Where we modern humans all came from has been a subject of intense debate. Some parties suggest that modern humans sprang up in several places around the globe whilst others have steadfastly insisted that, like Meryl Streep, we all came "out of Africa".
Now scientists have produced the strongest evidence yet that this latter argument is the correct one and that southeast Africa was the cradle out of which modern mankind climbed. Cambridge University's Andrea Manica and his colleagues found the genetic diversity of different populations around the world declined the further those populations were from Africa. They then measured the variation in the sizes and shapes of over 4000 human skulls representing 105 populations worldwide from the last 2000 years, and found an identical relationship. The greatest variation in skull structure was found in samples from east Africa. The loss of diversity with increasing distance from Africa is the consequence of population "bottlenecks" - abrupt reductions in population size during migration due to adverse conditions.
The further a population migrated the greater the number of these bottlenecks a population would have faced and hence the lower their diversity. To prove that they were on the right track the team tried to fit their data to other sites around the world that could have spawned modern man.
"This just did not work. Our findings show that humans originated in a single area in Sub-Saharan Africa," says Cambridge co-author Francois Balloux.