After a remarkable analysis of bacterial DNA from 1,000-year-old mummies, scientists have proposed a new hypothesis for how tuberculosis arose and spread around the world.

The disease originated less than 6,000 years ago in Africa, they say, and took a surprising route to reach the New World: It was carried across the Atlantic by seals.

The new study, published Wednesday in the journal Nature, has already provoked strong reactions from other scientists.

“This is a landmark paper that challenges our previous ideas about the origins of tuberculosis,” said Terry Brown, a professor of biomolecular archaeology at the University of Manchester. “At the moment, I’m still in the astonished stage over this.”