As normal, this argument has gone from discussion of evolution to discussion of the origin of the Big Bang. This always seems to happen. We begin with a misunderstanding or ignorance about evolution. When we explain what evolution is and the evidence for it, believers lose interest and switch to their favorite topic, the ultimate source of the universe, the ultimate cause of everything.
The answer to that is that ultimately we don't know what was behind the Big Bang. Scientists have a good idea what happened back to about the "Plank Time", when the universe was 10^-43 seconds old. (That is 0.000000000000000000000000000000000000000001 seconds, which is an extremely small number.) Beyond that the laws of physics as we know them break down.
So what was the ultimate cause behind it all? There was surely some guiding force behind it all, some laws of physics, some underlying nature of reality that "always" existed. I put the word "always" in quotes, because time itself loses meaning when we step beyond Plank Time, when we step outside the space time bounds of our universe. What does "time", "cause", "force", or "physics" even mean in that realm? Something was there. We don't know what.
That is where you step in and say the ultimate cause behind it all had a will, a mind, a personality, and was a personal being. But how can you know it had all these things?
But then many take it a step further and say this timeless ultimate cause stepped into the universe and flooded the whole earth, caused the earth to stop rotating so Joshua could kill more people, and commanded the Israelites to kill Amalakite babies. You are taking this way too far. How do we get from a timeless cause of the universe to a personal being to a Hebrew god who commands atrocities?