ETUTING NATIONAL PARK, Indonesia – Hoping to unravel the mysteries of human origin, anthropologist Louis Leakey sent three young women to Africa and Asia to study our closest relatives: It was chimpanzees for Jane Goodall, mountain gorillas for Dian Fossey and the elusive, solitary orangutans for Birute Mary Galdikas.

Nearly four decades later, 62-year-old Galdikas, the least famous of his "angels," is the only one still at it. And the red apes she studies in Indonesia are on the verge of extinction because forests are being clear-cut and burned to make way for lucrative palm oil plantations.

Galdikas worries many questions may never be answered. How long do orangutans live in the wild? How far do the males roam? And how many mates do they have in their lifetime?

"I try not to get depressed, I try not to get burned out," says the Canadian scientist, pulling a wide-rimmed jungle hat over her shoulder-length gray hair in Tanjung Puting National Park. She gently leans over to pick up a tiny orangutan, orphaned when his mother was caught raiding crops.

"But when you get up in the air you start gasping in horror; there's nothing but palm oil in an area that used to be plush rain forest. Elsewhere, there's burned-out land, which now extends even within the borders of the park."

The demand for palm oil is rising in the U.S. and Europe because it is touted as a "clean" alternative to fuel. Indonesia is the world's top producer of palm oil, and prices have jumped by almost 70 percent in the last year.

But palm oil plantations devastate the forest and create a monoculture on the land, in which orangutans cannot survive. Over the years, Galdikas has fought off loggers, poachers and miners, but nothing has posed as great a threat to her "babies" as palm oil.

There are only an estimated 50,000 to 60,000 orangutans left in the wild, 90 percent of them in Indonesia, said Serge Wich, a scientist at the Great Ape Trust of Iowa. Most live in small, scattered populations that cannot take the onslaught on the forests much longer.

Trees are being cut at a rate of 300 football fields every hour. And massive land-clearing fires have turned the country into one of the top emitters of carbon.

Tanjung Puting, which has 1,600 square miles, clings precariously to the southern tip of Borneo island. Its 6,000 orangutans — one of the two largest populations on the planet, together with the nearby Sebangau National Park — are less vulnerable to diseases and fires.

That has allowed them, to a degree, to live and evolve as they have for millions of years.

"I am not an alarmist," says Galdikas, speaking calmly but deliberately, her brow slightly furrowed. "But I would say, if nothing is done, orangutan populations outside of national parks have less than 10 years left."

Even Tanjung Puting is not safe, in part because of a border dispute between the central government, which argues in favor of a 1996 map, and provincial officials, who are pushing for a much smaller 1977 map. If local officials win, the park could be slashed by up to 25 percent.

Galdikas, of Lithuanian descent, was an anthropology student at the University of California in Los Angeles when she approached Leakey, a visiting lecturer, in 1969. She follows on the heels of Goodall, who today devotes virtually all of her time to advocacy for chimps, and Fossey, who was brutally murdered in her Rwandan hut in 1985.

Two and a half years later, she and her then husband, Rod Brindamour, arrived in Tanjung Puting and settled into a primitive thatch hut in the heart of one of the most biodiverse regions on the planet, with millions of plant and animal species.

Twice featured on the cover of National Geographic Magazine, she wrote an autobiography, "Reflections of Eden," describing how she fell in love with the sound of cicadas, and marveled at the sudden shifts of light that in an instant transformed drab greens and browns into translucent shades of emerald.

Her first challenge was simply finding the well-camouflaged orangutans in 100-foot-high trees. But eventually she was able to track them, sometimes for several weeks at a time.

She discovered that female orangutans give birth when they are around 15 and then only once every eight or nine years, making them especially vulnerable to extinction. They also have one of the most intense maternal-offspring relationships of all mammals, remaining inseparable for the first seven or eight years.

While orangutans are at first very gregarious, as adults they live largely solitary lives, foraging for fruit or sleeping. Orangutan" means "man of the forest."

One of her main projects today is her rehabilitation center in a village outside Tanjung Puting, overflowing with more than 300 animals orphaned when their mothers were killed by palm oil plantation workers.

With forests disappearing, the red apes raid crops, grabbing freshly planted shoots from the fields.

"Many come in very badly wounded, suffering from malnutrition, psychological and emotional and even physical trauma," says Galdikas, as she watches members of her staff prepare six young orangutans for release one overcast Saturday afternoon.

It is a three-hour journey along bumpy roads to the release site. By the time they arrive, it is raining and the last gray light is feebly pushing its way through the deep canopy of trees.

After years of being cared for, fed and taught the ways of the woods, the young orangutans scramble nimbly to the tops of trees. Branches snap as they make their nests for the night.

"It is getting harder and harder to find good, safe forest in which to free them," says Galdikas, who today spends half her time in Indonesia and most of the rest teaching at Simon Fraser University in British Columbia.

Forestry Minister Malem Kaban says the government is committed to protecting Indonesia's dense, primary forests and that no permit should be granted within a half-mile of a national park. Even so, one palm oil company has started clearing trees within Tanjung Puting's northern perimeter, leaving a wasteland of churned-up peat and charred trunks. Four others are seeking concessions along its eastern edge.

Derom Bangun, executive chairman of the Indonesian Palm Oil Association, says while his 300 members have vowed to stay clear of national parks, others have been known to operate within areas that should be off-limits. Sometimes it is not their fault, he notes, pointing to the need for better coordination between central and local government on border issues.

Galdikas, a passionate field researcher, says one of her great regrets is that she does not share Goodall's skills in raising awareness and funds for the great apes. But she is happy Tanjung Puting has over the years grown into a popular tourist destination. She says there's no better advertisement for conservation than being in a rain forest.

Some visitors are even lucky enough to come face to face with an orangutan on a slippery jungle trail.

"As he passes you, you nod and he nods back to you and continues on his way," she says, adding that looking in the eyes of a great ape, it instantly becomes clear that there is no separation between humans and nature.

"If they go extinct, we will have one less kin to call our own in this world," says Galdikas, who is also president of the Los Angeles-based Orangutan Foundation International. "And do we really want to be alone on this planet?"