Miocene Apes and The Smaller Yeti (Migu)

Reconstruction-portraits for the Scientific American article on Miocene apes, artwork by John Gurche on the left. The two reconstructions above represent forms of Sivapithecus, thought to have been directly ancestral to the Orangutans of Asia. Miocene apes in general seem to have gone through the three stages illustrated at left: the small and early Proconsuls which had apelike teeth but had be monkeys and lived much like them when they were in their heydays went more or less directly into the larger and more diversified Dryopithecines (best represented in Europe) and then on to the more fully apelike forms typified by Sivapithecus. John Gurche remarks that Sivapithecus took everything that made apes distinctive and then exaggerated the features as much as they could.l chart placing fossil apes and humans together and showing their assumed relationships.

Fig. 1 Reconstructions and partial reconstructions of the craniums of fossil apes: (a) Proconsul, (b) Afropithecus, (c) Oreopithecus, (d) Ouranopithecus, (e) Sivapithecus, and (f) Ankarapithecus.

Oreopithecus, one of the Miocene apes of which we have full skeletons, and its reconstruction below. It has bipedal adaptations and limb proportions about like a gorilla, and it evidently had an ecleclectic selection of locomotor modes including suspesnion by the arms ("Swinging through the Trees") Please note the widely opposed big toe of the foot in the painting below.

Ardipithecus feet, much more recent fossil form but evidently still the conservative form of the hands and feet, much like Oreopithecus (skeletons for Ardi hands and feet below)mal stance on the ground includes a widely-spread big toe. Ardipithecus survived until about four million years ago and is thought to have been directly ancestral to Australopithecus.

Hands of fossil apes. The two hands on the left are different specimens of Oreopithecus, which are smaller and more generalized than the later ape pictured on the right, with more obvious adaptations for brachiation and knuckle-walking.   are shown below, indicating how far out the opposed big toe could rotate.

Oreopithecus and the other conservative early apes, right up to Ardipithecus, had the same shorter toes and widely-separated big toe as shown in casts of the Orang Pendek feet. The orangutan and Chimpanzee ancestors both had feet of this type, it was the primitive pattern. More specializations related to climbing trees followed this stage, including having the fingers and toes grow longer and more curved, and the arms lengthened and legs shortened along with this (the primitive condition has all four legs at about the same length, and even in the conservative ape types this also tends to be true. Knuckle-walking developed at different times in all three lines of great apes (chimpanzees, gorillas and orangutans) and they all have different adaptations to it: the way that chimpanzees and orangutans hold the hands when they are on all fours are also quite distinctive from one another.

The Miocene apes began to radiate out into different ecological niches by exploring different modes of locomotion. The more conservative types of Miocene apes were upright on the ground on they had committed to climbing upright in the trees rather than running along branches on all fours like monkeys do. The pattern of locomotive flexibility survived up until the Australopithecines came along, and Bonobos still tend to be that way.The earlier types of apes such as Proconsul still had the limb proportions of a baboon and they walked flat on the soles and palms of the hands, like the monkeys still do.

Above, mural at the AMNH done by Jay Matternes showing Sivapithecus climbing upright and contrasted with Proconsuls running on all fours. At right, the skeleton for the primitive proconsuls and below, a reconstruction. A small proconsul would have been the size of a rhesus monkey and a big one the size of a big baboon: they rarely stood up on their hind legs alone.

Incidentally, NO species of Miocene or Pliocene apes known from fossils has been definitively identified as being a knuckle-walker like the modern great apes. NONE of them.

A variety of early apes at the Proconsul and Dryopithecus level. These early apes were ecologically replaced by Old World monkeys when it turned out the monkeys could breed faster. They are sometimes called "Dental apes" because about the only way you could tell they were apes was from their teeth. Gibbons also descended from them and developed arm-suspension tree-climbing and brachiation or "Swinging through the trees" independantly of the other apes. Some of thir early relatives also still had tails-and long tails at that

Above, some later African apes began to develop the adaptations typical of gorillas and chimpanzees. In Asia the descendants of Sivapithecus did also, but independantly with different adaptations.

Sivapithecus fossil and Orangutan skull.

Sivapithecus males and females were so dimporphic (differene from each other) that originally their fssils were put into distinct genera, the females being thought to be much more advanced. At the right, a very "Yeti"-like reconstruction portrait.

Above some more reconstructions showalking upright on the ground, and the skeleton of Ardipithecus which still showed adaptations for walking upright on the ground, in the conservative Miocene Ape pattern. The immediate ancestors of the orangutans were the descendants of Sivapithecus which lived in Southern Asia and were walking upright on the same primitive (Orang Pendek) pattern of feet, but they grew to about the same size as gorillas so we know they were NOT living in trees nor yet would they have any of the usual orangutan adaptations for living in the trees as a consequence. Paleontologists commonly call the remains "Fossil Pongo" in the absence of a better names no real agreement over the classification. The "Fossil Pongo" is undoubtedly the dirsct forerunner of the "Yetis", Yerens, Xing-xings and Hibagons. Below at left is Michel Raynal's depiction of "le Petit Yeti" of Heuvelmans, the smaller red-haired type of "Abominable Snowman" described by the Sherpas: educated Tibetans translate the meaning of its name as being  like "Chimpanzee". At the right is Dale Drinnon's reconstruction drawing of the same creature done as an illustration submitted to PURSUIT in the 1990s, ultimately never published. The two reconstructions shae many similarities and the fact that each one was made independantly and without any knowledge of the other is somsupport the idea tat the representations could be getting near to the truth of the matter.