I should preamble this by saying that the following is all my speculation.
From the scientific perspective in terms of space-time, God created the earth with evolutionary events, including dinosaurs, Neanderthals, etc.,
embedded in it. Homo sapiens neanderthalensis became extinct around 40,000 years ago. Homo sapiens sapiens replaced them. The unusual fact is that of all the dozens of homo (human) species that existed, home sapiens (sapiens) is the only one surviving today.
Today's humans, Adam, Eve, and so on, anatomically belong to Homo sapiens. Both Neanderthals and we have 46 chromosomes, though there is some
uncertainty about that. Neanderthals existed only in space-time and not in witnessed-time; as such, they never received a breath of God in their spirits. They would not be judged to go to heaven or hell. The last ice age maximum happened about 20,000 years ago. That's before Adam and Eve. The difference between the (space-time) homo sapiens and the descendants of Adam and Eve is that the latter are capable of languages with advanced complex grammar.
From the biblical point of view, God created Adam and Eve in witnessed-time as described in Genesis. Acts 17:
In terms of first-order logic, both perspectives are true: witnessed-time and space-time. Both are real. Scientists found
46,000-year-old roundworms alive beneath the Arctic ice.
Near the end of the last deglaciation, around 13,000 years ago, Adam and Eve were expelled from the Garden of Eden, and they entered the backdrop of the Neolithic Age of Mesopotamia. Physical evidence indicates that farming started around 12,000 years ago and humans domesticated sheep around 10,000 years ago. Cain was a farmer. Abel was a shepherd.
Was there evidence of deaths before Adam and Eve sinned?
From the point of view of witnessd-time, no. From the point of view of space-time, probably yes, or else God could have done the embedding after he cursed the ground. In either case, there was no evidence of deaths in the Garden of Eden before they sinned.
See also
How old is the earth?.