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Ancient Ape Discovered: Last Ape-Human Ancestor?

National Geographic News
November 18, 2004
 
In Spain scientists have discovered 13-million-year-old fossils of new species of ape. The species may have been the last common ancestor of humans and all great apes living today. (See pictures of the new ape species.)

The great apes—which later gave rise to humans and which now include orangutans, chimpanzees, and gorillas—are thought to have diverged from the lesser apes about 11 to 16 million years ago. Today's lesser apes include the gibbons.

The new species was christened Pierolapithecus catalaunicus, after the village, Els Hostalets de Pierola, and region, Catalonia, where it was found. Like great apes and humans, Pierolapithecus catalaunicus, had a stiff lower spine and other special adaptations for climbing trees.


The fossil skeleton's age would make it just old enough to be the last ancestor common to all modern great apes and humans, the researchers say in the November 19 issue of the journal Science. Or, if the ancestor wasn't Pierolapithecus exactly, it may have looked a lot like Pierolapithecus and been closely related.

Salvador Moyà-Solà of the Miguel Crusafont Institute of Paleontology in Barcelona, Spain led the team that made the discovery. He and his colleagues were just getting started at a new digging site near Barcelona when they discovered the first piece of the skeleton. It was a canine tooth, churned up by a bulldozer that was clearing the land for digging.

"Paleontologists in Spain say you don't find a good fossil, the good fossil finds you," Moyà-Solà said in a news release.

The researchers kept digging and uncovered one of the most complete skeletons ever found from this time period, the middle Miocene epoch.

Fossil evidence from this period is sparse. Researchers have long been searching for the great ape ancestors that emerged after the evolutionary split between the great apes and the lesser apes.

The scanty fossil record has revealed several contenders for the common ancestor, including Kenyapithecus and Equatorius or the older Morotopithecus and Afropithecus. But the fossils that do exist indicate that these ape species were more primitive than Pierolapithecus, Moyà-Solà said.

Why This Find Is Important

"The importance of this new fossil is that for the first time, all the key areas that define modern great apes are well preserved," Moyà-Solà said. The fossil find includes parts of the skull, ribcage, spine, hands, and feet, along with some other pieces (see picture gallery).

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.

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 Miocene—before 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 kilograms—a little smaller than a chimpanzee.

This report was compiled from press materials released by Science.

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