Primates have an assortment of differently shaped teeth that allows them to eat a variety of foods: gums, leaves, fruits, roots and tubers, nuts, insects, and meat.
Paleoanthropologist"...data does not allow us to reject
the single species hypothesis.”
Paleoanthropologist"...my research would suggest...
not one species but two species.”
RunTime: 290 secs
HUMANS ARE MEMBERS of the biological order Primates. This highly diverse group includes prosimians, monkeys, apes, and humans. Although they are very different from each other, all primates share many important similarities that make us, as a group, distinct from other animals.
Examine these skeletons to see what features humans share with the other primates.
THE EVOLUTION OF Homo was not a simple linear
story from habilis to erectus to sapiens.Scientists
debate whether Homo rudolfensis is a separate
species, or simply a varient of Homo habilis.
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Explore the changing physiology of our ancestors and discover the unique physical traits that define us as humans.
Because an ape's big toe is divergent the foot can grasp branches. The foot has a single transverse arch, distributing body weight over the sole of the foot. In humans, the big toe is enlarged and lines up with other toes, adding balance. The human foot has two arches: The transverse arch distributes body weight over the sole of the foot during standing and walking. The longitudinal arch (heel-to-toe) distributes body weight, absorbs shock, and pushes weight forward.
The knee joint is made up of several bones: the femur, the tibia, and the patella. Apes have a more mobile knee than humans that helps them in climbing. The top of the ape tibia is more concave to increase the knee's rotation. This roundness can be seen on the bottom of the femur as well. Humans require a stable knee during walking. The top of the tibia is flatter in humans to reduce the knee's rotation. This flatness can be seen on the bottom of the femur as well.
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In apes, the femur is straight instead of angling inward, as in humans. Apes rotate their pelvis toward the side every time they take a step. In humans, on the other hand, the femur angles inward so that the weight of the body is supported at the midline of the body. This makes walking more efficient because humans don't rotate the body side to side with every step. The human femur is also long, increasing stride length for more efficient walking.
Primate brains are large relative to their body size, in part because of their heavy dependence upon flexible, learned behavior. Unlike many other animals, primates take a long time to grow to maturity.
In apes, the iliac blades of the pelvis are not twisted, as they are in humans. Since the gluteal muscles of the buttocks are posi-tioned differently, they do not allow an ape to easily balance on one foot while walking bipedally. Human blades, however, are rotated inward to support the internal organs while humans are upright. Because the iliac blades are twisted, the gluteal muscles can balance the trunk while the walker stands on one foot by pulling against gravity.
Primates have retained the clavicle bone (the collar bone), which has been lost in some other mammals. Most animals, such as dogs or cats, move their arms and legs in a front-to-back motion. In contrast, primates frequently swing their arms side to side, as when they are climbing a tree. The clavicle acts as a strut to stabilize the shoulder so that the side-to-side forces don't dislocate it.
The spine has several curves to maintain balance. Because apes have no lumbar curve to pull the upper body back over their pelvis, their weight pulls them forward. Humans, however, have an additional lumbar curve that positions the body inward, over the pelvis.
The foramen magnum is the hole through which the spinal cord exits the skull. In apes the foramen magnum is angled backward rather than beneath the skull, as in humans. In humans the foramen magnum is located beneath the skull to balance the head and hold it upright.
Most primates have nails instead of claws on their fingers and toes. They also have ridges on their touch pads (fingerprints). Ridges provide fingers and toes with better friction for holding onto branches or food.
HUMANS MUST do three things to maintain balance when one leg is off the ground:
1) Keep the head positioned in the
mid-line of the body.
2) Keep upper-body weight over the pelvis.
3) Keep the leg stable to support the weight
of the body.Examine these skeletons to
learn about the features that help humans
balance as they walk.
Primates have opposable thumbs and big toes, which means they can grasp with their hands and feet. Humans have lost the grasping foot thanks to the constraints of bipedalism. Most primates, however, including humans, can touch their thumb to their forefinger—a precision grip allows them to pick up small items such as grass seeds.
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Anatomy ~ Continue the Documentary
Like many predators, primates have both eyes in the front of their heads. Each eye's visual field overlaps somewhat with the other's, producing three-dimensional sight. This 3-D vision helps primates catch prey or jump to the next tree branch high above the ground.
Primates do not rely as much on smell as other animals do. Instead, they depend heavily on their sense of sight. For this reason, primates have either an absent or reduced snout and small noses. These changes also appear in the size of the sight and smell regions of the brain.