To do so he looked at three well-studied parts of the linguistic family tree: the Bantu languages of Africa, the Indo-European group from Eurasia and the Austronesians of the Pacific.

• 为此，他考察了语言学族谱中的已经被彻底研究过的三个部分：非洲的班图语、欧亚大陆的印欧语系和太平洋上的南岛语族。