Archaeologists speculate that the Minoan civilization that thrived on the island of Crete from the 16th to 13th centuries BCE was an autonomous development by descendants of Neolithic island-dwellers, rather than an imported civilization. There is evidence that Cretans had extensive trade links, with Africa, Turkey, Cyprus, the Levant and Greece. The Cretans traded surplus olive oil and jewellery, pottery and figurines for gold, copper and tin. Trading colonies were established on neighbouring Aegean islands. Minoan cultural influence was transmitted via extensive maritime trade links, rather than through warfare or conquest – no weapons or armour have been found in Minoan graves. A ship fresco from Akrotiri, on Santorini, an island within the area of Minoan influence, indicates that the ships were about 115 ft (35 m) long with 25 oars on each side. The Minoan script, Linear A, probably evolved from hieroglyphic writing, and a later script, called Linear B, is an adoption of Linear A that was used by Greeks before they evolved an alphabet.