Dear Prim.......I do not think that "The only way to understand this situation is to lean toward the Old Earth belief."...is a statement of un-flexability. When reading my post, I think you will see IMHO!
As I stated, this topic will certainly bring in the Old Eart vs. the Young Earth theology and that is what is happening.
It comes down to Bible against science every single time. I am not say that YOU are but many believers view the scientific world with skepticism, believing that it is at heart an attempt to discredit faith in God.
May I say to you that In Romans 5:12–21, and in the Bible generally, death does not have an exclusively biological meaning.
In verses 12–14, thanatos is defined as a divine judgment upon all mankind for Adam’s transgression as the covenant head of humanity. In verse 21, death is contrasted with eternal life – which, everyone will agree, is not really a biological concept at all. Paul undoubtedly developed his theological understanding of death as divine judgment upon human sin from the Genesis creation account, where God warned Adam and Eve that “in the day that you eat of the tree you will surely die” (Genesis 2:16).
Yet they did not die biologically “in the day” that they ate of the tree. They lived another 930 years so death was not instant but put off.
Nevertheless, the divine judgment of death was executed against man, as shown symbolically in the removal of Adam and Eve from the garden, that they might not eat of the tree of life (Genesis 3:22–24). Certainly, this divine judgment included the physical cessation of biological life (Genesis 3:19), but it cannot be limited to that so to use Romans explanation of death was only AFTER the fall just does not work!
Also...please consider that In addition to misinterpreting thanatos, those who appeal to Romans 5:12 to deny pre-Fall animal death, must also assume a certain preselected definition of kosmos or world.
The world into which sin and death entered is assumed to be the creation as a whole, including the non-human realm. But this is not the meaning that Paul seems to have in view in the context.
For example, in verse 13, Paul says,........
“Before the Law, sin was in the kosmos.”
But sin cannot be “in the non-human realm.”
It is more likely that the term kosmos here refers to the world of humanity—a common usage of the term with which we are already familiar in John 3:16: ......"For God so loved the kosmos, that he gave his only begotten Son.”
In fact, Paul uses the phrase “all men” in the second clause of Romans 5:12 as a synonym for “world” (and again in verse 18).