The finding contradicts previous research indicating that the lineage of the human male dates back 338,000 years — long before the first modern humans are believed to have made their appearance, around 200,000 years ago. The earlier finding had suggested that the Y (male) chromosome came into being as a result of interbreeding between Homo sapiens females and the males of other hominin species. But this new study offers a different interpretation.
"There is no evidence to support introgression from other species," Dr. Eran Elhaik, a co-author of the new study and a genetic epidemiologist and lecturer at the University of Sheffield in the U.K., told The Huffington Post in an email. "Modern humans' male and female ancestors have emerged around the same time. Modern humans' ancestors have emerged or arrived to Africa a little over 200,000 years ago and gave rise to many of the populations in Africa who, in turn, passed their genetic information to contemporary people."
To reach that conclusion, the study researchers calculated an age for the Y chromosome by multiplying the average age fathers have their first child with the number of mutations found on the Y chromosome. This number was then divided by the chromosome's mutation rate, the International Business Times reported.
"We then carried the calculations using acceptable scientific methods and determined that age to be 209,000 years old," Dr. Elhaik said in the email. In other words, the age of 'Adam.' But there are still many questions left unanswered.
"The question to what extent did our humans forbears interbreed with their closest relatives is one of the hottest questions in anthropology that remains open," Dr. Elhaik said in a written statement. “Soon, we hope to publish a revolutionary new theory about it.”
This new study was published online Jan. 22 in the European Journal of Human Genetics.
Clarification: An earlier version of this story included the sentence "How old is our earliest male ancestor?" This was referring to 'Adam' as the male ancestor to anatomically modern humans, and not all humans. But to avoid confusion, the sentence was changed.