Bipedalism vs Brain Size: Analyzing Hominin Evolution

Activity: Bipedalism vs. Brain Size Typed Report All parts of the report MUST be typed and submitted digitally to Blackboard as a PDF or turned in as a printed hard copy . Hand written documents, photos of documents, and screenshots will not be accepted. Font: Times New Roman, size: 12. Page margins: 1 inch. You may wish to use a separate sheet of paper to take notes Include the following in your report: Part 1: Becoming Bipedal Recreate the chart in this activity and include your measurements A photo of your foot drawing with measurements Answer the response question Part 2: Comparative Brain Size Recreate the chart in this activity and include your measurements Answer the response question Part 3: Review and Reading Answer questions 1-6 ** images & diagrams will be available through blackboard if you wish to include them** Introduction Humans and Chimpanzees diverged in their evolutionary paths between 4 and 6 million years ago. Since then, Hominins (modern humans and their fossil ancestors) have developed a number of unique biological traits that set us apart from other primates. Today we will be examining one of those ancestors named Australopithecus afarensis to see what features they share in common with modern humans, or if they are more similar to the modern chimpanzee. Luckily for us, A. afarensis has left a number of traces for us to study. In class we will be using an illustration of one of the famous Laetoli footprints and a reconstruction of a fossil A. afarensis skull. Image: Mary Leakey with a cast of the Laetoli footprints. (Photo By Lyn Alweis/The Denver Post via Getty Images) ORIGIN & DIVERSITY OF HUMANKIND - Jennifer Hastings - Page 1 of 6

*** Do Not turn in this page*** Part 1: Becoming Bipedal Objective: Determine whether the hominin A ustralopithecus afarensis had feet that more closely resembled modern humans ( H. sapiens ) or modern chimpanzees (P. troglodytes) . Method: In this section of the activity, you will compare the footprints of Homo sapiens (yourself), A ustralopithecus afarensis (the laetoli footprint), and P. troglodytes . You will need to take three measurements of each specimen in centimeters : ➢ the distance between the hallux (big toe) and the second toe ➢ [W] foot width (the widest part of the foot usually around the toe area). ➢ [L] foot length (the length from the tip of the longest toe to the back of the heel) Use the images in the chart as a guide. Illustrations of a chimpanzee foot [A] and an A. afarensis footprint from Laetoli [B] will be provided. For the human foot, you will be expected to provide your own measurements. Step 1: Trace your bare foot on a clean sheet of paper. Step 2: Measure the required values for all three species and record your results in centimeters on the graph below. Step 3: Calculate the hallux divergence index by dividing the foot width by the foot length. Results: Compare the Hallux divergence of the three specimens. Does A . afarensis have a foot more like P. troglodytes or H. sapien ? Why or why not? ORIGIN & DIVERSITY OF HUMANKIND - Jennifer Hastings - Page 4 of 6

*** Do Not turn in this page*** Part 2: Comparative Brain Size Now that you have completed part 1, let's examine the cranial capacity of the three same species. Objective: Determine whether the relative brain size of A. afarensis was more similar to modern humans or modern chimpanzees. Method: In this section of the activity, you will take 3 measurements: ➢ [A] cranial width (the widest part of the skull, not including the cheekbones) ➢ [B] cranial length (the distance from the forehead just behind the eyebrows to the back of the skull) ➢ And [C] cranial height (the distance from the top of the cranium to just below the ear). Use the images in the chart as a guide. Photos of a chimpanzee, modern human, and australopithecine skull will be provided. Use digital calipers or a ruler to measure the requested values, record them on the chart in centimeters . To calculate the cranial volume (cc) for the three specimens, multiply the cranial width, by the length, height, and 1.333. Multiply the result by 3.14 (Pi), then divide your answer by 10. (ABC x 1.33) x 3.14 10 Results: Compare the cranial volume of the three specimens. Does A . afarensis have a brain more like Chimps or Humans? Why or why not? ORIGIN & DIVERSITY OF HUMANKIND - Jennifer Hastings - Page 5 of 6

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*** Do Not turn in this page*** Part 3: Review and Reading Using textbook chapter 6 and all available class material answer the following questions: 1) What is bipedalism? The Anatomy of Bipedalism 2) What are the biological characteristics of bipedalism ( A, B, C, & D)? Identify what about these features are different between humans and non-human apes 3) How did the savanna hypothesis explain the origins of bipedalism? a. Explain the hypothesis b. What was the ultimate issue with the hypothesis? 4) What are the earliest fossil hominins to show physical evidence of bipedalism? 5) Identify the differences between the following Hominins (How old are they in mya? What habitat did they live in? Were they bipedal? And how do we know?) Hominins: a. Ardipithecus “Ardi” b. Australopithecus “lucy” c. Sahelanthropus tchadensis 6) What evolved first in hominins: a big brain or bipedalism? ORIGIN & DIVERSITY OF HUMANKIND - Jennifer Hastings - Page 6 of 6

Johanson and Edgar 2006 Becoming Bipedal [B]: Australopithecus afarensis From the Laetoli footprints (Unkown male or female)

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