This is a puzzling finding with a significant implication. If Denisova 11’s mother was a Neanderthal whose genome resembled western European Neanderthals more than eastern Neanderthals, it suggests that Neanderthals were not isolated in separate regional populations throughout their range. They moved. Western and eastern Neanderthal populations exchanged individuals, or experienced migration events that shifted the genetic composition of eastern groups. The Neanderthal who became Denisova 11’s mother—or whose population contributed to the maternal line—may have been part of a wave of Neanderthals that moved from western Eurasia eastward, reaching the Altai region by the time period when Denisova 11 was born.
This movement history, inferred from a handful of chromosomes in a single bone fragment, adds texture to the picture of Neanderthal demography. These were not static populations clinging to fixed territories. They were human beings moving through landscapes, encountering other populations, sometimes settling in new areas. The Altai Mountains, where Denisova Cave sits, were accessible to populations from both the east and the west. The cave itself seems to have been a place where different hominin groups appeared and disappeared over hundreds of thousands of years—not because they were all there simultaneously, but because the cave was repeatedly occupied by whatever humans happened to be in the region.
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## Establishing Age and Dating
Two separate questions about age surrounded the Denisova 11 fragment. One was biological: how old was this individual at the time of death? The other was chronological: when did this person live?
The biological age question was answered through the bone itself. The cortical thickness of a long-bone fragment changes as an individual ages—children’s bones have thinner cortices that thicken through adolescence. The cortical measurement of the Denisova 11 fragment indicated that the individual was at least thirteen years old at death. This is a minimum estimate, not a precise determination. The individual was adolescent or older; the bone could not establish an upper bound on age at death.