New Defender's Study Bible Notes
1:28 replenish. God’s first command to man was that of producing abundant progeny sufficient to fill the earth (not “replenish,” a misleading translation of the Hebrew word male). Perhaps the animals had been created in large numbers of each kind, but the human population began with only two people. The function of subduing the earth and having dominion over it would necessarily require a long time–first, for the growth of a large enough population to fill the earth, and second, for the acquiring of enough knowledge and skill to enable man to bring it under full control and development.
1:28 have dominion. This primeval commandment to conquer and rule the earth has been called the dominion mandate, though a better term might be the primeval commission to mankind. It has never been abrogated, but was specifically renewed and extended after the Flood (see notes on Genesis 9:1-7). The military terminology in no way implies hostility and resistance from the earth, for it was all “very good” (Genesis 1:31). It suggests, rather, intensive study of the earth and its creatures (that is, “science”) and then application of that knowledge (that is, technology and commerce) for the optimum benefit of mankind and the animals, and for the glory of God.
Note that no instruction was given to exercise dominion over other men, but only over the earth and the animals. Had man not rebelled against God’s Word, all would have remained in perfect fellowship with God and, therefore, with one another. There was no initial need for the so-called social sciences and technologies, but only the natural sciences and their implementation. This situation was radically changed at the Fall, and God’s commandment accordingly expanded officially after the Flood.