James Walvin discovers a scholarly gold mine on the slave trade

Between the early 16th and the mid-19th centuries, the Atlantic slave trade was responsible for the enforced migration of millions of Africans from their varied African homelands to great swathes of the (primarily tropical and semi-tropical) Americas. Today the subject has become familiar to a wide audience, popular and academic, on both sides of the Atlantic.

Popular culture has disseminated an awareness of the slave trade round the world. Movies ( Amistad ), TV series ( Roots ), novels (notably Beloved ) and a public debate (in Africa, Europe and the Americas) about the rights and wrongs of the slave trade - and how best to deal with its consequences (if at all) - continue unabated. Indeed, the phrase, the slave trade, has come to signify the Atlantic slave trade, though there were plenty of other slave trades in history (across the Sahara, eastwards across the Indian Ocean - to say nothing of more ancient Asian slave systems, and slave routes in medieval Europe or the world of classical antiquity). It is, however, the Atlantic slave trade that sticks in the public mind. It is easy to see why. The black populations of the Americas are descended from the African victims of the Atlantic slave trade. So too are many of the recent black communities that have flourished in Europe in the late 20th century. Black societies in Europe and the Americas are, then, an obvious reminder of that historical process we call the Atlantic slave trade. And even the debates about the woes of contemporary Africa often return to the issue of the slave trade and its consequences for the development of sub-Saharan Africa. What happened to Africa and Africans in the course of the Atlantic slave trade has a resonance and significance that goes far beyond the scholarly arguments of historians.

In recent years there has been an astonishing outpouring of books, essays,collections and theses on every aspect of the Atlantic slave trade and especially on its consequences for the emergence of slave communities across the Americas. Occasionally, it is salutary to step back and see how far we have come in the space of a single academic generation. The work that has culminated in this CD-Rom, a quite outstanding achievement, began in earnest with the publication in 1969 of Philip Curtin's pioneering and masterly study, The Atlantic Slave Trade: A Census . Curtin, one of the great postwar Africanists, set out to find, as precisely as he could measure, the exact numbers of Africans shipped across the Atlantic into American slavery. His was a remarkable book that prompted a whole generation of scholars (some of them Curtin's own students) to refine and revise his initial calculations. It is a testimony to Curtin's achievement that, even now - when we know so much more, from many more sources, all analysed by a veritable army of historians (using technology that Curtin did not have access to) - the broad outlines of Curtin's arguments remain roughly correct.

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There were, of course, some who bridled at the reduction of this human story to a statistical exercise, though Curtin could never be accused of that. It was as if the statistical analysis of slavery was itself a dehumanising process applied to a story that was structured on the deracination and reduction of millions to the level of inanimate objects. Yet who could argue with the basic premise that if historians are to have any informed discussion about slavery, it is vital to ensure that the facts - in this case the figures - are correct? It is a simple if sometimes misunderstood fact that the figures really are important. It matters to know the order of magnitude we are discussing; it is important that we are able to discuss African slavery as an informed debate and not just on the basis of hunches and guesses. No other area of historical research would pretend that data are not important. The problem with the study of slavery - and I have said this too often for my own good - is how that data have been used by some historians. The data have a sensitivity, a moral charge, which historians ignore at their peril. Yet the basic point is simple: the figures are critical.

One main obstacle to discussing the data has been its fragmented and dispersed nature. The Atlantic slave trade effectively spanned the period post-Columbus to the 1860s, though the great bulk of trade was conducted from the late 16th through to the early 19th centuries. All the major European maritime powers (Spain, Portugal, Holland, England and France) hurried to involve themselves. So did mercantile communities in North and South America. So too, of course, did a host of African communities. For much of the history of Atlantic slavery, Europeans had only the most tenuous of toeholds on the African coastline and were dependent on traders and merchants in the interior for supplies of African slaves. The consequent drain of humanity towards the European presence on the coast had fundamental repercussions for a host of African societies. Polities waxed and waned through the upheavals spawned by the white man's demand for ever more Africans destined for the plantations.

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When we consider that the Atlantic slave trade spanned so long a period, and involved so many diverse communities on three continents, it becomes obvious that any overall analysis faces complex and daunting problems.

What we have under review is a triumph of enterprise, industry and imaginative reconstruction. It can be deceptively simple to describe this CD-Rom. But to say that it offers the data for ,233 slave voyages would be to mislead. First of all, we have in accessible (and relatively cheap) format all the known data on a great majority of the Atlantic slave voyages. The simple collection of that data (done under the auspices of Harvard's Du Bois Institute) is itself a remarkable achievement, not least because the material has lain locked in archives and papers scattered around the Atlantic rim.

As information technology has improved over the past 30 years, individuals and teams of scholars have committed themselves to the painstaking task of abstracting data from archives and transferring it to contemporary machine analysis. As the results of individual and team work began to materialise, a wider project took shape under the Du Bois wing and, with North American scholarly funding, this project flourished. But it could only be as good as the historians it attracted. Fortunately, it acquired a team of editors who are also remarkable historians. This whole project is an example of historical cooperation at its finest. No single historian could have achieved the results on offer here. And that in itself is testimony to Curtin's initial work in the 1960s.

It is worth looking at some of the detail. First, the data. This publication is a gold mine of information, most of which would have remained inaccessible to any single scholar. Now the raw data from thousands of ships, scattered in dozens of sources, are available at the push of a button. The CD-Rom is easy to use (if I can manage it, anyone can). Information about the ships -names, tonnage, port of origin, African destinations, time at sea, landfall, names of captains, owners - can be retrieved and reworked. It is possible to dip into the material, to ask questions of it, and tease out data of all sorts and conditions. And, of course, many of those questions are about the African victims: where they came from, how long they spent at sea, how many died, how many landed in the Americas, and where. The software enables users to create his or her own analyses and graphs. Similarly there is a complex of maps of the Atlantic world that locates the data in their more familiar geographical settings.

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There has been nothing like this before. And, as the editors readily acknowledge, changes will emerge as more data comes to light. But the present study is as good as it gets: rooted in remorseless archival investigations, subjected to critical intellectual scrutiny and debate and rendered into manageable format by a publisher and its technical assistants who deserve the highest praise. There must have been times when the end product seemed distant and perhaps unmanageable.

The four historian editors are well known for their individual scholarly work, which runs parallel to this publication. All have secured their reputations as historians of the first rank. When we set their published scholarship alongside this CD-Rom it becomes clearer what a formidable team they make. It is worth recalling that (as they acknowledge) they have also been the beneficiaries of other people's efforts and ideas, none more important or readily given than those of Stanley Engerman. The major advances in historiography in this field have been secured by the effort and generosity of many historians pooling their information. But without this team of editors and the faith of their publishers, it is unlikely that this massively important project would have seen the light of day.

Historians will certainly use and rework this data in the coming years, trying to re-evaluate it, ask new questions, offer their own interpretations of what lies within it. It is a scholarly work with massive implications for our understanding not simply of the Atlantic slave trade, but for our grasp of the complex cultural and social shaping of the Atlantic world. Would David Eltis and company please step forward for a curtain call - they deserve a standing ovation.

James Walvin is professor of history, University of York.

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