Man was created perfect. Man chooses to go his own way rather than The Way of God (his Creator). Man now lives with the results of his choice. This is called consequence. You have faced this before in both small and big ways. The problem is always bigger than we initially realize. If the consequence to our poor choices was small and limited that would be one thing...but it rarely is...
Adam and Eve have sinned and the consequence for their action has broad and eternal ramifications. Yes, they are expelled from paradise. Yes, they now age and die. Yes, they now labor (in both senses of the word). But it is not only them that have been changed. It is also their progeny. Every child they bear, every grand-baby they celebrate, each person to be born into the world was not born into the choice of 'knowing good/evil'.
As you have probably read before, the Old Testament word 'know' was much more than head knowledge. It involves intimate experience. It is the same word used here in Genesis 4 when Adam 'knows' Eve and they have children. Thus, our knowledge of evil became intimate with Adam/Eve's fall. They fell into a separation from God. This was sin. This was missing the mark. This was wilfully going against the perfect Way of God. It haunted them and still haunts us today.
So, they have children and we see that knowledge of evil show itself in the first murder. We see pride, anger and many other character faults in this account. Cain and Abel both bring sacrifices of their work to God. Abel brings of his best and God is pleased with his worship. Cain apparently brings of his leftovers and this is shown to be an inadequate response. God expresses this to Cain and rather than understanding and changing (repenting), Cain gets out his frustration by killing his brother in cold blood.
One generation removed from perfection and sin has brought man to our lowest form. More children are born and the world becomes populated over several hundred years. The sin that we saw in Adam and Cain has now become epidemic. God's justice and judgement has reached its target. Humanity would be obliterated from the earth. Sin would be purged. Cleansing in the most horrific way possible. All this could have been avoided if we had only chosen the Way of God rather than the way of man. Read Proverbs 14:12 for an apt description...
Questions to consider:
1. Is it easier to cover sin and mistakes or to turn from sin and mistakes?
2. Could something you are doing that is individually wrong have an affect upon others you care about?
3. Cain's question 'Am I my brother's keeper' is a slap in the face of the Community that God designed us to experience. What attitudes might you have that are preventing Community in your life?