Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem solving. This mental capability, combined with an erect body carriage that frees the hands for manipulating objects, has allowed humans to make far greater use of tools than any other species. Mitochondrial DNA and fossil evidence indicates that modern humans originated in Africa about 200,000 years ago.[5] With individuals widespread in every continent except Antarctica, humans are a cosmopolitan species. The population of humans was 6.8 billion in November 2009.[6]