KHARTOUM // The Nubian wrestlers, bare feet on red sand, enter the ring with more sway than swagger in their step. Murmurs of appreciation ripple through a crowd of men with bright white robes against the green-painted arena and startling blue sky.
The rules of this weekly contest on the outskirts of the Sudanese capital are simple. Each Friday, two local teams - this week it is Pisces and Unity - gather and each of their 10 competitors fight one bout each. They grapple with arms and legs to throw each other to the ground. Each fight lasts a few minutes and ends with a handshake. The first team to six victories is the winner.
Men watching sport at the weekend has a universality to it, but these bouts have another claim to tradition. It is part of the story of the Nubian people - who led powerful empires, speak their own languages and, according to ancient friezes interpreted by archaeologists, used to wrestle like this thousands of years ago.
Now, a number of shocks to their traditional homelands and attitudes have shaken the closeness of the Nubian communities, and seem to be shifting their identity.
An agricultural society spreading out from the banks of the Nile through what is now the south of Egypt and the north of Sudan, the Nubian civilisation rose alongside, and in competition with, the ancient Egyptians. Their pyramids and necropolises still stand along the road from the Egyptian border to Khartoum and they worshipped some of the same gods.
Over the past millennium, Arabic, Islam and Christianity have become part of the culture and most of about 300,000 ethnically Nubian people consider themselves Egyptian or Sudanese.
But some elements of society have remained distinctive - such as a matriarchal family structure, several languages, music and a gently tolerant approach to faith.
But a series of dams, built along the Sudanese and Egyptian stretches of the Nile, have flooded ancient villages and, especially in Sudan, some complain that an Arabising, Islamising government has purposely eroded Nubian culture.
At Khartoum University, Ali Osman, a scholar of Nubian archaeology and veteran of Nubian rights movements, rallies facts garnered over years of research to support his claims about Nubian society.
"Sudan is a land of civilisation and culture," he said. "So many people have their own languages and culture." Nubians, he said, have been using the same mud ovens for cooking and water wheels for irrigation for more than 4,000 years. Their matriarchal social structure still sees young grooms move in with their in-laws for the first years of marriage, and Mary, mother of Jesus, honoured in Nubian Islamic and Christian culture.
Religious tolerance has endured for more than 1,000 years.
But he blames the Sudanese government of Omar Al Bashir, which came to power in a military coup in 1989, for suppressing Nubian culture by outlawing campaigns and imprisoning some of the many Nubians - including him - who consider themselves Muslims but do not practise strictly.
"If the government knew what it wanted to change, we could discuss it," said Mr Osman. "But they just want to enforce a political system on the people of Sudan that doesn't allow a second opinion, and that means a diversity of culture. Because if you have a culture, you have an opinion."
In recent years, though, he says he has seen a change on the part of the government, with Mr Al Bashir speaking in Nubian-dominated areas during the 2010 election campaign, and allowing a diploma in Nubian language at the university.
In Egypt, the government's official stance is of pride and support for Nubian culture, and there is an impressive museum full of idiosyncratic sculptures, iconography and furniture in the southernmost town of Aswan. But the shocks to the culture have been far greater there, said Thanaa Hassan, the head of education at the museum.
When Egypt's modernising leader Gamal Abdel Nasser began the High Dam at Aswan in 1958, he flooded an area where tens of thousands of people, primarily Nubians, lived. Some relocated to villages on the outskirts of Aswan and in cities further north along the Nile, some headed to Cairo and many more to Saudi Arabia, Qatar and other countries to look for work.
Some people, like Ms Hassan, are nostalgic for the days when generations followed one another into agricultural life along the river.
"The old women tell me that the weather was good - hot in the summer and cold in the winter," she said. "They built houses from clay with domes, they used all the materials from the environment. They had three rooms and a court because the Nubian people sleep in the summer under the stars."
However, she concedes that this was back-breaking work in poverty, and that access to education these days is much better. In the villages around Aswan, largely populated by Nubians who cling on to many traditions, children attend government-funded schools, even if they help in the fields in the evening.
Ms Hassan herself lives in a multi-storey house and would not choose to give up her refrigerator or car.
While she berates young women for wanting to live alone in cities, she has allowed her daughters to leave for a university education and, having learnt to drive, argues a little with her husband about using their car every day, since she works further from home.
Like others gradually growing used to great change, she seems to struggle with some aspects of modernity. But in the museum, she is totally committed to the traditional, in particular the collection of oral history and music, which uses a different scale from Arabic music and is influenced by the drums and rhythms of sub-Saharan Africa.
One of the world's most famous Nubians was Hamza El Din, an oud player from Egypt who toured worldwide and died in 2006. Perhaps his best-known song is a mostly wordless hymn to the water-wheel, the ancient technology that begun this civilisation, a haunting melody inspired by the old songs from the now-drowned villages.
"The old Nubian songs are very, very beautiful ... when I hear the old Nubian songs, it's a very good meaning," said Ms Hassan. "So, we have to preserve."