It is believed that a mother language originally developed in asia eurasia india africa

A mother tongue, as in the first language ever spoken by humans? This would likely be in Africa, as humans are likely to have developed language before migrating to other contintents: as shown by the fact that languages are spoken on ALL continents.

if it developed in Eurasia, we would have to explain how people in Africa, who never left, developed language...

why dont you just ask Frank, he knows?