A lot of people racked their brains over this issue. As a young child, this was one of the reasons not to take the Old Testament too literally. At the same time, we had our weekly religion classes in which we were told beautiful stories and we sang songs about them. As I well remember, we also had coloring pages. To me, this is a kind of nostalgia because my parents (both coming from different religions) raised us without a defined religion as a compromise. They taught me not to take those texts too literally. They wanted us to know the essence of religion and not the letters written on paper.
My once devout catholic father had become a realistic thinking person (before it was more mainstream). He told us that the real father of Jesus had been Joseph the widower who took his former maid as a wife to take care of his children and household. Many, many years later I had a boyfriend who studied theology (catholic) and he said that in his very first class in university, the professor wanted to clear up that the old translation of the word 'virgen' was equal to a housemaid in that time. Actually, in my language this was the same in the older days, so not so weird. This all didn't contradict a study to a real understanding and study of religion.
According to my father, there were many more people next to Adam and Eve. Their story was to be taken allegorically (just like Klaud is saying). My father said that he was taught that Kain went to town after he had killed his brother. I looked this up in the old Bible from my great-grandmother (mother's side, so protestant Bible) and I guess they used a different translation because in this text Kain went to the land of Nod. He conceived a son and built a city himself. You could build a settlement with your wife (sister?? they didn't mention he kidnapped a sibling) and son, but to build an entire empty city is weird.
Apart from this, there is archeological evidence of human life long before 6000 years ago. The story of humans goes far back. One of my own self-regressions went back to a life as a baby wrapped in fur in a world full of ice and caves. A very happy memory. I wished I was so happy and content in my normal life today as I was as that baby in the past.
By the way, this baby knew it had come to Earth as a 'child of the Stars'. Fully aware of that and so happy and curious to start a life here.