The Chadic languages of Central Africa
On this website you will find research data and findings on a number of Chadic languages:
Speakers of languages of the Chadic family live in an area south of the Sahara Desert extending from Nigeria and Niger in the west to central Chad Republic in the east. The most obvious evidence that these languages are related (that is, we can, in principle, trace them all back to a single language spoken thousands of years ago) is similarities in many items of vocabulary that cannot possibly be the result of chance resemblance or adopting words from each other or from some other language. An example is the word for crocodile. In the short video below you can see the word for crocodile in eleven Chadic languages. These words all come from a single ancestral form, 
The following movie demonstrates the location and makeup of the Chadic language family.