Nearly all of today's Native Americans in North, Central and South America can trace part of their ancestry to six women whose descendants immigrated around 20,000 years ago, a DNA study suggests.

Those women left a particular DNA legacy that persists today in about 95 percent of Native Americans, researchers said.

The work was published this week by the journal PLoS One. Perego is from the Sorenson Molecular Genealogy Foundation in Salt Lake City, Utah, and the University of Pavia in Italy.

The work confirms previous indications of the six maternal lineages, he said. But an expert unconnected with the study said the findings left some questions unanswered.