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 to today in about 95 percent of Native Americans

The women lived between 18,000 and 21,000 years ago, though not necessarily at exactly the same time

Perego and his colleagues traced the history of a particular kind of DNA that represents just a tiny fraction of the human genetic material, and reflects only a piece of a person's ancestry.

This DNA is found in the mitochondria

Unlike the DNA found in the nucleus, mitochondrial DNA is passed along only by the mother. So it follows a lineage that connects a person to his or her mother, then the mother's mother, and so on.

The six "founding mothers" apparently did not live in Asia -- the DNA signatures they left behind aren't found there