Let's simply look at what the Bible does not say:
If animals were killed, Genesis 3:21 does not say that the creatures killed to make Adam and Eve’s clothing were the first animals to die. (Some theologians say this)
It's an assumption that there was no death of any kind before Adam sinned. This is not stated in the Bible.
Genesis 2:9 says that: The tree of life was in the midst of the garden. Was this not the means by which Adam and Eve were to live forever?
Genesis 3:22 ESV - Then the Lord God said, “Behold, the man has
become like one of us in knowing good and evil. Now, lest he reach out his hand and take also of the tree of life and eat, and live forever—”
If the tree of life was the means Adam and Eve were to live forever, two possible arguments arise. The first argument might look something like this:
- Premise 1: The tree of life was necessary for Adam and Eve to live
forever.
- Premise 2: If the tree of life was necessary for Adam and Eve to live
forever, then any being that did not have access to the tree of life
could not live forever.
- Premise 3: If animals did not have access to the tree of life they cannot live forever.
- Conclusion: Therefore, animals without access could not live forever.
We might write a second argument for the death of plants:
- Premise 1: God gave permission to eat fruit.
- Premise 2: Eating fruit results in the death of the fruit’s flesh and
its seeds (if they get chewed up).
- Premise 3: The fruit’s flesh and its seeds are alive and made of
living cells.
- Conclusion: Therefore, God’s permission to eat fruit implies the
death of the fruit’s flesh and its seeds.
According to Matt Fradd, a Byzantine Catholic and apologist:
If the tree of life was unique, it might have been enough for Adam and
Eve to eat from, but it would never have been enough for all of the
animals of the world to eat from. This may be another sign that the
animals were not understood to have the tree of life for their food.
If so, then the text of Genesis itself would suggest that, while man
was meant to be immortal, animals were not. That would support the
idea, based on St. Paul’s statement, that it was human death that
entered the world through the Fall, not animal death.
Thomas Aquinas also wrote in his Summa Theologica:
In the opinion of some, those animals which now are fierce and kill
others, would, in that state, have been tame, not only in regard to
man, but also in regard to other animals. But this is quite
unreasonable. For the nature of animals was not changed by man’s sin,
as if those whose nature now it is to devour the flesh of others,
would then have lived on herbs, as the lion and falcon. [1]
To conclude: I do not think that scripture allows us to assume that there was no death of any kind before Adam sinned.