Krishna now turns to a practical question: how do people's duties differ? His answer is clear — the duties of brahmanas, kshatriyas, vaishyas, and shudras are divided according to the gunas that arise from each person's own nature. Not by birth. Not by lineage. By the qualities that naturally express themselves in a person.
This is an important distinction. The word used is 'svabhavaprabhavaih' — born from one's own nature. A person whose nature inclines toward learning, restraint, and reflection naturally fits brahmana-dharma. One whose nature inclines toward courage and leadership fits kshatriya-dharma. The classification follows the person's inner disposition, not their family name.
Krishna is setting up a framework that leads to a powerful conclusion in the coming shlokas: whatever your natural calling, pursue it wholeheartedly. Perfection comes not from imitating someone else's path, but from fully embracing your own.