If eternal heaven is the greater good then is human existence on a hostile earth some kind of experiment? game? entertainment for God?
Humans came to existence by natural laws (evolution).
They developed a very sophisticated mind but they were not conscious (That's why Adam and Eve didn't knew about good and bad). They were just like the bicameral men proposed by Julian Jaynes.
In a very recent point in history (in Mesopotamia) God elevated human nature by giving an immortal soul to a couple of "bicameral" humans (Adam and Eve). This soul enables humans to have consciousness.
This process of unification between physical and spiritual nature in humans was interrupted by this couple someway somehow.
So the full double (physical + spiritual) human nature was broken.
This broken human nature are being repaired in a masterplan since then and will be complete in the Last Judgment.