By studying the fossil bones, the researchers could tell that they belonged to an ape that shared many important similarities with modern great apes and humans.
In particular, this ape had special adaptations for tree climbing, just like humans and other great apes do. Pierolapithecus had a wide, flat ribcage, a stiff lower spine, flexible wrists, and shoulder blades that lay along its back. These features would have helped Pierolapithecus assume an upright posture and climb up and down, the researchers say.
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Monkeys, which belong to a more primitive group, have more generalized, versatile movement abilities and lack these particular traits.
"The thorax [ribcage] is the most important anatomical part of this fossil, because it's the first time that the modern apelike thorax has been found in the fossil record," Moyà-Solà said. Pierolapithecus's thorax is similar to that of modern great apes because it is wider and flatter than a monkey ribcage.
Specimens of other apes, such as Proconsul or Equatorius, have included some rib fragments, "but the [structure] is primitive, completely like monkeys," he said.
In addition, Pierolapithecus's shoulder blades lie along its back, as do those of modern great apes and humans. In monkeys, the shoulder blades are on the sides of the ribcage, the way they are in dogs.
In Pierolapithecus, humans, and modern great apes, the lumbar section of the lower spine is relatively short and stiff. The vertebrae in this part of the spine therefore differ from monkey vertebrae, which are more flexible.
These adaptations would have affected Pierolapithecus's center of gravity, making it easier to assume an upright posture and to climb trees, the researchers say.
Also, in Pierolapithecus , humans, and modern great apes, only one of the two forearm bones "articulates," or attaches flexibly, to the wrist. This trait allows a relatively large degree of hand rotation and probably helped with climbing, according to Moyà-Solà.
Pierolapithecus's skull was also distinctly great ape-like, the scientists say. The face is relatively short, and the structure of the upper nose lies about even with the eyes. In monkeys, the nose protrudes between the eyes, interfering with the plane of vision.
The Fossil's Monkeylike Features
Pierolapithecus also had some more primitive, monkeylike features, such as a sloped face and short fingers and toes. Moyà-Solà and his colleagues think this is a sign that various traits emerged separately and perhaps more than once in ape evolution.
For example, climbing and hanging abilities are often thought to have evolved together, but Pierolapithecus's short fingers indicate that it didn't do a lot of hanging, the researchers say. Hanging-related traits may have evolved several times, showing up later in great apes, the researchers propose.
Although Pierolapithecus was discovered in Spain, Moyà-Solà believes that this species probably also lived in Africa.
"Africa is the factory of primates. In the fossil record of the lower and middle Miocene in Africa, we have found a fantastic diversity of primitive hominoids with monkeylike body structures. In Eurasia apes appeared suddenly in middle Miocenebefore then primates there were nearly unknown. For that reason, the source area in my opinion is Africa," he said.
The individual that the paleontologists discovered probably was male, was a fruit-eater, and weighed about 35 kilogramsa little smaller than a chimpanzee.
This report was compiled from press materials released by Science.
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