According to certain psychic's and the Urantia Book, Adam and Eve traveled to Urantia in order to produce children of a mixed Adamic/Human race.
During this ancient period, an alliance had been formed by Lucifer, Satan and Caligastia to initiate an interplanetary rebellion. This trio were not in accord with spiritual concepts. It was Caligastia, and now known as the Devil, who arranged the temptation and subsequent abortive mission of Eve. The authors of Urantia consider that this constituted the so-called "original sin."
As a result, the goal of mixing Adamic blood with human blood never reached the intended high percentage of Adamic blood in humans. Accordingly, the goal of eliminating human disease and sensitizing the human body through which to better receive spiritual communications and impressions was never achieved. This is why some believe that there are now disparities among the human race.
Certain psychic's and channeled sources maintain that like Atlantis, Adam and Eve are simply myths, or projected future events planted into our past.