1. We both share signs of pregnancy
Cheryl Knott, a biological anthropologist who studies orangutans in Gunung Palung National Park in Indonesia, made her own startling discovery about the similarities between humans and these shaggy red-haired great apes. “[W]e and orangutans are so similar that Knott can use standard drugstore test kits on urine from female orangutans to determine whether they’re pregnant,” reported National Geographic.
2. We both “talk” about the past
Recent findings suggest that orangutans can recall their history. As Science magazine reports, “When wild orangutans spot a pr.eda.tor, they let out a loud ‘kiss-squeak,’ a call that sounds like a human smooching. That noise tells tigers and other enemies, ‘I’ve seen you,’ scientists believe, and it also lets other orangutans know d.ang.er is near. Now, researchers report having heard orangutans making this call long after pr.eda.tors have passed—the first evidence that primates other than humans can ‘talk’ about the past.” Orangutans are only one of the animals that you didn’t know could talk.
3. They know how to laugh
“Perhaps the most humanlike behavior is the laughing by apes when they are being tickled,” Frans de Waal, a primatologist at Emory University, told LiveScience. “It is low-pitched compared to human laughter, but the facial expression and the waxing and waning of the laughing sounds are eerily human to the point that those of us familiar with these vocalizations cannot stop ourselves from laughing too.”
4. They have a hairline like us
It’s the physical traits, rather than the strictly genetic ones, that researchers say link orangutans so closely to humans. One of those traits: “Humans and orangutans actually have a hairline,” in contrast to virtually all primates, Jeffrey Schwartz Jeffrey Schwartz, co-author of a paper on the connections between us, told National Geographic told National Geographic.” We both have hair that “comes down to the top of the eyes.”
5. We have a common ancestor
One of the most controversial things Schwartz and his fellow researcher John Grehan concluded in their study was that humans and orangutans share a common ancestor that is not shared with other great apes. “We infer that the human–orangutan common ancestor had established a widespread distribution by at least 13 Ma [mega annum, or million years],” Schwartz and Grehan wrote. Sadly, orangutans made our list of wild animal species you didn’t know were end.ang.ered.
6. They pass that learning on to the next generation
Social learning that gets passed down through multiple generations is a building block of culture, and “the existence of culture in humans [was thought] to be one of the key factors that differentiates us from other animals,” writes Olivia Solon in Wired UK. But the fact that orangutans can do it, too, means that “culture in humans and great apes has the same evolutionary roots.” This may all be moot if we don’t protect their habitats, however—see how many orangutans are left in the world.
7. They learn from each other
It wasn’t so long ago that humans believed we were the only species that taught each other things that related to our own specific experiences. Not so, according to Orangutan Foundation International. In fact, orangutan populations in Borneo “use handfuls of leaves as napkins to wipe their chins while orangutans in parts of Sumatra use leaves as gloves, helping them handle spiny fruits and branches, or as seat cushions in spiny trees.”
8. They have similar mouth features
Orangutans share at least 28 physical traits with humans; that’s 26 more than chimps and 21 more than gorillas. Inside our mouths, we’ve both got flat molars that are covered with a thick layer of enamel. And, according to researcher Schwartz, “A hole in the roof of the mouth that was supposedly unique to humans is also present in orangs.”
9. They bond with Mom
“Probably only humans have a more intensive relationship with their mothers,” according to Orangutan Foundation International. “Primatologists believe that orangutans have such long ‘childhoods’ because there is so much that they need to learn before they can live alone successfully.” Juvenile orangutans hang with mom till they’re about 8 years old, and nurse for pretty much the whole time.
10. Brains, bones, and blades
Other tell-tale features that link orangutans to humans, to the exclusion of chimps, bonobos, and gorillas? According to National Geographic, they have “greater asymmetries between the left and right side of the brain, an increased cartilage-to-bone ratio in the forearm, and similarly shaped shoulder blades.”