Helena Petrovna Blavatsky was an esoteric thinker from the Russian Empire. In 1875 she founded the Theosophical Society in New York and spread Theosophy, which combined Eastern religious thought with Western mysticism.
In her major work The Secret Doctrine (1888), she described humanity as evolving through a series of “root races,” with Lemuria and Atlantis as their stages. The influence of Blavatsky and Theosophy is a major reason why Lemuria, originally a scientific hypothesis, came to be told of as a “lost civilization.”