* Language Evolution: Languages are constantly changing and evolving. Over thousands of years, languages branch off, develop new features, and lose others. This makes it impossible to trace a single language back to an absolute origin point.
* Lack of Written Records: Many ancient languages existed without written records, making it difficult to reconstruct their history.
* Definition of "Language": The definition of what constitutes a "language" is itself complex. Are we talking about a distinct spoken language, a written language, or a language family?
What we can say with some certainty:
* Proto-Indo-European: This is a reconstructed hypothetical language that is considered the ancestor of many languages spoken in Europe and parts of Asia, including English, Spanish, Hindi, and Persian. It is estimated to have been spoken around 4500-2500 BCE.
* Sumerian: This ancient language, spoken in Mesopotamia, has some of the earliest known written records, dating back to around 3500 BCE.
It's important to remember: There may have been other languages spoken before Proto-Indo-European and Sumerian, but we simply don't have the evidence to know for sure.
The question of the "oldest language" is more of a philosophical question about the origins of human communication than a question with a definitive answer.