I have read somewhere that if there ever was a world's first language*, that language must have had very much in common** with the Khoisan languages. Arguments in support of this hypothesis are:
- Khoisan languages have click consonants, a feature that has not developed independently in other languages. Bantu languages, for example, have borrowed them from Khoisan. So, this was probably some sort of an "early invention" that was not very "fit" and got abandoned along the way.
- If you look at a map depicting where Khoisan languages are spoken, you will see a major area over parts of Namibia (eastern part, mostly), Botswana and South Africa and two small pockets (one in central Tanzania and one in the western coast of Namibia). These small pockets suggest that Khoisan languages once dominated most parts of Africa and then got replaced by Bantu languages (which, in fact, sorround those pockets).
- Genetic and archeological evidence suggests that Homo Sapiens originated in that part of the world.
Are these arguments generally accepted among linguists? How much of this is "good science" and how much is just "pop science"?
* In the sense of a single language from which all other languages of the world came out.
** The first version of this question contained the expression "direct ancestor". But, as was pointed out in the answers and comments, this is not an appropriate term.