Kra-Dai is descended from various Pre-Austronesian components that had also contributed to Formosan languages, but did not directly descend from any languages spoken in Taiwan.
Malayo-Polynesian forms such as 'snake' and 'liver' show up in Proto-Hlai, whereas they do not show up in other branches of Kra-Dai. This is evidence for a small-scale limited back-migration from Taiwan to Hainan, but it was not the large-scale back-migration that Blench and Sagart claimed had taken place.