Click languages

The Kalahari Bushman tribes have four different clicks that they use as consonants. Other South African tribes employ clicks to lesser degrees. The first consonant in the name of Nelson Mandela's tribe, the Xhosa, is a click. Based on DNA evidence, Bushmen groups are thought to be remnants of groups that split off from all of the rest of us, some tens of thousands of years ago, before all of the rest of us split into blacks and whites and Asians and Native Americans and such things. Several extinct Australian Aborigine languages -- spoken by descendents of people who took the first major migration out of Africa, about 40,000 years ago -- were click languages. Some linguists factor in the Aborigines and the Bushmen and triangulate back, and figure that the earliest human languages were probably click languages. I was talking about that with my students and one of them pointed out that nowadays, people use clicks to communicate with animals. You can get the attention of a dog or cat with a few clicks. Some people click at horses to get them moving. Soon after, this video http://video.on.nytimes.com/?fr_story=cae7e462bfa605f980fa6844326075a875e13c10 appeared on the New York Times' website, showing a Dinka boy in Sudan taking care of his family's cattle and talking with them using clicks and clucks and other sounds. So I wonder if using clicks to talk with animals might go back thousands and thousands of years. Maybe at some point they fell out of fashion for talking with people, but stayed on in our animal talk as a forgotten remnant of what once was.