91Èȱ¬

Kilwa pot sherds (made between tenth and fourteenth century). Ceramic fragments; found on a beach in Tanzania

Don't worry! We've just heard the sound of a piece of crashing china, but that was not a priceless piece of porcelain from the British Museum's collection, it was a chipped old mug from the staff kitchen. I just wanted to remind you of that terrible moment when one of your favourite plates, pots or vases plunges to the floor and is destroyed, beyond the help of glue, forever. This programme is about pottery - but it's not about the high ceramic art which usually survives only in treasuries or in ancient graves, it's about the crockery of everyday life, which as we all know usually survives only in fragments. It's a paradox that while a plate or a vase is whole it's alarmingly fragile, but once it's smashed, the pieces of pottery are almost indestructible - and broken bits of pot have told us more than almost anything else about the daily life of the distant past.

I've got a handful of fragments with me now which have survived for about a thousand years on a beach in East Africa. An alert beachcomber picked them up and presented them to the British Museum, knowing that these broken oddments - of no financial value at all - would open up not just life in East Africa a thousand years ago, but the whole world of the Indian Ocean.

"This is the history of the first evidence for international trade that existed between East Africa and the rest of the world." (Bertram Mapunda)

"Knowing about India, knowing about China, knowing about all these places - that was really important." (Abdulrazek Gurnah)

For much of history, history itself has been landlocked. Most of us tend to think in terms of towns and cities, mountains and rivers, continents and countries, but if we stop thinking about, say, the Asian land mass or a history of India, and put the oceans in the foreground instead, then we get a completely different perspective on our past. This week we've been looking at the ways in which ideas, beliefs, religions and people travelled along the great trade routes across Europe and Asia between the ninth and the thirteenth centuries. Today we're not on land, but on the high seas - sailing around the Indian Ocean. In the last programme we were at its eastern edge, in Indonesia; today I'm on the opposite shore, in Africa.

Africa and Indonesia are nearly five thousand miles apart, and yet they can reach each other easily, just as they can also reach the Middle East, India and China - thanks to the ocean winds. In stark contrast to the Atlantic, where the winds make crossing extremely difficult, the winds of the Indian Ocean obligingly blow north-easterly for one half of the year and south-westerly for the other. This means that traders can sail long distances knowing they're going to be able to come back. Merchant sailors have been criss-crossing these seas for thousands of years and, as always, they carried not just cargoes of goods, but plants and animals, people, languages and religions. The shores of the Indian Ocean, however diverse and however far apart, nonetheless belong to one great community. And we can glimpse the extent and the complexity of this community in our broken bits of pot.

There are a lot of bits here in this drawer in the British Museum, but the handful that I've just picked out can tell us a great deal. The largest piece is about the size of a postcard, and the smallest roughly half the size of a credit card. And the pieces fall easily into three distinct groups. There's a couple of smooth, pale green pieces that look very like modern expensive china. Then there are other small pieces with blue patterning - and then there's a third group, that are of unglazed natural clay, decorated in quite high relief. The pots that these fragments were once part of, in fact, come from widely different parts of the world, but between six and nine hundred years ago all these fragments were thrown away in one place - on the same beach in East Africa. They were found at the bottom of a low crumbling cliff at Kilwa Kisiwani island, in Tanzania.

Today Kilwa is a quiet Tanzanian island with a few small fishing villages, but around the year 1200 it was a thriving port city, and you can still find the ruins of its great stone buildings and of the largest mosque of its time in sub-Saharan Africa. A later Portuguese visitor here describes the city as he found it in 1502:

"The city comes down to the shore and is surrounded by a wall and towers, within which there may be 12,000 inhabitants. The streets are very narrow, as the houses are very high, of three and four stories, and one can run along the tops of them upon the terraces, as the houses are very close together. And in the port are many ships."

Kilwa was the southernmost, and the richest, of a chain of towns and cities strung along the East African coast, running from Tanzania north though Mombasa in modern Kenya to Mogadishu in Somalia. These communities were always in touch with each other, sailing up and down the coast, and they also mixed constantly with traders coming across the ocean.

Back with the evidence of all this trade - the broken crockery - it's quite clear even to me that the pale green sherds are Chinese porcelain, fragments from beautiful, luxury bowls or jars - Celadon ware, which the Chinese were manufacturing in industrial quantities and exporting not just to south-east Asia but across the Indian Ocean to the Middle East and to Africa. Novelist Abdulrazek Gurnah remembers finding his own bits of Chinese pottery on the beach as a child:

"We used to see these things, these bit of pottery, we used to see them on the beaches. And sometimes older people would say to us, �That's Chinese pottery', and we'd think, �Yeah, yeah' - we'd heard lots of stories of this kind of thing - you know, flying carpets, princes lost etc. So we took it as just another one of those stories. It was only later on, when you begin to go into museums or hear these persistent stories of great Chinese armadas that visited East Africa, that the object then becomes something valuable, something that is a signifier of something important - a connection. And then you see the object itself, and you see its completeness, and its weight, and its beauty, and it makes this inescapable - this presence over centuries of a culture as far away as China."

As well as the Chinese porcelain, there are other bits of pot here that have clearly travelled a long way to get to Kilwa. I'm looking at the moment at a blue piece with black geometric patterning on it, that obviously comes from the Arab world and, when you look at this fragment under the microscope, you can see that the composition of the clay means that it was made in Iraq or Syria. And there are other pieces here that come from Oman or different parts of the Gulf. These fragments alone would be enough to demonstrate the strength and the extent of Kilwa's links with the Islamic Middle East.

The people of Kilwa clearly loved foreign pottery. They used it for dining and they also adorned their houses and mosques with it, setting decorated bowls into walls and arches. Pottery, of course, was only one element in the thriving import-export trade that made Kilwa's fortune - but it happens to be the toughest and the most enduring. Also coming in, though, were cottons from India - a trade that continues to this day - Chinese silks, glass, jewellery and cosmetics. In exchange, Kilwa was trading luxuries, commodities and slaves. A later Portuguese visitor conjured up the rich exchanges that took place at harbours like Kilwa:

"They are great traders in cloth, gold, ivory and diverse other wares, with the Moors and other heathen of India. And to their haven come every year many ships with cargoes of merchandise, from which they get great store of gold, ivory and wax."

Other exports included iron ingots much in demand in India, timber used for building in the Gulf, rhino horn, turtle shell and leopard skin. Many of these were brought over huge distances from inland Africa. Gold, for instance, came from Zimbabwe far to the south, and it's the trade from Kilwa that eight hundred years ago made Zimbabwe such a rich and powerful kingdom, that it could construct that supreme, mysterious monument, Great Zimbabwe.

All this trade made Kilwa very rich, but it changed it in more than material ways, because this was a trade with a distinct and unusual annual rhythm. Because the ocean winds blow north-east for one half of the year and southwest for the other, merchants from the Gulf and India usually had to spend months waiting for the wind home. And in these months they inevitably mixed closely with the local African community, and transformed it. In due course, thanks to these Arab traders, the coastal towns were converted to Islam, and Arabic and Persian words were absorbed into the local Bantu language to create a new lingua franca - Swahili. The result was a remarkable cultural community running through the coastal cities from Somalia to Tanzania, from Mogadishu to Kilwa - a kind of Swahili strip, if you like, Islamic in faith and cosmopolitan in outlook. But the core of Swahili culture remains unquestionably African. As the historian Bertrum Mapunda explains:

"We know that when these immigrants came to East Africa they came here because there were attractions here. And one of the attractions was trade. It was because of these local people who had attracted them, that the Swahili culture later on was born. So it's not true to say that this is something which was bought from outside, when we know that there were local people here who had contributed the starting point, and from there, then people from outside came and were interested."

The last piece of pottery makes this point very well. It's brown, it's a fragment of fired clay, and it's got bold raised decoration. It's pottery clearly made for cooking and for everyday use, the clay is local and the manufacture is distinctly African. And it shows that the African inhabitants of Kilwa, while happily enjoying and collecting foreign pottery, continued, as people always do, to cook in their own traditional way with their own traditional pots. And it's pots like this one that also tell us that the Africans were themselves sailing and trading across the Indian Ocean, because fragments like these ones have been found in ports across the Middle East. And we know from other sources that African merchants traded to India, and that cities of the Swahili strip were sending their own envoys to the Chinese court.

As I said at the start of this programme, when we put an ocean and not a country at the centre of our histories, it can radically change our perceptions of what happened in the past, and why. It's a theme that's been explored by Abdulrazak Gurnah:

"Well I have tried to write about this, and that sense of being in the world - partly, for example, in the kind of stories that were common to many of these cultures. Whereas you'd imagine that these were your stories, they turn out to be actually stories that belong to all sorts of other people as well. You felt as much that you belonged to Istanbul as you did to Dar es Salaam. That sort of sense of being in the world, that's really what I mean."

Like all seas, the Indian Ocean unites far more than it separates the people living round its rim. In the next programme, we'll be with another sea - the Atlantic. We'll be in the Hebrides, with a board game invented in India, played in Persia, taken to medieval Europe, and played there with pieces made of the ivory of Atlantic whales and Arctic walrus ... we'll be with the Lewis Chessmen.