"The strange, half-human figures painted on the wall of a cave in southern France by a Magdaleniese artists in the Old Stone Age, and labeled "Sorceror" by archaeologists, may easily be construed as an attempt to portray an ancestral dragon" (Source: Dragons and Dragon Lore, pg 15.)

Some French dragons live near rivers in caves and eat the unfortunates who pass their way. They also like to catch nursing mothers and force them to nurse their hatchlings.

If captives rub eel-paste on their eyes they'll always be able to recognize a dragon in human form.