Шинэ судалгаагаар орчин үеийн хүмүүсийн геномд өмнө нь олдоогүй устаж үгүй болсон хүний хоёр өөр удам угсааны генетикийн ул мөр хадгалагдаж үлдсэнийг тогтоожээ.
Калифорнийн их сургуулийн Бөрклийн эрдэмтдийн хийсэн энэхүү судалгаа долдугаар сарын 30-нд Science сэтгүүлд нийтлэгдсэн бөгөөд хүний хувьслын түүх эрдэмтдийн урьд өмнө тогтоосноос хамаагүй нарийн төвөгтэй байсныг харуулж байна. Судалгаагаар эртний хүмүүс хоорондоо олон удаа нийлж байсныг илрүүлсэн бөгөөд 화석 буюу эртний DNA-д найдалгүйгээр амьд хүмүүсийн геномын мэдээллийг ашиглан эртний генетикийн ул мөрийг олж тогтоожээ.
Судалгааны баг “TRACE” буюу TRacking Archaic Contributions via ARG Estimation нэртэй шинэ аргачлал боловсруулж, амьд хүмүүсийн DNA-ийн хэсгүүдийн гэр бүлийн түүхийг сэргээн судалсан байна. Энэхүү аргын тусламжтайгаар өнөөгийн хүний геномын үүсэл гарлыг маш алс тэртээх үе хүртэл мөрдөх боломжтой болжээ. Эрдэмтэд Неандертал болон Денисовын хүний DNA-г илрүүлэхээс гадна аль ч бүлэгт хамаарагддаггүй эртний үл мэдэгдэх хүний угсаатны ул мөрийг олж илрүүлсэн байна.
Шинээр илрүүлсэн эхний угсаа нь 50,000 гаруй жилийн өмнө Африкт орчин үеийн Homo sapiens хүнтэй үржилд орж байсан “хий үзэгдэл өвөг” юм. Энэхүү үл мэдэгдэх хүн ам амын геном нь орчин үеийн хүмүүсийн DNA-ийн ойролцоогоор 0.5-аас 1 хувийг эзэлж байгаа бөгөөд тэдний салбар орчин үеийн хүний өвөг дээдсээс ойролцоогоор 800,000 жилийн өмнө салжээ. Энэхүү генетикийн ул мөр нь Африк болон Африк тивийн бусад бүс нутгийн хүн амд хоёуланд нь илэрсэн нь уг холигдох үйл явц Африкаас нүүдэллэхээс өмнө болсныг гэрчилж байна.
Судлаачид мөн 1.8 сая жилийн өмнөх салбараас гаралтай хэт эртний хоёр дахь угсааны ул мөрийг илрүүлжээ. Энэхүү эртний бүлэг нь 200,000 жилийн өмнөөс Евроазийн нутагт Денисовын хүнтэй холилдож, улмаар орчин үеийн хүмүүст дамжсан байна. Эртний DNA-ийн эдгээр сегментүүд нь дархлааны тогтолцоо болон бодисын солилцоотой холбоотой генийн бүсэд байрладаг бөгөөд эртний хүмүүст шинэ орчин, эмгэг төрүүлэгчид болон хоол хүнсний нөхцөлд дасан зохицоход генетикийн олон янз байдлыг бий болгожээ.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Modern humans still carry DNA from two previously unknown extinct human lineages, according to a new study from the University of California, Berkeley. The findings suggest our evolutionary history was shaped by far more encounters between different human groups than scientists had previously been able to document.
For years, discoveries involving Neanderthals and Denisovans have changed the way scientists think about human evolution. Instead of a simple family tree, the picture has gradually become much more complex, with different human populations crossing paths and having children together over long periods of time.
Now, researchers have uncovered evidence of two additional extinct lineages that left their mark on the genomes of people alive today. According to the University of California, Berkeley, the study, published on July 30 in Science, identified these ancient genetic traces without relying on fossil DNA.
A Mysterious Human Relative Found In Everyone
The first newly identified lineage is what researchers call a ghost ancestor. It appears to have interbred with Homo sapiens in Africa more than 50,000 years ago, before modern humans spread into Europe and Asia.
The team estimates that DNA from this unknown population makes up about 0.5% to 1% of the genome of modern people. The lineage itself split from the ancestors of modern humans around 800,000 years ago, roughly when the ancestors of Neanderthals and Denisovans began to diverge.
The study published in Science said this ghost ancestry is present in both African and non-African populations, showing that the interbreeding happened before the major migration out of Africa.
Graduate student Yulin Zhang, one of the paper’s first authors, said earlier studies had hinted that unknown archaic ancestry might exist, but this research was able to pinpoint where those DNA fragments are found in modern genomes and show that they are shared across human populations.
A New Way To Uncover The Past
The discovery came from a method developed by the Berkeley team called TRACE, short for TRacking Archaic Contributions via ARG Estimation. Instead of comparing modern DNA with ancient fossil genomes, TRACE reconstructs the family history of DNA segments found in living people.
The University of California, Berkeley said that the method builds detailed genealogical maps known as ancestral recombination graphs, allowing researchers to identify pieces of DNA whose origins stretch much further back than expected.
That approach helped the team recover well-known Neanderthal DNA and also detect Denisovan ancestry in populations from Asia and Oceania. At the same time, it revealed many ancient DNA segments that matched neither group, pointing instead to previously unknown human relatives. As senior author Priya Moorjani explained, these genealogies preserve a record of our evolutionary history, making it possible to detect genetic contributions from extinct populations even when no ancient DNA has ever been recovered.
“We often think of human evolution as a branching tree, but new genomic data and analytical methods reveal a much more interconnected history, more like a complex web of populations connected by repeated episodes of migration and mixing,” he said.
An Even Older Lineage Survived Through Denisovans
The researchers also identified evidence of a second, much older population, described as a super-archaic lineage. This group descended from a branch that dates back around 1.8 million years. This ancient population likely interbred with Denisovans in Eurasia more than 200,000 years ago. When they later mixed with Homo sapiens, they passed along a small amount of that older DNA.
The genetic signal is strongest in populations from Oceania, where Denisovan ancestry can reach 4% of the genome. Denisovan genomes themselves contain an estimated 3% to 5% super-archaic ancestry, although only part of that genetic material eventually reached modern humans.
“TRACE allowed us to contextualize how the ancestry segments from these previously uncharacterized hominins are distributed throughout the human genome,” Arjun Biddanda, who co-led the study as a first author. “We found that these contributions are widespread throughout the genome, and ghost ancestry is detected even in regions previously thought to be intolerant of Neanderthal and Denisovan ancestry.”
The paper also found that many of these ancient DNA segments are located in regions linked to immune function and metabolism. The university release explained that these inherited variants may have given human populations useful genetic diversity as they adapted to new environments, pathogens and food sources, leaving a legacy that is still present in our DNA today.
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