They’re our closest living relatives of the animal world, some sharing almost 99% of our DNA. They are far more intelligent than scientists once realized, with elaborate social structures and family networks. They make sophisticated use of tools. And they are among the most endangered mammals on the planet. These are the apes, a group of animals about whom we still have much to learn despite decades of scientific research.
The ape most famous for close genetic ties to humans is the chimpanzee, one of the “great apes.” Chimpanzees live only in tropical forests of Central Africa, the continent where modern humans first evolved some 100,000 years ago. Despite this long history of chimps and humans living in close proximity, the scientific community knew little about their behavior in the wild until the 1960s, when primatologist Jane Goodall began studying chimps at Gombe Stream in Tanzania. By carefully and patiently observing them in their natural habitat, Goodall became the first scientist to witness chimpanzees making tools, hunting and eating meat, and displaying complex social behaviors, among many other discoveries.
Today we know chimpanzees live in loosely connected social groups of as many as a few hundred individuals, divided into more closely knit subgroups. Mother chimps spend years caring for their offspring and family ties can remain important even once chimps reach maturity. Chimpanzees use a wide array of vocalizations and facial expressions to communicate. Scientists have even observed cultural differences between chimpanzees over different parts of their range, with groups in some areas practicing behaviours that are never seen in other chimpanzee communities.
It is now widely known among even the general public that chimpanzees share almost 99% of humans’ DNA. However, in the last few years evidence has emerged that another ape species may be as or even more closely related to us. This is the bonobo, formerly known as the “pygmy chimpanzee.” Genetic studies suggest it’s a toss-up whether chimpanzees or bonobos actually deserve the title of closest living human relative. But studies of human, chimpanzee, and bonobo muscular systems show bonobos appear to be more physically similar to us.
Whereas as chimpanzee societies are male-dominated, bonobos are matriarchal. They are also known for being less prone to social conflict than chimpanzees, and for using sex to maintain social bonds. Bonobos eat mainly fruit, other vegetation, and insects, and unlike chimpanzees they hunt meat only occasionally. From a conservation standpoint, another important fact about bonobos is they are restricted to only a single country: the Democratic Republic of the Congo.
Only slightly less closely related to us than chimpanzees and bonobos are gorillas. There are actually two species, the eastern and western gorillas. Eastern gorillas are divided into two subspecies: the eastern lowland gorilla and mountain gorilla. The western species is likewise divided into the western lowland and Cross River gorillas. Like other African great apes gorillas are social, but their networks are smaller than those of chimpanzees. Gorillas travel in groups related by family ties, consisting of as few as five or as many fifty individuals. Groups are dominated by an older male known as the silverback.
The only great apes found outside of Africa are orangutans. They differ from African great apes in several important respects, including their habits. While gorillas, chimpanzees, and bonobos are all social, orangutans are solitary with adults normally coming together only to mate. They are also the only great apes to spend most of their time in the trees. This makes orangutans the largest truly arboreal, or tree-dwelling animals in the world.
Orangutans are found only on the Southeast Asian islands of Borneo and Sumatra, and for many years scientists recognized two species, each confined to one of the islands. However, in 2017 a third species was announced. Known as the Tapanuli orangutan, this species lives in northern Sumatra and was previously thought to be simply a population of the Sumatran orangutan. Tapanuli orangutans are the most recently-described great ape species–and with only 800 individuals are also the most endangered.
More than a dozen additional ape species live in the tropical forests of Southeast Asia. These are the gibbons, or “lesser apes.” They get this name not because they are somehow less important than great apes, but simply because they are much smaller. Like orangutans, gibbons are mainly arboreal. They are famed for swinging hand-over-hand through the tree branches at speeds of up to 35 miles per hour,
Sadly, all or most apes are at risk of extinction due to factors like deforestation and hunting for the meat and pet trades. Although Tapanuli orangutans have the smallest population of any great ape, all the others are classified as endangered or critically endangered. In Africa threats like logging, poaching, and armed human conflict threaten great apes. Gorillas have also been seriously affected by the spread of the Ebola virus, which is deadly to them just as it is to humans. While the outlook for Africa’s great apes is grim, there are rays of hope. For example, thanks to conservation efforts mountain gorillas has seen a modest population increase recently.
In Borneo and Sumatra the single largest threat to orangutans–and gibbons found on the islands–is the conversion of rainforests into palm oil plantations. Used both as biofuel and an ingredient in everything from peanut butter to shampoo, palm oil production has skyrocketed as demand for these products increases worldwide. Limiting this industry’s expansion represents the best hope for Borneo and Sumatra’s apes. Fortunately, consumer-driven campaigns led by groups like Greenpeace and the Rainforest Action Network have had success pressuring some U.S. food companies–including Kellogg’s, Mars, and General Mills–to adopt policies limiting their use of palm oil that is not sustainably grown. More public pressure is needed to persuade additional companies to cut ties with palm oil deforestation.
Most people know iconic great apes like the mountain gorilla are endangered. However, the apes at greatest risk of imminent extinction are gibbons. With only about two dozen individuals in existence, the Hainan crested gibbon has the smallest population of any primate species. They live only in a single forest on the island of Hainan in the South-China Sea and have lost 99% of their habitat. Only slightly better off is the world’s second-rarest primate, the Cao-Vit gibbon. Only 100 members of this species survive in a forest in Northeast Vietnam. Though not quite as rare as these two, most other gibbon species are also at severe risk. Habitat loss is the most serious threat, but gibbons are also hunted for meat, with babies sometimes being sold into a life of captivity in the pet trade.
If our ape relatives survive into the latter part of the twenty-first century, it will be because of the caring actions of people all over the world. Whether by writing to major food brands and encouraging them to adopt sustainable palm oil policies, or supporting conservation groups working to protect great apes and gibbons from poaching and habitat loss, you can take action wherever you live. If you travel to Central Africa or Southeast Asia, consider patronizing eco-tourist organizations that help local communities profit from conservation.
With their intelligence, complex societies, and human-like expressions, apes are a reminder that humans are not as separated from our animal ancestry as we sometimes like to think.
By saving these remarkable primates from extinction, we are also preserving links to our own rich evolutionary heritage.