SCIENCE fiction? No, it actually happened. Between 20 and 7 million years ago, Earth really was the planet of the apes. At least 100 species roamed the world before the first humans appeared. They were remarkable in number and diversity, but are more fascinating still for what they tell us about our own origins. Key human traits including big brains, dexterous hands, erect posture and long childhood can be traced back to this period. And the really surprising thing is that these features all evolved in European apes.
The news is full of discoveries that change our ideas about human evolution. But when we think about our ancestors, we tend to focus on the past 8 million years, after our lineage split from that of chimpanzees. What came before that, though? Three decades of study have convinced me that this early period was absolutely crucial. There鈥檚 no doubt that apes originated in Africa, or that our more recent evolution happened there. But for a time between these two landmarks, apes hovered on the verge of extinction on their home continent while flourishing in Europe. What鈥檚 more, the transformation of European species during this time made us who we are.
The fossil record indicates that apes started out in Africa about 26 million years ago, and were firmly settled there 4 million years or so later in the form of . A close relative that lived 18 million years ago paints an extraordinary picture of these early apes. Remains of Ekembo were found preserved Pompeii-like in layers of volcanic ash on Rusinga Island, Kenya. What we have is an animal with arms and legs of equal length, a horizontally oriented backbone and a brain about the size of a modern baboon鈥檚. In other words, Ekembo looks like a largish monkey, but with a key difference 鈥� no tail. Tails allow many monkeys to balance, but Ekembo compensated with more limber wrists and hips and more powerful hands and feet for grasping. .
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鈥淲ithout the developments that happened in Europe, humans would never have evolved鈥�
A second momentous change arose in a contemporary of Ekembo, called Afropithecus. The two look remarkably similar from the neck down, but have quite . Those of Afropithecus are far more robust, adapted for powerful crushing and grinding. Equipped like this, it could extract nutrients from foods with husks and shells impenetrable to the more slender jaws of Ekembo. It may not sound too impressive, but this ability had huge repercussions for apes. With the capacity to eat a wider variety of foods, they could expand their range out of Africa and into Europe and Asia.
belong to the genus Griphopithecus and date from 17.5 million years ago. They inherited the powerful bite of Afropithecus but their teeth were a little different, more like those of our earliest direct ancestors in Africa. According to the fossil record, griphopiths were living in parts of what are now Germany and Turkey, about 17 million years ago. At this time much of . Seasonality was low and the climate was suitable for animals, like apes, that rely on a continuous year-round supply of fruit. However, as griphopiths migrated north, conditions would have proved more challenging 鈥� ultimately driving them to evolve new adaptations.
As well as moving northwards, griphopiths returned south, so that by some 15 million years ago their range covered an area from Europe to East Africa. One member of the family, around this time, had evolved limbs with larger elbows and wrists, perhaps anticipating the development of the longer arms found in living apes and the earliest humans. However, griphopiths seem to die out in Africa, though we don鈥檛 know why. In fact, the fossil record indicates that between 14 and 8 million years ago, apes were a rarity there, and most were from ancient lineages related to Ekembo and bound for extinction.
Kings of swing
By contrast, in Europe, truly modern-looking great apes were emerging. Around 12.5 million years ago, the first ape with a more upright posture appeared. Pierolapithecus, sometimes called Dryopithecus, was unearthed in Catalonia, northern Spain. The partial skeleton has a more vertical backbone, a broad chest, arms longer than legs, very mobile wrists, and long, curved, powerfully grasping fingers. These features made Dryopithecus look more like today鈥檚 great apes. They also indicate a major transition from walking like a monkey on all fours to , hanging and swinging below branches.
Hispanopithecus, living in what is now Catalonia a few million years later, had longer arms and an even more upright back. So did Rudapithecus, its contemporary in what is now Hungary. More significantly, to our knowledge, Rudapithecus is the first ape to evolve two other key features of modern great apes 鈥� a big brain and extended childhood.
In 1999, my team recovered from the site at Rudab谩nya. Structural details 鈥� including the braincase, jaw and base of the skull 鈥� all resemble the anatomy of living African apes, especially gorillas. The brain was comparable in size to that of living chimpanzees. And evidence from dental growth studies indicates that Rudapithecus had a more lengthy childhood than its ancestors.
In my new book, The Real Planet of the Apes, I argue that these and other key developments in ape evolution were stimulated by the challenging ecological conditions they encountered in Europe. Apes colonised the continent during the warmest phase of the Miocene, but by 14 million years ago it was cooling, forests were becoming less dense and food scarcer. To survive, apes had to develop new strategies to find food both in the trees and on the ground. This led to physical and cognitive changes. Big brains and extended childhoods are associated with higher levels of intelligence, memory, complex learning and strategic thinking, important tools for apes living in challenging seasonal environments 鈥� and characteristic attributes of our own species.
Gradually, conditions in Europe became too tough for apes and about 10 million years ago they quit the continent for Africa. There, the separate lines of our closest living relatives evolved, the gorillas branching off first and then chimps and humans veering apart. But the anatomy and behaviour of the earliest humans makes sense only in the light of the Miocene apes. I鈥檇 go as far as to say that without the developments that happened in Europe, humans would never have evolved.
This article appeared in print under the headline 鈥淭he grand tour that made us鈥�
