The diversity of sounds in various languages can be used to trace back to the origin of language. The results point to an African origin of modern human language, and more precisely, a western African origin.  Read this article by Quentin Atkinson. Science 332, 346-349 (2011).
Here is the title, abstract, and Figure 2: 

Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa
Quentin D. Atkinson

Human genetic and phenotypic diversity declines with distance from Africa, as predicted by a serial founder effect in which successive population bottlenecks during range expansion progressively reduce diversity, underpinning support for an African origin of modern humans. Recent work suggests that a similar founder effect may operate on human culture and language. Here I show that the number of phonemes used in a global sample of 504 languages is also clinal and fits a serial founder–effect model of expansion from an inferred origin in Africa. This result, which is not explained by more recent demographic history, local language diversity, or statistical non-independence within language families, points to parallel mechanisms shaping genetic and linguistic diversity and supports an African origin of modern human languages.



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