Study Suggests All Men Have Common Ancestor

Every man on Earth today is related, linked by a Y chromosome to a common ancestor who lived about 190,000 years ago, a study suggests.

This so-called ancestral Adam was among many males who lived before anatomically modern humans evolved, but he’s the only one purported in the study to have a genetic legacy that persists today.

“We would all have a Y chromosome that existed in the same guy,” said Michael Hammer, an assistant research scientist at the University of Arizona whose study appeared Thursday in the journal Nature.

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.

Hammer compared the detailed makeup of a tiny piece of the Y chromosome 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 different 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 for about 188,000 years to the same person.

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.

While many scientists say anatomically modern people arose about 100,000 years ago in Africa, others say modern humans arose in different parts of the world at different times.

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

The study found evidence that modern-day humans resulted from a relatively small breeding population. The group was so small that it’s hard to believe its members could have been spread over more than one continent, Hammer said.