The fact that all humans have a common origin and migrated out of Africa around 70,000 years ago is supported by scientific evidence from genetics and archaeology. This migration is known as the "Out of Africa" theory, which proposes that modern humans originated in Africa and gradually migrated to other parts of the world, eventually populating the entire globe.
However, the lack of direct linguistic evidence for this shared origin is due to the nature of language and how it evolves over time. While genetic and archaeological evidence can provide clues about human migrations and population movements, languages do not fossilize in the same way. Languages are dynamic, constantly evolving systems of communication, and they change over time as people interact, move, and exchange ideas.
When populations migrate and settle in new areas, they may develop new dialects or languages influenced by the languages spoken by neighboring groups. Over thousands of years, these linguistic changes can lead to the development of completely distinct languages. Additionally, languages can be influenced by various factors, including environmental conditions, cultural interactions, and contact with other language-speaking groups.
As a result, after thousands of years of migration and separation, the original linguistic roots of human languages become challenging to trace directly. However, linguists and researchers can use the comparative method to study similarities between languages, identify linguistic families (groups of languages with a shared origin), and infer information about ancient languages and human migration patterns.
While there might not be direct remnants of the original human languages from 70,000 years ago, linguistic research and the study of language families do provide important insights into human history and migration. The process of language evolution has shaped the rich linguistic diversity we observe in the world today, reflecting the complex and dynamic interactions of human populations over millennia.