科學家表示，法國發現的洞穴可能解釋了尼安德特人消失的原因 (2/2)

Recently CNN News on-line reported the following:

Cave discovery in France may explain why Neanderthals disappeared, scientists say (2/2)

Katie Hunt, CNN

Thu, September 12, 2024 at 7:11 a.m. PDT·5 min read

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DNA from Homo sapiens fossils from that time show that these early arrivals interbred with Neanderthals — traces of those encounters remain in present-day human populations. However, no corresponding genetic evidence of that interbreeding has been found in Neanderthal fossils from that time, including Thorin’s remains, the study noted.

Whatever behavior led to this lack of genetic intermingling on one side, along with small and isolated Neanderthal populations such as the one Slimak and his colleagues identified, likely contributed to the disappearance of the Neanderthals, said Chris Stringer, research lead in human evolution at London’s Natural History Museum who wasn’t involved in the study.

“Whatever the reasons for this imbalance (social, biological?) it contributed to the demise of the last Neanderthals, since their already small populations were losing reproductive age individuals to the other species, without any replenishment in return,” Stringer said via email.

“Coupled with economic competition from the newcomers over resources, this could have been a recipe for demographic collapse.”

It’s not clear whether Thorin’s full skeleton is interred within Grotte Mandrin, as the rock shelter in the Rhône Valley near Malataverne, France, is known. The remains were found near the surface in soft, unstable ground, and the excavation continues slowly, Slimak said, with archaeologists tweezing out “one grain at a time.” It’s also unclear whether the specimen, which is male, was deliberately buried or not.

Archaeologists have excavated more of Thorin’s remains: 31 teeth, part of the jaw and five finger bones, so far. The shape of his teeth is typical of a Neanderthal, but he had two extra lower molars — a trait sometimes suggestive of an inbred population, the study noted.

Genetic mystery resolved

The initial genetic analysis suggested that Thorin was much older because his genome was distinct from other later Neanderthals, resembling the genomes of ancient humans who lived more than 100,000 years ago.

To understand Thorin’s origins and confirm the age of his remains, the team analyzed chemical isotopes in his bones and teeth to infer what type of climate he lived in based on the water he would have drunk and other factors. A Neanderthal in Europe 105,000 years ago would have a enjoyed a much warmer climate than one living 45,000 years ago during the Ice Age.

“We worked for seven years to find out who was wrong — archaeologists or genomicists,” Slimak said in the news release.

Slimak has been involved in the excavation of Grotte Mandrin for more than three decades and made a number of exciting finds at the rock shelter. It’s the only known site to have been home to alternating groups of both Homo sapiens and Neanderthals, plus the earliest evidence of bow and arrow use outside Africa.

“Grotte Mandrin keeps delivering surprises,” Stringer said.

Translation

科學家稱，法國發現的洞穴可能解釋了尼安德特人消失的原因 (2/2)

（繼續）

當時智人化石的 DNA 顯示，這些早期到達者與尼安德特人進行了雜交 - 這些相遇的痕跡仍然存在於當今的人類群體中。然而，研究指出，那時的包括Thorin的遺骸的尼安德塔人化石中並沒有發現這種雜交的相對應遺傳證據。

沒有參與這項研究的倫敦自然史博物館人類演化研究負責人Chris Stringer表示，無論是什麼行為缺乏導致, 這種缺乏遺傳的混合，再加上像Slimak和他的同事所發現的小而孤立的尼安德特人族群，很可能導致了尼安德特人的消失。

Stringer在電子郵件中說：「無論這種不平衡的原因是什麼（社會的、生物的？），它都導致了最後一批尼安德特人的滅亡，因為他們本來就有很小的人口, 失去正處於生育年齡的羣體給其他人種，而沒有得到任何補充」。

“再加上新來者對資源的經濟競爭，這可能會導致人口崩滅。”

目前還不清楚Thorin的完整骨架是否埋葬在Grotte Mandrin內，即已知的法國Malataverne附近羅納河谷的岩石庇護所。Slimak說，現有遺骸是在地表附近的柔軟、不穩定的地面上所發現，挖掘工作仍在緩慢進行，考古學家把問題慢慢小心「一個個來處理」。目前還不清楚這個男性標本是否是故意安葬的。

到目前為止，考古學家已經挖掘出更多Thorin的遺骸：31 顆牙齒、部分下顎和 5 塊指骨。研究指出，他的牙齒形狀是典型的尼安德特人的，但他有兩顆額外的下臼齒 - 這一特徵有時暗示著近交群種。

基因之謎已解開

最初的基因分析表明，Thorin的年齡要大得多，因為他的基因組與其他後來的尼安德特人不同，類似於生活在十萬多年前的古人類的基因組。

為了了解Thorin的起源並確認他遺骸的年齡，研究小組分析了他的骨骼和牙齒中的化學同位素，根據他喝過的水和其他因素來推斷他生活的氣候類型。 105,000 年前生活在歐洲的尼安德特人比 45,000 年前冰河時期的尼安德特人享受著溫暖得多的氣候。

Slimak在新聞稿中說: 「我們花了七年的時間來找出誰錯了 - 是考古學家還是基因學家」。

三十多年來，Slimak一直參與Grotte Mandrin的發掘工作，並在岩石掩體中取得了許多令人興奮的發現。這是唯一已知的智人和尼安德特人交替居住的遺址，也是非洲以外最早使用弓箭的證據。

Stringer說:「Grotte Mandrin 不斷帶來驚喜」。

              So, until now, geneticists thought that at the time of Neanderthal extinction there was one population that was genetically homogeneous, but the new study reveals at least two populations were present in Western Europe at that time — and they lived surprisingly close to each other. The discovery suggested that Neanderthal communities were small and insular. Isolation is generally considered to be an evolutionary disadvantage. Less genetic variation could make it harder to adapt to changing climate or disease, harder to share knowledge and technology. Neanderthal were happy to stay in one place while Homo sapiens all the time want to explore, an instinct that I think is similar to human’s current desire to explore the moon and beyond.