Fossil Apes

At present monkeys far outnumber the apes, but back in the Miocene, the situation was reversed. There are comparatively few monkey fossils in the Miocene. At that time, apes had radiated to fill most niches that monkeys later took over and fill today. The ape diversity decreased through time so that by the Pliocene, monkeys were dominant and there is a rich monkey fossil record from around the Old World to prove it. Possibly, monkeys simply outbred apes. Great ape mothers wait over four years between births because their offspring develop much slower than monkeys.

Most of the fossil record for apes hails from East Africa and Europe with a few species found in Asia and Indonesia. Early apes show an increase in body size and a diversity of locomotor modes from those of their monkey-like ancestors. Although there are numerous Miocene apes on record, not one is confidently placed on the direct lineage leading to humans. The mosaic nature of the apes, that is their mixture of traits that makes them unlike any living apes today, creates a challenge for paleontologists to interpret them.

During the Miocene, East Africa was covered in rain forests and filled with apes of a broad variety of sizes and diets. These fossil species shared trends with living apes: large brains, fewer vertebrae, long upper limbs, and no tails. Their skulls and teeth show they ate fibrous foods like fruits, nuts, and tough vegetation. They had thick tooth enamel, rounded cusps, flared cheekbones for jaw muscles (temporalis) to fit underneath. Postcranial adaptations of these apes included anatomy built for arbo-reality, climbing, and brachiation.

Only one Miocene ape has an agreed-upon ancestor-descendent relationship with a living ape and that is Sivapithecus from 14 Mya in the Siwalik Hills of Pakistan. Sivapithecus is an ancestor of modern orangutans. There are many candidates, but as of now here is no consensus as to which one(s) is the ancestor of the African great apes: gorillas, chimpanzees, and humans.

The best-known genus of Miocene ape is Proconsul known mostly from sites on Rusinga Island in the Kenyan waters of Lake Victoria, dating from 20 to 18 Mya (Figure 3.5). There are over twelve partial skeletons of Proconsul and several jaws, isolated bones and teeth, and one well-preserved skull. Proconsul is best imagined as having a monkey-like body with ape-like traits in the teeth (fruit-eating adaptations), skull, some aspects of the limbs, and lacking a tail. Certainly the lack of evidence for something, especially in the fickle fossil record, does not prove it does not exist. However, none of the partial skeletons have preserved caudal (tail) vertebrae and the sacrum does not appear to have any anatomical ties to a tail. Since it is assumed that tails were lost only once in hominoid evolution, the lack of tail in Proconsul lends support to its ape status.

Numerous Miocene apes with ape-like features could have been direct ancestors to living apes. Morotopithecus from 21 Mya in Uganda is

Figure 3.5 Two 18 Mya feet of the stem ape Proconsul were discovered still in anatomical articulation at the Kaswanga Primate Site on Rusinga Island, Kenya. Photograph by Mark Teaford.

interpreted to have brachiating and suspensory characteristics like the great apes. As fossil apes approach the middle Miocene in age, they take on many more modern characteristics. The African fossil apes Na-cholapithecus, Kenyapithecus, Kamoyapithecus, Samburupithecus, Otavipithe-cus, and Afropithecus are all contenders for African ape ancestors. But there are even more ape-like species in Europe. Around 12 Mya Dryop-ithecus emerges in Spain, Romania, France, and Hungary. Oreopithecus is so ape-like, it has been interpreted to even have adaptations for incipient bipedalism, but those notions are not strongly supported. Other European fossil apes include Ouranopithecus (Greece), Ankarapithecus (Turkey), Griphopithecus, and Grecopithecus. The most recent find, a well-preserved partial skeleton of Pierolapithecus shares many traits with living great apes. The Miocene ape record is puzzling. It is assumed that since all but one of the great apes live in Africa that they evolved there, but the fossil apes from Africa are more of a mosaic of monkey-like features than their less monkey-like, more ape-like relatives in Europe. After more fossils are found in the late Miocene of both Africa and Europe, the story of ape evolution and the emergence of the hominin lineage will be much clearer. --

GlGANTDPITHECUS! A REAL BlGFOOT

Perhaps the legend of Bigfoot has such staying power because of its ancient roots. The Pleistocene fossil record of China contains teeth and jaws of a prehistoric Bigfoot called Gigantopithecus blacki. Although no skeletons (or foot bones) have been discovered, the estimated body size based on the size of the teeth is enormous, at over 400 kg (880 lbs), and that is a conservative estimate. Even if the teeth were larger than expected for body size, Gigantopithecus was still the largest known primate to ever exist. Unlike the legendary Bigfoot, Gigantopithecus would have probably walked quadrupedally like another comparable legendary character, King Kong. The giant ape only went extinct about 100 Kya, so it had plenty of temporal and geographic overlap with Homo erectus.

Gorillas have humanlike feet because adaptations for carrying their large heavy bodies and for spending time on the ground actually mimic adaptations in human feet that accommodate for bipedalism and terres-trialism. As a consequence, gorilla footprints also look similar to those of humans. If Gigantopithecus was anything like modern gorillas, which it probably was, its feet could have been gorilla-like and maybe even humanlike. Perhaps the Bigfoot trackers of the world should trek to China to find fossilized footprints of a genuinely real, albeit ancient Bigfoot.

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