* Slang is dynamic: It constantly evolves, with new words popping up and old ones fading away.
* Slang is often informal: It doesn't typically get recorded in official dictionaries until it becomes widespread.
* Language is constantly changing: Even standard language evolves over time. What was considered slang in one era might be standard language in another.
However, we can look at some historical evidence:
* Ancient Greek and Roman slang: There are documented examples of informal language and jargon in ancient texts, suggesting that slang existed even then.
* Middle English slang: The "Cant" language of thieves and beggars in medieval England is a well-known example of a highly specialized slang.
Ultimately, slang is an inherent part of human language. It's a way for groups to express themselves in a unique way, and to create a sense of identity and belonging. As long as language exists, slang will likely exist too.