primal

serving as an essential component

• “a cardinal rule”
• “the central cause of the problem”
• “an example that was fundamental to the argument”
• “computers are fundamental to modern industrial structure”

having existed from the beginning; in an earliest or original stage or state

• “aboriginal forests”
• “primal eras before the appearance of life on earth”
• “the forest primeval”
• “primordial matter”
• “primordial forms of life”