Work on the study of language change: how languages change and evolve through time.
Niger-Congo, Bantoid, Bantu
Work on the Niger-Congo languages, with a particular attention to Bantoid languages, including Bantu.
Currently working on Indo-European languages.
Use of phylogenetic methods, techniques borrowed from biology, in order to examine the historical relationships among languages.
Work on genetic classifications of languages (classification into families, based on descent from a common ancestor)
Evolution of languages
Study of language evolution in order to better understand human history.