Analysis of the of Species by Skull Features - Lab Report Example

Index of condylar position- This index is used to tell how far forward or backwards the occipital condyles are located. These occipital condyles are projections from the bottom of the skull that attach the head to the atlas and axis of the cervical vertebrae. This indicates how upright the organism stood. The more centred that the occipital condyles are along the Frankfurt plane, the higher the probability the hominid was upright.

Total facial index – earlier hominids had wider faces due to the larger facial bones for muscle attachment. Larger facial size, thus indicating a more primitive hominid. Cranial volume- Primitive hominids are believed to have smaller cranial vault sizes than the more recent/evolved hominids. Lower nasal spine- more prominent nasal spines imply the European origin of the hominid skull. A smaller one suggests a sub-Saharan origin. Nasal cavity shape – the nasal cavity shape helps establish ancestry and racial heritage. A wider nasal chamber indicates a sub-Saharan source compared to a narrower flared/heart-shaped one in the European skull.

Mystery skull 1 belongs to anatomically modern Homo sapiens. I assigned this taxon due to the high UV/tv ratio. This implies that the hominid had a lower brow; thus, the frontal lobes were higher than the eye level. The two/tv ratio is also immense, meaning the foramen magnum is high. This implies an upright posture. The index of condylar position is also extensive, indicating that the foramen magnum is nearly centrally placed under the skull. This also means a near-upright gait. The facial features, such as zygomatic bones, are not as prominent, thus showing that the hominid did not need large mastication muscles. The maxillary jaw is also less protruded. This is characteristic of the more evolved hominids. The sagittal sutures are also close to forming a well-rounded calvaria characteristic of higher hominids.

Mystery skull 2 belongs to the Neanderthal. I assigned this taxon because the UV/tv ratio is relatively large. This implies that the brow ridge is not as high; thus, the brain is slightly higher placed than the eyes. The two/tv ratio shows that the foramen magnum is lower on the skull; thus, the hominid may not have been upright. The XY/xz ratio is quite large. This implies that the foramen magnum was almost centred, meaning that although the hominid was not altogether upright, it may have employed a bipedal gait. The skull also exhibits a certain degree of maxillary prognathism with protruding zygomatic bones. This, therefore, implies a need for solid mastication muscles.

The new-found skull belongs to Australopithecus robustus. This is due to the prominent zygomatic bones that imply large muscles of mastication. The head also has prominent prognathism and tapering of the calvaria at the sagittal suture. The UV/tv ratio is 50, indicating that the brow is high. This means that the brain is posterior to the eyes and, thus, a trait of primitive hominids. The two/tv ratio shows that the foramen magnum is lowly placed in the skull; therefore, the hominid was not likely upright. This also coincides with the XY/xz ratio at 56. This implies that the foramen magnum and condyles are more posteriorly placed. This coincides with a less upright posture.