Step 1: Understanding the Concept:
This question asks about the most primitive or earliest forms of human communication, predating complex systems like structured language.
Step 2: Detailed Explanation:
Before the development of structured words and language, early humans relied on non-verbal methods to communicate. This included using their body parts (gestures, posture) and facial expressions. These forms of communication are fundamental and instinctual. Cave paintings, dating back to 30,000 BCE, are among the earliest forms of symbolic communication. Words and language are more evolved and complex systems that developed much later. "Mail" is a modern system for sending written correspondence and is not relevant to early human communication. Therefore, the most basic and earliest method of expressing feelings and experiences was through body parts and expressions.
Step 3: Final Answer:
The most fundamental method of expression for early human beings was non-verbal communication. Therefore, option (D) is the correct answer.