* Non-verbal communication: This is likely the oldest form, predating language. Think of animal communication using gestures, facial expressions, postures, and sounds. Even simple organisms like bacteria can communicate through chemical signals.
* Early forms of language: This could include grunts, whistles, and other sounds, potentially coupled with gestures, that may have evolved into more complex language systems.
* Cave paintings and rock art: While not technically communication in the "real-time" sense, these forms of artistic expression likely held meaning and could be considered early forms of communication.
Essentially, the "first" form of communication is a complex question with no single definitive answer. We can say with certainty that communication has existed in some form for millions of years and has evolved significantly throughout history.