Maybe life evolved on this old earth after it was placed here in primitive form 550,000,000 years ago, and will-conscious man sprang onto the scene 1,000,000 years ago, and the fist administration of spiritual leadership was the bright "prince of this world" who fell into sin, caught up in the Lucifer rebellion, becoming the "crafty beast" who would trip up the worlds 2nd administrators, Adam and Eve once they arrived leading to further complications on a previously fallen world.
* The "beast" was already fallen, already sinful, working against Gods will for Adam & Eve.
* True though, had Adam & Eve stayed loyal they would have effected the illumination of disease and defective genetic strains. We would be a much more homogeneous world. But sadly they did not remain loyal, their genetic infusion into the human races has spread in an imbalanced way.