The number of islands reported to be in the Mediterranean ranges from asfew as 150 to as many as 5,000 (including islets), of which the vast majoritylie in the western part alone (see Chapter 2). For ecologists and biologists studying the region’s fragile ecosystem, each and every one of the islands and islets is important. But in terms of studying human settlement, the vast majority of these are small rocks of little use, except as providing convenient landmarks for navigation. Of this extensive list, just under 200 are habitable, and archaeological data show that at least 147 were colonised at least once in the prehistoric period. This extensive body of evidence-divided, for convenience’s sake, into two groups, western and eastern-will be discussed in this and the following chapter.