Step 1: Concept Identification:
This query concerns the earliest and most basic forms of human communication, preceding organized language.
Step 2: Explanatory Details:
Prior to the emergence of structured vocabulary and language, early humans utilized non-verbal communication techniques. These encompassed body movements (gestures, stance) and facial expressions, which are innate and instinctual. Cave art, dating as far back as 30,000 BCE, represents an early instance of symbolic communication. Spoken and written languages are more advanced and complex systems that evolved later. "Mail" refers to a contemporary method of transmitting written messages and is unrelated to primitive human interaction. Consequently, the most rudimentary and initial means of conveying emotions and experiences involved bodily signals and expressions.
Step 3: Concluding Statement:
Non-verbal communication constituted the primary method of expression for early humans. Accordingly, option (D) is the accurate selection.