Will Sudan split set an African precedent?
On Sunday the people of Southern Sudan will vote on whether to become an independent nation. There is every indication they will vote in favour of cutting their links with Khartoum and become Africa's 54th state. BBC Africa analyst Martin Plaut considers whether this will increase demands from other African regions for independence.
The slogan adopted by the Africa Union - the body representing the continent - is simple: Africa must unite.
In the 1960s the leaders who brought Africa to independence were faced with a terrible dilemma.
Most of the borders they had inherited had been drawn by the European powers who divided the continent in the 1880s, during what was known as the "scramble for Africa".
They cut through ethnic groups, dividing peoples and even families. The countries threw together men and women who had differences of language and religion.
Yet Africa's leaders decided to accept these frontiers: Unpicking them would have set every new country against the other. The independence borders were treated as sacrosanct.
So does the referendum in Sudan mark the end of this principle?
Southern Sudan would not be the first new post-independence country to be recognised in Africa. Eritrea broke away from Ethiopia in 1993. But the Eritreans could argue that they had been an independent state under the Italians and that Emperor Haile Selassie had violated a United Nations resolution when the territory was annexed as just another Ethiopian province in 1962.
So, it is said, Eritrea does not break the African injunction on new states. But a string of territories might argue that they have a case for secession.
These include Somaliland, which was independent from Somalia for just three days in the 1960s. There are movements fighting for greater autonomy in the Casamance region of Senegal, the Cabinda region of Angola or parts of the Democratic Republic of Congo, such as Katanga.
And one should not forget the Libyan leader, Muammar Gadaffi's call for Nigeria to be divided. There is also deep concern in Khartoum that the independence of the south could lead to a disintegration of the country, with some in Darfur also demanding independence.
The emergence of Southern Sudan is likely to increase the paranoia of African leaders, says Knox Chitiyo, head of the Africa programme at the Royal United Service Institute.
"The independence of south Sudan will force governments to pay greater attention to the concerns and grievances of marginalised areas. Regions which have had long-standing secessionist threats are likely to receive closer attention from African leaders," he says.
There are also pressures that will drive the continent towards greater integration. Market forces are bringing Africans closer together.
As Patrick Smith, editor of the newsletter Africa Confidential puts it: "African unity is not at risk. African integration is being driven by strong market-driven forces, as the continent's economies grow to meet the rising demand from Asia."
These trends have been supported by institutional developments.
The African Development Bank and institutions like the World Bank are keen to support projects which increase regional trade.
There are also attempts to reduce the inhibiting impact of border tariffs and customs duties.
The East African Community, for example, is making progress in reducing restrictions on trade and employment, even if these are sometimes painfully slow.
There has also been progress towards providing the African Union with a military capability drawing on regional forces.
There are already African troops in conflict zones including Darfur and Somalia. The crisis in Ivory Coast is the next test of how far this has developed and to what extent the international community is prepared to support institutions like the West African grouping, Ecowas.
All of the continent's nations still recognise the African Union as their representative body on the global stage.
Certainly the international community does not want to see Africa splintering into fragments.
The West has gone out of its way to reassure the Sudanese government that it will not see the independence of the south as the beginning of the disintegration of the state.
Both Sudan and the South are reliant on their oil revenues, which account for 98% of South Sudan's budget. But the two countries cannot agree how to divide the oil wealth of the former united state. Some 75% of the oil lies in the South but all the pipelines run north. It is feared that disputes over oil could lead the two neighbours to return to war.
Although they were united for many years, the two Sudans were always very different. The great divide is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. South Sudan is covered by green swathes of grassland, swamps and tropical forest.
Sudan's arid north is mainly home to Arabic-speaking Muslims. But in South Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own languages and traditional beliefs, alongside Christianity and Islam.
The health inequalities in Sudan are illustrated by infant mortality rates. In South Sudan, one in 10 children die before their first birthday. Whereas in the more developed northern states, such as Gezira and White Nile, half of those children would be expected to survive.
The gulf in water resources between north and south is stark. In Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In the south, boreholes and unprotected wells are the main drinking sources. More than 80% of southerners have no toilet facilities whatsoever.
Throughout the two Sudans, access to primary school education is strongly linked to household earnings. In the poorest parts of the south, less than 1% of children finish primary school. Whereas in the wealthier north, up to 50% of children complete primary level education.
Conflict and poverty are the main causes of food insecurity in both countries. In Sudan, many of the residents of war-affected Darfur and the border states of Blue Nile and South Kordofan, depend on food aid. The UN said about 2.8m people in South Sudan would require food aid in 2013. The northern states tend to be wealthier, more urbanised and less reliant on agriculture.