Trade Routes is, in essence, the massive catalogue of the Second Johannesburg Biennale, which ended on January 18. The biennale, which has no fewer than five venues in Johannesburg and which extends a thousand miles or so to Cape Town where it uses two more galleries, is probably the largest exhibition of modern art ever to be seen in Africa. The first thing to point out is that it is not an exhibition of African art. Although there is a very proper proportion of contemporary African works from many African countries on display, this biennale is wholly international, and as such it merits comparison with Venice, or Documenta at Kassel in Germany.

Furthermore the book is not precisely a catalogue of the exhibition in that, although it does give information about every artist on view and represents at least one work by that artist, decently reproduced, almost invariably in colour, the work reproduced is not always the work displayed. This is particularly the case with several of the installation artists. Having uttered that caveat, the book does more than justice to the show and its several themes, each theme being housed in a different gallery.

Although the book begins with several essays on wide-ranging topics usually, at least peripherally, linked to the theme of the Biennale, each of the six separate exhibitions receives a major chapter in the book.

The editor and principal curator is Nigerian-born Okwui Enwezor who, at one point, states that his "interest in globalisation, and what the critic Saskia Sassen would term its strategic agents, is to respond to the evolving nature of contemporary culture today as transmitted from a very limited enclosure of Eurocentrism".

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Although I am not a stranger to South Africa and am a passionate devotee of African tribal art, I have to plead guilty to Eurocentrism, which is one of the many reasons why I made the long journey to the exhibition. I wanted to know just how the biennale would cope with Eurocentrism and the possibly deleterious influence of the United States. Above all, I wanted to see how the curators and particularly the African artists coped with the legacy of tribal art that is so crucial to our understanding of painting and sculpture in the 20th century.

It is a critical truism that the great modern movement, the work of Picasso and the Cubists, was profoundly influenced by African sculpture just as Whistler's generation was affected deeply by the arrival in Europe and America of Chinese and Japanese art.

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Given the effect of the Picasso generation on everything that followed, it is actually difficult to overestimate the influence of African art on the progress of art in the whole of our century. Yet what an impossible conundrum is presented to a European student of 20th century art going to see if an African strand is present at all in a distinct form; and, if it is, whether it encompasses the greatest art, that of Benin, Ife, Dogon and others, that the continent has produced.

Surely, merely to look at the Biennale in those terms is to invite the rebuke that one is still at heart at best a colonialist of the kind abhorred in the texts of this book, at worst a regressive and patronising white supremacist. Part of the conundrum is the paradox that much tribal art has been popularised, some would say vandalised, into "airport art" and is quite dreadful. Much of it has also been rejected by contemporary Africans on the grounds that, according to whether they are Christians or political radicals, tribal art is pagan and therefore wrong or superstitious and thus inappropriate to modern times.

Now, while I try, Eurocentric as I am, to see art in global terms, in its aspects of international aesthetic influences such as those on Whistler or Picasso, Enwezor sets out "to examine this history of globalisation, by exploring how economic imperatives of the past 500 years have produced resilient cultural fusions and disjunctions I To bring about pointed discussions around these issues, we will privilege works and artists who address both explicitly and conceptually new readings and renderings of citizenship and nationality, nations and nationalism, exile, immigration, technology, the city, indeterminacy, hybridity, while exploring the tensions between the local and global."

It is, I think, the "tensions between the local and the global" that make both book and exhibitions not merely a conundrum for both reader and viewer. They are a kind of watershed for our present-day conception of modern art; they illuminate that key distinction between the "modern" and the "contemporary" as in "post-modern" architecture.

What strikes one so forcibly is not just that there is hardly any trace of African tribal art, of what one might perhaps call ethnicity, in the vast majority of the works on display by artists from the host continent, but that, apart from certain local, geographical references, the African contributors have largely set out to impress on an international scale and in an international style.

Just occasionally the African content is total, as in William Kentridge's Ubu Tells the Truth, a video installation of photographic images of apartheid mingled with animated cartoons of a grim rectangular fortress, presumably Johannesburg Central Prison, and the usual activities of that scoundrel time: beatings, torture and defenestration. Or Vivienne Koorland's decorative large collages of old-fashioned maps, the kind with photographs of key city buildings mixed up with paintings of the local flora. Yet the method of the art is universal, appropriate to any up-to-the-minute smart dealer's gallery anywhere. And why should it be otherwise? This Biennale, like others around the world, is ultimately a display of the latest fashions, and globalisation is all.

I clearly have no right to expect a tribute to tribal art just because it represents a peak from the past and a crux of modernism. The African village is, after all, not the global one Marshall McLuhan spoke about, and Enwezor's globalisation goes further and deeper than that of the sage of Toronto.

Trade Routes is, in fact, an international art book just as the Johannesburg Biennale is an international exhibition. There is little painting, virtually no sculpture. Most of the exhibits are installations, with or without video, single photographs, photographic montages and endless television screens showing only video tapes, many of which have all the solemnity and concomitant aesthetic appeal of home movies. Whoever told young students that pointing your Super-8 camera at anything that you find moderately interesting is art has much to answer for. It is not so much the lack of artistic appeal, or even content, that annoys so much. It is the sheer laziness and absolute lack of wit.

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This is not to say that all the installations are bad or witless. Only some of them are, and there are several pieces that are genuinely thoughtful and stimulating, particularly those in the wonderful surroundings of the Electric Workshop, a 1929 generating station turned into an exhibition hall, retaining the original dramatic structure like something out of Fritz Lang's Metropolis and completely apt for the biennale exhibits.

Peter Spaans from Holland shows in Expectations of a City an endless series of picture postcard-size photographs in colour and black and white of New York around a huge black-and-white photograph of Manhattan. It is a pleasant photography exhibition all by itself, but is it actually more than you get in a Sunday colour supplement? In fact, most of the photographic exhibits are perfect fodder for those magazines and, in the high-quality exhibition prints on view, do a lot for the art of photography as such-but it is hard to see what they do for a Biennale beyond highlighting the back seat that actual painting now occupies.

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Even Sophie Calle's magnificent sequence of photographs of the city formerly known as East Berlin, which really makes aesthetic as well as political points, belongs in somewhere like the Photographers' Gallery.

In fact, some of the best exhibits are exclusively photographic. Apart from Calle, there are the wonderful human portraits by the Finn Esko Mannikko and "The Black Photo Album" called Look at Me 1890-1910. The album consists of studio portraits of black Africans ranging from virtual slaves to bright young couples on their wedding day. They remind one strongly of E. J. Bellocq's Storyville portraits from Louisiana; they are intensely moving and make one wonder about the quality of much of the dross from the 1990s, which posterity will see as our fin de si cle much as we see those old monochrome photographs as the end of the previous century.

Perhaps it is inevitable, so close to the millennium, that the Chinese Huang Yong Ping (now living and working in Paris) should have an installation called Doomsday. He shows close-ups of large black-and-white photographs of supermarket produce bar codes, sell-by dates etc, with elaborate strings and seals attached to them and looking out over three gigantic (three-feet high by about four-feet wide) pots made to look like cheap 19th-century Chinese export pottery, with what look like old colonial Hong Kong scenes.

They contain cheap, junky supermarket produce, and they do at least raise a wry smile. Perhaps in combination they perfectly express the concept of trade routes and globalisation sought by the book. Certainly there is a strong sense of history in much of this, from the tacky millennialism of Doomsday to the sardonic approach of the American Carrie Mae Weems who gives us African Series 1991-93. This installation is part art, part anthropology, reminding me of the English artist Susan Hiller. Weems mingles photographs, wall posters and dinner plates with texts, combining in what at first looks like a caricature of Roots, but which on closer acquaintance packs a lethal punch. One of her texts reads:

ASHANTI KINGS AND QUEENS

FOUND THEMSELVES

DESCENDING THE STAIRWAYS

OF HEAVEN

LANDING

HEADFIRST

IN THE DUNGEONS

ALONG WITH ALL THE OTHER

NIGGAS OF THE NIGER

I presume Ms Weems is black to get away with that one, and her sharp wit and humour shine a beam of light among some pretty dull and solemn surrounding works.

This book contains interesting essays not specifically part of the exhibition, including some written not only in a different context but some years ago, such as Julia Kristeva's "By what right are you a foreigner?" from Strangers to Ourselves, published in 1991. I find the inclusion of the Kristeva essay merely fashionable. On the other hand, Predrag Finci, professor of aesthetics at the University of Sarajevo, is all too relevant with his piece written in 1992-93, "The work of art in the time of war destruction".

"Eros," writes Finci, "is reduced to Thanatos. And there is no question of a genuine work of art I But while the humiliated and impoverished war hostage roams around looking for water and bread, the artist still wants, although less and less so, to contribute to culture. However, there is no paper, there are no printers. There are no oil paints, no exhibition space."

It is not easy to absorb Finci's hard-hitting words at the same time as one looks at some of the more frivolous exhibits. The words "there is no paper, there are no printers" resound painfully when one contemplates Felix Gonzales-Torres's Memorial Day Weekend in which the words of the title are (beautifully) printed on a sheet of (superb quality hand-made) paper on top of a couple of hundred or so identical sheets of paper, presumably similarly imprinted. But how can you tell, and does it matter? This is seriously disturbing, in the context of Finci's anguish, because of its desperate triviality of a kind that makes the over-hyped American artist Jenny Holzer seem profound.

The most provocative essay in the book is Francesco Bonami's analogue of art and ancient trade routes such as those of central Asia, which have disappeared. "Are we living," asks Bonami, "a final stage of Art History, or has it been over for a while? I We are a civilisation of explorers turned into one of brokers of ideas."

Bonami has a point; perhaps just as historic and deeply romantic trade routes have been replaced by massive cargo jets, so the aesthetic and sensual traditions that make great art have been replaced by the globalisation of installations and videos, which are simply home-made television. In all senses, not a pretty thought.

Tom Rosenthal is chairman, Institute of Contemporary Arts, and author of The Art of Jack B. Yeats.