We reproduce like animals because like them we die. When we no longer die the urge to reproduce is not our master.
Hmm but God told them to multiply in Genesis 1:28..
I suppose this could be 'after' Genesis 3. The preceding verse 1:27 is actually describing a time after Genesis 2 - so I can understand how 1:28 is actually taking place after Genesis 3.
Hebrew literature is written sometimes in a way not like we do; it's not necessarily in order of time, but of importance and relevance.