Marlowe is right. If there is no sin in the Garden of Eden, then there is no transmitted sin, and there is no need for a savior to save us from those sins. That makes Jesus Christ unnecessary at best and a madman at worst.
An earlier comment says that there is variation within a kind and not the change of one kind to another. I don’t think this is contradicted in any fossil record that I know of. At what point do the bones of a primate belong to an extinct species and at what point do they belong to one within the ‘human kind?’
Alamo-girl has the neat idea that the Garden of Eden was in both the heavenly and the earthly dimension. This is based on the Tree of Life being in the Garden and also appearing in the heavenly in New Jerusalem at the end of Revelation. Time didn’t really begin for Adam and Eve until their expulsion from the Garden. Some 900+ years later Adam died.
My addition to that, in reference to ‘human kind’, is that humans did not begin until that point. Those without the spirit, even the dead carnal spirit, are not “man.”