Did you ever wonder why God, who is supposed to be loving and merciful, created Adam and Eve as male and female, of which they were unaware, put them in Eden with two trees, the tree of life and the tree of knowledge, to tempt them, and when they fell for it, evicted them? We wouldn't put our babies in a playpen with a box of chocolates and punish them for eating some. The explanation, of course, is that the temptation was for Satan, not Adam and Eve. When God gave Satan this solar system as his kingdom, He knew that Satan was overly ambitious and evil, knew what he would do, and set the stage to stop him.
Satan could not create life, but he was the original genetic engineer. Thus, evolution came into being. He fooled around with dinosaurs for millions of years, decided he wanted beings in his own image, which was God's image, to worship him, so he got rid of the dinosaurs and started the long evolution of lower forms of life into homo sapiens. All this time, Adam and Eve were in Eden blissfully unaware of what was going on outside. When the evolved man reached a point in development where he was able to function as a thinking person looking for a deeper meaning in life, God allowed Adam and Eve to succumb to Satan's tempting. Notice that he tempted them with the tree of knowledge, not the tree of life, because he knew that once out of Eden they would begin to age and would eventually die, and he wanted them DEAD, because they were God's, and he did not want anything of God's on Earth. God had made Adam and Eve as male and female, because once out of Eden, they would have to be indistinguishable from the evolved humans, who needed sex to reproduce.
Adam and Eve did not bring sin out of Eden; it was already here, only it would not ever have been recognized as sin without their being sent out. What they brought into the world was God's law. Adam and Eve were not punished for sinning, they were a sacrafice along with all their descendants, including Jesus, to save the Gentiles. Because, of course, the Jews, as descendants of Adam and Eve, were created, and the Gentiles, who would not be saved without this sacrafice, were evolved. And yes, I am a Gentile, without a drop of Jewish blood so far as I know, and I accept the fact that I am evolved from a lower form of life.
If Satan had not tempted Adam and Eve, they would never have known that they could have children, and Jesus would not have been born. It is likely that Satan did not know that they could have children when he tempted them. He just wanted to get rid of them. But in so doing, he set into play the seeds of his own destruction.
God gave Satan many opportunities to save himself. When He had Noah build the Ark, if Satan had not interfered, all the evolved humans would have died in the flood, and there would have been no reason for Christ's coming, but I am satisfied that there was a second Ark floating around out there with evolved humans on it. The "Epic of Gilgamesh" could very well be the historical record of this.
Read the Bible with both creation and evolution in mind, and there are no contradictions in it. The Old Testament is a history of the Jews, with the Gentiles always off in the distance because they were considered unclean. The New Testament brings the unclean ones into the fold, and the Jews are no longer banned from breaking bread with them. Once Jesus was born , it was unnecessary to keep the two separated.
There was a time, before Jesus was born when the Jews were starting to cohabit with the Gentiles, but Jesus could not have tainted blood in his line, which is the reason Joseph ended up in Egypt with his family. The Egyptians were more prejudiced than the Jews (Hebrews) about intermarriage, so the line was kept pure. Only Joseph, because pharaoh liked him, was allowed to marry an Egyptian. But while he kept Jesus' line of descendancy pure, he was not in it because the Egyptians are Gentiles. So the Jews spent 400 years in Egypt growing as a nation, keeping their bloodline pure. They became slaves, but slavery was preferable to miscegenation.
The reason Satan will be allowed to come back for a short time after a thousand years is to give the souls who chose to go with him a second chance to be saved. For those who are loyal to him, it will be the bottomless pit, which is falling forever into the endlessness of space, completely isolated from other souls.