４７．６万年前の木造構造物発見　ザンビア

【パリＡＦＰ＝時事】アフリカ南部ザンビアで、約４７万６０００年前につくられた世界最古の木造構造物が見つかった。化石人類がこれまで考えられていたよりも高度な知能を持っていた可能性があるという。（写真はザンビア・カランボ滝近くで行われた木造建造物の発掘の様子。英リバプール大学提供）
　論文は２０日、科学誌「ネイチャー」に掲載された。
　見つかったのは大きな丸太２本で、北部のタンザニアとの国境近くにある落差２３５メートルのカランボ滝のすぐ上流の川辺で出土した。
　現生人類ホモサピエンスが出現するはるか前の少なくとも４７万６０００年前につくられたものだが、保存状態は極めて良いという。
　丸太には、これを組み合わせるために石器で付けられた切り込みがあった。ぬれないように作られた足場か通路、水上家屋の一部だったと考えられる。
　木で作られたくさびや穴を掘る道具なども周辺から見つかった。
　当時の人類の祖先は木を利用していたことは知られていたが、火をおこすときや狩猟など、用途は限られていたと考えられていた。
　英リバプール大学の考古学者で論文の筆頭執筆者であるラリー・バーラム氏はＡＦＰに、知る限りでは、これまで発見された最古の木造構造物は約９０００年前のものだったと述べた。
　バーラム氏によると、今回発見された構造物は２０１９年にカランボ川の河原で発掘している際に「偶然」発見された。
　木は腐敗して痕跡が残りにくいため、これほど古い木材の発見は珍しい。
　川の水位が高かったため、何万年にもわたり保存されていたと考えられる。
　バーラム氏によると、この地域では７０万～２０万年前に生存していたとされる「ホモハイデルベルゲンシス」の化石が見つかっている。木造構造物の発見で、ホモハイデルベルゲンシスに対する見方が変わったとしている。
　「川辺で雑用をするために座る場所を作っただけだとしても、生活を楽にするために身の回りの環境を変えた」ことが分かると述べた。
　これは理論的な思考と、おそらく「言語」もあったことを示唆しているという。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2023/09/22-16:02）

Archaeologists said on Wednesday they have unearthed the oldest wooden structure ever discovered, dating from nearly half a million years ago, which suggests that our ancestors may have been more advanced than previously thought.
The exceptionally well-preserved wooden structure was found at Kalambo Falls in the north of Zambia near the border with Tanzania.
It dates back at least 476,000 years, well before the evolution of Homo sapiens, according to a study describing the find in the journal Nature.
The wood bears cut-marks showing that stone tools were used to join two large logs to make the structure, which is believed to be a platform, walkway or raised dwelling to keep our relatives above the water.
A collection of wooden tools, including a wedge and a digging stick, were also discovered at the site.
The ancestors of humans were already known to use wood at this time, but for limited purposes such as starting a fire or hunting.
Larry Barham, an archaeologist at the UK's University of Liverpool and the study's lead author, told AFP that to his knowledge the previous record-holder for oldest wooden structure dated back around 9,000 years.
Barham said the structure was a chance discovery made in 2019 while excavating at the site located on the banks of the Kalambo River, above a 235-metre-high (770-foot) waterfall.
Discoveries involving such ancient wood are rare, because it tends to rot leaving behind little trace for the historical record.
But the high level of water at Kalambo Falls is believed to have preserved the structure over the centuries.
- 'Imagination and skills' -
Excavations at the Kalambo site in the 1950s and 1960s unearthed some wood, but it was not able to be accurately dated.
However this time around, the researchers used a new method called luminescence dating, which determines age by measuring the last time minerals were exposed to sunlight.
This revealed that the structure was much older than the researchers had thought, dating back at least 476,000 years.
The earliest evidence of Homo sapiens is from around 300,000 years ago.
But fossils of human relative Homo heidelbergensis, thought to have lived between 700,000 to 200,000 years ago, have been found in the region, Barham said.
The discovery of the wooden structure changed how I thought about these people, Barham added.
They transformed their surroundings to make life easier, even if it was only by making a platform to sit on by the river to do their daily chores, he said.
They used their intelligence, imagination and skills to create something they'd never seen before, something that had never previously existed.
This suggests an abstract level of thinking and probably language, he added.
Sophie Archambault de Beaune, an archaeologist at France's Lyon 3 University not involved in the study, said the structure presupposes cognitive abilities such as planning and the ability to visualise the finished product.
But these capacities were already assumed from the study of cut stone tools, she told AFP.
The authors of the study also said the discovery challenges the idea that human ancestors were nomadic, because the structure seems to be a permanent dwelling near the waterfalls, a perennial source of water.
Archambault de Beaune cautioned that this hypothesis had not yet been proven, because the structure could have been installed for the season, rather than permanently.