Different Lengths of the Skull - Essay Example

Identifying Skulls Introduction Many changes that have occurred in hominid evolution have been the change in proportion of the skull. Skull proportions show the different parts of the skull. The changes are noticeable when the two hominid trends: brain versus face size and the position of the occipital condyles, are measured. In this task, we are going to measure different lengths of the skull and calculate the skull indices and then compare the calculated value with some known recognized hominin species. Theory The main parts of the skull are the porion, occipital condyles, prosthion and the inion. The porion is the utmost point of the margin of the external auditory meatus. The condyles are the bony crests located at the bottom of the skull around the foramen magnum, roughly below the auditory meatus. The prosthion is the lowermost point on the maxilla, between the two front incisors. The inion is the place on the back of the skull that is the grates t distance away from the front of the skull. Indices calculated are the index of supraorbital height, index of nuchal area height and the index of condylar conditions. The index of supraorbital height is the relationship between the distance of the Frankfort plane to the highest point of the skull and the distance of the top of the eye orbit to the top of the skull; a high number indicates a high forehead or a tall head while a low number indicates a slanted skull. The index of nuchal area is the relationship between the distance of the Frankfort plane to where the inion lies on the back of the skull and the distance of the Frankfort to the highest point on the skull; a high number indicates a short nuchal area while a low number indicates a tall nuchal area. The index of the condylar position is the relationship between the porion and the back of the skull and porion and the front of the skull; a high number indicates the foramen magnum is at the center of the skull while a low number indicates the foramen is closer to the back of the skull. Task 1 The points for identification of the skull B were dully noted and marked on the figure. Task 2 The marked locations were then connected with fine lines using a sharp pencil. A line was drawn to intersect the porion and the lowest point on the lower margin of the eye orbit. A line was also drawn to from the inion, perpendicular to the line drawn above (Frankfort Plane) and the point of intersection labeled as Y. Another line was drawn from the occipital condyles perpendicular to the Frankfurt Plane and the point of intersection labeled X. Another line was drawn from the prosthion perpendicular to the Frankfort plane and the point of intersection labeled Z. Another line was drawn from the Frankfort plane to the highest point of the upper margin of the eye and the point labeled V and U. Task 3 & 4 The lengths of the line were then measured, where the bones start or stop. The measurements were taken in millimeters as it is more accurate than inches. The measured lengths were then recorded in a table. The indices were then calculated using the above measurements. Findings Figure# skull uv tv tw xy xz Index of Supraorbital Height Uv/tv Index of Nuchal Area Height Tw/tv Index of Condylar-position Xy/xz C-chimpanzee 38 54 20 36 53 0.704 0.370 0.679 D-Austrlopithecus africanus 27 39 20 19 70 0.692 0.513 0.271 E-Australopithecus robustus 29 41 15 26 58 0.707 0.366 0.448 F- Homo habilis 37 44 24 31 55 0.841 0.545 0.564 G-Homo erectus 39 49 21 34 60 0.796 0.429 0.567 H- Neanderthal 39 50 22 39 43 0.780 0.440 0.907 I-Archaic Homo sapiens 30 44 15 38 47 0.682 0.341 0.829 B- Anatomically modern homo sapiens 37 41 15 31 40 0.902 0.366 0.775 Mystery skull #1 33 41 15 35 39 0.805 0.366 0.897 Mystery skull # 2 28 42 14 25 54 0.667 0.333 1.042 Newly found skull 28 37 18 28 49 0.757 0.486 0.571 Mystery skull # 1 Index of Supraorbital Height-0.805 This value is closer to that of Homo erectus (0.796) and of anatomically modern Homo erectus (0. 902). It lies between Homo erectus and of anatomically modern Homo erectus. Index of Nuchal Area Height-0.366 This value is the same as of Australopithecus robustus and anatomically modern Homo sapiens.it lies between Archaic Homo sapiens and chimpanzee. Index of Condylar-position- 0.897 This value is closer to that of Neanderthal (0.907). It is between Archaic Homo sapiens (0.829) and Neanderthal (0.907.) Mystery skull# 2 Index of Supraorbital Height-0.667 This value is next to Archaic Homo sapiens (0.682). Index of Nuchal Area Height-0.333 This value is close to (below) that of Archaic Homo sapiens (0.341). Index of Condylar-position-1.042 The value is closer to (above) Neanderthal (0.907). Newly found skull Index of Supraorbital Height- 0.757 The value is between Neanderthal (0.780) and Australopithecus robustus (0.707). Index of Nuchal Area Height-0.486 The value is between Neanderthal (0.440) and Homo habilis (0.545). Index of Condylar-position- 0.571 The value is between Homo erectus (0.567) and Chimpanzee (0.679). Identification The taxonomic status of mystery skull #1 is the modern Homo sapiens The reasons I assigned to this taxon are: The index of supraorbital height and the index of nuchal area height are close to that of modern Homo sapiens. Moreover, the medium index of supraorbital indicates that the head was upright with minimal orientations, just like the modern Homo sapiens. The value of the index of condylar position is also high, indicating that the foramen magnum is closer to the rear of the skull, just like the modern Homo sapiens. The taxonomic status of the mystery skull # 2 is the archaic Homo sapiens The reasons I assigned to this taxon are: The index of supraorbital height and the index of nuchal area height are close to that of archaic Homo sapiens. Moreover, the medium index of supraorbital indicates that the head was upright with minimal orientations, just like the Homo sapiens. The value of the index of condylar position is also high, indicating that the foramen magnum is closer to the rear of the skull, just like the Homo sapiens. The taxonomic status of the newly identified skull is the Neanderthal man. The reasons I assigned to this taxon are: The index of supraorbital height and the index of the Nuchal Area Height are close to that of the Neanderthal. The high index of supraorbital height (0.7) also indicates the creature had a slanted backward, which is a feature of the Neanderthal man. Read More