Recently CNN.co.jp reported the following:
７０００年前に死んだ１０代女性のＤＮＡから未知の現生人類の系統を発見 インドネシア
2021.08.26 Thu posted at 19:00 JST
（ＣＮＮ） ７０００年以上前にインドネシアのスラウェシ島で死んだ狩猟採集民の１０代女性のＤＮＡを分析したところ、これまで世界のどこからも見つかっていない現生人類の系統に属していることが分かった。
２５日刊行の科学誌ネイチャーに、当該の研究論文が掲載された。
豪グリフィス大学人類進化研究センターの考古学教授、アダム・ブラム氏は電子メールで今回の発見について、アジアとオーストラリアの間に位置する島嶼（とうしょ）地帯「ウォーレシア」で見つかった初めての古代人のＤＮＡだと説明。世界の中でも知見の少ない地域の初期現生人類について、遺伝子上の多様性と集団史を探る新たな手掛かりになるとの認識を示した。
スラウェシ島、ロンボク島、フロレス島といったインドネシアの島々で主に構成されるウォーレシアを経由し、初めて現生人類がユーラシア大陸からオーストラリア大陸に渡ったのは５万年以上前と考えられている。具体的な経路や航行の手段は不明だが、かなり精巧な舟を使ったはずだとブラム氏はみている。当時は最終氷期で、地球上の海面の高さは現在より最大１４０メートル低かったが、それでも島々をつなぐような陸地は存在していなかったという。
ＤＮＡは錐体（すいたい）骨と呼ばれる楔（くさび）形の骨から採取した。論文筆頭著者のセリーナ・カールホフ氏によると、熱帯性の気候の中で分解が著しく進んだ残骸からの採取は非常に困難だったという。
現在、この系統の子孫は生き残っていない。
女性のＤＮＡはさらに、今は絶滅し謎めいたデニソワ人の痕跡も含んでいる。これまでデニソワ人の化石は主にシベリアとチベットから出土している。
論文の共著者でドイツのマックス・プランク進化人類学研究所の考古遺伝学教授、ヨハネス・クラウゼ氏は、スラウェシ島の女性からデニソワ人の遺伝子が見つかったことは「デニソワ人がこれまで考えられていたよりはるかに広い地域に広がっていたという我々の仮説を支持する」と語る。
ただ、ウォーレシア西部に住んでいた他の狩猟者のＤＮＡを見ると、デニソワ人の痕跡はない。
「ウォーレシアでは現生人類とデニソワ人の地理的分布が重なっていたのかもしれない。もしかしたら、そこはデニソワ人とオーストラリア先住民やパプア人が交雑した重要な場所である可能性もある」と、共著者で独テュービンゲン大学のコジモ・ポスト教授は指摘する。
今回の発見は、研究者が東南アジアにおける古代の遺伝子的な歴史を理解しようとする中で、パズルをひもとく一つのピースになる。
Translation
A research paper was published in the scientific journal
Nature on the 25th.
Adam Brumm a professor of archeology at Griffith
University's Center for Human Evolution explained in an email that about this discovery,
it was the first ancient human DNA being found in the island region of Wallacea
that located between Asia and Australia. He acknowledged that early modern
humans in lesser-known regions of the world could provide new clues to the
genetic diversity and population history.
It was believed that more than 50,000 years ago modern
humans first crossed from Eurasia to Australia via Wallacea, which was mainly
composed of Indonesian islands such as Sulawesi, Lombok, and Flores. The
specific route and means of navigation were unknown, but Brumm believed that a fairly
sophisticated boat could have been used. At that time, it was the last glacial
period, and the sea level on the earth was down to 140 meters lower than it was
now, yet it was said that there was no land connecting these islands.
From the discovery of tools and cave paintings, it was
believed that these islands were inhabited 47,000 years ago. The bones analyzed
this time were from a women aged 17-18 that were found in a cave on Sulawesi
Island in 2015. The body was buried dating back to 7,200 years in the cave that
was also part of an archaeological site.
DNA was collected from a wedge-shaped bone called cone bone.
According to the lead author of the treatise, Selina Carlhoff, it was extremely
difficult to collect DNA from the broken remains that had been significantly
degraded in a tropical climate.
DNA analysis revealed that the woman was the first modern human descendant who come to Wallacea 50,000 years ago. They were among some of the first humans to settle in the combined Ice Age land mass of Australia and New Guinea. According to Brumm, she was the ancestor of today’s Australia indigenous people and the Papuans.
It was also found that this woman was the ancestor of another lineage of Asian origin. According to Brumm, it was previously thought that humans with Asian genes first settled in Wallacea about 3,500 years ago. However, the findings this time suggested that there might be a group of modern humans in the area that was completely unknown to us up to this moment.
Currently, no descendants of this lineage had survived.
The women's DNA also contained traces of the now extinct and mysterious Denisovans. To date, Denisovan fossils had been found primarily in Siberia and Tibet.
Johannes Krause, co-author of the paper and professor of Department of Archaeogenetics at the Max Planck Institute for Evolutionary Anthropology in Germany, said that about the discovery of the Denisovan gene in the women in Sulawesi, this “supports our hypothesis that the Denisovans had spread over a wider area than we previously thought "
However, looking at the DNA of other hunters who lived in
western Wallacea, there are no traces of Denisovans.
Co-author and Professor Cosimo Posth of the University of Tuebingen
in Germany pointed out that, "In Wallacea, the geographical distribution
of modern humans and Denisovans might have overlapped. Maybe it is an important
place where Denisovans cross-bred with Aboriginal Australian and Papuans".
For those researchers seeking to understand the ancient
genetic history of Southeast Asia, this discovery would be a piece of the
puzzles.
So, the
DNA of a teenage female hunter-gatherer who died on Sulawesi of Indonesia more
than 7,000 years ago reveals that it belongs to a lineage that has never been
found anywhere in modern human in the world.
Note:
a. This research paper is published in Nature volume
596, pages543–547 (2021), it can be viewed in the following web-site: https://www.nature.com/articles/s41586-021-03823-6
b. Adam Brumm is a professor of archaeology. He has active
field research programs in the Wallacean archipelago of central and eastern
Indonesia ('Wallacea'), the myriad of oceanic islands lying east of mainland
Asia and the gateway to the continent of Australia. (https://experts.griffith.edu.au/7090-adam-brumm?_gl=1*1i9rfjj*_ga*OTQ0MjMyNjc4LjE2MzEwNjMwODM.*_ga_5GKYJEBSN9*MTYzMTA2MzA4Mi4xLjEuMTYzMTA2MzA5Mi4w)
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