This is a radiometric technique since it is based on radioactive decay. Particular isotopes are suitable for different applications as a function of the type of atoms present in the rock or mineral and its approximate age.Ĭarbon-14 (or radiocarbon) dating, which is used to date organic remains. Radiometric dating is based on the known and constant rate of decay of radioactive isotopes into their radiogenic daughter isotopes. Usually based on the physical or chemical properties of the materials of artifacts, buildings, or other items that have been modified by humans. In contrast, our teeth and jaws are relatively small, and our faces are nearly vertical.Ībsolute dating provides a computed numerical age.
From the side view, early hominin faces were concave or dish-shaped and projecting forward at the bottom due to their relatively small brain cases and huge teeth and jaws. In modern humans, the jaw muscles are much smaller and attach onto the skull in the temple region. The size and shape of these muscles is indicated by flaring zygomatic arches click this icon to hear the preceding term pronounced, or cheek bones, behind which the major jaw muscles pass and the presence of a sagittal crest click this icon to hear the preceding term pronounced, which is a jaw muscle attachment ridge of bone on top of the skull in the robust species (paranthropoids). They had large jaws, and powerful jaw muscles. By comparison, their front teeth were small. They had comparatively big molar teeth with thick enamel. Early hominin faces were large relative to the size of their brain cases. For modern humans, it usually is in the temple region. As a result, the widest part of the skull of these early hominins was below the brain case. Their adult brain size was about 1/3 that of people today. While the late australopithecines were similar to humans anatomically below the neck, their heads were significantly different from ours in several key features. "Killed ape" instead of "killer ape" because they were not hunters. africanus indicate that it walked bipedally, but its shoulder and hand bones indicate they were also adapted for climbing. afarensis, the pelvis, femur (upper leg), and foot bones of Au. africanus had a rounder cranium housing a larger brain and smaller teeth, but it also had some ape-like features including relatively long arms and a strongly sloping face that juts out from underneath the braincase with a pronounced jaw. afarensis, with a combination of human-like and ape-like features. africanus was anatomically similar to Au. The "S" shape helps in weight distribution caused by walking upright. They have one curve in their spine, whereas bipedal hominids have an "S" shaped spine. Chimps have an elongated pelvis.Īn ape's spine is straighter than a human's because they do not walk on two legs constantly. The human pelvis is also more circularly shaped to hold abdominal organs. The broader and shorter structure allows for stronger muscles used in holding the body upright.
The human pelvis has a shorter ilium (one of the three pelvic bones) than chimpanzees and other apes. In humans, the femur slants in and down, angled toward the knee joint and keeping within the centerline of the body.
This position of the knees makes balancing easier, because much of human walking consists of balancing on one foot while the other leg moves. The knees in bipedal hominids are under the pelvis's center of gravity. Humans use feet as a type of platform, so the foot is more rigid, the big toe points forward, and the foot contains an arch to aide in walking and running. Apes use their feet to hold onto branches, so they have increased flexibility and sideways-pointing big toes. In humans, the foramen magnum is in the skull's center and the head is balanced on vertebra.Īpes and bipedal hominids use feet for different purposes, their shape is different. In apes, the foreman magnum is closer to the skull's rear.
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