Bipedalism in apes: a plesiomorphic trait?

I have felt for some time that the capability for bipedalism would be older than currently theorized, and that the range of bipedalism vs quadrapedalism is more a matter of degree than of kind. Certainly all members of the hominoid superfamily are capable of walking on two legs in varying degree, as are many old world monkeys (the capuchin "organ grinder" monkey for example).I looked up Morotopithecus and found several articles discussing the find, such as: BU Professor Digs Up Clues To Human Origins

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Most primate fossils that date to more than 20 million years ago show adaptations for movement on four legs, called quadrupedalism. The Morotopithecus discovery, however, shows a completely different locomotor pattern: suspensory locomotion, like swinging from branch to branch in trees.

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This suspensory pattern is believed to fill an important transitional role in the development of primates. Many anthropologists believe primates evolved from quadrapedal ancestors into suspensory primates and finally into the bipedal creatures we see today in humans.

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Morotopithecus shows a mixture of both primitive and modern features. It had a face and teeth resembling earlier species, while the lower spine, legs, and shoulders show a new design allowing suspension from branches. Being able to support an upright posture more easily than previous species meant Morotopithecus could more easily take advantage of the food and shelter found in trees.

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Hanging from branches would tend to favor adaptation to a body capable of being verticle from head to toe, and would act to "pre-adapt" apes for occasional bipedalism. More like a baboon, a gibbon (without long arms), or an orangutan it seems to me. Capable of bipedalism but not attached to it. Because there was an opportunity for a bipedal ape and our bipedal capable ancestors were able to take advantage of it. Once taken there was not much opportunity for turning back. Suspensory behavior would also adapt our spines (and hips and knees) for a vertical orientation without requiring much bipedal activity. And our necks and skulls, etc.Enjoy.

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The opportunity was there, but there were other opportunities as well, and "our uncles" took one of those other opportunities.Not everyone becomes a banker to become a millionaire.Enjoy.

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There is also the case of the black macaque:MSN | Outlook, Office, Skype, Bing, Breaking News, and Latest Videos

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A young monkey at an Israeli zoo has started walking on its hind legs only ” aping humans ” after a near death experience, the zoo's veterinarian said Wednesday.

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Natasha, a 5-year-old black macaque at the Safari Park near Tel Aviv, began walking exclusively on her hind legs after a stomach ailment nearly killed her, zookeepers said.

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Natasha, a 5-year-old black macaque, walks at the Safari Park near Tel Aviv on Tuesday.

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This really shows how unremarkable the human ability to walk upright really is - when looked at in comparison to other primates it is really a difference of degree.The only real difference that I can see is that since adapting an upright posture, subsequent human evolution has made it awkward and counter-productive to use a quadrupedal lifestyle (the turkish "hand walkers" notwithstanding). The difference is more that we are no longer able to not use bipedal locomotion.Enjoy.

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