No. 44 IN SCIENCE NEWS: A recent study has given strong evidence that all humans have a common African ancestor. The study says a common ancestor first appeared in Africa about 170,000 years ago. The study also says that humans left Africa to populate other parts of the world about 50,000 years ago. The study was done at the University of Uppsala in Sweden. Researchers looked at the DNA of 53 people from all over the world. The chief researcher of the study said looking at the DNA of each person permitted researchers to find their genetic ancestry.