The Ape Family Tree
Where Gibbons are the strange cousins
Imagine an ape family reunion, theres a gorilla sitting in the corner, an orangutan hanging from the rafters, the chimps and bonobos running round the room, and us, probably eating some small sausage rolls. And the gibbons of course, but everyone tends to forget about them.
Apes make up the superfamily Hominoidea which includes gibbons, orangutans, gorillas, chimps, bonobos and humans. What separates us from monkeys is our lack of tail and a difference in an enzyme that regulates fat accumulation. These small adaptations have led to us, and our cousins. Our superfamily is then divided into two families, the lesser apes (Hylobatidae) which is just the gibbons and great apes (Hominidae) which is the rest of us.
Gibbons
Gibbons are the forgotten ape. To look at them, they look a bit more like a spider monkey than a gorilla. But they are part of our family. Well our superfamily at least. Gibbons are considerably smaller than other apes. They also don’t make nests, which is a defining features of great apes (except us of course, but we do so much weird stuff that we’re always the exception) and they make long-term pair bonds which is unusual in other apes. They inhabit the tropical and sub-tropical forests of Asia and are usually seen swinging through the trees. In fact they are the fastest tree-dwelling, non flying mammal. Quite a record. There are twenty species of gibbon which are divided into four genera, based on their diploid chromosome number (the number of chromosomes we have in total from both parents). The genera with the smallest number is Hoolock which have 38, the one with the most being the genera Symphalangus which is only the siamang, who have 50 chromosomes compared to our 46.
Gibbons diverted genetically from other apes between 24-16 million years ago. They provide a bridge between the old world monkeys (monkeys in Europe, Africa and Asia) and the great apes. Their genome was first sequenced in 2014 by the German primate centre, which showed that we share 96% of our genome with them. They are truly beautiful animals which shouldn’t be left out of our family reunion, even if they are more like third cousins than siblings.
Orangutans (Pongo)
So, the gibbons have diverged and we are left with the common ancestor of all great apes. Who were they? We don’t know. Searching the fossil record, there are some candidates but nothing can be known for sure. But we do know, of modern great apes, orangutans diverged first from our ancestor, with their genus splitting off between 19 and 15 million years ago (although like almost everything in zoology, this is debated). They were originally found across South East Asia, but are now only found in Borneo and Sumatra. There are three living species, the Bornean Orangutan, the Sumatran Orangutan and the Tapanuli Orangutan which was first categorised in 2017. They are all part of the genus Pongo, but if you go one level higher, they are in the sub-family Ponginae. Many extinct apes are also in this sub-family, including Gigantopithecus - the Giant Ape. Modern orangutans are considered to be most closely related to the Khoratpithecus genus, a group of extinct great apes that lived in Thailand between 5-7 million years ago.
Gorillas (Gorilla)
So the Gibbons and the Orangutans have gone on to another party - the next to leave were the Gorillas. They diverged from the common ancestor around 7 million years ago. We know a lot less about their evolutionary path than we do orangutans because the fossil record is so poor in the areas where they live. There are two species of living gorilla, the Western Gorilla and the Eastern Gorilla (although there is a debate about whether there is a third). It is believed that these species, or subspecies as some would argue, diverged from each other during an Ice Age when the populations were separated. And they have the very creative genus name, Gorilla. Its nice when something in zoology is self-explanatory.
Chimpanzees and Bonobos (Pan)
Both Chimpanzees and their lesser known cousins, Bonobos, are in the genus Pan. They began on their own evolutionary path soon after gorillas, and split from each other around 2 million years ago. Chimpanzees are bigger than bonobos, which are the smallest species of great ape. Chimps are especially adaptable, able to live in wetland, dry forest and rainforest environments and eat a wide variety of food, including both plants and meat. Both species are noted for their incredible intelligence and their ability for wide ranging emotions, such as empathy and patience. Previously, it has been argued that Bonobos are much less aggressive than Chimpanzees but this has been contested, including this year when a study put forward evidence that wild Bonobos were nearly as aggressive as Chimps.
We’re nearly at the point in the evolutionary story where we appear, but before we do, let’s discuss the world that the Great Apes evolved in. The Miocene is the time period between 23 million years ago and 5 million years ago. Throughout this period, the earth cooled significantly, causing a series of ice ages. Importantly, Afro-Arabia collided with Eurasia, allowing species like the orangutan to leave Africa. The Mediterranean almost completely evaporated during this time too, only refilling when the Straight of Gibraltar opened up. Grasslands massively expanded during this era, causing forests to reduce. This could be a reason why humans evolved to walk upright to be able to cross more land and see above the long grasses. At the end of the Miocene, the world looked much like it did today. The only land feature that wasn’t complete was there was no land bridge between North and South America. Many modern animals existed too, including bears, canids, equids, beavers and whales.
Humans (Homo)
After the Miocene was the time where we made our first appearance. And by we, I mean species in the Homo genus. There have been approximately 21 species of human and at least eight existed at the same time as our species - Homo Sapiens. The Homo genus first appears around 2.75-2.8 million years ago, but our species only appears around 300,000 years ago. It is possible the earliest human species was Homo Habilis - the handy man. Homo Habilis used both tools and lived in groups, like both Chimpanzees and Humans. While this was social, it was also for protection from predators - Homo Habilis skeletons have been found with crocodile and leopard bites! Some time after came Homo Erectus who spread further afield, into Europe and all the way into South-East Asia. With some species in-between, we eventually arrive at our two most recognisable Homo species, us and Neanderthals. Both species lived together for many years, until Neanderthals went extinct leaving us the sole survivor of the Homo genus, and with Chimpanzees as our closest living relative as humans and chimpanzees share 98.4% of DNA. But some argue that not all other species of human have gone fully extinct, as modern European DNA contains about 2% Neanderthal DNA, while modern Melanesian DNA contains around 6% Denisovan DNA (another species of human who ranged across Asia). So maybe they aren’t totally gone after all. Maybe ancient humans were more lovers than fighters. Or probably like we are now, they were all a bit of both.
So, there we go, the Ape family tree. It is an incredible complex and diverse group, and a fascinating evolutionary story. Unfortunately all species of Great Ape apart from us are endangered, most critically so. Chimpanzees are the most numerous apart from us, with 200,000 in the wild. However there are still 40,203 times more humans than Chimps and we are continually destroying the habitats and endangering the lives of all other Great Ape species. Maybe we should all consider our relationships beyond our own species more, especially when it comes to our own family. Not all families get on, but there is no reason why this has to be the case for the Ape family. Nothing can be more incredible than when you look into the eyes of an Ape and see someone who looks like yourself. It should remind us how we are still part of nature, however much we pretend we aren’t. After all, family is everything.