Archaeological excavations in Crete have uncovered substantial quantities of Murex shells suggesting the Minoans may have pioneered the extraction of purple dye several centuries before the Phoenicians of Tyre. Dating of associated pottery points to production during the Middle Minoan period, between the 20th and 18th centuries BC. Four tablets in Linear B script from Knossos confirm that the dye was produced, albeit at small scale, in late Bronze Age Minoan Crete. This evidence has led historians such as Carolina López-Ruiz to suggest that purple was first discovered by the Minoans, and that the Phoenicians' historical role was to export and commercialize the technology at industrial scale throughout the Mediterranean, not necessarily to discover it. Minoans and Phoenicians are distinct civilizations: the Minoans are centered on Crete during the Bronze Age (c. 3000-1100 BC), with Linear A (undeciphered) and Linear B writing, while the Phoenicians are a Semitic people of the Levantine coast who especially flourish from 1200 BC onward, after the collapse of Minoan/Mycenaean civilization.