上图：来自菲律宾各个岛屿的自我认同的 Negritos。
奥菲莉亚·佩森
直到最近，科学家们还认为拥有最高比例的丹尼索瓦血统的现代人生活在巴布亚新几内亚和澳大利亚。然而，根据昨天（8 月 12 日）在 Current Biology 上发表的一项新研究，菲律宾一个名为 Ayta Magbukon 的土著群体的丹尼索瓦人 DNA 比这些其他领跑者多 30% 到 40%，占他们基因组总数的近 5% .
丹尼索瓦人是一群古老的人类，最初是从西伯利亚洞穴中的一块小指骨中发现的。它们与现代人类和其他古老的人类物种（例如尼安德特人）共存了数十万年，直到它们在大约 30,000 到 50,000 年前灭绝。根据 Gizmodo 的说法，只有太平洋岛民和东南亚人拥有大量的丹尼索瓦血统。相比之下，亚洲大陆其他地区的大多数人的丹尼索瓦血统不到 0.05%，而非洲和欧洲血统的人则没有。
“[Ayta Magbukon] 拥有比当今地球上任何其他人都多的丹尼索瓦血统，”乌普萨拉大学生物学家和研究合著者 Mattias Jakobsson 告诉 Inverse。 “所以这对我们来说是一个惊喜。”
参见“3万多年前人类在青藏高原上制造工具”
根据 Gizmodo 的说法，研究人员最初对研究菲律宾的人类历史感兴趣，这是与土著社区、地方政府、菲律宾国家文化和艺术委员会以及乌普萨拉大学的研究人员进行大规模合作的一部分。
作为早期研究人类迁移到菲律宾的研究的后续研究，“我们打算通过评估人口中古老血统的水平来审视遥远的过去，特别是这些地区的一些人口以前被证明已升高丹尼索瓦人的血统水平以及东南亚岛屿上居住着各种古老的人类物种，”人口遗传学家和研究合著者马克西米利安·拉雷纳告诉 Gizmodo。
为此，研究人员分析了属于菲律宾 118 个不同种族群体的 1,107 个人的基因组，其中包括 25 个自称为“内格里托斯”的群体，他们被认为是菲律宾最早的现代人类居民。作者。通过将这些基因组与丹尼索瓦人和尼安德特人的基因组进行比较，他们发现虽然尼安德特人血统的程度在他们的研究人群中相当一致（与世界其他地区的现代人相当），但丹尼索瓦人的血统程度差异很大，并且Negritos 中的比例明显高于其他群体。
这些发现“与菲律宾内格里托斯人和丹尼索瓦人之间独立杂交事件的模型一致，这表明丹尼索瓦人可能在任何现代人类族群出现之前很久就已经在岛上了，”拉雷纳告诉 Gizmodo。
未参与这项研究的图宾根大学古遗传学??家 Cosimo Posth 告诉《科学新闻》，这份新报告表明“今天仍有一??些种群尚未完全被基因描述，而且丹尼索瓦人在地理上分布广泛。”
目前，丹尼索瓦人的化石记录稀少，据《科学新闻》报道，丹尼索瓦人的化石不能仅靠形态来识别。它们必须进行基因测序，这在从古代 DNA 降解更快的热带气候中提取化石时可能很困难。
见“藏洞发现丹尼索瓦人化石”
阿德莱德大学人口遗传学家若昂·特谢拉 (João Teixeira) 告诉《科学新闻》(Science News)，这些发现“进一步增加了我对丹尼索瓦人化石隐藏在人们视线中的怀疑”，这是之前在东南亚岛屿上挖掘出的发现之一。特谢拉没有参与当前的研究。
“谈到东南亚和东南亚岛屿，我们的问题多于答案，因为我们没有良好的考古记录，”科罗拉多大学博尔德分校人口遗传学家费尔南多维拉尼亚告诉 Inverse。没有参与这项研究的 Villanea 补充说：“现在我们有了这些令人难以置信的基因发现，我们很难把一个有凝聚力的故事放在一起。”
“通过在未来对更多基因组进行测序，我们将更好地解决多个问题，包括遗传的古老区域如何影响我们的生物学以及它如何促进我们作为一个物种的适应，”拉雷纳在新闻稿中说。
OPHELIA PERSSON
Until recently, scientists thought the modern humans with the highest proportion of Denisovan ancestry lived in Papua New Guinea and Australia. According to a new study published yesterday (August 12) in Current Biology, however, an Indigenous group in the Philippines called the Ayta Magbukon have 30 to 40 percent more Denisovan DNA than these other frontrunners, for a total of nearly 5 percent of their genomes.
Denisovans were a group of archaic humans first identified from a single pinkie bone in a Siberian cave. They coexisted with modern humans and other archaic human species, such as Neanderthals, for hundreds of thousands of years, until they went extinct an estimated 30,000 to 50,000 years ago. According to Gizmodo, only Pacific Islanders and Southeast Asians have substantial Denisovan ancestry. By comparison, most people in other parts of mainland Asia have less than 0.05 percent Denisovan ancestry, and people of African and European descent don’t have any.
“[The Ayta Magbukon] possess more Denisovan ancestry than anybody else on the planet today,” Uppsala University biologist and study coauthor Mattias Jakobsson tells Inverse. “So that was a surprise to us.”
See “Humans Made Tools Atop the Tibetan Plateau More than 30,000 Years Ago”
According to Gizmodo, the researchers were originally interested in studying the human history of the Philippines as part of a massive collaborative effort with Indigenous communities, local governments, the National Commission for Culture and the Arts of the Philippines, and researchers at Uppsala University.
As a follow-up study to an earlier one studying human migrations to the Philippines, “we intended to look at the distant past by assessing the levels of archaic ancestry among the populations, especially that some populations in these regions were previously shown to have elevated levels of Denisovan ancestry and that Island Southeast Asia is known to be inhabited by various archaic species of Homo,” population geneticist and study coauthor Maximilian Larena tells Gizmodo.
To do this, the researchers analyzed the genomes of 1,107 individuals belonging to 118 distinct ethnic groups in the Philippines—including 25 groups self-identifying as “Negritos,” who are regarded as the earliest modern human inhabitants of the Philippines, according to the study’s authors. By comparing these genomes to Denisovan and Neanderthal genomes, they found that while the degree of Neanderthal ancestry was fairly uniform in their study population (and comparable to modern humans in other parts of the world), the degree of Denisovan ancestry was highly variable, and substantially higher among Negritos than in other groups.
These findings “are consistent with a model of an independent interbreeding event between Negritos and Denisovans within the Philippines, suggesting that Denisovans may have been in the islands long before the presence of any modern human ethnic group,” Larena tells Gizmodo.
University of Tübingen paleogeneticist Cosimo Posth, who was not involved in the study, tells Science News the new report suggests that “still today there are populations that have not been fully genetically described and that Denisovans were geographically widespread.”
Currently, the Denisovan fossil record is sparse, and according to Science News, Denisovan fossils can’t be identified by morphology alone. They have to be genetically sequenced, which can be difficult when extracting fossils from tropical climates where the ancient DNA degrades more quickly.
See “Denisovan Fossil Identified in Tibetan Cave”
The findings “further increase my suspicions that Denisovan fossils are hiding in plain sight,” among previously excavated discoveries on Southeast Asian islands, University of Adelaide population geneticist João Teixeira tells Science News. Teixeira was not involved with the current study.
“When it comes to Southeast Asia and the Southeast Asian Islands, we have more questions than answers as we don’t have a good archaeological record,” University of Colorado Boulder population geneticist Fernando Villanea tells Inverse. Villanea, who was not involved with the study, adds, “Now we have these incredible genetic findings and we’re having a hard time putting together a cohesive story.”
“By sequencing more genomes in the future, we will have better resolution in addressing multiple questions, including how the inherited archaic tracts influenced our biology and how it contributed to our adaptation as a species,” Larena says in the press release.
See “Neanderthal DNA in Modern Human Genomes Is Not Silent”
