prior to 3000 BCE
This is the sum of duty:
do naught to others
which if done to thee
would cause thee pain.
....The Mahabharata 5:1517
One should not behave towards others
in a way which is disagreeable to oneself.
This is the essence of morality.
All other activities are due to selfish desire.
Anusasana Parva 113.8