Bible scholars say it has more to do with a collective vocation than collective capacities (intelligence, moral awareness, etc.) Obviously, were a species to lose capacities, they may become unfit for the vocation, but I think it’s good to keep in mind that image of God is a relational, covenental, choseness kind of thing, not something humans evolved and can therefore devolve. If you accept that God is sovereign over creation and shepherding the human species in a personal way toward his desired ends, it would seem out of line with his character to allow a scenario you are describing. That would require a theology where God is super hands off with regard to the destiny of the world, and if that’s the theology, I wonder what place the concept of image of God has in it anyway. If creation is not proceeding toward a divinely willed telos, why would it matter that humans were called to participate in that?