How Humans Evolved 7th Edition by Robert Boyd – Test Bank

How Humans Evolved 7th Edition by Robert Boyd – Test Bank

CHAPTER 10: From Hominoid to Hominin

MULTIPLE CHOICE

1. During the late Miocene, Africa
a. became warmer and wetter.
b. had an expansion of dense forests.
c. experienced less rain and was more seasonal.
d. shifted farther north.

ANS: C DIF: Easy REF: At the Beginning
OBJ: Discuss why natural selection may have favored bipedal locomotion in early hominins.
MSC: Remembering

2. The transition from hominoid to hominin occurred during a transition
a. from forest to savanna. c. from arboreality to terrestriality.
b. from savanna to forest. d. Both a and c.

ANS: D DIF: Easy REF: At the Beginning
OBJ: Discuss why natural selection may have favored bipedal locomotion in early hominins.
MSC: Remembering

3. The very first hominins date to about
a. 60 million years ago. c. 600,000 years ago.
b. 6 million years ago. d. 60,000 years ago.

ANS: B DIF: Easy REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering

4. Between 4 and 2 mya we see some of the distinctive features that differentiate hominins from apes. These features include
a. evidence of bipedal locomotion. c. large canines.
b. small posterior teeth. d. the loss of a tail.

ANS: A DIF: Easy REF: At the Beginning
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

5. Derived traits that distinguish modern humans from apes include
a. facultative bipedalism. c. a large brain-to-body-size ratio.
b. a short juvenile period. d. less body hair.

ANS: C DIF: Easy REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Understanding

6. Genetic data indicate that the last common ancestor of humans and chimpanzees lived between
a. 2 and 1 mya. c. 5 and 3 mya.
b. 4 and 2 mya. d. 7 and 5 mya.

ANS: D DIF: Easy REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering

7. The oldest hominin is
a. Australopithecus. c. Zinjanthropus.
b. Sahelanthropus. d. Pithecanthropus.

ANS: B DIF: Easy REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering

8. Compared with the dentition of chimpanzees, Sahelanthropus tchadensis had
a. larger canines.
b. upper canines that are not sharpened against the lower premolar.
c. thinner enamel.
d. larger incisors.

ANS: B DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Understanding

9. Orrorin tugenensis is identified as a very likely hominid on the basis of what evidence?
a. Features of the base of the skull
b. Footprints preserved in volcanic ash
c. Features of the femur
d. Features of the spine and ribs

ANS: C DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Understanding

10. The cortical bone on the femur of ________ has a humanlike pattern of thickness.
a. Sahelanthropus tchadensis c. Orrorin tugenensis
b. Ardipithecus kadabba d. None of the above.

ANS: C DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering

11. Among the pre-4-mya fossils that some paleoanthropologists include in the hominin family, ________ is thought to be a biped based on information from a single toe bone.
a. Sahelanthropus tchadensis c. Orrorin tugenensis
b. Ardipithecus kadabba d. Ardipithecus ramidus

ANS: B DIF: Easy REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Understanding

12. Ardipithecus ramidus is apelike in that it had
a. small molars.
b. thick enamel.
c. a forwardly placed foramen magnum.
d. a femur that angles inward.

ANS: A DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Understanding

13. Orrorin tugenensis
a. was quadripedal.
b. was ancestral to Sahelanthropus tchadensis.
c. is dated to 4 million years ago.
d. lived in a mix of woodland and savanna.

ANS: D DIF: Easy REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering

14. Surprising findings regarding Ardipithecus ramidus include
a. limb proportions like those of modern great apes.
b. specialization for below-branch feeding.
c. limb proportions like those of monkeys.
d. hands that are similar to those of African apes.

ANS: C DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Evaluating

15. Compared with great apes, Ardipithecus ramidus was characterized by
a. thicker molar enamel and larger canines.
b. thicker molar enamel and smaller canines.
c. thinner molar enamel and larger canines.
d. thinner molar enamel and smaller canines.

ANS: B DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering

16. Fossil candidates for the “first” hominins include
a. Pan, Pongo, Hylobates
b. Sahelanthropus, Orrorin, Ardipithecus
c. Paranthropus, Homo erectus, Homo ergaster
d. Homo heidelbergensis, Neanderthals, Homo sapiens

ANS: B DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Understanding

17. The distribution of cortical bone in the femur
a. is diagnostic of locomotor patterns.
b. can be used to estimate body weight.
c. cannot be measured in fossils.
d. tells you how strong a species was.

ANS: A DIF: Medium REF: At the Beginning
OBJ: Understand that the evolution of bipedal locomotion altered the postcranial skeleton in many important ways. MSC: Remembering

18. Humans have
a. a femur that descends vertically from the pelvis.
b. a knee joint that is not slanted or angled toward the midline of the body.
c. cortical bone that is evenly distributed around the femur.
d. a divergent big toe.

ANS: C DIF: Hard REF: At the Beginning
OBJ: Understand that the evolution of bipedal locomotion altered the postcranial skeleton in many important ways. MSC: Remembering

19. Based on fossil evidence, which feature is thought to have evolved first in hominin evolution, bipedalism or large brains?
a. Bipedalism.
b. Large brains.
c. Both evolved at the same time.
d. This answer cannot be obtained from currently available data.

ANS: A DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Understanding

20. Bipedalism may have evolved because it allowed hominins to
a. keep cool in savanna environments. c. travel easily in the trees.
b. plant and cultivate food. d. swim as well as travel on land.

ANS: A DIF: Easy REF: The Adaptive Advantages of Bipedalism
OBJ: Discuss why natural selection may have favored bipedal locomotion in early hominins.
MSC: Analyzing

21. Bipedalism may have evolved because it allowed hominins to
a. keep warm. c. harvest food from small trees.
b. sit upright. d. run.

ANS: A DIF: Easy REF: The Adaptive Advantages of Bipedalism
OBJ: Discuss why natural selection may have favored bipedal locomotion in early hominins.
MSC: Analyzing

22. Bipedalism may have evolved because hominin ancestors were
a. above-branch quadrupeds. c. vertical clingers and leapers.
b. below-branch, suspensory primates. d. amphibians.

ANS: A DIF: Easy REF: The Adaptive Advantages of Bipedalism
OBJ: Discuss why natural selection may have favored bipedal locomotion in early hominins.
MSC: Analyzing

23. Which of the following is NOT a feature associated with bipedal locomotion?
a. A femur angled inwards toward the body
b. Arched feet
c. Narrow and long pelvis
d. A foramen magnum positioned more anteriorly (centered under the skull)

ANS: C DIF: Easy REF: The Hominin Community Diversifies
OBJ: Understand that the evolution of bipedal locomotion altered the postcranial skeleton in many important ways. MSC: Understanding

24. Australopithecines were
a. prehominin apes from the Miocene from which hominins evolved.
b. toothless wonders from the late Cretaceous.
c. bipedal primates.
d. primates with brains larger than hominoids.

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Analyzing

25. The fossil specimen known as “Lucy”
a. is a 3.2-million-year-old australopithecine.
b. is a complete skeleton.
c. was not bipedal.
d. was named after the Peanuts character.

ANS: A DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

26. Primitive characteristics that distinguish Australopithecus anamensis from later australopithecines include
a. large canines. c. the shape of the tibia.
b. a parabolic dental arcade. d. a sagittal crest.

ANS: A DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

27. Derived features of Australopithecus afarensis include
a. bipedalism. c. a tail.
b. a large brain. d. prognathism.

ANS: A DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

28. Features showing that Australopithecus afarensis is a hominin include
a. a large brain. c. bipedalism.
b. lack of a tail. d. thin molar enamel.

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

29. Features of Australopithecus afarensis that are intermediate between those of apes and humans include
a. the shape of the skull. c. the size of the brain.
b. the size of the canines. d. both a and b.

ANS: B DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

30. The first lower premolar of chimpanzees has ________, the first lower premolar of humans has ________, and Australopithecus afarensis had ________.
a. two equal cusps; no cusps; a small and a large cusp
b. one cusp; no cusps; two equal cusps
c. one cusp; two cusps; no cusp
d. one cusp; two cusps; a small and a large cusp

ANS: D DIF: Hard REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

31. It is likely that Australopithecus afarensis
a. matured more slowly than chimpanzees.
b. had a brain size three to four times bigger than those of chimpanzees.
c. made and used stone tools to scavenge meat.
d. lived throughout West, Central, East, and South Africa.

ANS: A DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

32. Which of the following bones can provide evidence that a fossil animal was bipedal?
a. Humerus, fingers c. Ear bones (related to balance)
b. A hand with an opposable thumb d. Pelvis, femur, skull

ANS: D DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

33. A femur from a bipedal primate ________ than that of a quadrupedal primate.
a. has more torque c. is angled inward more
b. is shorter d. is angled outward more

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Understand that the evolution of bipedal locomotion altered the postcranial skeleton in many important ways. MSC: Analyzing

34. The Laetoli footprints show that Australopithecus afarensis was
a. an efficient biped compared with humans.
b. an inefficient biped compared with humans.
c. about as equally efficient a biped as humans.
d. not bipedal.

ANS: C DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Evaluating

35. Which of the following skeletal features indicate arboreal adaptations?
a. Long lower limbs
b. Eyes moved toward the side of the head
c. Curved fingers and toes
d. Reliance on the sense of smell

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Understand that the evolution of bipedal locomotion altered the postcranial skeleton in many important ways. MSC: Understanding

36. Australopithecus afarensis was
a. sexually dimorphic. c. monogamous.
b. a stone-tool manufacturer. d. older than Ardipithecus ramidus.

ANS: A DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

37. Dental characteristics of hominins, relative to previous species, include
a. thin enamel. c. a parallel dental arcade.
b. thick enamel. d. both a and c.

ANS: B DIF: Hard REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

38. Australopithecus garhi had a unique fin of bone on its skull known as a
a. Sagittal crest. c. Sagittal mohawk.
b. Sagittal keel. d. Sagittal protuberance.

ANS: A DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

39. Australopithecus africanus is most similar to which of the following species?
a. Australopithecus afarensis c. Ardipithecus ramidus
b. Australopithecus boisei d. Sahelanthropus tchadensis

ANS: A DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

40. Australopithecus africanus shares which of the following traits with humans?
a. More air pockets in the skull c. More prognathism
b. Canines that are less dimorphic d. Height

ANS: B DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

41. Australopithecus africanus has derived features not shared with humans. These include
a. a fully bipedal gait. c. heavy chewing adaptations.
b. large canines. d. a modified pelvis.

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

42. Raymond Dart argued that the Taung child was bipedal because it possessed
a. a femur angled toward the midline of the body.
b. an S-shaped spinal column.
c. footprints at Laetoli.
d. a foramen magnum at the bottom of the cranium.

ANS: D DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

43. Australopithecus africanus matured
a. more slowly than modern humans.
b. at about the same rate as modern humans.
c. more quickly than modern humans.
d. at variable rates, depending on geographic location.

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

44. Australopithecus africanus’s maturation rate was determined by
a. the cranial suture closure. c. relative tooth eruption.
b. the long bone suture closure. d. relative nail growth.

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

45. The recent discovery of ________ in 2008 sparked controversy regarding its finders’ claims that it is the most likely candidate of the ancestors of genus Homo.
a. Australopithecus africanus c. Australopithecus sediba
b. Australopithecus afarensis d. Australopithecus ramidus

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

46. Imagine you have found a skull with an ape-size brain, sagittal crest, very large back teeth, and large cheekbones. Based on this information, this is most likely a specimen of
a. Australopithecus afarensis. c. Australopithecus africanus.
b. a robust australopith. d. a modern human.

ANS: B DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

47. Paranthropus robustus had skull structures specialized for
a. cannibalism. c. carnivory.
b. heavy chewing. d. speech.

ANS: B DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

48. Paranthropus robustus
a. was about 4.5 ft. tall and bipedal c. had very small molars.
b. was not fully bipedal. d. had very large incisors.

ANS: A DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

49. Evidence that the robust australopithecines ate hard foods includes
a. the browridge. c. flared zygomatics.
b. the nuchal crest. d. a small brain.

ANS: C DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

50. Which early hominin had molarized premolars and megadont molars for extremely heavy chewing?
a. Paranthropus robustus. c. Paranthropus boisei.
b. Australopithecus afarensis. d. Australopithecus africanus.

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

51. Studies of tooth enamel tell us that
a. C4 plants are woody plants while C3 plants are grasses and sedges.
b. Australopithecus africanus and Paranthropus robustus shared a variable diet that may have included animals that fed on C4 plants.
c. chimpanzees feed mainly on C4 plants.
d. Paranthropus boisei ate mostly C3 plants.

ANS: B DIF: Hard REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

52. Compared to the gracile australopiths, the robust australopiths
a. were twice the body size.
b. exhibit a number of derived features of the cranium and teeth.
c. were not appreciably different in any way.
d. have all come from East African sites.

ANS: B DIF: Hard REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

53. Chemical analysis of robust australopith teeth suggests that these hominins ate
a. only insects. c. tough foods and meat.
b. only tough foods. d. only meat.

ANS: C DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

54. The skull ________ invalidates the theory that robustness in the skull and teeth was a derived state for the australopithecines.
a. WT 17000 c. ER 1813
b. OH 15 d. ER 1470

ANS: A DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

55. A recently discovered early hominin, which dates to 3.5–3.2 mya and has a flat face, is
a. Orrorin tugenensis. c. Australopithecus afarensis.
b. Ardipithecus ramidus. d. Kenyanthropus platyops.

ANS: D DIF: Easy REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering

56. Paranthropus aethiopicus
a. is the most robust of the robust australopithecines.
b. retains many primitive characteristics of Australopithecus afarensis.
c. shares many derived characters with the genus Homo.
d. is the direct ancestor of genus Homo.

ANS: B DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Understanding

57. Despite some confusion at present about hominin phylogeny, which of the following statements is true?
a. Humans evolved from one of the robust australopiths.
b. Humans evolved from one of the australopithecines.
c. Humans evolved from a non-australopithecine ancestor.
d. There is not enough evidence to speculate about human ancestry.

ANS: B DIF: Medium REF: Hominin Phylogenies
OBJ: Understand why efforts to construct phylogenies of early hominins are unproductive.
MSC: Evaluating

ESSAY

1. Compare and contrast the characteristics of Sahelanthropus, Orrorin, and Ardipithecus. What kinds of environments did they live in? How did the environment shape the evolution of their morphology?

ANS:

Sahelanthropus tchadensis: 7–6 mya, Chad
Wide geographic range, forested
Anterior foramen magnum
Small brain: 320–350 cc
Teeth: small canines, no sectorial premolar, thick enamel
Flat face, browridge
Orrorin tugenensis: 6 mya, Kenya
Woodland, savanna
Small molars, thick enamel
Fingers and arms imply climbing
Long femoral neck, cortical bone similar to humans (lower edge)
Ardipithecus: Ethiopia
Woodland, grassland
Ar. kadabba: 5.8–5.2 mya
Sectorial premolar, thick enamel, shape of the canine
Toe bone
Ar. ramidus: 4.4 mya
Woodland
“Ardi” 51 kg, 1.2 m, female
Equal-length arms and legs
Small brain: 300–350 cc
Flat upper face, midface prognathic
Anterior foramen magnum
Thick enamel, smaller teeth, less canine sexual dimorphism, no sectorial premolar,
U-shaped dental arcade, small incisors, and low cusps (omnivore/frugivore)
Foot: opposable big toe, but other four toes imply bipedality
Pelvis: ileum shorter and broader, sciatic notch, but lower part of pelvis apelike
Hands: shorter bones in hand and fingers; longer, more robust thumb
Locomotion: above-branch walking, bearing weight on palms and bridging
Although these species still occupied forested areas, these forests were drier than the moist forests of the early Miocene. This resulted in increased seasonality and dispersed, different, and more seasonal food sources. This selective pressure may have favored bipedalism.

DIF: Easy REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering | Understanding

2. The evidence is compelling for either Sahelanthropus or Orrorin to have been most like the first hominin. Pick one, and make your case for why you think so.

ANS:
Students can answer either way, as long as they use appropriate dates and evidence:
Sahelanthropus tchadensis: 7–6 mya, Chad
Anterior foramen magnum
Teeth: small canines, no sectorial premolar, thick enamel
Flat face, browridge
Orrorin tugenensis: 6 mya, Kenya
Woodland, savanna
Small molars, thick enamel
Long femoral neck, cortical bone similar to humans (lower edge)

DIF: Medium REF: At the Beginning
OBJ: Describe why the earliest members of the human lineage were basically bipedal apes.
MSC: Remembering | Analyzing

3. What is the anatomical evidence that early australopithecines were bipedal?

ANS:
There are several lines of evidence from several species of early gracile australopithecines that indicate bipedality. Students can choose one or more of the following lines of evidence.
a. Lucy: nearly 50% complete skeleton of a bilaterally symmetrical species; one side tells us that she had a short, wide pelvis; long femoral neck; valgus knee; foot arch; nonopposable big toe
b. A. anamensis: tibia
c. Implied locations of foramen magnum for the species for which we have skulls

DIF: Easy REF: At the Beginning | The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya, and understand that the evolution of bipedal locomotion altered the postcranial skeleton in many important ways. MSC: Analyzing

4. What was the diet of the robust australopiths? What are the anatomical features associated with their diet?

ANS:
The robust australopiths ate hard, tough foods, probably mostly from C4 plants. The anatomical features associated with this include pronounced sagittal crest, postorbital constriction, flaring zygomatics, and large molars with thick enamel and cusp shape.

DIF: Medium REF: The Hominin Community Diversifies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya.
MSC: Remembering | Understanding

5. Which known member of the genus Australopithecus is most like an ancestor to later australopiths and even of our genus, Homo? Support your suggestion with information about features of the hominins noted in the chapter.

ANS:
Students can draw on multiple phylogenies if they provide the appropriate anatomical evidence, but predominantly they should respond with A. afarensis, A. africanus, or A. garhi as they were presented in the text. The points they should focus on are the derived features of hominins noted in the chapter (teeth and bipedal adaptations). It is important that students provide tracts that are generalized enough and not too specialized already (for example, no Paranthropus species).

DIF: Medium REF: The Hominin Community Diversifies | Hominin Phylogenies
OBJ: Summarize the key attributes of the hominin species that lived in Africa 5 to 2 mya, and understand why efforts to construct phylogenies of early hominins are unproductive.
MSC: Remembering | Analyzing | Evaluating

6. Discuss three hypotheses concerning the evolution of bipedalism.

ANS:
a. Apes walked almost upright in trees, above branches, using hands to steady themselves, to feed at terminal branches and bridge from tree to tree. Although chimpanzees and orangutans currently use this behavior, the earliest bipeds like A. ramidus had equal-length arms and legs like monkeys and not apelike adaptations.
b. Bipedal shuffling on the ground allowed the early hominins or their ancestors to move between small fruiting trees. This is based on observations of chimpanzees.
c. Bipedalism allows for efficient cooling, which is necessary in hot, savanna environments. It is particularly important for the brain to stay cool. The problem is that bipedalism appeared to evolve in a more forested, cooler habitat.
d. Bipedalism leaves hands free for carrying things, like tools or food. However, there may be other ways to solve this problem, and we have no evidence of food or tool carrying.

DIF: Easy REF: The Adaptive Advantages of Bipedalism
OBJ: Discuss why natural selection may have favored bipedal locomotion in early hominins.
MSC: Remembering | Understanding

7. Why might there be uncertainties about the relationship of different hominins to each other?

ANS:
a. The richness of the fossil record makes it difficult to determine relationships among hominins.
b. Convergent traits (convergence or parallelism) are present as different species respond to similar selective pressures.
c. Different traits may result in differing phylogenies.

Students may refer to Skelton and McHenry’s study in which different phylogenies are created depending on what groups of traits are analyzed.

DIF: Hard REF: Hominin Phylogenies
OBJ: Understand why efforts to construct phylogenies of early hominins are unproductive.
MSC: Evaluating