LAB 9 CHAPTER 15: exercises 1-6 and critical thinking questions 1-5
Exercise 1
Work in a small group or alone to complete this exercise. Refer to the casts provided by your instructor (or the pictures in the lab Appendix) to answer the following questions.
- Which of these mystery australopithecines is a later, more robust form?
- Mystery primate A is the later, more robust primate.
- Describe two anatomical traits you used to make this determination. (Be sure to describe how each trait varied in the two fossils.)
- First we can see that the zygomatic arch is much bigger than primate B, which is a trait of later australopithecines. We can also infer from this that (although the jaw is missing) the mandible and posterior teeth were probably also very large, which is also a trait of later australopithecines.
Exercise 2
Work in a small group or alone to complete this exercise. Review the casts provided by your instructor (or the pictures in the lab Appendix) and answer the following questions.
- Which of these mystery fossils is Australopithecus robustus?
- Mystery primate A is robustus.
- Which of these mystery fossils is Australopithecus boisei?
- Mystery primate B is boisei.
- Describe one trait you used to make these identifications. (Be sure to describe how the trait varied in the two fossils.)
- One difference we can use to tell the two apart is that Au. boisei has a much larger sagittal crest so it must be primate B.
Exercise 3
Work in a small group or alone to complete this exercise. Review the casts provided by your instructor (or the picture in the lab Appendix) and answer the following questions.
- Describe two postcranial traits that indicate afarensis was adapted for bipedalism.
- afarensis has an angled femur as well as several key foot distinctions like the double arches and non-divergent big toe that show us they were adapted for bipedalism.
- Compare the Lucy ( afarensis) postcranial to the human (Homo sapiens) postcrania depicted in Figure 5.11 (Lab 5). Describe two postcranial traits that differ between these species.
- Besides these key similarities afarensis has many differences with us including that it doesn’t have a bowl shaped pelvis and curved phalanges.
- What does this suggest about the kind of bipedalism practiced by afarensis?
- Considering the features afarensis has we would consider it a habitual biped meaning they spent most of their time walking and occasionally they were arboreal.
Exercise 4
Work in a small group or alone to complete this exercise. Use the casts provided by your instructor (or the pictures in the lab Appendix) to answer the following questions.
- Describe two traits that differ between these fossils. (Be sure to describe how each trait appears in the two fossils.)
- We can see two key differences just in the shape of the skull of each primate. Primate B has a much wider, or flaring, zygomatic bones, as well as a sagittal crest. The skull of primate A is much more gracile and lacks the sagittal crest.
- Based on this information, which of these fossils is an australopithecine?
- Based on this information, primate B is an australopithecine.
- Based on this information, which of these fossils is a member of the Homo genus?
- Based on this information, primate A is a member of the Homo genus.
Exercise 5
Work in a small group or alone to complete this exercise. Refer to the casts provided by your instructor (or the pictures in the lab Appendix) to answer the following questions.
- Describe two traits that differ between these fossils. (Be sure to describe how each trait appears in the two fossils.)
- Although these two fossils look very similar there are a couple important differences we can see between them. First of all fossil A lacks the sagittal and partial coronal suture that fossil B has. Secondly we can see that the zygomatic bone is much bigger on fossil A than on fossil B.
- Do you believe these differences are the result of sexual dimorphism or different adaptations? Why?
- Based on the fossils I believe the differences aren’t enough to be different adaptations. The biggest difference between the two is size and considering how similar they are in shape and adaptations, a difference in size usually means that one is male and one is female.
Exercise 6
Work in a small group or alone to complete this exercise. Review the casts provided by your instructor (or the pictures in the lab Appendix) and answer the following questions.
- What type of tool form is this?
- This tool is most likely a bifacial chopper.
- Describe the features of this tool that led you to identify it as this tool form.
- This is most likely a bifacial chopper because of its size and because it has a sharp edge on top as well as along its side, with a smooth rounded side for gripping.
- What tool technology does it belong to?
- This belongs to the Oldowan technology.
- Name one fossil species that may have made this stone tool.
- garhi is the oldest possible species that may have used tools such as this.
Critical Thinking Questions
- This question may be completed independently or as a group exercise. Biological anthropologists disagree about the best way to classify the robust australopithecines. Describe the two approaches to classifying these species. Which classification do you support? Why? (Be sure to support your decision with specific evidence.)
- One approach to classifying the robust australopithecines is to leave them classified as they are, whereas the second is to put them into their own group, paranthropus, because of the differences they have from the rest. I suppose it could be beneficial to put them into their own category to help fill in more of the empty spaces we have in our history. However, it would probably be best to wait until more fossils are found in order to solidify that they need their own category. It’s hard to assume so much based on the little evidence we have. Maybe some of the fossils we find are different because they were malformed individuals, not because they are a totally different species.
- This question may be completed independently or as a group exercise. The Australopithecus sediba finds demonstrate that evolution is mosaic, meaning that species often have a combination of ancestral and new traits. How would this fossil material be interpreted if only the arm bones were found? How would this fossil material be interpreted if only the pelvis were found? Based on this example, what problems do paleoanthropologists face when trying to interpret the fragmentary fossil record?
- A lot of problems can occur when we find only certain body parts and make assumptions on them rather than having more of a collection of parts to build a solid picture. In the case of sediba we can show how problematic this could be. If we only found the arm we might assume they were brachiators because of how long it is without realizing that their phalanges weren’t curved meaning they probably did very little in the trees. If we found just their pelvis we might assume they were much closer to Homo than they are because we didn’t have the other body parts to show the differences they had from Homo. The problem with a fragmentary fossil record is that it’s extremely difficult to really be sure of anything without having more of the picture. This also shows how important it is to find
fossils of other animals and plants from the same time period to get an idea of the environment that the species lived it.
- This question may be completed independently or as a group exercise. During a period of almost a million years, Australopithecus boisei and Homo habilis lived in the same region of East Africa. If these species shared a habitat, how did they not outcompete one another? (Hint: Think about their possible ecologies and adaptations.)
- Although boisei and H. habilis lived during the same time, they wouldn’t need to compete because of how different their diets were. They both had a diet that consisted mostly of plants, but the key difference is in H. habilis’s tool use. Since H. habilis had more of a capacity to use tools, it increased the possibility of food that they could eat. This increase in diet possibility makes competition for food much less likely.
- This question may be completed independently or as a group exercise. In this lab we discussed the earliest known stone tools. Do you think this was the first time our extinct relatives used tools? Why might older tools not be preserved in the fossil record? For comparison, describe three tools from your own life (a cell phone, a pencil, a plastic fork, etc.). Do you think these tools will be preserved 2.5 million years from today?
- Although we don’t have the fossil record of earlier tool use it’s very possible that earlier ancestors were using tools. If we assume that they were using tools from the environment, such as stone or wood, the normal weathering processes in the natural environment would likely destroy the tools over time, at least beyond recognition. Another problem is us recognizing what is a tool or not. As in the question, even if a phone survived 2.5 million years without being destroyed by the elements, would future species even recognize what it is? Parts of it might survive but they might not think it was related to us at all, or if they did maybe they would assume it was used for something totally different because only pieces of it are left.
- In this lab we reviewed a lot of different fossil species and their defining characteristics. To help you make comparisons across these species and understand larger trends in our evolutionary history, complete the following Australopithecine and Early Homo Chart.
|
Fossil |
Dates/Location |
Cranial Traits |
Postcranial Traits |
Suggested Behavior |
||||
|
Australopithecus Anamensis |
4 mya |
Large outer cusp on third premolar Large canines Parallel tooth ros in upper jaw |
Curved hand phalanx Less than 3.3 ft. tall |
Lived in woodlands habitual biped with some adaptations for walking on two feet |
||||
|
Australopithecus afarensis |
3.6 - 3 mya |
430 cc brain size Smaller canines Equal sized cusps on third premolar Parabolic tooth rows in upper jaw |
Curved hand phalanges Short legs In line big toe |
Lived in open woodlands Bipedal, had adaptations for arboreal locomotion |
||||
|
Australopithecus africanus |
3 - 2 mya |
450 cc brain size Moderate sized teeth Equal sized cusps on third premolar |
Phalanges not curved Short legs Long arms |
Lived in open grasslands a mix of bipedal and arboreal adaptations sexual dimorphism |
||||
|
Australopithecus garhi |
2.5 mya |
450 cc brain size Equal sized cusps on third premolar Larger teeth and Au. afarensis |
Closer ratio of arm to leg length Curved foot phalanx |
Lived in grasslands, on lakeshore more bipedal lifestyle with less use of arboreal locomotion produced and used the first stone tools to butcher animals |
||||
|
Australopithecus (Paranthropus) aethiopicus |
2.5 mya |
410 cc brain size Massive posterior teeth Robust skull with sagittal crest |
N/A |
Lived in open grasslands enlarged fea- tures indicate Au. aethiopicus had a diet that required heavy chewing. |
||||
|
Australopithecus (Paranthropus) boisei |
2.3 - 1.2 mya |
510 cc brain size Massive posterior teeth Robust skull with sagittal crest |
N/A |
Lived in open grasslands had a diet that more narrowly focused on sedges and grasses. |
||||
|
Australopithecus (Paranthropus) robustus |
2 - 1.5 mya |
530 cc brain size Massive posterior teeth Robust skull with sagittal crest |
N/A |
Lived in open grasslands diets and dietary adaptations were probably complex and variable in our ancient ancestors |
||||
|
Australopithecus sediba |
2 mya |
420 cc brain size Small teeth Equal sized cusps on third premolars Gracile face and jaws |
Phalanges not curved Short finger, long thumbs Long arms Small body Homo-like pelvis |
Lived in open grasslands suggest that Au. sediba may have descended from Au. africanus, |
||||
|
Homo habilis (including H. rudolfensis) |
2.5 - 1.8 mya |
650 cc brain size Smaller face smaller teeth, mandibles, and zygomatic arches, and it lacked the sagittal crests |
Small body 3.5 ft. Shorter legs long arms |
Stone tool use habitual biped - obligate biped due to its lack of an opposable hallux and the presence of a longitudinal arch in its foot. |
||||
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