Ancient DNA that is more than one million years old has been recovered from two specimens of mammoth, reports a study in Nature. The oldest previously sequenced DNA dates from 780,000 to 560,000 years ago.
Ancient DNA has improved our understanding of prehistoric populations. However, some evolutionary processes, such as speciation (the formation of new and distinct species), often occur over time periods that are thought to be beyond the limits of DNA research. Nonetheless, theoretical models suggest that DNA might be able to survive on the timescales required.
Love Dalén and colleagues report the recovery of DNA from the molars of three mammoth specimens from the Early and Middle Pleistocene subepochs from northeast Siberia. On the basis of the age of the deposits from which the teeth were collected, two of the samples (designated Krestovka and Adycha) are more than one million years old. DNA-based age estimates obtained using mitochondrial genome data suggest that Krestovka is approximately 1.65 million years old, Adycha is around 1.34 million years old, and the final specimen (Chukochya) is 0.87 million years old.
Genomic data from these specimens suggest that there were two lineages of mammoth in eastern Siberia during the Early Pleistocene. Adycha and Chukochya come from the line that gave rise to the woolly mammoth, whereas the Krestovka mammoth represents a previously unrecognized lineage. The authors estimate that the Krestovka genome diverged from that of other mammoths around 2.66 to 1.78 million years ago, and that this lineage was ancestral to the first mammoths to colonize North America.
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