Колумбын өндөрлөг газраас олдсон 6000 жилийн настай хүний үлдэгдлийн ДНХ-ийн шинжилгээ нь тухайн үеийн хүн амын удамшил өнөөгийн хүн амд огт үлдээгүй болохыг харууллаа.
Тюбингений их сургуулийн судлаачид Колумбын Богота хотын хойд хэсгийн өндөрлөг газарт орших Чекуа археологийн дурсгалт газраас 6000 орчим жилийн тэртээ амьдарч байсан долоон хүний үлдэгдлийг олж илрүүлэн, геномыг нь анх удаа дараалуулжээ. Эдгээр анчин-түүгчдийн удамшил нь 2000 жилийн өмнөх болон түүнээс хойших үеийн хүн амын бүлгүүдэд огт илрээгүй бөгөөд Өмнөд Америкийн орчин үеийн хүн амд ч генетикийн ямар нэгэн ул мөр үлдээгүй байна. Судлаачид эдгээр хүнийг тус бүс нутгаар дамжин Өмнөд Америкт тархсан анхны хүн амын бүлэгт хамаарна гэж үзэж байгаа ч тэдний удам яагаад тасарсан нь тодорхойгүй хэвээр байна.
Судалгааны багийнхан Чекуагаас гадна 6000 жилийн хугацааг хамарсан таван өөр газрын 21 хүний үлдэгдлийг судалжээ. Үр дүнд нь 2000 жилийн өмнөх Эррерагийн үеэс эхлэн тус бүс нутагт Төв Америкийн гарал үүсэлтэй хүн ам давамгайлах болсныг тогтоосон байна. Тэдгээр шинэ суурьшигчид нь керамик эдлэл болон Чибчан хэлний бүлгийг авчирсан байх магадлалтай гэж судлаачид үзэж байна.
Өмнөд Америкийн бүс нутагт соёлын томоохон өөрчлөлтүүд гарсан ч генетикийн хувьд ийм бүрэн тасалдал үүсэх нь тун ховор тохиолдол юм. Эрдэмтэд эртний хүмүүсийн удамшил яагаад бүрмөсөн алга болсныг хүрээлэн буй орчны өөрчлөлт, бусад бүлгүүдэд шахагдах эсвэл холигдон уусах зэрэг олон таамаглалаар тайлбарлаж байна. Цаашид илүү олон эртний үлдэгдлийг судалснаар Төв Америкийн хүн ам хэзээ, хэрхэн тархсаныг нарийвчлан тогтоох шаардлагатай байгааг судлаачид онцоллоо.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Seven people who lived about 6,000 years ago were excavated at Checua, an archaeological site roughly 3,000 meters (about 9,800 feet) up on the high plains north of Bogotá. They were hunter-gatherers from a comparatively small population, and their bones and teeth still held DNA.
Sequencing it produced the first ancient human genomes ever published from Colombia, said Cosimo Posth, the University of Tübingen paleogeneticist who was the study’s senior author. Then the team went looking for the seven’s descendants and found none.
The lineage is missing from people who lived on the same plains 2,000 years ago. It is missing from every later group the team sampled there, and the researchers report that it contributed nothing to South American populations living today.
“We couldn’t find descendants of these early hunter-gatherers of the Colombian high plains,” said Kim-Louise Krettek, the study’s first author, in the university’s announcement. The genes, she said, “were not passed on.”
An Early Branch With Nothing After It
South America was settled from the north, and the first hunter-gatherers entered through what is now Colombia. Andrea Casas-Vargas, a geneticist at the Universidad Nacional de Colombia and a co-author, told the AP the region is “the gateway to the South American continent.”
The Checua people were not a separate branch of humanity. Krettek said they “derive from the earliest population that spread and differentiated across South America very rapidly.”
What sets them apart is everything that did not follow. The authors said that the group shows no particular affinity to ancient North American groups and made no genetic contribution to ancient or present-day South Americans.
That caught outside researchers off guard. “This is unexpected,” Andre Luiz Campelo dos Santos, a Florida Atlantic University archaeologist who was not part of the study, told the AP. “Up to this point, we didn’t believe there was any other lineage that would appear in South America.”
Until this study, Colombia had been “a blank spot in ancient DNA studies of the Americas,” Harvard University anthropologist Christina Warinner, who was also not involved, told CNN.
The People Who Came Next Carried Central American Ancestry
The team sequenced 21 individuals from five sites on the Altiplano, the high plains around Bogotá. Together they cover almost 6,000 years, ending shortly before Spanish colonization.
After the seven from Checua, the next group is nine people from the Herrera period, about 2,000 years ago. Their ancestry is predominantly related to populations from Central America. So is the ancestry of the remaining five: three people associated with the Muisca culture, who lived between 1,200 and 520 years ago, and two from the Los Curos area, about 530 years ago.
The newcomers brought more than genes. Casas-Vargas said they probably carried ceramics and the Chibchan languages into what is now Colombia. Branches of that language family are still spoken in Central America.
A turnover this complete is rare on the continent. “That genetic traces of the original population disappear completely is unusual, especially in South America,” Casas-Vargas said. In the Andes and the southern cone, researchers have found strong genetic continuity over long periods and through cultural change.
The Altiplano itself shows that pattern once the Central American ancestry arrives. It holds from the Herrera period through the rise of the Muisca until Europeans arrived about 500 years ago, even though, as Casas-Vargas put it, “there was massive cultural change.”
Before finishing the study, the team met with the Guardia Indígena Muisca, living descendants of the Muisca culture on the high plains. “The genetic disposition must not be viewed as equal to cultural identity,” Posth said.
Four Thousand Years the DNA Does Not Cover
Nobody knows what happened to the Checua lineage. Casas-Vargas told CNN the findings raise questions “as to where they came from and why they disappeared.”
The AP reported that scientists are not sure whether the group was absorbed into larger populations or pushed out. Smithsonian magazine listed the possibilities archaeologists have raised: environmental change, replacement by other groups, or mixing with neighbors until the distinctive DNA was diluted away.
The genomes cannot choose among them yet. The researchers have proposed sequencing more ancient remains to pin down when the Central American populations arrived and how far they spread, Live Science reported.
For now, the seven people from Checua are the only known members of their lineage, and the next genomes in the study belong to people who lived about 4,000 years after them.
Enjoyed this article? Subscribe to our free newsletter for engaging stories, exclusive content, and the latest news.
