The Sagittal Crest is a ridge of bone running lengthwise along the midline of the top of the skull. The brow ridge was one of the last traits to be lost in the path to modern humans Without this reinforcement the eye sockets would collapse. In Apes they are much larger due to the tremendous strain put on the cranium by their temporal (jaw) muscles. Its purpose is to reinforce the weaker bones of the face (reduces vertical stress). This is a bony ridge located above the eye sockets. They are much larger in apes to accommodate much larger temporal muscles. They provide a gap for the temporal muscles to pass through (see above). These are a bony arch just behind the cheeks. This probably corresponded to a much more primitive diet that included a lot more fibrous plant material that needed to be ground down. The temporal area is where these muscles attach onto the skull. These are the muscles that pull up the jaw (bite). Apes have very large nuchal areas and associated neck muscles because greater muscle strength is required keep the skull looking forward when the spine is attached further to the rear of the skull. This is the area where the neck muscles attach onto the back of the skull, to keep it balanced on the spinal column / looking forward. The bones of the skull that balance on the vertebra / spine, called '''occipital condyles''' show the same trend (at the rear of the skull in apes, central in humans) In humans, the foramen magnum is at the '''fulcrum''' (balance point). The foramen magnum is towards the back of the skull in apes, whose posture was not fully upright. This is the hole at the base of the skull where the spinal cord enters the brain. This is common in early Hominins also, but later Hominins have a much flatter face. '''Prognathism''': Apes have a pronounced muzzle, the teeth protrude out from their face. This is an indication of their brain size. Humans and chimpanzees share at least 98.5% of their DNA.'''Cranial Capacity''': Hominins have a larger cranial capacity (apes have a cranial capacity of approx '''400cm^3^''' compared with '''1400cm^3^''' in humans).Blood group studies show many differences between bonobos and common chimpanzees, enough that some researchers have suggested they should be in a separate genus.Common chimps are either group A or O, and the A antigen of their red cells differs from those in human red cells.Pygmy chimpanzees show few individual differences in their blood groups (unlike P.The only other animals with some form of VEN cells are whales, dolphins, and elephants, all animals with large brains and highly evolved social awareness, including empathy.Neither gorillas nor chimpanzees have a VEN brain cell organized in clusters like those of humans and bonobos.VENs help regulate complex social interactions requiring knowledge of other individuals' mental state.Bonobos share with humans a similar pattern of distribution of brain neuron cells called VENS (also called spindle cells or Von Economo Neurons).Of all the great apes, bonobos are the most human-like in their leg length.Bonobos are quite similar in overall body size, cranial capacity, and lower limb length to an ancestral hominid, nicknamed Lucy, who lived some 3 million years ago in Africa.More body weight (heavier muscles) in lower legs of bonobos.More centrally positioned opening in skull for spinal cord (foramen magnum).Compared to chimpanzees, bonobos have body characteristics that are better for bipedal or upright posture: (Myers Thompson 2002).Bonobos have shorter upper limbs and longer lower limbs (Zihlmann 1996).In overall size, bonobos are not smaller than chimpanzees (most anatomical measurements overlap) but there are differences in proportion:.Nostrils are "thick-walled" and more gorilla-like.Lips are lighter, often reddish colored.Chimps' ears stand out more from the head.Ears smaller and almost completely covered by cheek whiskers.More slender build, narrower chest, bone and muscle of lower limbs is heavier.Head is more rounded, with smaller ridges above eyes, less developed muzzle, less jaw protrusion.Brow ridges and facial bone structure are less pronounced.Baldness does occur, although "perhaps later in life" than in other chimpanzees. Hair on top of head appears to be parted down the middle.Many adults retain the white rump tuft common to infants.Black face, ears, palms and soles of feet individuals in managed care may have lighter pigmentation.
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