WAIGEO ISLAND, Indonesia >>

When I enter the rainforest of Indonesia’s Waigeo Island, the first thing I notice is the equatorial air. It’s so thick, I feel as if I’m walking through a cloud.

The next thing that hits me is the deafening hum of cicadas. They drown out the noise of my feet crunching leaves as I step ever closer to my destination: a tiny thatched-roof hut in a muddy riverside clearing.

It’s hard to imagine spending a single night here, much less two months, but that’s exactly what British naturalist Alfred Russel Wallace did in 1860 while studying birds-of-paradise, an aptly named group of about 40 species whose lavish plumage and elaborate courtship dances helped inform early research on evolution.

Few people realize that there were actually two men who co-founded the theory of evolution through natural selection. Charles Darwin and the Galapagos Islands are familiar names, but Wallace and the isles he studied (such as this one in the Raja Ampat archipelago) have largely been lost to the sands of time.

Intrigued by the story of this unheralded thinker, I set off on a trip to West Papua, Indonesia, on the western half of the expansive island of New Guinea, for a cruise with SeaTrek Sailing Adventures, which runs educational and excursion-heavy 10-day trips on small, two-masted sailboats to remote Indonesian islands (all-inclusive Jewels of Raja Ampat cruise from $5,350). My goal was to trace Wallace’s journey through the four main islands of Raja Ampat and find his beloved birds-of-paradise. Along the way, I would discover a startlingly virgin archipelago that remains little changed in the 150 years since Wallace left.

The 1,500-odd islands (mostly islets) that make up Raja Ampat are at the center of the Coral Triangle, a hot spot of marine biodiversity at the crossroads of the Pacific and Indian oceans that’s often called “the Amazon of the sea.” This wild frontier lies off the west coast of New Guinea, the world’s second-largest (and some say least explored) island, and has been an in-the-know spot within the scuba community for about a decade. Divers from around the world flock here to swim with massive manta rays and glide through undersea forests of brain corals, blue staghorns and orange sea whips.

In recent years, the islands have emerged as a trendy destination for nondivers too, with new live-aboard expedition boats, eco-resorts and village homestays (with over-the-water bungalows for less than $25 a night). Two new airports — one in West Papua and one on Waigeo, the largest of Raja Ampat’s islands — have made it more accessible than ever. Foreign visitor numbers climbed to 13,000 in 2016, a big jump from fewer than 2,000 a decade ago.

I began my own journey in the port city of Sorong, a haphazard collection of basic homes, modern energy-company offices and karaoke bars at the tip of New Guinea’s Bird’s Head Peninsula. With little to hold my attention, I set sail the following morning toward Misool, the Raja Ampat island at the heart of a 300,000-acre marine reserve.

Foliage clings, improbably, to dramatic karst formations that rise out of the sea like shards of green glass on Misool’s edge. Many of these formations hide turquoise lagoons that are so crystal-clear you can see blue sea anemones swaying in the water as you glide above. The lagoons are a favorite hangout spot for hornbills, who fill the air with their guttural moans as they whoosh overhead like helicopters en route to coconut palms.

I sailed north from Misool to the Fam Islands, where pincushions of bush-clad rock jut out from the sea, forming a labyrinth of earth and water. Then it was off to investigate Papuan culture at Arborek Tourism Village and, eventually, find Wallace’s cabin on the nearby island of Waigeo.

Now, on my penultimate day in Raja Ampat, I’m finally ready to find the birds that helped Wallace cement his groundbreaking theories. To do so, I must wake up at the uncomfortable hour of 4 a.m. and prepare myself for an hourlong hike into the jungle.

A full moon sends icicles of white light across the sea as I motor away from the sailboat to a small dock. All I can make out in the distance is a tiny cove and the perky shadows of palm trees. As we get closer, I spot my bird guide, Daniel, waving a flashlight.

Papuans have a reputation among other Indonesians as fierce, man-eating warriors. Yet Daniel, like everyone else I’ve met in Raja Ampat, smiles and high-fives as I exit the boat onto the south side of Waigeo and head into rainforest.

We hike together under the soft glow of a flashlight, stepping over rocks, roots and moss-covered logs on our way to a crude viewing blind in a hilltop forest 650 feet above the sea. A cacophony of birdsong greets us as we rise higher into the jungle. Though my eyes can only see a few feet ahead of me, my ears are flexing their muscles. I’m reminded that Wallace collected 73 species of birds on Waigeo, 12 of which were entirely new to science.

I manage to reach the viewing blind by sunrise and survey my surroundings. There are sturdy buttress roots below and pen-thin palms towering above the forest canopy. Vines swirl around a nearby eucalyptus tree, choking it.

I spot the first signs of movement in a distant branch. It takes a few long minutes, but a creature finally emerges from the leaves. It has an elaborate outfit that even a peacock would envy: crimson red wings, emerald green cheeks, yellow shoulder tufts and wispy purple tail feathers that curve away from its body. It truly is paradise embodied. (Indonesia has 29 species of birds-of-paradise, nine of which are found only in this country, according to experts at the Cornell Lab of Ornithology in New York.)

It’s not long before more birds-of-paradise arrive, heeding the bleating calls of their brethren. They hover around what appears to be the mating branch where, one after another, males congregate to woo females with their decadent plumes and elaborate dances. One bird twists his way up and down as if playing a game of hopscotch on the branch. Another taps his wings and gyrates his tail feathers. Each male seems to have his own signature move.

By 7 a.m. the sun has crested above the horizon and the birds, like clockwork, dissipate into the forest in search of food.

For Wallace, this would mark the end of a productive day and the return to his meager hut.

For me, it’s the culmination of a long journey to a faraway archipelago I won’t soon forget.