Hookworms hitched rides with nomads.

Horseback-riding herders known as Scythians or Scythes once traveled far and wide across Eurasia. Their dead have the parasites to prove it.

A man and a woman who were buried separately about 2,300 years ago and recently excavated in Berel, Kazakhstan, were infected with hookworms during their lifetimes, researchers have determined. Hookworms weren't then and still aren't typically found in the steppes of central Asia.

"This finding demonstrated that Scythes, a nomadic people, roamed across large areas," says parasitologist Jean-Francois Magnaval of Paul Sabatier University in Toulouse, France. Hookworm transmission requires a warm and wet climate, he adds, but the closest such weather to the graves is at the Caspian Sea, about 1,200 kilometers away.

Archaeologists suspected that Scythians buried at Berel had traveled extensively because their graves contained artifacts from as far as 1,500 km away.

The rectums of the two Scythians from Berel contained hookworm eggs, the researchers report in the May 6 Lancet. The peripatetic pair may have become infected while visiting a seaside settlement or campsite. There, they could have had contact with mud or wastewater that contained human feces, the primary mode of transmission for hookworm infections, Magnaval says. Untreated hookworm infections can persist for at least 10 years.--B.H.