Hi again, everybody!
I comment briefly here about some claims regarding ‘clicks’, the consonants technically described as ‘velaric ingressives’ (produced with airstreams drawn INTO the mouth and by movement of the velum aka the soft palate rather than by the lungs). These consonants are especially associated with the Khoisan or ‘Bushman’ languages of Namibia and neighbouring areas of southern Africa, as famously portrayed in the movie The Gods Must Be Crazy. Some of them resemble the sound stereotypically used to ‘gee up’ horses.
The mainstream palaeoanthropologist (etc.) Alice Roberts comments upon the long early period when pre-literate humans probably already had language (for the details of which little concrete evidence survives, naturally); she includes an interesting discussion of ‘click’ consonants in a range of African languages, comparing their distribution with genetic data and suggesting (with others, and not unpersuasively) that the development of these phones may well have pre-dated sapiens expansion from Africa.
There are also some more specific, less mainstream (and less persuasively argued) book-length works along broadly similar lines, such as that of Roman Stopa on alleged links between Indo-European and Khoisan.
Dan Willmore and Nicholas Wade are advocates of the view that some aspects of the phonology of Proto-World can be reconstructed; both Willmore (apparently familiar with the relevant aspects of human genetics and with palaeo-anthropology) and Wade argue that Proto-World featured ‘clicks’. At present the only non-Khoisan languages which extensively feature clicks are the languages of the Hadzabe and Sandawe of Tanzania. The two groups of languages are not otherwise similar, and their speakers are hardly close relatives: mitochondrial DNA evidence suggests that the two peoples have been separate from each other for more than 50,000 years. Willmore holds that modern humans began to leave Africa around 50,000 years BP, which itself would imply that any ancestral features which Khoisan and Hadzabe/Sandawe now have in common must have been shared at that date (compare Roberts as cited above). Australian evidence suggests that the beginning of homo sapiens movement out of Africa must be dated earlier than this, perhaps around 70,000 years BP; but the data are still striking. (In addition, Willmore holds that the overall evidence shows that there was just one Proto-World and that it can be reconstructed in part. He is also ‘certain’ that Neanderthals could speak; and he seems to believe (very oddly) that ‘imagination’ is somehow involved even in PHONOLOGICAL change.)
A manifestly non-mainstream article by T. Kluge argues that the human capacity for speech results from features of the brain, notably the ‘language centre’, which have become strengthened through the use of the arms, which in turn arose from the overall arrangement of human limbs (two arms, no wings). Kluge also associates many phonetic features with physiological characteristics; he claims, for instance, that clicks are associated with certain ‘racially’ determined mouth structures. (He further holds that variations in auditory perceptions of phonetic pitch in speech correlate with air-density and thus with the altitude at which a language is used; this is an extreme version of the commonly-expressed folk-linguistic view that differences in prevailing atmospheric conditions generate accent differences, for instance the ‘adenoidal’ quality of the speech of once fog-bound Liverpool).
As ever, detailed references on request. Another new topic area next time!
Mark
Skeptical Humanities 
Thanks that was interesting. It also goes with the idea that I’ve read elsewhere that clicks in languages go way back.
I am curious about just how widespread these languages were before the slow migration of Bantu speakers. If languages with clicks were spoken by populations of hunter-gathers their rather low population density would presumably help to explain the lack of clicks among the farming and pastoral Bantu has they migrated into the areas occupied by the hunter-gathers.
In southern Africa, I.E., South Africa proper. About 2000-2500 years ago the ancestors of the Koisan people adopted or invented a pastoral way of life for themselves. They apparently migrated from from part of modern day Bostwana into South Africa. The population of these pastoralists was much denser than a group of !Kung hunter-gathers. This presumably explains why when Bantu migrants entered South Africa proper, (depending on what book you read it started as early as 200 C.E. r as late as 1000 C.E., I personally thing the archaeology supports c. 400 C.E.) Since they encountered much denser populations of people speaking click languages. they some groups, especially on the costal zones, with a greater density of pastoral Koisan, adopted some of the clicks along with significant intermarriage. I’m not sure but I believe Zulu as at least 4 clicks,
!Xosa I believe as at least 6. When the Europeans came the Koisan still controlled the area around the Cape of God Hope.
One of the most extraordinary things I’ve ever read is a Dutch description shortly after the founding of Capetown of the arrival of the Koisan to the Cape of Good hope area with their vast, and I mean vast!, herds of cattle for the winter grazing.
Thanks! Yes, some Bantu languages (Xhosa, Zulu, etc) have acquired clicks through contact with Khoisan, but as you note they have only a few clicks each, whereas some Khoisan languages have over 20. Mark