Student Exploration Human Evolution - Skull Analysis

Name: Date: Student Exploration: Human Evolution - Skull Analysis Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: bipedal, canine, cranial capacity, cranium, evolve, foramen magnum, hominid, hominin, index, maxilla, orbit, palate, skull Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. Label one of the skulls below as human and the other as a chimpanzee skull. human chimpanzee 2. What features did you use to identify which skull was human and which was chimpanzee? There is more space for the brain in the human skull as well as the jawline of the skull is not as much out as the chimpanzee Gizmo Warm-up In 1924, a fossilized skull that looked very similar to a chimp skull was discovered. But the skull most definitely did not belong to a chimp. The location of the foramen magnum—a hole in the skull where the spinal cord exits—indicated that the individual was bipedal, or walked on two legs. This fossil was some of the earliest evidence of human evolution. Using the Human Evolution – Skull Analysis Gizmo, you will discover some of the ways that skulls can be used to learn about human evolution. Start by comparing two modern hominids: a human and a chimpanzee. 1. Examine the Front view of the Homo sapiens (modern human) skull. Then, use the Select skull menu to examine the same view of the Pan troglodytes (chimp) skull. How do the skulls compare? The size on the bottom of the eye is the same size in both skulls. 2. Now, examine the Bottom view of the two skulls. How do they compare? They both compare in somewhat same features like the eye parts, and the teeth. Activity A: Foramen magnum Get the Gizmo ready: ● Select the Homo sapiens (modern human) skull. Introduction: Skulls, even from the same species, can have a wide variety of shapes and sizes. To compare skulls, scientists use measurements of certain features to calculate indexes. An index is a ratio of one measurement to another. An important index for measuring hominid skulls is the opisthion index. This index indicates the position of the foramen magnum in the base of the cranium. The opisthion index can indicate whether a hominid species was bipedal or not. Question: How does the location of the foramen magnum indicate if a species was bipedal? 1. Measure: Select the Bottom view. To determine the opisthion index for humans and chimps, follow the steps below and complete the table. ● Turn on Click to Measure Lengths. Measure the distance from the opisthocranion to the opisthion, as shown at top right. Record the opisthocranion-opisthion distance in the table below. ● Measure from the opisthocranion to the orale, as shown at bottom right. Record the opisthocranion-orale distance in the table. ● To calculate the opisthion index, divide your first measurement by your second measurement. Multiply this number by 100. Species Homo sapiens Pan troglodytes Opisthocranion-opisthi on distance (cm) 7.27cm 2.25 cm Opisthocranion-ora le distance (cm) 20.73 cm 20.73 cm Opisthion index 35.06 10.85 2. Analyze: The opisthion index is an indicator of where the foramen magnum is situated. The greater the opisthion index, the closer the foramen magnum is to the center of the cranium. This position is usually found in species that stand upright. A low value for the opisthion index occurs when the foramen magnum is situated in the rear of the cranium. This may indicate that the species walked on its knuckles or on four legs. Using the index values you calculated, what can you conclude about humans and chimps? The conclusion can be made that humans have a foramen magnum closer to the of the cranium which allows the humans to stand straight. 3. Gather data: Humans, chimpanzees, and the other great apes are hominids. Hominids evolved from a common ancestor that lived about 13 million years ago. Hominins are hominids that belong to the lineage that led to humans. Measure the opisthion index of the other hominids available in the Gizmo. (Note: the foramen magnum was not preserved in the Homo naledi skull.) Species A. afarensis A. africanus P. boisei H. habilis H. erectus H. heidelbergensis H. sapiens neanderthalensis H. floresiensis Opisthocranion-opisth ion distance (cm) 3.09 4.88 4.79 4.73 4.92 6.81 Opisthocranion-ora le distance (cm) 17.34 19.09 20.3 18.97 21.33 24.19 Opisthion index 17.82 25.56 23.59 24.93 23.06 28.15 6.74 24.43 27.58 4.43 17.58 25.19 4. Analyze: Hominins are characterized by bipedalism. A. Based on their opisthion indexes, which of the hominids in the Gizmo are hominins? afarensis, africanus, boisei B. Based on opisthion indexes, which hominin skulls are most similar to human skulls? erectus, heidelbergensis, neanderthalensis, floresiensis, 4. Explain: Why do you think the foramen magnum is positioned near the rear of the cranium for knuckle-walking species and near the center of the cranium for bipedal species? The estimate knowing that the foramen magnum is positioned near the rear of the cranium for knuckle walking species and near the center of the cranium for bipedal species since it positioned there to keep the skull in line with the posture of the vertebrae, which comes in at an angel to the skull knuckle walkers. Activity B: Get the Gizmo ready: Cranial capacity ● Select Side view. ● Turn off Ruler, and turn on Click to measure area. Introduction: The brain is housed inside the cranium. The internal volume of the cranium is called the cranial capacity. The larger an organism’s cranial capacity is, the larger its brain tends to be. Question: How does the cranial capacity compare amongst hominids? 1. Measure: To estimate the cranial capacity of each skull in the Gizmo, measure the area of the part of the cranium that houses the brain. This part of the cranium is roughly behind the red line in the diagram at right. You can also use the three skull images below as a guide for measuring the rest of the skulls in the Gizmo. After you measure the area of each cranium, multiply the result by 5. This will give you a very rough estimate of the species’ cranial capacity. Homo sapiens Species Pan troglodytes A. afarensis A. africanus P. boisei H. habilis H. erectus H. heidelbergensis H. s. neanderthalensis H. floresiensis H. naledi H. sapiens Pan troglodytes Area of cranium (cm2) 97 85 120 118 104 136 194 199 138 117 219 2. Analyze: Examine the estimated cranial capacities you calculated. A. Which species probably had the largest cranial capacities? Australopithecus afarensis Estimated cranial capacity (cm3) 485 425 600 590 520 680 970 995 690 585 1,095 sapiens, neanderthalensis, heidelbergensis B. What do you think cranial capacity is a good indicator of? When there is an increase in the cranial capacity it implies that there is a larger brain which automatically leads to an increase in intelligence. C. Did any hominids have a larger cranial capacity than humans? If so, which species? Neanderthalensis has around the same size as the size of the human skull 3. Compare: Turn off the Area tool. Using the Front view, compare the size and shape of the forehead of a chimpanzee and the forehead of a modern human. How are they different? A. How are they different? the human forehead is much bigger compared to the chimpanzee B. Why do you think humans have such large foreheads in comparison to chimps? That is because of the brain size that is in our head. That allows us to think beyond what chimpanzees can think about. 5. Draw conclusions: Compare the data you collected in activity A with the data you collected in this activity. Which evolved first in hominins: bipedalism or large brains? Explain. Bipedalism of course came first. Since everyone knows and understands the evolution of humans for many years. Which explains why we are so much similar to them. After many centuries passed by it had changed to large brains where intelligence and a change happened in nature. Activity C: Maxilla and mandible Get the Gizmo ready: ● Select Side view. ● Turn on Click to measure angles. Introduction: Teeth and the bones around the mouth give a great deal of information about both a species’ diet and how it eats. Take a look at the skull features below. Question: How do the mouths of hominids compare? 1. Measure: As shown at right, place one of the protractor’s circles on the top of the zygomatic process. Place the vertex of the protractor at the top of the nasal opening (Hint: You may have to look at the Front view in order to see where the top of the nasal opening is in relation to the orbit). Place the other circle on the edge of the maxilla. The resulting angle is the maxillary angle. Complete the table. (Note: You will not be able to do this measurement on incomplete skulls.) Species Pan troglodytes Maxillary angle 137.48 Species Homo erectus Maxillary angle 106.07 Australopithecus afarensis 145.05 Homo heidelbergensis — Australopithecus africanus 128.19 Homo sapiens neanderthalensis — Paranthropus boisei 126.95 Homo floresiensis 117.47 Homo habilis — Homo sapiens 104.82 2. Observe: Select the Bottom view and look at the size and shape of each species’ palate. How does the maxillary angle and palate shape relate to the size of each species’ mouth? The way they all relate to each other the bottom view if each species is that they all involve in the length of the mouth or the width 3. Compare: Compare the human’s and chimp’s teeth. A. How many teeth are found in each species’ maxilla? Pan troglodytes: 16 Homo sapiens: 16 B. How do the size and shape of human canines compare with chimp canines? The human canines are more round while the chimp canine is longer. 4. Form hypothesis: Chimps and humans eat similar foods. What do you think could explain the differences between the maxillary angle, teeth, and palate of these two species? We know that chimps need sharper teeth than humans to process the different types of food that they eat. Which means that they put a lot more pressure on their teeth. As well as there needs to be more space in the mouth for them to chew. 5. Infer: What is the relationship between the evolution of bipedalism, the increase in cranial capacity, and the decrease in tooth and mouth size of hominins? (Hint: As cranial capacity increased, the use of sophisticated stone tools became more common.) The relationship between the evolution of bipedalism is that they begin walking on 2 legs more often where their hands become used less and less every time. Unless they start to use their hands to break their food where an increase of brain development would happen. Which will automatically reduce the need to use the teeth to digest food. 6. Summarize: On a separate sheet of paper, record the age of each fossil. Then, look over all the data you collected. Summarize how hominins changed as they evolved. The way hominins changed as the time went by means that they went from walking around on legs and arms. To using only legs and allowing their arms to help them with taking apart their food for easier digestion. Which allowed for the intelligence to grow. 7. Evaluate: Of the fossils presented in this Gizmo, Homo floresiensis is the youngest. In what ways does this species NOT follow the pattern of human evolution you described above? The way the hoo floresiensis doesn’t follow with the human evolution parent knowing that it is a recent skull is that the size of it. it is so much smaller compared to today's skull. Which allows us to see from the side view is that the intelligence wasn’t prograsoing as much as it supposed to.