Y chromosome analysis moves Adam closer to Eve
Web edition: August 1, 2013
Print edition: September 7, 2013; Vol.184 #5 (p. 14)
Men might need some more pages in their family album.
The largest analyses to date of the human Y chromosome suggest that modern men can trace their family tree further back in time than previously thought. One of the studies, an analysis of 69 men from nine populations worldwide published in the Aug. 2 Science, finds that their most recent common ancestor lived 120,000 to 156,000 years ago. That’s roughly the same time that the last common ancestor of women is estimated to have lived, researchers report.
The Y chromosome, passed down from father to son, and mitochondrial DNA, passed down from mother to child, are useful in retracing ancestry because they don’t undergo genetic reshuffling as the rest of the genetic instruction book does. Researchers analyze mutations in these parts of the genome to assess when groups split apart. The hypothetical common ancestors of these genetic lineages are sometimes called Y Chromosome Adam and Mitochondrial Eve.
“We’re not saying they’re exact contemporaries or they actually met or all men and women descended from the same couple,” says study coauthor Carlos Bustamante of Stanford University. Y Chromosome Adam and Mitochondrial Eve aren’t the first human male and female but instead represent the common ancestors of the modern Y chromosome and modern mitochondrial DNA.
The findings may overturn previous results that suggested Y Chromosome Adam was only a half or a third as old as Mitochondrial Eve. Previous analyses date the Y chromosome common ancestor to between 50,000 and 115,000 years ago and the mitochondrial DNA common ancestor to between 150,000 and 240,000 years ago.