There are only five kinds of great apes alive today. Chimpanzees, gorillas, bonobos, orangutans, and us. Among the non-human apes, orangutans are unique. Orangutans live only in Asia - in the forests of Sumatra and Borneo. They’re intelligent, solitary animals that feed mostly on fruit. There is a lot we can learn from them - but it’s not an easy job.
There are only five kinds of great apes alive today. Chimpanzees, gorillas, bonobos, orangutans, and us. Among the non-human apes, orangutans are unique. Orangutans live only in Asia - in the forests of Sumatra and Borneo. They’re intelligent, solitary animals that feed mostly on fruit. There is a lot we can learn from them - but it’s not an easy job.
Further learning
About The Leakey Foundation
The Leakey Foundation is a nonprofit organization dedicated to funding human origins research and sharing discoveries. The Foundation was established in 1968 to fund work at the forefront of fossil and primate studies and provide opportunities for a global community of scientists. Learn more at leakeyfoundation.org.
Discovering Us: 50 Great Discoveries in Human Origins
In 50 lively and up-to-the-minute essays illustrated with full-color photographs, Discovering Us: 50 Great Discoveries in Human Origins presents stories of the most exciting and groundbreaking surprises revealed by human origins research.
Prepared in consultation with leading experts and written by Evan Hadingham, senior science editor for NOVA, Discovering Us features stunning photographs, some taken at the actual moment that groundbreaking discoveries were made. The book presents a highly accessible account of the latest scientific insights into the ultimate question of humanity’s origins. Discovering Us was published by Signature Books.
Find Discovering Us at your local library, bookstore, or amazon.com.
Show Credits:
Discovering Us was made possible by generous support from Camilla and George Smith, the Ann and Gordon Getty Foundation, and the Joan and Arnold Travis Education Fund.
Meredith Johnson:
This is Discovering Us from The Leakey Foundation and Signature Books … an audio companion to the book Discovering Us: 50 Great Discoveries in Human Origins. Written by Evan Hadingham and read for you by Ashley Judd.
I’m your host, Meredith Johnson. We’ve reached the final installment of Discovering Us. But don’t worry! If you want more stories of science, exploration, and discovery - you can find them in the book - Discovering Us: 50 Great Discoveries in Human Origins. Available now at your local bookstore or online.
For our last story, we’re circling back to primates. There are only 5 kinds of great ape alive today. Chimpanzees, gorillas, bonobos, orangutans, and us. Among the non-human apes, orangutans are unique.
Orangutans live only in Asia - in the forests of Sumatra and Borneo. They’re intelligent, solitary animals that feed mostly on fruit. There's a lot we can learn from them - but it’s not an easy job.
Here’s Ashley Judd…
Ashley Judd:
SECRETS OF THE ORANGUTAN CYCLE
Studying orangutans is a challenging business.
As these solitary apes travel with ease through the canopy of Indonesian forests, human observers struggle to keep up, crashing through spiny undergrowth and wading through waist-high swamps.
For primatologist and Leakey Foundation grantee Erin Vogel, the daily routine starts at 3 AM with a trek to the orangutan nest.
“We like to get there before daylight breaks so we don’t miss them coming out of their nest. Eventually they wake up and the first thing they do is urinate. It’s messy and you do get urine on you and you smell bad for the rest of the day. But you smell bad anyway, because it’s 105° and 98 percent relative humidity.”
Strangely enough, the daily urine shower is more than an occupational hazard for researchers like Vogel; it turns out to be the key to unlocking an evolutionary puzzle with implications for humans as well as orangutans.
At first glance, orangutans might seem an unlikely choice for insights into our distant past.
Splitting off from the great ape family tree at least 12 million years ago, they are the least closely related to us of all large living primates.
Yet one striking fact makes orangutans—and their urine—an immediate target of interest to science.
Orangutan mothers give birth only every six to nine years, the longest birth interval of any mammal.
Seeking to understand this unusual pattern, primatologist and Leakey grantee Cheryl Knott got the idea of collecting urine to analyze hormone levels and began tracking the elusive apes in Indonesia’s Gunung Palung National Park in the 1990s.
“At the time we started here,” Knott says, “no one had really worked on hormones in wild apes. People said I was crazy.”
She collected the urine by spreading plastic sheets under their sleeping nests, then devised an ingenious way to preserve dried samples using filter paper, which she later analyzes in the lab.
When Knott matched the hormone levels of her female orangutans against daily observations of their calorie intake, she found they were responding like women.
“When orangutans are losing weight,” she says, “during times when there isn’t much fruit around to eat, they have lower hormonal levels, which makes it more difficult to get pregnant.”
Moreover, her urine tests showed that—just like humans but unlike any other great ape—orangutans store fat when food is abundant and burn fat, and ultimately muscle, when times are lean.
Why should such a distinctive, humanlike reproductive cycle have evolved? The forests of Borneo and Sumatra where orangutans live are far less lush and predictable than the African rainforests where chimps and bonobos thrive.
The result is a “boom and bust” environment, partly driven by the irregular pattern of the El Niño climate cycle.
Long intervals of little or no fruit are punctuated by explosive growth events every four to seven years known as masting, in which many tree species produce massive amounts of fruit simultaneously.
From Knott’s work, it is clear that orangutans’ reproductive and energetic cycles have evolved in response to extreme ups and downs in food supply.
During masting events, the apes gorge on fruit and put on weight; their estrogen levels are high and they mate frequently.
During times of scarcity, they survive on less nutritious leaves, stems, and bark, supplemented by termites; they lose weight and their urine contains ketones (key-tones), a byproduct of fat breakdown, which indicates that they are burning off their fat reserves.
When nitrogen isotopes appear in the urine, it is a signal that they are tapping into muscle protein, as humans do when they are on the brink of starvation or suffering from anorexia.
Despite long periods of deprivation, however, orangutans manage to get by—or so Erin Vogel concludes from more than a decade of fieldwork in Borneo’s Tuanan forest.
“We find no evidence that females stop reproducing,” she says, “and infant survivorship remains high.”
In fact, as in humans, calorie-restricted diets often appear to have a positive health impact, with less damage to cells from oxidative stress, or free radicals.
Such similarities, including their ability to store fat, “make orangutans a very interesting model for understanding our current obesity crisis,” says Vogel.
The similarities also imply that our ancient ancestors, too, may have adapted to the same kind of boom-and-bust extremes that orangutans cope with in Indonesia.
Meanwhile, Borneo has lost an estimated 100,000 orangutans in the first 16 years of the 21st century.
If this assessment is correct, the loss represents more than the total remaining population of this graceful and highly intelligent ape.
With record rates of deforestation due to palm oil development, they now face vanishing or impoverished habitats that no amount of fine-tuned survival mechanisms can overcome.
I hope you enjoyed our journey exploring thrilling discoveries in human origins research.
This audio series and the companion book, Discovering Us were inspired by the 50th anniversary of The Leakey Foundation.
The stories I read to you show how scientists work and how their discoveries help us understand ourselves and our place in the natural world. They represent just a sliver of the insights gleaned from the thousands of grantees and scholars supported by The Leakey Foundation.
It’s vitally important that our species make sense of our biological origins, and that we get the details right. That’s why I think this work is so vital, and it’s why I became an advisor to the Foundation in 2019.
I’m proud to be part of an organization whose mission provides critical support for a growing field of research through targeted grants that help us understand what it means to be human.
There’s so much more to discover and I hope you’ll join me in supporting The Leakey Foundation.
And I hope these stories inspire you to follow your curiosity and learn more about the wonders of the human journey.
Meredith Johnson:
Thank you for listening to Discovering Us. Discovering Us: 50 Great Discoveries in Human Origins was written for The Leakey Foundation by Evan Hadingham and published by Signature Books and read for you by Ashley Judd.
We are so happy you joined us on this adventure.
You can find Discovering Us at your local bookstore or wherever you buy books. Use the link in your shownotes to get your copy!
The Leakey Foundation is a nonprofit organization dedicated to funding human origins research and sharing discoveries. The science you heard about today was made possible by Leakey Foundation supporters. Visit our website to learn how you can get involved. Go to leakeyfoundation.org. That’s l-e-a-k-e-y foundation dot org.
If you want to keep learning about human evolution, I invite you to subscribe Origin Stories - The Leakey Foundation podcast - hosted and produced by me - Meredith Johnson You can find Origin Stories wherever you listen to podcasts.
Another fun way to keep in touch and meet the scientists working to uncover the human story - is through our web series Lunch Break Science. This show brings you interviews, short talks, and a chance to ask your questions. You can find out more at leakeyfoundation.org/live or on our YouTube channel. There are links for Lunch Break Science in your shownotes.
This project was made possible by generous support from Camilla and George Smith and the Ann and Gordon Getty Foundation.
Thank you for listening!