The Great Sea: A Human History of the Mediterranean. By David Abulafia. Allen Lane; 783 pages; £30. To be published in America in September by Oxford University Press; $34.95. Buy from Amazon.co.uk

DAVID ABULAFIA'S marvellous history of the Mediterranean is an excellent corrective to oversimplified views of geopolitics. Some people home in on distinctive landmasses, an island such as Crete or a clear shape like Iberia or Anatolia, and assume these have long formed a single cultural or political space, embracing coast and interior, and different from places “across the water”. At the other extreme, romantic types regard a lake or sea as a friendly space where ideas, expertise and merchandise are traded to perpetual mutual advantage. The second view is the more likely. True, the various ports and shores of the Mediterranean influenced one another (if war is regarded as a form of influence), but the impact of hinterlands and of distant powers, like Russia and America, was also huge.

Marshalling a vast array of intricate detail, Mr Abulafia takes the reader from the age of the Phoenicians and Trojans to the advent of modern tourism. He distinguishes epochs when the sea was kept safe by a single power—the Roman empire, the Royal Navy or the Sixth Fleet—from periods of intense strategic conflict and from times of free-for-all between small powers, slave-traders and pirates.

In most phases of history, Mr Abulafia shows, the Mediterranean was a net exporter of economic and cultural might. In the Middle Ages, for example, city-states in present-day Italy or Spain traded from a position of strength with north European suppliers of textiles and north African sellers of gold. They also established bases in the eastern Mediterranean, exploiting Byzantium's decline, gaining access to merchandise from farther east. In the modern era the Suez Canal reduced the role of the sea to that of thoroughfare, between the Atlantic and Asia.

Mr Abulafia enjoys using arcane detail to bolster his arguments. Explaining the rise of Barcelona as a naval power to rival Italian city-states like Pisa and Genoa, he notes the balanced diet of Catalan sailors: more biscuit and cheese than the Venetians, less wine than the Neapolitans, but plenty of garlic, onions and spices to make hard biscuits more palatable.

Choosing his superlatives carefully, he concludes that the Mediterranean has been “the most vigorous place of interaction between different societies on the face of this planet”. Indeed, its role in the history of civilisation has “far surpassed [that of] any other expanse of sea”. But as the book makes clear, these interactions were not always mutually beneficial.

The cargoes transported across the Mediterranean included terrified slaves and prisoners (like the apostle Paul, whose ship was smashed to pieces) as well as exotic spices. Voyages, whether military or commercial, were undertaken in a spirit of ruthless calculation, not open-hearted adventure. Despite the warm feelings it now evokes in north European hearts, as a locus of healthy food and blissful ecology, the Mediterranean is a perilous place for sailors. In winter, storms can brew up fast and rage for days. That is one reason why Mediterranean people who make their living from the sea do not share the romantic emotions of those who splash about for fun. Indeed before the age of tourism not many littoral folk learned to swim; the risk of drowning was too high.

Cross-fertilisation between cultures and religions did, of course, take place, often despite the efforts of secular and religious leaders to stop it, or to ensure that influence only flowed one way. In Tunis you can see the tomb of a Majorcan friar who studied Islam in Bologna and then moved to north Africa where he became a learned and distinguished Muslim.

Mr Abulafia notes with approval that Sephardic Jews, such as his own forebears, forced to leave Spain for Ottoman Smyrna, have been especially open to integration with surrounding cultures. Whereas modern Judaism celebrates the Jewish revolt against the Hellenised dynasty that ruled the Levant, Mr Abulafia prefers to focus on Alexandria, where there was a more productive symbiosis between Hellene and Hebrew. Its fruits include a great Greek translation of the Hebrew scriptures and Philo's brilliant exposition of Jewish metaphysics—written in Greek.

Mr Abulafia is too conscientious a historian to speculate much about the future, or even to prejudge how the modern age will fit into the sweep of Mediterranean history. But using his analytical tools, it is surely possible to sketch out a rather dark outlook for the sea, thanks not just to the ebbing of European power but to avoidable crises of governance and demography. As things stood until recently, an unhealthy sort of system linked northern and southern Europe, with subsidies and tourist euros from the north helping to mask and preserve dysfunctional politics and sclerotic societies south of the Alps.

An even less healthy dynamic connected Europe as a whole with north Africa: the European Union absorbed some of the Maghreb's surplus labour, while helping to prop up the region's authoritarian regimes. Both those political ecosystems are now collapsing, with the euro-zone crisis, the advent of Arab people power and the war in Libya. The crises present a challenge to both regions; the Maghreb needs to loosen political control and strengthen its institutions and Europe must support such moves, both politically and economically. Failing to seize the opportunity may result in the flow of desperate people northward becoming uncontrollable. That may not be so unusual when set against three millennia of conflict in the Med. The worst outcome would be for Europe and north Africa, both losing relative weight in the world, to reinforce one another's decline. That would be a lamentable fate for the “Great Sea”, invoked in a Jewish prayer which gives this book its title.