How long were Adam and Eve in the Garden? If I recall correctly ( and I might not be), the Bible doesn’t start counting his age until he leaves the Garden.
A bigger problem would be of 6+ billion individuals descending out of one mating pair, primarily through incest, initially.
Such a model would develop so many genetic abnormalities in less than a dozen generations, humans would have been extinct a long time ago.
Then we have the problem of humanoids / Neanderthals, etc.
I believe they were there for abot 103-105yrs prior to getting kicked out.