Did we come close to extinction?

Li and his colleagues think this bottleneck was probably due to climate change, with global cooling around this time leading to severe drought in Africa and Eurasia. John Hawks at the University of Wisconsin, who wasn't involved in the study, points to a paper from earlier this year suggesting that early humans in Africa were split into several distinct populations with only occasional migrations and mergers between them. Population bottlenecks occur when an existing population is reduced in size, for instance as a result of a catastrophe or when a small number of individuals leave one population to found a new one. [Extracted from the article]