Studies of genetic diversity have been performed on "Coffea arabica" varieties, which were found to be of low diversity but with retention of some residual heterozygosity from ancestral materials, and closely related diploid species "Coffea canephora" and "C. liberica"; however, no direct evidence has ever been found indicating where in Africa coffee grew or who among the natives might have used it as a stimulant or known about it there earlier than the seventeenth century. The original domesticated coffee plant is said to have been from Harar, and the native population is thought to be derived from Ethiopia with distinct nearby populations in Sudan and Kenya.