The history of numerals as a history of East African languages

Abstract The paper discusses a shift in the number system of Proto-Tanzanian Cushitic from the word for “three” to mean “four”, and the one for “two” to mean “three”. This shift was brought about by contact between an incoming group of northern Cushitic speakers and the already present group of Tanzanian Cushitic speakers due to similarity in form between the words for “four” in Tanzanian Cushitic and “three” for in the incoming group. This shift pulled the word for “two” to fill the gap of the old “three” and triggered the innovation of a new internally derived word for “two”. This scenario provides a more intricate view on the Cushitic migration from Ethiopia to Tanzania. Kw’adza joins the rest of Tanzanian Cushitic undergoing this complex and unique set of shifts, but Aasa does not.