Without going into the details of how well the chimp knew the human visitor, or what the effect may have been of the Xanax in his tea, we should consider that this was a 15-year-old male. This is precisely the age at which males begin to domineer females of their species and challenge more established males. If you have ever seen male chimps work on their status it is obvious that they are real risk-takers, employing their considerable strength to move up and not caring one bit about the injuries they may incur. Travis was a time bomb waiting to be set off.
What makes apes so strong? Muscle density may be part of the answer, which would also explain why apes can't swim: they lack buoyancy. The pound-for-pound output power of ape muscles is estimated to be twice that of our own species.
The most striking difference between the chimpanzee and human shoulder is in the proportions of the scapula. Human arm strength, much less powerful in movements when in a raised position, is reflected in the shape of the scapula that provides attachment surfaces and lever arms for muscles....
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The chimpanzee distal humerus contrasts with the human. The human lacks the robust lateral supracondylar ridge, a high and robust lateral epicondyle, and the steep, sharp, lateral margin of the olecranon fossa . The chimpanzee forearm is relatively long in comparison to humans . Chimp radius and ulna are more curved than in humans and the chimpanzee distal radius has a radiocarpal joint surface that diverges medially. The major differences between human and chimpanzee limbs are contrasts in relative proportion. Chimpanzees have large powerful arms, slightly longer than their very short legs. Human arms are about 70% as long as human legs.
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Brachiation (arm swinging) is a special form of locomotion in which the body is suspended below branches. It allows utilization of small branches near the fringe of a tree canopy since the brachiator is suspended beneath its handholds. In contrast, a large bodied quadruped that tries to walk on a small branch has difficulty balancing as the supporting tree limb bends. A brachiator can easily exploit the very fringe of a tree canopy by dispersing its weight to the ends of several branches. New World brachiators use their prehensile tail as a fifth prehensile limb to further disperse weight. Most rapid brachiation is attained by using gravity to convert vertical height to speed. IM index is 100 or above.
Brachiation generally is associated with major alterations in the arm, hand, and thorax. The shoulder joint is positioned laterally and cranially on a barrel-shaped thorax. Robust muscles attach to the sternum, vertebral column, head, and rib cage, stabilizing the shoulder. The more powerful the arm movements, the more robust the stabilizing musculature must be. The clavicle acts a strut to stabilize the shoulder joint against a sternum whose segments unite to form a single bone. This clavicular-sternal joint is very strong and is not easily dislocated. A relatively round head of the humerus reflects a very wide range of motion. Additional elbow strength results from a more distinct separation of the radius and ulna on the articular surfaces of the distal humerus. The olecranon process of the ulna is small, allowing full extension of robust forearms. Brachiators tend to have reduced thumbs. If a thumb is present, it is folded out of the way against the palm where it does not interfere with elongated fingers that hook or snag handholds. The lumbar region of the vertebral column is shortened and stabilized, and a very mobile hip joint allows the foot to grasp anchorage in a wide range of positions.
There are several types of brachiators. Gibbons and siamangs, who use arm swinging as a major means of travel, are the best brachiators. Chimpanzee, gorillas, and humans are capable of this type of brachiation, but do not practice it as a primary means of locomotion.
The muscular and skeletal anatomy of the joints, such as the shoulder, differs between humans and chimps. Chimps are much stronger for their size than humans, and they commonly use their arms for locomotion, both on the ground and in trees, obviously unlike humans. The chimps scapula has larger depressions, or fossae, which allow the attachment of the large muscles used for climbing.
The long bones also differ between the two species. Humans have much longer legs than chimps, thereby having femurs (thigh bones) which are much longer than the humeri (upper arm bones). These two bones are nearly the same length in the chimpanzee. The chimp radius is relatively longer, compared to the humerus, than it is in humans. Except for the radius and ulna, the arm bones are heavier in chimps, whereas their leg bones are more slender than human bones.
It's a lot easier to get a chimp in roller skates than it is to get him to pump iron — hence, most of the data on chimp strength is anecdotal and decidedly unscientific. In tests at the Bronx Zoo in 1924, a dynamometer — a scale that measures the mechanical force of a pull on a spring — was erected in the monkey house. A 165-pound male chimpanzee named "Boma" registered a pull of 847 pounds, using only his right hand (although he did have his feet braced against the wall, being somewhat hip, in his simian way, to the principles of leverage). A 165-pound man, by comparison, could manage a one-handed pull of about 210 pounds. Even more frightening, a female chimp, weighing a mere 135 pounds and going by the name of Suzette, checked in with a one-handed pull of 1,260 pounds. (She was in a fit of passion at the time; one shudders to think what her boyfriend must have looked like next morning.) In dead lifts, chimps have been known to manage weights of 600 pounds without even breaking into a sweat. A male gorilla could probably heft an 1,800-pound weight and not think twice about it.
"He bit both of her hands off," said Herold's friend, Lynn Mecca. "The cop said he was eating … it’s terrible. I don’t want to talk about it."
But Travis was acting “rambunctious” Monday afternoon. Herold reportedly said she thought it may have been a reaction to medication he was taking for Lyme disease. She gave him some tea with Xanax in it, but the potion failed to calm the animal down.
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