Humans are unique among primates in that they alone practice obligatory bipedalism and their skeletons show distinctive adaptations for this form of locomotion. Humans' ability to regulate their body heat over long periods of heavy activity is also unique, as are their large brains that are highly developed organs that allow for technology, and diversity of culture and language. These qualities enable humans to travel over water, in the air, and into space. Humans live permanently in almost all terrestrial parts of the planet, and occupy inhospitable environments such as the Sahara and the Antarctic temporarily. Homo sapiens is the only extant human species.