If you want to look at real statistics from ancient times, take Troy, the Iliad and the Odyssey. It wasn't until the 19th century when Heinrich Schliemann discovered the ruins of Troy that people believed it was real and not just a Greek story. Similarly the Iliad and the Odyssey have been shown to be based on real events.
Interpretations on Sumerian and Egyptian texts by Zecharia Sitchin point to the Gods Of Old being real, not just mythical creators, and with far more detailed stories of the Flood and other stories from Genesis coming from Sumerian texts, it's likely that the Great Flood (of Noah and Gilgamesh) was real.
If you think back over the last 20 years even, how much have we learned about the past to be based on real events, and how much have our history books changed.
It seems naive to think that all these creatures were just made up, especially considering many of them are known throughout the whole world from the earliest of times.