There has been only limited scholarly support for a theory developed by W. B. Henning, who proposed that the Yuezhi were descended from the Guti (or Gutians) and an associated, but little known tribe known as the Tukri, who were native to the Zagros Mountains (modern Iran and Iraq), during the mid-3rd millennium BC. In addition to phonological similarities between these names and *ŋʷjat-kje and Tukhāra, Henning pointed out that the Guti could have migrated from the Zagros to Gansu, by the time that the Yuezhi entered the historical record in China, during the 1st millennium BC. However, the only material evidence presented by Henning, namely similar ceramic ware, is generally considered to be far from conclusive.