GENETICS × PEOPLING

The Denisovans Discovered

2010 CE

History · Contemporary · Holocene · Meghalayan

The Denisovans are an extinct human population identified from DNA before any informative fossil was known. In 2010 a complete mitochondrial genome was read from a fragment of finger bone excavated two years earlier in Denisova Cave, in the Altai Mountains of southern Siberia; the sequence matched no known type, and its common ancestor with the mitochondrial DNA of Neanderthals and of modern humans lay about one million years back. A nuclear genome from the same bone, published in December at about 1.9-fold coverage, gave another view of the same individual: the population it came from shares an origin with Neanderthals and contributed 4 to 6 per cent of its genetic material to the genomes of present-day Melanesians. The two readings do not conflict: a mitochondrial genome follows one maternal line, while a nuclear genome averages an entire ancestry. The name Denisovans was proposed with the second paper, alongside a molar from the cave whose mitochondrial genome was closely similar.

Why it matters

A human population was named from its genome, which reversed the usual order of palaeoanthropology: rather than a skeleton described and then placed, there was a sequence, and fossils had afterwards to be matched to it. One consequence is that the group is better attested in the living than in the rock, since its inheritance persists in people settled thousands of kilometres from the cave, in Melanesia. The high-coverage genome published in 2012 added a measurement of the diversity of these hominins, which proved extremely low.

Dating & uncertainty

The year names a publication, not a bone. The finger fragment was excavated in 2008; its mitochondrial genome appeared in March 2010, the nuclear genome of the same bone in December, and the population was named only with the second. The choice of month changes what is being dated. In March an unknown lineage had been recognised and its divergence placed near one million years, which seemed to set it well apart; in December it had a name, a sister group in the Neanderthals themselves, and descendants among the living. The age of the bone is a separate measurement, and not the one the year records.

Sources

1. Krause et al. (2010), Nature · The complete mitochondrial DNA genome of an unknown hominin from southern Siberiadoi:10.1038/nature08976
2. Reich et al. (2010), Nature · Genetic history of an archaic hominin group from Denisova Cave in Siberiadoi:10.1038/nature09710
3. Meyer et al. (2012), Science · A high-coverage genome sequence from an archaic Denisovan individualdoi:10.1126/science.1224344
4. Stringer et al. (2015), Proceedings of the National Academy of Sciences · Deciphering the Denisovansdoi:10.1073/pnas.1522477112

Our species’ history as one day

23:59:554.4 s before midnight

if the 315,000 years of Homo sapiens were compressed into a single day