It is not about Abel being born to balance out the evil. Both were given a choice of how to think and live, and they both chose differently.
I have reasoned before about the connection to the tree of knowledge and what happened to Cain and Abel. This will show the I the connection that I sight.
I think Revelation is the natural destination of a divided society, a society that doesn't see everything as One life.
In the beginning when Adam and Eve ate the fruit, they saw their nakedness and covered theirself with leaves. Jah, after seeing what they have chosen. Gave them their desire and gave them coats of skin to cover themselves.
I interpret this as Adam and Eve bringing this concept of separation and division into their minds. Before this they only saw One, so they were One flesh, One life.
24 Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh.
25 And they were both naked, the man and his wife, and were not ashamed.
So I see the placing of the leaves as a representation of them putting up a "wall" between them, because they saw theirself as separate. So when Jah saw that this was what they desired, he granted them their wish and put the full clothing over them, which created a larger "wall", and an even furthur separation.
The reason why Jah told them that they would surely die if they ate of the fruit is because Jah knew that when the generations of Adam and Eve no longer saw eachother as One, they would kill eachother.
This mind concept of separation led to Cain killing Abel:
8 And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.
9 And the LORD said unto Cain, Where is Abel thy brother? And he said, I know not: Am I my brother's keeper?
The question Cain asked "Am I my brother's keeper?" represents the kind of separation that came into the minds of men. If Cain realized that they were One, he would have known that when he keeps his brother, he is keeping his self. But he didn't see his brother's life as his own, so he killed him.
In a world like this, things must come to an end. Because as time passes, people become more separate from eachother, and care less and less for the people in the world, even their family and friends.
So as we can see in the world, this leads to greed, where people try their hardest to take from others, and exploit others, so that they can gain their selfish desires. And the more time has passed, the worse man and woman has become. And the only way for someone to have more than their share, is to take from others. So the rich can't exist without the poor, because otherwise, who will do the work to make them so rich. They can't do all that work by themselves.
In a world like this, conflict will surely arise, and the power struggle will become more fierce. And it is not only the rich with this wicked mentality, but it is also much of the poor. The only difference is their positions. Many of the poor would do the same as the rich, if they figured out a way to be on top. Many accept that this is the way of the world, and they think that is what we must strive to be.
So if one goes up, another goes down, another goes up, so another goes down. As one learns a more wicked technique to rise, the other learns his technique and then makes it stronger so that he can rise higher. So they become more and more wicked, to out-wicked the other. Look at the armies of the world, and what evil they have created.
So Revelation shows the only destination of this kind of society. A house divided against itself will fall.
Genesis to Revelation