Studies in Genesis 1
So God created the great sea creatures and every living creature that moves, with which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good.
And God blessed them, saying, “Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth.” (Genesis 1:21-22 ESV)
God uses two terms in these verses to show how He has set up the natural order and the laws of nature to propagate each species to increase their numbers. He states that the sea creatures and the bird exist “according” or “after their kind” or “after its kind.” He uses a word which means to sort or group according to form and likeness. This word is used only 31 times, all of which are in the Pentateuch, except for one instance in Ezekiel (47:10).
While there are swarms of creatures, large numbers filling the seas and sky, there are uncounted groups of like creatures. They are “after their kind.” Though God made a single human He made large numbers of each kind of creature.
Then God commanded these creatures “be fruitful and multiply.” He wanted them to fill the Earth with life. The emphasis of the words is the ability to produce offspring of their kind. We know now God created male and female of each species because He determined the way the animals would have offspring. He set up the natural system according to natural laws so the population of each species would increase naturally.
This may seem an obvious statement yet the current reaction to the way God introduced life on Earth rejects the evidence of His involvement so as to skew the natural order and reinterpret the natural laws. Yet, God’s work and the laws He established are minutely intricate, profoundly simple and point to Him as Creator.