The researchers sequenced DNA from two key sources -- the Y-chromosome, which is passed only from father to son; and mitochondria, which provides energy for cells and is transmitted only from a mother to her children. Both can serve as useful tools for tracing ancestry since they don’t swap genetic material, unlike the rest of the human genome.
Until now, scientists estimated that Eve lived about 190,000 to 200,000 years ago, while Adam lived much more recently -- between 50,000 to 115,000 years ago. But that “didn’t make a lot of genetic sense,” said Theodore Schurr, an anthropological geneticist at the University of Pennsylvania who was not part of the study. How could two individuals living as much 150,000 years apart not give rise to separate species?
The disparity might have resulted from limitations in gene sequencing. Up until about five years ago, scientists could sequence only a few regions of the genome. As a result, they could study only a few snippets of the long, structurally complex Y-chromosome genome, Schurr said.
But they were able to examine a significant portion of the mitochondrial genome, which is thousands of times shorter than the Y chromosome and easier to work with.
Thanks to recent technological advances, researchers can sequence more DNA cheaper and faster, allowing them to flesh out the details of humanity’s origins.