Khoisan

The Khoisan languages are spoken by the San (Bushmen) and Khoekhoe (Khoikhoi) peoples of southern Africa and by two isolated languages — Sandawe and Hadza — in Tanzania. The term "Khoisan" is a convenience grouping based on two shared features: the use of click consonants (produced by the tongue or lips creating negative pressure in the mouth) and association with pre-agricultural populations of southern and eastern Africa. However, most linguists today consider Khoisan to comprise several distinct language families with no demonstrated common ancestor, rather than a single genetic unit.

Despite their relatively small number of speakers (estimated at 300,000–400,000 total), the Khoisan languages are of extraordinary scientific importance. Population genetic studies have consistently identified the southern African San as the most genetically divergent of all living human populations, bearing the earliest-diverging lineages in the human family tree. The divergence between San populations and all other modern humans may date to 250,000–100,000 years ago, deep in the Middle Stone Age. This extreme genetic antiquity suggests that the ancestors of the Khoisan have occupied southern Africa for an enormous span of human prehistory, making them the custodians of one of the oldest continuous cultural and linguistic traditions on Earth.

The click consonant systems of the Khoisan languages are among the most complex phonological inventories documented in any human language. The Taa language (|Xam), now nearly extinct, contains up to 164 distinct phonemes — the largest documented phoneme inventory of any language — including five distinct click types, each with multiple phonemic variations. Clicks have been borrowed into neighbouring languages: Zulu and Xhosa, Bantu languages that absorbed Khoisan contact during the southward Bantu expansion, both contain click consonants derived from this contact.

Hadza and Sandawe, the two Tanzanian languages sometimes grouped with Khoisan, appear to be language isolates unrelated to each other or to the southern African Khoisan families. Hadza speakers are particularly notable: genetically, Hadza people carry one of the most divergent non-African-derived lineages and represent a very ancient East African population. Their click-rich language may preserve features of the phonological systems of early modern humans in eastern Africa, though this hypothesis requires caution — click consonants can evolve independently.