I am kneeling on the grass, tensed, my right arm raised in the air, waiting to be publicly whipped. Above me stands one of the men of Noipus, a microscopic dot of a village on one of the marginally larger dots of islands that make up Papua New Guinea's Bismarck Archipelago.
Over his head, a stick longer than his body is poised. We are a study in contrasts. Me: submissive, doubtful, white, sweating. He: aggressive, certain, dark, cool. As I wait for the blow, a thought crosses my mind: "Well, this is exotic."
It is my second day, and first time, in Australia's nearest neighbour. After an endearingly shambolic welcoming "sing-sing", the men of Noipus are demonstrating the "whipping ceremony", an initiation ritual that involves one man cracking a two-metre-long solid reed across the upraised arm of another. Each crack reverberates like a rifle shot and I've noticed even the locals flinch as they take their turn.
It is this that I have, literally, put my hand up for (something about "when in Noipus") and I have serious doubts that the protection offered me - a mouthful of chewed-up leaves and coral lime spat onto my wrist in a green band - will offer any protection at all.
Using the full weight of his muscled body, my initiator belts the stick unerringly across the thin green shield on my arm. It wraps completely around my wrist and then snaps, the force of it like a concentrated punch. It hurts, though not as much as I had feared.
To complete the theatre I pause for a moment, arm still in the air, then fall face first on the ground. Laughter. Applause. Am I initiated?
An hour later, what had been a red welt on green skin has entirely disappeared and, with it, all trace of pain.
Over the next 10 days I will discover that Papua New Guinea has other skins, each a cause for wonder.
I'm aboard True North, a luxury Australian cruise ship built to take no more than 36 passengers to remote wilderness areas. A chartered jet has flown us north from Cairns to Kavieng, the capital of New Ireland Province, which lies 860 kilometres north-east of Port Moresby. From here, for the next 11 days, we will sail south, then due west, along the Bismarck Archipelago, through the Admiralty Islands and, finally, to Papua New Guinea's most remote territories, the Hermit and Ninigo islands, before turning south once more for the mainland and the tribes of the Sepik River.
The first week is a checklist of tropical clichés. White sand? Check. Palm-fringed islands? Check. Reckitt's-blue seas clear to the bottom? Check.
Pristine coral reefs? Check. Volcanic peaks and craters? Again, check. Sunsets to make a poet weep? Check.
It comes as no surprise to learn that American movie star William Holden was so enamoured of these islands' untouched beauty he tried to buy several of them in the 1970s. What is surprising is that, 40 years later, the word "untouched" is still not out of place.
It is difficult to recall the last place I travelled where there was virtually no sign of tourist infrastructure.
But it is not the blessed absence of Visa, Coca-Cola, backpackers' hostels or WiFi that most delights.
What makes this experience shine is an unambiguous sense that the warmth and welcome of the people we meet is real.
Nowhere is this more apparent than Ponam Island, a dead-flat sliver of land - two and a half kilometres long and 360 metres across at its widest- that sits just off Manus Island. From the air, Ponam resembles nothing so much as an aircraft carrier, which, during World War II, it effectively became, turned into an airstrip by the Allies as they drove the Japanese, inch by bloody inch, from the Pacific.
Our welcome today could not be further removed from that grimness. Even before our boats reach the shore we are swamped by waves of rhythm and colour. On the beach a phalanx of women and children are dancing to the beat of unseen garamut slit drums that echo across the island. Stepping ashore we are each taken in hand by children whose bodies, like those of the women, are adorned in intricately woven outfits of beads, shells, plants and twine.
As we are led the dancing never stops: rhythmic movement from foot to foot set to a continuous drumbeat, ending on every eighth beat with a loud cry of "aaiii!", a twist of the body and what may, or may not, be some kind of pelvic thrust.
In our sweaty, rhythmless way, we try to keep up but it hardly matters. The children guide us to the triangle at the centre of the village where we are surrounded by warriors, women and children of all ages, dancing with all the excitement of Christmas morning. Beyond them, what must surely be the rest of Ponam's population revels in the show, laughing and calling out in shared delight.
It is such an overwhelming, raucous, heartfelt welcome that I feel unexpectedly emotional. Others, passengers and even crew, confess to tears. In a world where so much travel is sliced and diced into packages, this feels different.
The welcome at Ponam, while more spectacular than other islands, is typical. Wherever we go, people are excited to meet us. Ships don't come by often and our visit inspires both curiosity and pride. Simon Tewson, True North's local guide, has lived in Papua New Guinea almost all his life: "This is probably the most white people they've seen for a long time in one hit. For us to go there, that means so much to them. Forget what we spend or donate, they're more interested in, hey, that boat came to our village."
And people are keen to talk: 21-year-old Leroy dreams one day of opening a bar for tourists. Barun, also 21, has a chemistry degree but no work. "It is not what you know but who you know in this country," he says, sadly. Mina and Vincenzia ask me if I am Catholic and, when I tell them I was born so but am not any more, look at me astonished - how is that possible? - then burst out laughing.
Here is another of Papua New Guinea's skins: the missionaries - Germans, British, Irish, Australian - sowed their seeds deep in these islands. It's like walking into a tropical edition of the Old Testament. Wherever I go men welcome me with names such as Elijah, Isaiah and Abraham, even Judas.
And just beneath that skin lies an even older one. On one island the primary school has a list of denominations on the wall of Class 4a. At the bottom, after Catholics (2), Baptists (1), and Seventh-day Adventists (6), sits Wind Nation (2). "What is Wind Nation?" I ask the teacher. "They believe the wind is a spirit," comes the easy reply.
For all the tropical bounty and beauty, it is clear that life here is also fragile. At night, villagers can see the lights of the Filipino fishing boats and Chinese supertrawlers 20 kilometres offshore, sucking in marlin, dolphin - whatever they can - in industrial amounts, canning them on board, then moving on. Even if the locals could afford the petrol to go and remonstrate, they know they have no power.
Many of these islands are so low in the water that, if someone left a tap running, they would disappear. On Ponam, I ask another son of the Bible, Luke, if he has seen any sign of the water rising. He considers this for a moment, then replies: "We have probably lost three-eighths of our island."
Yet resilience, says Tewson, is what best characterises Papua New Guineans. "The people here are pretty stubborn," he says. "Come back in 20 years' time, there might be salt water but they'll be living on stilts." He may be right. When I remark on the precarious position of huts just centimetres above the water, someone responds, "Yes, but I have the best view."
The sea is also the shining thread that binds these lives together. They live from it, hunting dugongs ("the pigs of the sea") from canoes, spearing lobsters on the reef, closing their pandanus-leaf traps around fresh hauls of sweetlips. And they live on it; we are constantly surrounded by a flotilla of tiny, fragile, wooden canoes, kids and adults alike intensely curious about our impossibly large boat.
The tropical waters embrace us, too. As a first-time diver I am spoilt by, reputedly, some of the best diving in the world. So much is happening, in such clear water, it feels like flying in a sky full of fish. At the famous Krakafat Reef, I have to fight the urge to take the regulator out of my mouth and say to the others, "Are you guys seeing this?" For the snorkellers, it's as though they are swimming in a warm aquarium.
After eight days of island light, we turn due south for the turbid waters of the Sepik River and a sense that we are swapping Blue Lagoon for Heart of Darkness.
Although missionaries set up shop in the Sepik a long time ago, the spirit world is still very real here. The people are different as well: happy to see us, but cooler than their island cousins. On the river, with little income and few opportunities to trade, our presence means business.
At Angoram, the oldest and largest settlement on the Sepik, we are met by competing dances from rival clans within the one tribe. Not the warm and cheerful welcomes we have become used to, these are aggressive and muscular. To one side, men and women of the eagle totem, with ochre-smeared faces, bodies adorned with cassowary feathers, pig's tusks, dog's teeth, shells and plants, chant and stamp their way towards us, their leader wearing a grotesque, outsized spirit mask - and Pokémon slippers (nothing goes to waste here). To the other, the crocodiles do battle: two enormous puppets made from feathers and painted wood, each carried aloft by two men, surrounded by spear- and drum-wielding villagers in multi-coloured grass skirts and pig's tusk headdresses. It feels ancient. Tribal. Serious. It is also thrilling.
Our next stop, 30 kilometres up the river, is more confronting: the village of Kambaramba. If Mad Max had been set on the water, this is what it would look like. A collection of maybe 80 ramshackle huts made of sago palms but open to the elements - including the malarial mosquitoes that killed 37 people here last year - the village crouches shakily on stilts above the brown, still water. Children are in tattered hand-me-downs, dogs and pigs share ramps where crocodiles can't reach them.
It feels desperately poor. And sad. Later, we find out how sad. The people of Kambaramba were forced onto the water by other tribes and the only things they had to trade for the crops they could no longer grow were their women. They are still an outcast people today. A shadow tribe of ill repute. It is a disquieting visit and there is a feeling of relief when we head upriver to Tambanum, famous for its art.
This is a happier, healthier place. They haven't seen tourists for a long time and their carvings are exceptional. The spirit house, where racks of skulls were once kept as trophies, is itself a work of art: an intricately thatched roof nearly two storeys high, supported by a framework of giant carved and painted poles, topped by a six-metre-long carved eagle totem.
Think of a spirit house as the ultimate in men's clubs. Men spend much of the day sitting around smoky fires, playing garamut drums, putting the world to rights. On some evenings they dance wearing full-length spirit costumes and masks, others playing flutes for effect. The women and children of the village, convinced these are actual spirits, live in fear of them and stay well away.
It could all be quaint if not for the knowledge that if you pulled out the supporting posts you would find the bones of enemies buried alive here, the life force of their souls giving the place its spiritual strength.
For our final day on the Sepik, we take True North's chopper ("eggbeater bilong Jesus Christ" if you believe the local joke) upriver to Palumbi. Here is where all the skins of Papua New Guinea fall away to reveal a world of sorcery, headhunting and cannibalism.
Climbing the rickety log ladder of the spirit house, we enter a smoky half-lit space filled with carved statues and masks of competing grotesquery. Giant tambaran spirit costumes are suspended from the ceiling. Men sit quietly in the shadows coolly appraising our goggle-eyed looks as we try to take it all in. It is easy to imagine the many masks hanging in the dimness as human heads and, in times not so long past, they might have been.
One man points to a notched rope suspended from the ceiling. Each notch, he says, represents a head that has been hunted by this village. Tewson tells me that headhunting and cannibalism were still happening on the Sepik in the 1950s and that to eat another human being was to get their power.
In Palumbi, the most powerful spirit is the crocodile and we head 20 minutes further upriver to see just what that means.
We see a single hut, isolated from the rest of the village behind a high screen of woven palm leaves. Here, for the past six weeks, is where the crocodile initiation has taken place.
Inside the screen we see five young men, naked but for grass skirts and a covering of clay on their bodies and heads. We see older men in ceremonial outfits of leaves and shells, wearing striking headdresses made of feathers. We see their skin. They have become crocodile. Across their backs, buttocks, arms and around their nipples are hundreds of raised scars: crocodile markings.
Village elders revived this old initiation ceremony in the past few years. They put the word out to younger men, some at university, offering the chance to be initiated like their forefathers and there has been no shortage of takers.
They are held down and their skin cut deep, up to a centimetre, with a razor in the pattern of the crocodile. It can take a whole day to carve one man's back. Then, after a few days' break, the front. This is the worst part. The men can't look away and the carving around the nipples is excruciating.
Tewson has been to one and says he's never heard people scream so loud.
The skin is then beaten, forcing the blood out; then clay and mud are jammed into the wounds to make them protrude. For the first week or two while the wounds are open, the only salves are stinging hibiscus oil, clay to keep mosquitoes at bay, and betel nut to take away some of the pain.
For two to three months the men stay hidden behind the screen; food is left outside for them by women who hear their screams and think the crocodile is doing its work. Traditionally, this was the start of them becoming men. Their next duty would be to go murder someone and bring their head back to the village. Nowadays, they skip that part.
It sounds barbaric, it's certainly brutal, but the markings are strangely beautiful and, for these young men, they carry weight.
"It makes them powerful," says Tewson.
"You might find one of these men in a court of law one day, he might be a defence lawyer, and someone will look at those marks and he'll get a lot of respect out of it because they know how much pain he's gone through." This, less than two hours' flight from Australia.
After three days we emerge from the darkness of the Sepik for one more day of play in the warm, crystal-clear waters of Bagabag Island.
Dark and light, it has been a journey of rare natural beauty and authenticity. These people have an unbroken link with their land and traditions. Their welcome, cool or warm, is unmistakably theirs, not a construct for us.
Long after we have returned home, a moment stays with me. We are on Ponam Island and word has got around that one of the passengers, whose birthday it is, has made a donation towards the reconstruction of their church. Before he can quietly leave, the children surround him on the beach and sing happy birthday. Then, spontaneously, they burst into their national anthem - "O arise all you sons and daughters of this land, let us sing of our joy to be free." Their harmonies soar and in their wide smiles and shining faces there really is joy.
If silence can settle on a beach it does then for us. For those who have so little, to give so richly to we who have so much is powerful. Deeply moved, we make our farewell, a word of pidgin saying it all: Thankyoutrue.
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