In a field with a reputation for bitter feuds and rivalries, the notion of humankind’s African origins unifies human evolution researchers. “I think everybody agrees and understands that Africa was very pivotal in the evolution of our species,” says Charles Musiba, a paleoanthropologist at the University of Colorado Denver.
But human evolution was not a gradual, linear process, as it appeared to be in the 1940s and ’50s. It did not consist of a nearly unbroken chain, one hominin evolving into the next through time. Fossil discoveries in the ’60s and ’70s revealed a bushier family tree, with many dead-end branches.
…
Over the last decade, as genetic and fossil revelations have painted a more complex picture of human origins, paleoanthropologists have moved beyond both the multiregional and simple Out of Africa scenarios.
Rather than a tree with separate branches or a trellis, human evolution was probably more like a braided stream, a concept traced to paleoanthropologist Xinzhi Wu of the Chinese Academy of Sciences in Beijing, who used a river metaphor to describe patterns of human evolution in China.
Different human populations may have emerged, with some floating away and petering out and others connecting to varying degrees.
