Modern research, mainly in London and Turku (Finland), examines paleontological evidence and modern test-subjects on how the unique human sense of nudity roots in biological evolution. It proves nudity, except for patches on skull and genitals, was an advantage in hot Africa about 3 million years ago, and cloths evolved 500,000 years ago giving greater flexibility. Humans are conditioned to select 'healthy' mates from corresponding indicators, such as limited hairiness and features discernible under clothing. Part of BBC's Horizon documentary series.