Much like us, chimpanzees, occupy diverse habitats and exhibit extensive behavioural variation. Human genetic variation however changes along a gradient, with no races and some areas of local genetic adaptation. Chimpanzees, on the other hand, are divided into four subspecies separated by geographic barriers like rivers. Previous studies attempting to understand chimpanzee population histories have been limited either by a poor geographic distribution of samples, samples of uncertain origin or different types of genetic markers. Due to these obstacles, some studies have shown clear separations between chimpanzee subspecies while others suggest a genetic gradient across the species as in humans.