Researchers have identified extensive ancient environmental DNA within fossilized squirrel excrement preserved in Canadian permafrost, spanning a period of up to 700,000 years.

研究人員在加拿大永久凍土保存的松鼠糞便化石中，發現了大量古環境 DNA，時間跨度長達 70 萬年。

The investigation, published in Nature Communications, utilized samples from the Yukon to reconstruct prehistoric ecosystems in Beringia. Unlike osteological remains, which provide anatomical data, coprolites serve as multiplexed archives of biological interactions. The Arctic ground squirrel's behavioral patterns—specifically the caching of diverse organic materials and a broad diet—facilitated the accumulation of genetic signatures from various taxa. Consequently, the study recovered over 18 mitochondrial genomes, including lineages of woolly mammoths, steppe bison, horses, and various predators such as wolves and felids, alongside more than 200 plant groups.

這項發表於《自然-通訊》（Nature Communications）的研究，利用來自育空的樣本來重建白令陸橋（Beringia）的史前生態系統。與提供解剖數據的骨骼遺骸不同，糞便化石是生物互動的多功能檔案。北極地松鼠的行為模式——特別是儲存多種有機物和廣泛的飲食——促進了來自各種分類群的基因標記積累。因此，研究恢復了超過 18 個線粒體基因組，包括長毛象、草原野牛、馬，以及狼和貓科動物等各種捕食者的譜系，以及 200 多個植物組。

Preservation was facilitated by the rapid entombment of burrows in permafrost, which ensured low-oxygen conditions and minimal microbial activity, thereby mitigating the enzymatic degradation of DNA. This technical achievement is significant given that genomic fragmentation typically renders sequences unusable beyond 100,000 years. Furthermore, the data indicates a genetic turnover in ground squirrel populations, revealing a lineage with closer affinities to modern Siberian populations than previously hypothesized. This finding challenges the assumption of long-term lineage continuity in the region. While the genetic data will be made public, potentially aiding efforts by entities such as Colossal to reconstruct extinct species, lead researcher Tyler Murchie indicated that the existing genomic datasets available to such organizations are already substantial.

由於洞穴迅速被永久凍土掩埋，確保了低氧條件和極低的微生物活動，從而減輕了 DNA 的酶促降解。鑑於基因組碎片化通常使 10 萬年以上的序列變得無法使用，這一技術成就具有重要意義。此外，數據顯示地松鼠種群出現了基因更替，揭示了一個與現代西伯利亞種群親緣關係比先前假設更近的譜系。這一發現挑戰了該地區長期譜系連續性的假設。雖然基因數據將公開，可能會幫助如 Colossal 等實體重建滅絕物種，但首席研究員 Tyler Murchie 指出，此類組織現有的基因組數據集已經相當豐富。

The study demonstrates that coprolites are viable high-resolution archives for reconstructing ancient food webs and evolutionary transitions.

研究證明，糞便化石是重建古代食物網和演化轉變的高解析度可行檔案。