Million-year-old DNA sheds light on the genomic history of mammoths
Million-year-old DNA sheds light on the genomic history of mammoths
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DOI：
10.1038/s41586-021-03224-9
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发表时间：
2021-02-17
期刊：
影响因子：
64.8
通讯作者：
Dalen, Love
中科院分区：
文献类型：
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作者：
van der Valk, Tom;Pecnerova, Patricia;Dalen, Love
时间基因组数据在研究物种形成等进化过程方面具有巨大的潜力。然而，在许多情况下，跨物种形成事件的采样需要基因组时间序列，这些时间序列可以很好地追溯到更新世早期的亚期。虽然理论模型表明DNA应该在这个时间尺度上存活(1)，但到目前为止发现的最古老的基因组数据来自780-56万年前的马标本(2)。在这里，我们报道了从三个猛犸象标本中恢复全基因组数据，这些标本可以追溯到早、中更新世，其中两个样本的历史超过一百万年。我们发现，在早更新世，东西伯利亚存在两个截然不同的猛犸象谱系。这些血统中的一个产生了长毛象，另一个代表了一个以前未被认识的血统，它是第一批殖民北美的猛犸象的祖先。我们的分析表明，北美的哥伦比亚猛犸象的祖先可以追溯到这两个血统之间的中更新世杂交，混合比例大致相同。最后，我们发现，与毛猛犸象冷适应相关的大部分蛋白质编码变化在100万年前就已经存在了。这些发现突出了深部时间古基因组学在扩大我们对物种形成和长期适应性进化的理解方面的潜力。
Temporal genomic data hold great potential for studying evolutionary processes such as speciation. However, sampling across speciation events would, in many cases, require genomic time series that stretch well back intothe Early Pleistocene subepoch. Although theoretical models suggest that DNA should survive on this timescale(1), the oldest genomic data recovered so far are from a horse specimen dated to 780-560 thousand years ago(2). Here we report the recovery of genome-wide data from three mammoth specimens dating to the Early and Middle Pleistocene subepochs, two of which are more than one million years old. We find that two distinct mammoth lineages were present in eastern Siberia during the Early Pleistocene. One of these lineages gave rise to the woolly mammoth and the other represents a previously unrecognized lineage that was ancestral to the first mammoths to colonize North America. Our analyses reveal that the Columbian mammoth of North America traces its ancestry to a Middle Pleistocene hybridization between these two lineages, with roughly equal admixture proportions. Finally, we show that the majority of protein-coding changes associated with cold adaptation in woolly mammoths were already present one million years ago. These findings highlight the potential of deep-time palaeogenomics to expand our understanding of speciation and long-term adaptive evolution.