LONDON — Broadcasters in more than 20 territories have bought the BBC, Discovery and France Televisions co-production “Human Planet,” the first skein from the BBC’s Natural History Unit to focus on the human species.Countries acquiring the docu include Japan (Wowow), Italy (RAI), Israel (IBA), Slovakia (RTV Slovak), Spain (Wanda Films) and Thailand (Thai PBS), distributor BBC Worldwide said. The sales were announced ahead of Worldwide’s annual U.K. Showcase mart, which bows Feb. 27 in the seaside resort of Brighton. “Human Planet” is narrated by John Hurt with a soundtrack by Nitin Sawhney. The eight-part series examines the relationship between humans and nature. Each episode focuses on a particular habitat and shows how people have adapted to life there.