The distance that came out of bone

A team screened 1,400 ancient human remains from eastern Eurasia dated 8,000-400 years ago and recovered three prehistoric Yersinia pestis genomes, including one from East Asia. Integrated with 136 published ancient and modern genomes, those three produce a branching: at about 5,300 years ago, a node tying Scandinavia, Central Europe and northern China together. Low single-nucleotide distances and tip-dating indicate splits over century-scale intervals across more than 7,500 kilometres, with a median lower-bound dispersal rate of 32.9 kilometres a year.[1]

A rate of thirty-three kilometres a year is less than a day's walk. Over a lifetime it comes to two thousand kilometres; in ten generations it reaches from one end of the continent to the other. The number does not paint a picture of swift catastrophe. What it paints is more unsettling: steady, ordinary, unbroken contact. The bacterium did not cross that distance alone; people, animals, goods and roads carried it.[1]

Reframing what came before history

The words we use for prehistoric communities — isolated, local, scattered — grew largely out of the silence of the evidence. Pottery and graves travel slowly; a disease, while being carried, also describes its carrier. Of the seven deep phases examined, only the basal stem of the LNBA+ lineage shows significant enrichment of disruptive genomic remodeling relative to the genome-wide background distribution of mutation categories, including acquisition of the ymt gene. The bacterium did not merely journey through this network; it was altered along the way.[1]

The caution here is real. The findings rest on a phylogeny built from genomes, and not on direct observation of caravan routes. The genomes do not say which route was used in which direction; what they say is that the ends were connected. Even so, the connection alone counts as large evidence. We are in the habit of treating an epidemic crossing continents in weeks as a defect particular to the modern world. This study suggests the speed changed while the pattern stayed the same: we have been in the same room for five thousand years, and only the sound now travels faster.[1]