Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, November 23, 1995                   TAG: 9511240040
SECTION: NATIONAL/INTERNATIONAL                    PAGE: A-20   EDITION: HOLIDAY 
SOURCE: Associated Press
DATELINE: NEW YORK                                LENGTH: Medium

GRANDDADDY OF ALL Y CHROMOSOMES

There were many males around at the time, but only this one left a Y chromosome legacy that persists today, said researcher Michael Hammer.

The Y chromosome is one of the 24 kinds of microscopic threads that hold genes. Unlike the other chromosomes, it is passed only from father to son.

The new study also supports the idea that modern humans arose in one place, rather than evolving on more than one continent.

Hammer, an assistant research scientist at the University of Arizona in Tucson, published the work in today's issue of the journal Nature.

He compared the detailed makeup of a tiny piece of the Y chromosome as sampled from eight Africans of various backgrounds, two Australians, three Japanese and two Europeans. The idea was to look for how varied that piece was among the ethnic groups, and then calculate how long it would take for evolution to produce the diversity he found.

The results suggest that all men alive today could trace their Y chromosomes back about 188,000 years to the same person. ``We would all have a Y chromosome that existed in the same guy,'' Hammer said.

Hammer said the study suggests that the ancestor lived just before anatomically modern humans appeared around 100,000 years ago, a date that is in some dispute among scientists

Last May, other scientists published a study saying the Y chromosome in modern-day men can be traced back 270,000 years. But a reanalysis of that data shrank that estimate to 160,000 to 180,000 years

Hammer said his findings also suggest a single place of origin for modern humans. The findings don't indicate where, but Africa is a good bet, he said.