. Энэхүү олдвор нь эртний хүмүүс, тухайлбал Денисов болон Неандерталчууд тухайн бүс нутагт амьдарч байх үедээ энэхүү сарлагийг агнаж, хүнсэндээ хэрэглэдэг байсан байх магадлал өндөр болохыг харуулж байна. Судлаач Жонас Оппенхаймерын үзэж буйгаар, Алтайн бүс нутаг нь Плейстоцений галавын үед цаг уурын хувьд тогтвортой байсан нь амьтны төрөл зүйлийн олон янз байдлыг хадгалахад чухал нөлөө үзүүлсэн байх боломжтой юм.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Genetic analysis of bone fragments from Denisova Cave has uncovered a previously unknown extinct bovine, nicknamed “yak X.” Researchers recovered at least 20 genomes from the animal, which split from the modern Himalayan yak around 400,000 years ago.
Denisova Cave, in the foothills of the Altai Mountains, has once again delivered a surprise. This time the discovery is not a lost human lineage, but the find still confirms the site’s importance and offers hints about the lives, and perhaps the diets, of the ancient hominins who lived there.
The cave holds over 250,000 bone fragments, from various groups of prehistoric humans and a healthy collection of other mammals. Making sense of that collection is, quite literally in some cases, a mammoth task.
A Needle in 250,000 Bone Fragments
The sheer size of the collection is the first obstacle. Around 95 percent of the skeletal remains are so small and incomplete that their shape alone cannot reveal what animal they came from, so scientists have to turn to DNA to pinpoint the species.
In the latest study, published in the journal Current Biology, genetic analysis was applied to dozens of bones that once belonged to bovines, the subfamily that includes cattle, bison, buffalo, yak and other similarly beefy creatures. The work revealed at least 20 genomes of the new species, which the team named yak X.
Cousins on Separate Paths
Yak X was a relative of modern yaks, the shaggy bovines that currently lumber around the Himalayas and the Tibetan Plateau. Even so, the two followed separate evolutionary paths for hundreds of thousands of years. Patterns of genes suggest yak X started diverging from modern-day yaks around 400,000 years ago and became fully separated around 250,000 years ago.
What it looked like remains an open question. According to Love Dalén of Stockholm University, speaking to IFLScience, a shared ancestor only 400,000 years ago makes it reasonable to assume the two looked similar. He was quick to add a caveat.
“With that said, brown and polar bears diverged around the same time, and they certainly look very different from each other,”he said.
Dalén also said the team is working on a follow-up study investigating, among other things, which protein-coding genes made this bovine unique compared to Himalayan yaks.
Sharing the Cave with Ancient Humans
The most recent yak X genome the team recovered dates to just 27,000 years ago, while the oldest is from up to 247,000 years ago. Because the animal shows up in the cave time and time again during periods when ancient hominins are known to have frequented the site, it is a fairly safe bet that the two interacted. How, exactly, is unclear, but yak X may have been one of the many species on the menu. Study author Jonas Oppenheimer, also at Stockholm University, told IFLScience that:
“Although we don’t have direct evidence of these interactions, I think it’s likely that ancient humans, including Denisovans and Neanderthals, may have hunted yak X over this time period.”
There is a neat parallel here, too. The Denisovans were the first extinct human group described primarily through DNA analysis rather than anatomical features, and they were also identified from remains at Denisova Cave. Only a small handful of Denisovan remains have been recovered from the site, which is unfortunate given how little is known about them.
Oppenheimer said the broader Altai region was likely a hotspot of biodiversity and potential refugium during the glacial cycles of the Pleistocene, as hinted at by the incredible diversity present there. Some recent modeling work, he explained, suggests the region had an incredibly stable environment across the drastic Pleistocene climatic fluctuations, which seems likely to have played a major role.
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