Data from: Ancient DNA reveals differences in behaviour and sociality between brown bears and extinct cave bears
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Ancient DNA studies have revolutionized the study of extinct species and populations, providing insights on phylogeny, phylogeography, admixture and demographic history. However, inferences on behaviour and sociality have been far less frequent. Here, we investigate the complete mitochondrial genomes of extinct Late Pleistocene cave bears and middle Holocene brown bears that each inhabited multiple geographically proximate caves in northern Spain. In cave bears, we find that, although most caves were occupied simultaneously, each cave almost exclusively contains a unique lineage of closely related haplotypes. This remarkable pattern suggests extreme fidelity to their birth site in cave bears, best described as homing behaviour, and that cave bears formed stable maternal social groups at least for hibernation. In contrast, brown bears do not show any strong association of mitochondrial lineage and cave, suggesting that these two closely related species differed in aspects of their behaviour and sociality. This difference is likely to have contributed to cave bear extinction, which occurred at a time in which competition for caves between bears and humans was likely intense and the ability to rapidly colonize new hibernation sites would have been crucial for the survival of a species so dependent on caves for hibernation as cave bears. Our study demonstrates the potential of ancient DNA to uncover patterns of behaviour and sociality in ancient species and populations, even those that went extinct many tens of thousands of years ago.
古DNA（Ancient DNA）研究已彻底革新了已灭绝物种与种群的研究范式，为系统发育（phylogeny）、系统地理学（phylogeography）、遗传混合（admixture）及种群历史动态提供了关键见解。然而，针对行为与社会性的相关推断却极为罕见。 本研究聚焦西班牙北部的两类物种：已灭绝的晚更新世（Late Pleistocene）洞熊（cave bears）与中全新世（Middle Holocene）棕熊（brown bears），二者均栖息于该区域内多个地理邻近的洞穴中，并对其完整线粒体基因组（mitochondrial genomes）展开分析。 针对洞熊的分析结果显示，尽管多数洞穴的占领时间大致同步，但每个洞穴几乎仅独有一类独特的近缘单倍型（haplotypes）谱系。这一显著模式表明洞熊对其出生洞穴具有极强的栖息地忠实性，可将其概括为归巢行为（homing behaviour），且洞熊至少在冬眠（hibernation）期间会形成稳定的母系社会群体（maternal social groups）。 与之形成鲜明对比的是，棕熊并未表现出线粒体谱系与洞穴之间的显著关联，这说明这两种近缘物种在行为与社会性特征上存在差异。 这种差异或推动了洞熊的灭绝：彼时人类与熊类对洞穴的竞争大概率十分激烈，而对于依赖洞穴冬眠的洞熊而言，快速开拓新冬眠栖息地的能力本应是其生存的关键——而洞熊的归巢习性恰恰使其无法做到这一点。 本研究证实，古DNA研究具备揭示古代物种与种群行为及社会模式的潜力，即便这些物种已于数万年前灭绝。
