I believe that God caused the Big Bang 14 billion years ago, and also was responsible for evolution, performing each step of evolution, which is what Genesis describes. The humans that started appearing 50,000 years ago did not have the Spirit of God breathed into him, and were not sentient. But 6,000 Years ago, God created Adam and Eve out of dirt, and gave them His Spirit, so they were sentient. The unsentient humans either then died of or merged with the sentient humans.
This is still possible even with a literal interpretation of Genesis because the word day in Genesis is a translation of the Hebrew word Yom, which can also mean an era. This is why I also believe that we are still in the seventh "day". It is actually an era. Especially since God never said that there was morning and evening on the seventh day, which he did do for the other six days.