And God blessed them. And God said to them, "Be fruitful and multiply and fill the earth and subdue it and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth."God's word for man is established a few verses back when He decides to make man and give him purpose. In this verse God reveals His word to man. God's revealed word to man at this point is only this. Nothing more is revealed to Him, that we have record of. Man's responsibility is now to obey God's word.
In many ways, things have not changed. God has revealed His word to us, in a much grander scale, but the call is still the same. We are to obey His word.