John McBeth, Timika – For centuries, Papua's warlike mountain tribesmen have used bows and arrows, spears and knives to settle their differences over women and pigs – and not necessarily in that order of priority.

But a recent pitched battle on the outskirts of the lowland boom town of Timika on the south coast of the Indonesian province has underlined what can happen when urban migration and traditional practices collide. The resultant clashes – and an influx of illegal highland miners – represent the latest headache for US mining giant Freeport McMoRan Copper & Gold, far and away Indonesia's largest foreign taxpayer.

The battle stemmed from the drowning of the epileptic seven-year-old son of a Dani tribal headman. Angry that better care had not been taken, the boy's hot-tempered uncle – a member of the closely related Damal tribe – killed one the headman's brothers and wounded another with a bow and arrow.

In the days that followed, tribesmen from both sides engaged in a week-long series of running skirmishes that left 12 of the combatants dead and another 150 wounded from arrow and spear wounds. Then, true to tradition, the two sides held pig roasts and an arrow-breaking ceremony in a show of reconciliation and agreed to let matters rest.

Three weeks later, fighting erupted again in Kwamki Lama, a largely Dani settlement. Three more tribesmen died and another 80 were hurt before security forces managed to separate the two sides. But with a third tribe, the Ekari, now joining in the clashes, community workers are wondering how to bring an end to the continuing spiral of violence.

This, after all, isn't Papua's rugged mountains, where deep valleys separate tribes and provide the space needed to calm emotions and work out peace deals. In the villages scattered around Timika, a town of 60,000 people, seven different tribal groups – some of them harboring age-old grudges – live in uncommon and uncomfortable proximity.

Once a clapboard settlement serving only ethnic-Javanese transmigrants, Timika owes its lifeblood to the Freeport Indonesia copper and gold mine, which has acted as a magnet for thousands of highland tribesmen and migrants from other parts of Indonesia looking for jobs and economic opportunities unavailable on other more crowded islands. With more than 18,000 workers, Freeport is one of Indonesia's biggest employers.

By the time Freeport's Grasberg operation goes underground, scheduled for 2012-14, Papuans will have become the core of the company's workforce, rather than the minority that they are now. But the recent outbreak in ethnic tensions adds a new complication to the planned changeover.

The attraction Timika holds for the highlanders, in particular, underlines the fact that for all their isolation and ancient customs, they are just as interested in money and an education for their children as anyone else. But it may take more than a generation for them to come to terms with an urban environment where historic grievances have no place.

Money also creates its own problems. "There's a lot of social jealousy," said anthropologist and author Kal Muller, who has spent three decades in Papua. "In many highlands societies the basic ethic has been egalitarian, with respect gained not by accumulating capital, but by distributing capital. Here, a lot of money is spread around and the distribution is very uneven."

Tribe on tribe

There has also been a dramatic change in the demographic balance. Mimika, the district surrounding Timika, was once home to only the highland Amungme and the lowland Kamoro tribes, who lived in relative harmony. But Freeport's rich Grasberg mine, into which the company has poured more than US$12 billion in investment over the decades, has drawn an increasing number of Dani, the dominant Papuan tribe that now makes up 60% of Timika's highland population.

Dani migration is nothing new. Originally from the Balien Valley, 200 kilometers northeast of Timika, they have been pushing westward for centuries. Indeed, those who have settled on the more fertile northern slopes, well to the north and west of Freeport's high-altitude mine, are now known as the Western Dani, or the Lani as they like to call themselves. Even their language is different in a region with 250 different dialects.

The only reason thousands of Amungme tribesmen ended up where they are now is that the Dani expelled them from their original home before the turn of the 20th century. There was no mine then, but since it opened in the early 1970s the Amungme have found themselves under pressure again from the same tribe that pushed them out of the more fertile northern side of the highlands.

In 1997, with over-aggressive Dani settlers intruding on their hillsides and sweet-potato gardens and taking the virginity of young girls whose bridal bounties had already been paid, the Amungme hit back. Eleven people died in the fighting, which ended with authorities relocating most of the more than 3,000 Dani to a new lowland area west of Timika.

Although they continue to populate 17 valleys, the 10,000 Amungme still feel increasingly like strangers in their own land. Those who have settled in the lowlands have been nudged out of Kwamki Lama, and the tribe itself now faces the prospect of losing the privileged position it once enjoyed as the original benefactor of Freeport's largesse.

The Damal may have fared even worse. Enforced inter-marriage with the dominant Western Dani has, over the years, in essence reduced them to little more than a sub-clan – even if the recent clashes suggest that old enmities remain a lot closer to the surface in an urban setting than they do in the highlands.

Added to Timika's melting pot have been settlers from the Nduga, Ekari and Moni, three other highland groups. There are also stragglers from the Asmat and Senpan tribes who have drifted in from further down the swampy southeast coast, which borders the shallow waters of the Arafura Sea separating Indonesia and Australia.

The town itself has a similar yet different mix. Old-time Javanese migrants mix with tens of thousands of native Buginese – traders from distant South Sulawesi – and lowland Papuan settlers from as far away as Maureke, on the Papua New Guinea border in the east, to the island of Biak and the provincial capital Jayapura on the north coast and the former oil center of Sorong in the west.

With the world gold price rocketing from $250 to $650 an ounce in just two years, hundreds more Dani have been trekking south to join an army of illegal gold miners now working in the tailings, or waste rock, flowing downstream from the Freeport mill. The number of gold panners has grown from several hundred to more than 3,000, most of whom sell the gold to military middlemen who then pass it on to dealers in Timika.

There are concerns that with the gold running out in an alluvial deposit near Nabire, on Papua's north coast, more fortune hunters will head across the highlands to Timika, potentially adding more ethnic tension to a problem authorities seem unable or unwilling to solve.

[John McBeth is a former correspondent with the Far Eastern Economic Review. He is currently a Jakarta-based freelance journalist.]