Why has the origin of click consonants in Khoisan languages remained unknown?

The origin of click consonants in Khoisan languages remains a mystery because scientific attempts to explain their development have proven inconclusive.1

Early theories suggested that clicks might have evolved as natural vocal adaptations, such as onomatopoeic sounds or methods for hunters to camouflage their presence while stalking prey. However, this line of reasoning has been largely dismissed; while some clicks function as sound symbolism, their typical role in language is as unremarkable as that of any other consonant.1

Furthermore, the study of these sounds is complicated by the fact that Khoisan is not a language family in the strict sense, but rather a group of languages that share certain features, such as clicks, while exhibiting radical differences in vocabulary, grammar, and sentence structure. Because conventional linguistic methods have failed to establish regular sound correspondences or reconstruct common ancestral roots, researchers cannot definitively trace the genesis or evolution of these unique sounds. The difficulty in demonstrating clear linguistic relationships may also be due to the limitations of comparative methods in penetrating the significant time-depth separating these language groups.12