Biological Anthropology Lab 8

Exercise 2

Work with a small group or alone to complete this exercise. Review the primate descriptions below. For each primate, describe the primate’s likely body size and digestive tract.

1. Primate A is an insectivore that eats a lot of moths, stick insects, and grasshoppers. These foods provide small packets of energy that are easy to digest.
   1. Body size: Small
   2. Digestive tract: Small and Simple
2. Primate B is a frugivore that eats a lot of berries, figs, and other tree fruits. These foods provide intermediate packets of energy that are relatively easy to digest.
   1. Body size: Medium
   2. /Digestive tract: Small and Simple
3. Primate C is a gummivore that eats a lot of tree sap. This food provides small packets of energy that are easily digested.
   1. Body size: Small
   2. Digestive tract: Small and Simple
4. Primate D is a folivore that eats a wide variety of leaves, stems, and young plant shoots. This food provides limited, slow-burning energy and is difficult to digest.
   1. Body size: Large
   2. Digestive tract: Long and Complex

Exercise 3

Work with a small group or alone to complete this exercise. Use the mystery primate skeletons provided by your instructor (or those depicted in the lab appendix) to complete the chart below. Describe the scapula position, body and limb proportions (arm and leg length, size of chest, etc.), and tail of each mystery primate. Using this trait information, also determine the likely form of locomotion of each mystery primate, and name an example of one primate that has this form of locomotion.

	Mystery Primate A	Mystery Primate B
Scapula Position	Lateral	Lateral
Body and Limb Proportions	Longer legs than arms	Relatively same size
Tail	Long tail	Short Tail
Locomotion	Arboreal Quadrupedalism	Terrestrial Quadrupedalism
Example Primate	Golden Lion Tamarin	Baboon

Exercise 4

Work with a small group or alone to complete this exercise. Use the mystery primate skeletons provided by your instructor (or those depicted in the lab appendix) to complete the chart below. Describe the scapula position, body and limb proportions (arm and leg length, size of chest, etc.), and tail of each mystery primate. Using this trait information, also determine the likely form of locomotion of each mystery primate, and name an example of one primate that has this form of locomotion.

	Mystery Primate A	Mystery Primate B	Mystery Primate C
Scapula Position	Lateral	Posterior	Lateral
Body and Limb Proportions	Relatively Similar Length	Extra Long Arms	Extra Long Legs
Tail	Long (probably prehensile)	No Tail	Long
Locomotion	Semi - Brachiation	Brachiation	Vertical Clinging and Leaping
Example Primate	Capuchin	Gibbon	Tarsier

Exercise 5

Work with a small group or alone to complete this exercise. Examine the mystery primates provided by your instructor

(or those depicted in the lab appendix). These represent adult individuals from the same species.

1. Which mystery primate is female?
   1. Mystery primate B is female, because of its smaller canines and cranium.
2. Which mystery primate is male?
   1. Mystery primate A is male, because it has much larger canines as well as more robust cranium.

Exercise 6

Work with a small group or alone to complete this exercise. Examine the mystery primate species provided by your instructor (or those depicted in the lab appendix). These represent an adult male and an adult female from two mystery primate species, a and b.

1. Which mystery primate species has a single-male polygynous group?
   1. Primate species B has a single male polygynous group.
2. Which mystery primate species has a multimale polygynous group?
   1. Primate species A has a multimale polygynous group.
3. Describe one trait you used to make this distinction.
   1. We can tell which social group they belong to just by their skull size. Single male polygynous groups have even more exaggerated sexual dimorphism because

males will act more violently in competition towards each other. This exaggeration leads the males to be much bigger in comparison to the females than in other social groups.

CH 14

Exercise 1

Work in a small group or alone to complete this exercise.

Part A:

Examine the skeletal material provided by your instructor (or depicted in the lab Appendix).

1. Which mystery primate is a biped?
   1. Mystery primate A is a biped.
2. Describe one adaptation seen in this primate’s cranium that indicates it practices this locomotion.
   1. Mystery primate A has a foramen magnum positioned more anteriorly than primate B.
3. How does this adaptation help the primate to move bipedally?
   1. The position of the foramen magnum at the base of the cranium like this allows primate A to move bipedally face forward rather than with its head tilted upwards.

Part B:

Examine the skeletal material provided by your instructor (or depicted in the lab Appendix).

1. Which mystery primate is a biped?
   1. Primate B is a biped.
2. Describe one adaptation seen in this primate’s cranium that indicates it practices this locomotion.
   1. Primate B is a biped because of it’s larger mastoid process.
3. How does this adaptation help the primate to move bipedally?
   1. Having a larger mastoid process allows for more muscle attachment in the neck giving its head more mobility and support for walking upright.

Exercise 2

Work in a small group or alone to complete this exercise. Examine the skeletal material provided by your instructor (or depicted in the lab Appendix).

1. Which mystery primate is a biped?
   1. Primate A is a biped.
2. Describe one adaptation seen in this primate’s vertebral column that indicates it practices this locomotion.
   1. Primate A is a biped because of the s-shape curve in it’s vertebral column.
3. How does this adaptation help the primate to move bipedally?
   1. The s-shape curve of primate A’s vertebral column allows it to balance the weight of its upper body directly over its lower body rather than bending outward like in the c-shape vertebral column.

Exercise 3

 Work in a small group or alone to complete this exercise. Examine the skeletal material provided by your instructor (or depicted in the lab Appendix).

1. Which mystery primate is a biped?
   1. Primate A is a biped.
2. Describe one adaptation seen in this primate’s pelvis that indicates it practices this locomotion.
   1. Primate A is a biped because of its bowl shaped pelvis.
3. How does this adaptation help the primate to move bipedally?
   1. Primate A’s bowl shaped pelvis helps it hold up the internal organs and upper body weight for upright locomotion.

Exercise 4

Work in a small group or alone to complete this exercise. Examine the skeletal material provided by your instructor (or depicted in the lab Appendix).

4. Which mystery primate is a biped?
   1. Primate B is a biped.
5. Describe one adaptation seen in this primate’s femur that indicates it practices this locomotion.
   1. Primate B is a biped because it’s femur angles in medially.
6. How does this adaptation help the primate to move bipedally?
   1. The angle of primate B’s femur helps position its knee and lower leg in front of its body rather than outwards allowing it to move bipedally in a straight central way instead of wobbling.

Exercise 5

Work in a small group or alone to complete this exercise. Examine the skeletal material provided by your instructor (or depicted in the lab Appendix).

7. Which mystery primate is a biped?
   1. Mystery primat B is a biped.
8. Describe one adaptation seen in this primate’s foot that indicates it practices this locomotion.
   1. The big toe of primate B is in line with the rest of its toes.
9. How does this adaptation help the primate to move bipedally?
   1. Having the big toe in line allows primate B to balance itself better for bipedal locomotion and steady itself on the big toe.

Exercise 6

Work in a small group or alone to complete this exercise

Part A:

Match each of the pre-australopithecines described below to its corresponding description.

1. I lived about 6 mya in eastern Africa. My femurs had long necks with grooves for my obturator externus muscles.

a. Orrorin tugenensis

2. I lived about 7–6 mya in central Africa. I had a small cranial capacity, large brow ridge, and anteriorly positioned foramen magnum.

a. Sohelanthropus tchodensis

3. I lived about 4.4 mya in eastern Africa. I had long arms and fingers and a relatively short, broad pelvis.

a. Ardipithecus ramidus

• Sohelanthropus tchodensis
• Orrorin tugenensis
• Ardipithecus ramidus

Part B:

Examine the material provided by your instructor (or depicted in the lab Appendix). What adaptations for bipedalism are seen in this Ardipithecus ramidus pelvis?

• The Ardipithecus ramidus has a bowl shaped pelvis as well as ilia that are positioned more laterally. Both traits are seen in bipedal locomotion.

Part C:

The pre-australopithecine fossils are especially significant because they challenge some of the long-standing explanations of our evolutionary history. Describe two reasons the pre-australopithecines force us to rethink the savanna hypothesis in particular. (Hint: Think about the anatomical traits of the pre-australopithecines and the environmental and temporal context in which they lived.)

• Pre-australopithecines were considered habitual bipeds because they had traits that suggest they still spent time in the trees. These traits include such things as longer arms for brachiation and a divergent hallux for grasping feet. On top of this the plant and animal remains recovered from the dig sites also suggest that they lived in forested environments. This challenges the savanna hypothesis because it suggests that it wasn’t the changing environment that forced bipedalism to become a selected trait if it was already beginning to become one in a forest environment.

Exercise 7 

Work in a small group or alone to complete this exercise.

 In this lab, we considered the savanna hypothesis and provisioning hypothesis as different explanations for the evolution of bipedalism. Other explanations for the shift to bipedalism exist as well. For example, an alternate explanation focuses on the issue of thermoregulation. According to the thermoregulation hypothesis, bipedalism was selectively favored because it helped our ancestors to stay cool in their warm environment.

Your instructor has provided you with a lamp (representing the sun) and a doll (representing one of our extinct relatives). Using these tools, follow the steps below to further explore the thermoregulation hypothesis.

Step 1: Position the lamp so it is above the doll and facing directly downward (as if the sun were directly overhead).

Step 2: Position the doll so that it is on all fours under the lamp, similar to a baboon wandering the open savanna. Note the amount of sun exposure the doll receives in this position.

Step 3: Position the doll so that it is standing on two legs under the lamp, similar to a human wandering the open savanna. Note the amount of sun exposure the doll receives in this position.

Step 4: Answer the following discussion questions:

1. In which position did the doll have the least sun exposure?
   1. The had the least overhead sun exposure when it was on two feet.
2. Why might having less sun exposure be an advantage in a warm environment?
   1. In a warm environment having less sun exposure is beneficial to keeping internal temperature at a homeostatic state without spending too much energy to do it.
3. In which position do you think the doll has the most exposure to wind and air circulation?
   1. In the upright standing position the doll has the most exposure to wind and air circulation.
4. Why might having more exposure to the wind be an advantage in a warm environment?
   1. As with less sun exposure, having more exposure to wind in a warm environment helps the body stay at a cooler temperature without having to spend extra energy to do it.
5. Based on this test, do you think the thermoregulation hypothesis might provide a valid explanation for the evolution of bipedalism? Is it challenged by the pre-australopithecine finds?
   1. The thermoregulation hypothesis does provide a valid explanation of bipedalism if we are considering that it was a selected trait in an open environment. However, because many of the findings suggest that bipedalism evolved in a forest environment both sun exposure and wind exposure can be challenged. In a forested environment the sun and wind can be mostly blocked by trees, meaning these were mild factors that probably had no effect on the evolution of bipedalism.

Critical Thinking Questions

1. This question may be completed independently or as a group exercise. Describe the three different types of bipedalism. For each one, be sure to discuss the frequency of bipedal locomotion, describe the extent of bipedal adaptations, provide at least one sample primate who practices this type of bipedalism, and describe why the sample primate uses this form of bipedalism.
   1. The first type of bipedalism is occasional. Occasional bipedalism is used by primates such as chimps or bonobos. Occasional means that these primates use it very rarely for instances where they are carrying something in their hands. Occasional bipedalism has no real adaptations for walking upright. The second type is Habitual bipedalism and it is what we expect our ancestors used. In this type of bipedalism the primate has adaptations for arboreal locomotion and for bipedalism and uses a mix of both in its day to day life. Such adaptations include a wider pelvis, longer neck on the femur, or, like in Sahelanthropus tchadensis, a foramen magnum located more anteriorly at the base of the cranium. The last type is Obligate bipedalism and its what we as humans use. Obligate means we only use bipedalism for locomotion. Our angled femur, wide pelvis, anterior foramen magnum, s-shaped vertebral column, large lumbar vertebrae, shape and length of our feet, are all just a few examples of the adaptations that make bipedalism the best mode of locomotion for humans.
2. Although bipedalism is unusual, humans are not the only living bipeds. For example, some flightless birds are also bipedal. Identify a living non primate animal that is also a biped. Then, compare its bipedalism to our bipedalism. Try to consider how it moves and some of its possible adaptations (such as limb length). Use material in your classroom, online, or in books to help you if necessary.
   1. An example of a non primate that is also a biped would be a kangaroo. Just as in humans kangaroos have a lot of power in their legs as well as a vertebral column that curves in to help support their weight in an upright position. However, there are a lot of key differences, even within the similarities. Even though a kangaroo is a biped, it doesn’t walk it leaps. Its legs are much bigger than its arms so that it can push its whole body off the ground at once rather than one foot at a time. It also doesn’t have a foramen magnum under its cranium meaning that its entire body is sort of leaning rather than being set upright. Having long feet as well as a tail make up in balance for leaning like this and still allow it to move on two feet.
3. This question may be completed independently or as a group exercise. A paleoanthropologist has uncovered a fossilized pelvis in Africa. She has sent you the drawing below and wants your opinion. Was this individual bipedal? Provide two traits that support your interpretation.
   1. I would assume this was a bipedal primate based on two reasons. The pelvis is a wide bowl shape like in humans meaning it carries its upper body weight on top of its lower body rather than in front of it as in other apes. The ilia are also much broader and positioned more laterally than in many apes, which is an adaptation in humans for bipedal locomotion.