***According to Genesis, when Adam and Eve at that apple***
Are you familiar with the concept of myth? The notion behind myth is that universal truths are embedded in the story even if the details are factitious. For example, the Flood has universal truths, but what we know of the Middle East flood is that it was mainly a regional event - not the worldwide catastrophe portrayed in the scriptures.
***According to Genesis, when Adam and Eve at that apple, they introduced sin into the world. The penalty for sin is death, so how could
animals have been dying for millions of years before sin even entered the picture? Anyway, I do enjoy these questions, and I hope my answers are satisfactory.***
From my perspective (one of a liberal Christian such as myself), evolution presents no problem with the notion of sin. The matter can be resolved in terms of what we mean by 'cause'. In Genesis the decision of Adam (first man) caused God to make the world with thorns and bristles and expel man from paradise. If we interpret this action as a temporal cause (e.g., cause A occurs immediately seconds before effect B), then obviously evolution doesn't make sense since humanity emerged billions of years after biological species experienced death.
On the other hand, if we interpret 'cause' as meaning 'logical cause', then what we mean is that cause A brought about effect B as a deductive truth. In this manner, if God anticipates our decisions before the fact then the consequences can affect how history occurred. This is a Christian principle. For example, "the Lamb of God was slain before the foundation of the world" can be interpreted to mean that the consequence of sin destined the slain Lamb even before (in time) the creation of the world.
If you think about the phrase "the Lamb of God was slain before the foundation of the world", then I think you'll see that this could only make sense if 'causes' can be events of the future that affect the past (interestingly, there are even scientific hypotheses that talk about the future affecting the past - e.g., causal loops).
So, the myth of Adam bringing sin in the world can be reunderstood in this perspective: The nature of free will is such that natural selection and evolutionary processes are required to have a world where free will can exist to accomplish God's will. Far from contradicting a Christian perspective, natural selection actually enhances the Christian view.
You should adopt evolutionary theory and big bang cosmology. Christianity will make a lot more sense once you do.
Warm regards, Harv