She has published fiction and non-fiction books and articles on animal behavior, Paleolithic life, and the !Kung Bushmen of the Kalahari Desert.
[2] 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.
[3] During these trips, Thomas kept a journal which she later drew on when writing her first book, The Harmless People.
[1] She later drew on this experience in her fiction, depicting the life of paleolithic hunter gatherers in the novels Reindeer Moon[4] and The Animal Wife.
A popular success and New York Times bestseller,[2] her book The Hidden Life of Dogs[5] also drew criticism from some in the scientific and dog training communities for Thomas' observational methods and analysis.