A group of humans migrating out of Africa some 40,000 to 70,000 years ago mingled with an as-yet unknown branch of humanity, researchers say. Modern humans originated about 150,000 to 200,000 years ago in Africa. However, scientists have long debated when and how the modern human lineage spread out of Africa to nearly every corner of the globe. Nearly everyone outside Africa descended from an exodus that occurred between 40,000 and 70,000 years ago, but recent archaeological findings and climate models suggest that migrations of modern humans from Africa began at least 100,000 years ago. One way to find out whether, in the past, modern humans dispersed from Africa in one wave or many — and to see if they intermingled with any other human lineages along the way — is to examine the genomes of present-day modern humans. "We're interested in understanding how our species has come to be how it is through the lens of ancient DNA," said Swapan Mallick, bioinformatics director at Harvard