Lab 12: Human Evolution. Exercise 12.1: Relationship between Brain Size, Diet, and Evolution within the Hominid Clade

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1 Name Date Lab 12: Human Evolution The objectives of this lab are to: o Understand the relationship between brain size, diet and evolution within the Hominid clade. o Determine whether Australopithecus afarensis ( Lucy ) was a bipedal upright walker similar to modern humans. o Determine, using the information from this lab, the evolution and relationships of the species within the Hominid clade. Exercise 12.1: Relationship between Brain Size, Diet, and Evolution within the Hominid Clade Materials: o Pencil o Skull samples o Checklist and diagrams of skull measurement techniques o Table for data collection - Table 12.2 o Food For Thought reading assignment Instructions: 1. Teams of 2-3 students examine sets of skulls. 2. Teams will make qualitative observations of all skulls, as well as taking quantitative measurements of their teammates to calculate cranial capacities. 3. From the data collected we will calculate a class average for modern human cranial capacity. 4. Students will record this information and analyze results, including developing a graph of time vs. brain size. Make SURE that everyone on your team has a turn taking measurements. ALWAYS MEASURE AND RECORD DATA IN MILLIMETERS [mm]. All students should make all qualitative observations. This is important for the final lab practicum! PLEASE DO NOT ADD ANY PENCIL OR PEN MARK "TATTOOS" TO THESE CRANIA. Lab 12 1

2 Skull Observation and Measurement Techniques: Observations Qualitative 1. Supraorbital brow ridge: Look for a bony ridge protruding above the eyes. Large, small, or medium? 2. Sagittal crest: This is the bony ridge along the top of the skull to which large chewing muscles attach. Is there a sagittal crest? (present or absent) If present, how pronounced is it? Is it large, small, or medium? 3. Jaw Shape: The arch, or shape of the jaw will be either box shaped (sides parallel), "U"-shaped (parabolic sides), or intermediate. 4. Size of molars: Carefully examine the molars in the jaw. Are they large or small? As a point of reference, modern humans have small molars. How to Collect Your Measurements Quantitative 1. Cranial Capacity: Calculating the capacity provides a rough numerical value for the size of the cranium. a. First orient the skull in the Frankfurt Horizontal Position by lining up the lower edge of the eye orbit with the upper edge of the ear hole so the line formed is horizontal. b. Measure the Maximum Length of the skull (in millimeters) by placing one end of the calipers on the center of the skull, just behind the brow ridge, and the other end on the most posterior point at the back of the cranium. Use a ruler to determine the length from the caliper measurement. BE CAREFUL NOT TO MOVE THE CALIPERS as you take your measurement. c. The Maximum Width is determined with the calipers on the sides of the skull at the widest point, near the ear hole. Remember we are measuring the CRANIUM (which surrounds the brain) so stay above the zygomatic arch. d. The Maximum Height is measured by using two rulers held at right angles to measure the vertical distance from the top of the ear hole to the highest point on the cranium. If you were to measure a skull with a sagittal crest, do not include the bony ridge of the sagittal crest in your measurements. e. Calculate Cranial Capacity by using the formula below: Cranial Capacity (CC) = Maximum Length * Maximum Width * Maximum Height 2300 f. Once you have measured and calculated the cranial capacity for each team member, write your results on the chalkboard. Your instructor will calculate a class average for you to record in Tables 1 and 3. Your measurements Modern human You! max length (mm) max height (mm) max width (mm) total capacity (L*H*W)/ 2300) Lab 12 2

3 Table Data collection table for hominid skulls. Specimen Name 1. Australopithecus (Paranthropus) aethiopicus AGE - first appearance Cranial Capacity average (cc) ~ 2.7 mya 410 Qualitative Data Brow Sagittal Ridge Crest (Large, (Present Medium or or Absent) Small) Jaw Shape (Box, U, or Int) Size of molars (Large or Small) 2. Australopithecus afarensis ~ mya Australopithecus africanus ~ 3.5 mya Australopithecus (Paranthropus) boisei ~ 2.3 mya Homo erectus ~ 1.8 mya Homo ergaster ~ 1.9 mya Homo habilis ~ 1.9 mya Homo heidelbergensis ~ 800,000 ybp Homo rudolphensis ~ 1.9 mya Homo sapiens (you!) Use the class average for cranial capacity. 11. Homo sapiens neanderthalensis ~ 130,000 ybp ~ 200,000 ybp Kenyanthropus platyops ~ 3.5 mya Ardipithecus ramidus ~4.4 mya Sahelanthropus tchadensis ~ 7 mya Homo floriensis ~18,000 ybp 417 To determine a species diet, examine the skull s characteristics (such as jaw shape, teeth size, sagittal crest). From your examination, you should be able to divide the species into two groups: those that are primarily omnivores, incorporating more meat in their diet, and those that are herbivores. Remember that meat is a more energy dense food than plants. The larger brain requires animals to seek out more the energy-dense foods. Lab 12 3

4 1. Graph the relationship between diet and brain size. Construct a graph (Use Figure 12.1) with the Y axis equal to time of first appearance (millions of years ago) and X axis equal to percent of resting energy allocated to the brain. Be sure to plot a point for every skull on the data sheet and label it with its appropriate name. To determine the percent of resting energy allocated to brain use Table 1 below. Table Percent of resting energy allocated to brain use. The size of the brain (cc) and the resting energy allocated to the brain (%) Brain Size CC % Resting Energy Table Hominids, cranial capacity, and their age of first appearance. Specimen Name 1. Australopithecus (Paranthropus) aethiopicus AGE - first appearance Cranial Capacity average (cc) ~ 2.7 mya Australopithecus afarensis ~ mya Australopithecus africanus ~ 3.5 mya Australopithecus (Paranthropus) boisei ~ 2.3 mya Homo erectus ~ 1.8 mya Homo ergaster ~ 1.9 mya Homo habilis ~ 1.9 mya Homo heidelbergensis ~ 800,000 ybp Homo rudolphensis ~ 1.9 mya Homo sapiens (you!) Use the class average for cranial capacity. ~ 130,000 ybp 11. Homo sapiens neanderthalensis ~ 200,000 ybp Kenyanthropus platyops ~ 3.5 mya Ardipithecus ramidus ~4.4 mya Sahelanthropus tchadensis ~ 7 mya Homo floriensis ~18,000 ybp 417 Lab 12 4

5 0 Millions of years before present Resting Energy Allocated to Brain (%) Figure Resting energy allocated to the brain (%) vs. millions of years before present 2. Compare the changes of jaws, teeth, and sagittal crest between the species. How did they change among the species? How are these changes related to diet? Lab 12 5

6 3. In a paragraph or two discuss the relationship between diet, brain size, and energy needed for the brain. First, cite the information from your chart and graph. Second, address the relationship between diet and brain size (i.e. % resting energy allocated to the brain) and how this changed with time. Use specific examples from your data that support your claims for how diet and brain size changed over time. WRITE LEGIBLY!!! 4. What is the evolutionary implication of your findings? In other words, of all the changes in teeth, jaws, sagittal crest, brain size, and diet, what led to what? In what order did these changes occur? Lab 12 6

7 Exercise 12.2: Could Lucy Walk Upright? Materials: o Pencil o Lucy and Modern Human Pelvic and Femur Bones o Diagram of proper bone alignment o Lucy, Ardi, the hobbit, modern human, and gorilla skulls o Food For Thought reading assignment Instructions: 1. Each team will examine the pelvic and leg bones of the chimpanzee, Lucy, and the modern human to determine the key characteristics that indicate bipedalism. 2. Answer the questions on pages 7 and 8 to explore the data and determine if Lucy walked upright. Compare the three sets of pelvic and femur bones. Describe your qualitative observations below. 1. Pan troglodytes (chimpanzee): a. Pelvis (width) b. Femur (length) c. Note the angle between the hip and the knee. 2. Australopithecus afarensis (Lucy refer to bones and poster): a. Pelvis (width) b. Femur (length) c. Note the angle between the hip and the knee. 3. Homo sapiens (modern human): a. Pelvis (width) b. Femur (length) c. Note the angle between the hip and the knee. 4. Compare/contrast the pelvic and femur bones of the chimpanzee, Lucy and the modern human. Include your observations of the knee positions for each. Lab 12 7

8 5. Compare/contrast the skulls of these Lucy (Australopithecus afarensis) and the modern human (Homo sapiens) with the gorilla skull. Briefly describe the differences in brow ridge, sagittal crest, jaw shape, and teeth below. 6. Sketch the location of the foramen magnum (hole in the back of the cranium) within the crania of Australopithecus afarensis, Sahelanthropus tchadensis, Ardipithecus ramidus, Homo sapiens, Homo floriensis and Gorilla gorilla. Homo sapiens A. afarensis S. tchadensis A. ramidus Homo floriensis Gorilla gorilla 7. How does the position of the foramen magnum relate to the body posture? 8. Based on the crania, and femur and pelvic bones, was Lucy bipedal? Justify your answer with specific evidence from your data. Lab 12 8

9 9. Sketch and then compare and contrast the feet of Ardi, Lucy, the hobbit, and modern human. Focus on the bone structure and arch of the bones. 10. Compare the relative proportion of the foot to femur of the human and hobbit. Carefully measure the femur and foot of the modern human, and then do the same for the image of the hobbit foot and femur. For the foot, measure from the heel to the end of the longest toe. For the femur, be sure to measure along the greatest extent. Calculate the relative proportion of each foot to its corresponding femur by calculating the percent. Compare your results. Compare H. floriensis feet to your feet. Hobbit femur = length in cm Hobbit foot = length in cm Percent = (foot l / femur l)*100 = Human femur = length in cm Human foot = length in cm Percent = (foot l / femur l)*100 = 11. Suppose you are running a 5K race and your competitors are Ardi, Lucy, and the hobbit. Based on your observations of the foot bones, foot prints, and foramen magnum, describe their gates. Would they run like we do? Lab 12 9

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11 Exercise 12.3: Evolutionary Relationships between the Hominid Species Materials: o Pencil o Data collected in lab today o Food For Thought reading assignment o Creative thinking Instructions: Using the samples given, your qualitative observations of the skulls, and your best judgment, discuss and interpret the phylogenetic tree below. Would you have developed the tree the same way? Why or why not? Developed from: Institute of Human Origins, Lab 12 11

12 Present Homo neanderthalensis Homo sapiens Homo erectus Homo heidelbergensis 1 MYA Paranthropus (Australopithecus) boisei Homo ergaster Homo habilis 2 MYA Paranthropus (Australopithecus) aethiopicus Australopithecus africanus?? Australopithecus rudolphensis 3 MYA Kenyanthropus platyops Australopithecus afarensis ( Lucy ) 4 MYA?? Ardipithecus anamensis Great Apes?? Ardipithecus ramidus ( Ardi ) Lab 12 12