Humans Sailed the Aegean 15000 Years Ago

According to this US News and World Report:

A new technique which dates obsidian—volcanic glass which can be fashioned into tools—suggests that people were mining for obsidian in Mediterranean waters and shipping the once valuable rocks from the island of Melos in modern day Greece as far back as  15,000 years ago.

 The article concludes

Using the new SIM-SS method, Laskaris and his colleagues were able to determine that Melos obsidian artifacts were making it to the mainland earlier than previously believed. That naturally implies that people were crossing between islands very early in some unknown types of boats.

http://www.usnews.com/science/articles/2011/08/29/volcanic-artifacts-imply-ice-age-mariners-in-prehistoric-greece