Ok, true story time!
If I have the flu, which thankfully isn't often, I do a bad thing. I drink TheraFlu and Nyquil at the same time, and I sleep the sleep of the innocent, believe me! For hours and hours. I also have very vivid dreams. It's interesting!
Anyway, so one time I took this mixture and wow, I had THE MOST VIVID DREAMS of the distant past. In one dream, which was very vivid, I dreamed that I was a middle aged woman in London, in basically a hovel, and it was about 300 or more years ago, and I was just waiting for my husband to come home and beat me. It was terrible. Another dream I had at that same time was much more pleasant. In it, I was a young teen, I think a girl, and I was running through the woods to my grandmother's house (about 150 or 200 years ago), and when I got there, she had gone to market already, and I could look down from the mountain I was on, and see a small town and a market, and I knew my grandmother was there, and it was just a very pleasant dream. It was in the early morning, I know that much. It was sunny but wet-ish. In the other dream, it was night time and very, very wet - in fact, it was raining.
Since then, though I don't believe in reincarnation, I do believe in what many call genetic memory, and I believe that's what I was experiencing then, but really, who knows?