Modern humans arose after 2 distinct groups in Africa mated over tens of thousands of years

Modern humans arose after a complex history of intermingling between ancestors on at least two different but closely related evolutionary branches, a new study suggests. 
While these genetically distinct branches had divided, people on each branch continued to occasionally mix over time, the researchers found.
The new results upend previous suggestions that our species may have interbred with extinct relatives in Africa who had significantly different anatomy from us. What's more, it jettisons the idea that humans evolved from a single river branching off from our closest relatives. 
"It is exciting that people are starting to model these more complex models and that datasets are becoming available to do this," Carina Schlebusch, a population geneticist at Uppsala University in Sweden who did not take part in this research, told Live Science.
Modern humans arose after 2 distinct groups in Africa mated over tens of thousands of years