Between 1950 and 1956, she took part in three expeditions to live with and study the Ju/'hoansi (!Kung Bushmen) of the Kalahari Desert in Namibia and Botswana. During these trips, Thomas kept a journal which she later drew on when writing her first book, The Harmless People. She later drew on this experience in her fiction, depicting the life of paleolithic hunter gatherers in the novels Reindeer Moon and The Animal Wife.