Cains statement to God in Genesis 4 is future tense…he is clearly referring to future events in that what he has done will incur the wrath of subsequent individuals when they learn of what he did to his brother will seek to do to him.
What this story describes is that Cain reaslises that his own bad behaviour, the evil that clearly possess him, this behaviour will exist in others who will seek revenge.
13But Cain said to the LORD, “My punishmentd is greater than I can bear. 14Behold, this day You have driven me from the face of the earth, and from Your face I will be hidden; I will be a fugitive and a wanderer on the earth, and whoever finds me will kill me.”
15“Not so!”e replied the LORD. “If anyone slays Cain, then Cain will be avenged sevenfold.” And the LORD placed a mark on Cain, so that no one who found him would kill him.
16So Cain went out from the presence of the LORD and settled in the land of Nod,f east of Eden.
The statement has nothing to do with inferences of earlier existing humanity outside the garden.
Theres another problem…why would hominids, who are not intellectually competent, who know nothing of God setting aside a special people (Adam and Eve)…why would they give a d.amn about Cain and seek to kill him? Are you now attempting to facilitate the idea that once they were kicked out of the garden, Adam and Eve were in danger for their lives at the hands of hominids who were less intelligent? Where is that in the bible?
Attempting to make such inferences starts to sound a lot like a God who decides to create an Arian society (Hitler planned that with his Nazi empire) The religion of the bible is not nor has it ever been a play for Arian supremacy. Christ modelled the exact opposite of that “from the foundation of the world”
Eph 1:4 For he chose us in him before the creation of the world to be holy and blameless in his sight.
If we try to read into Ephesians that God set Adam and Eve apart from hominids, we are destroying the very essense of Christs ministry and the gospel. I would argue that we actually lend strong evidence to Satans charge against God in the book of Job
9Satan answered the LORD, “Does Job fear God for nothing? 10Have You not placed a hedge on every side around him and his household and all that he owns? You have blessed the work of his hands, and his possessions have increased in the land. 11But stretch out Your hand and strike all that he has, and he will surely curse You to Your face.”
Im sorry to be so blunt, however, the theological disaster that is presented by that kind of view…its huge. The apostle John tells us in Revelation that Lucifer and his angels were cast out of heaven to this earth (the planet…not a localised spot on it)
The notion of pre-existing hominids outside the garden before the life of Adam and Eve… I do not accept that hominids are not men (human) deserving of the gospel and salvation. If they are primative on the scale of evolution and could not make sinful choices because animals dont sin, then that is a theological nightmare for the entire plan of salvation and the gospel.
If hominids can sin, then sin entered this world (into us) before it is even raised in the bible story. Christ specifically says that sin is along his own lineage in the genealogies…even for those who see two creations in genesis 1 and 2…that becomes highly problematic…which lineage is sinful…Hominids or Adam and Eve? (clearly its Adam and Eve - Christs ancestors)
We know that the gospel doesnt apply to animals that they cannot sin (they were not created as independent moral agents) however, i have great difficulty with the notion that, after the new heavens and new earth in Revelation 21, hominids who dont sin are going to come back as essentially part of the animal kingdom.
Its an interesting concept that im willing to consider, but highly problematic i think in that we start making up theological concepts and biblical history in an attempt to reconcile the huge gaps in that kind of theology…stuff that simply is not biblical or even mentioned by dozens of bible writers who received their revelation directly from God often through visions - visual images/pictures in their minds. They would have had little difficulty seeing the difference between hominids and Adam and Eve in these visions because even our Darwinian artists draw them very very differently
(image below from American museum of natural history)