In March of 1838, an orangutan named Jenny at the London Zoo had a profound impact on a young Charles Darwin. He had just returned from his voyage around the world in the HMS Beatle, and his ideas of natural selection and evolution were only notes in his journal. He couldn’t help noticing how this young orangutan’s behavior was very similar to that of a human child, and spent months studying her. These interactions with Jenny ultimately shaped Darwin’s ideas of human evolution, and led him to the provocative conclusion that humans were not created separately from other animals.

Today, two species of orangutans can be found in the wild. Bornean orangutans are found exclusively on the island of Borneo, Indonesia, while Sumatran orangutans are found exclusively on the island of Sumatra, Indonesia. Bornean orangutans have darker hair, wider faces, are slightly larger, and are more likely to move on the ground than Sumatran orangutans. Sumatran orangutans are known to form closer social bonds than their Bornean sister species. Despite their differences, both orangutan species are threatened with extinction. The IUCN Red List classifies both orangutan species as critically endangered.

Orangutans display sexual dimorphism, which means that there are distinct differences in appearance between males and females. On average, adult males weigh twice as much as adult females. Males exhibit bimaturism: Some adult males develop large throat sacs and cheek pads called flanges, while others do not. Having flanges is a sign of dominance, and females prefer flanged males over non-flanged males. Research suggests that the development or absence of these flanges might be socially controlled. Flanged males use their large throat sacks to help them long call, a vocalization that can carry for almost a mile, that attracts females and warns other males of their presence.

Tool-use varies greatly across orangutan populations. The way that tools are used is passed down from generation to generation, suggesting that orangutans exhibit the first signs of cultural transmission. This pushes our understanding of the origin of culture, and culturally transmitted behavior, back to 14 million years ago – the time when orangutans evolved. The study of culture in orangutans shows how much we still have to learn about the species, and how critical they are to our understanding of human evolution.

Orangutans are so integral to the rainforest ecosystem that they are often called the “gardeners of the rainforest.” Their diet covers over 400 food types, and 65%-90% of their daily diet are fruits. Because they cover large ranges of habitat, they play an important role as seed dispersers. With the help of orangutans, plant communities receive exotic seeds from far reaches of the forest, and the next generation of plant communities benefit from having high genetic diversity. With genetic diversity, more plant communities inherit the resilience needed to survive in extreme or stochastic weather patterns. In this way, orangutans support forest regeneration, and defend these rainforests against climate change.

The palm oil industry is one of the greatest threats to the future of the orangutan species. Palm oil is an ubiquitous ingredient found in 50% of all of our food and household products, including cookies, lipstick, laundry detergent, ice cream, candles, peanut butter, and many more. Because it is the most productive, versatile and cost effective oil seed in the world, it is still in great demand. The conversion of rainforests to oil palm plantations reduces and fragments the habitats of orangutans. Because orangutans are used to large habitat ranges, fragmentation causes them to be stranded on “islands”, leading to more competition and stress. As more of their habitats disappear, more orangutans raid crops for food, and are killed by farmers in the process.

Organizations are taking notice that one of our closest remaining relatives may disappear from the face of the Earth without our help. NGO’s work with the local government to enforce the protection of designated areas, and ensure that corridors connect the rainforests. Multinational establishments promote products that are made from sustainable palm oil and responsible forestry practices so that consumers can be more educated in their purchase decisions. Local conservation programs help to rehabilitate orangutans, reintroduce orangutans back into the wild, and are research hubs for orangutan researchers around the world.

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