So then, how does a theistic evolutionist explain how that soul was implanted in humans? Was it in homonids?
I would imagine by saying that God did it. It's a theological concept regarding a supernatural substance and a supernatural being. The allegory in Genesis is that the "breath of life" was breathed by God.
Was it in homonids?
By definition, it was in hominids. What else do you think has souls? Canids?