 In ancient times, Xenophanes (570–480 BC), Herodotus (484–425 BC), Eratosthenes (276–194 BC), and Strabo (64 BC-24 AD) wrote about fossils of marine organisms, indicating that land was once under water.The ancient Chinese considered them to be dragon bones and documented them as such.During the Middle Ages, fossils were discussed by Persian naturalist Ibn Sina (known as "Avicenna" in Europe) in "The Book of Healing" (1027), which proposed a theory of petrifying fluids that Albert of Saxony would elaborate on in the 14th century.