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 A105 Human Origins and Prehistory
A105 Exam 2 Answer Key

Best answers to the multiple choice questions are italicized.  The answers given for the short answer questions are very complete answers -- you don't necessarily have to put in everything I mention to get full credit.  However, they are your most reliable guide to what I'll be looking for should those questions show up again on the final :-). Also, I've made notes in purple on questions that proved to be the most difficult...these questions are also likely to show up in some form on the final.
 

                 A105 Human Origins and Prehistory, Spring 2002
                                               Exam 2

Part I, Multiple Choice.  Choose the best answer to each question.  (1 point each.)
1.  Which of the following must be true if a behavior is to evolve?
     a. It must help the species as a whole to survive.
     b. It must make individuals strong enough to beat up rivals.
     c. It must have a genetic component.
     d. It must help females maximize their number of copulations.
     e. Behavior does not evolve.
Many of you chose answer A, which implies group selection.  Keep in mind that selection acts at the level of the individual, whether we're talking about physical traits or behavior.

2.  What social arrangement is not seen in apes?
     a. Monogamous
     b. Female bonded
     c. Female choice
     d. Community/fission-fusion
     e. Solitary
Bonds between female apes are generally weak compared to bonds between female monkeys, for ecological reasons we discussed.  There is an ape representative for each of the other societies.

3.  In a female-choice social system like that seen in gorillas,
     a. Each individual lives mostly alone, except for females and their offspring
     b. Related females bond together to defend their favorite fruit trees
     c. Infants are so hard to raise that each female bonds to two males
     d. A single dominant male lives with a group of females, who are much  
         smaller than he is
     e. Females find a male and pair off for life, cooperating in raising offspring   
         and defending their territory

4.  Many primates spend large amounts of time grooming one another.  What would be the most  important benefit of this behavior?
     a. It reinforces social bonds and alliances.
     b. It keeps primates clean and parasite-free.
     c. It alleviates boredom.
     d. Well-groomed primates are more attractive to potential mates.
     e. Grooming has no known benefits.

5.  Which of the following is NOT a characteristic of ape societies?
     a. Males may form bonds with each other
     b. Females transfer groups at maturity (or form new groups)
     c. Males often stay in the group they are born into
     d. Females may form bonds with males
     e. Groups of related females tend to bond together to defend resources

6.  From the material presented in lecture, what would be an accurate characterization of the language capabilities of chimpanzees and/or bonobos in language studies?
     a. They are prevented from full human language only by their inability to 
         produce articulate speech
     b. Those who have participated in sign language experiments show that all 
         they can do is imitate signs; they cannot understand language at all
     c. They are able to understand English quite well, and can     
         communicate with researchers using abstract symbols
     d. They can only communicate using sign language; they have been unable to 
         understand abstract symbols
     e. They show no interest at all in communicating with humans except by their 
         normal calls and gestures

7.  Many primates are known to make and use tools in the wild.  Which primate has the most extensive toolkit in the wild, based on current knowledge?
     a. Japanese macaque (snow monkey)
     b. Chimpanzee
     c. Capuchin monkey
     d. Orangutan
     e. Bonobo

8.  We talked about differences in hunting strategies among chimpanzees at Gombe and Tai; Tai chimp hunts are more planned, with Tai chimps cooperating more in the hunt than seen at Gombe.  What explanation did your instructor give for this difference?
     a. Gombe chimps are not as intelligent as Tai chimps
     b. Gombe chimps hunt monkeys that are less difficult to catch, so they don’t 
         need to work together as much
     c. Tai chimp hunters are more closely related, so they work together more to 
         increase their inclusive fitness
     d. Tai chimps live in a closed canopy environment, making monkey 
         capture more difficult and requiring closer cooperation
     e. Gombe chimps are more selfish, wanting to keep meat for themselves

9.  Which fossil is thought to be among the earliest apes?
     a. Proconsul
     b. Purgatorius
     c. Aegyptopithecus
     d. Cantius
     e. Orrorin
The same number of people chose B as chose the right answer...Purgatorius is an early possible primate, but it's not an ape (it's a prosimian, if anything).

10.  Which of the following IS NOT a trend seen in fossil primate evolution?
      a. Eyes face more toward the front
      b. Teeth become more numerous
      c. The postorbital bar and then postorbital closure appear
      d. Brain size increases
      e. Snout size decreases

11.  Which of the following statements is true?
      a. There are more ape species living today than ever before due to the   
          greenhouse effect
      b. Ape fossils have been found only in Africa
      c. It is possible to trace the ancestry of chimpanzees directly through fossil 
          ancestors
      d. During the Miocene, drier conditions caused an adaptive shift, 
         leaving fewer ape species and more monkey species today
      e. The total number of primate species has increased during the Pleistocene

12.  Which of the following IS NOT an advantage of bipedalism, as seen in modern people?
     a. Leaves hands free to manipulate and carry objects
     b. Allows individuals to see possible predators over grasses
     c. Allows for faster sprinting, to evade predators or catch prey
     d. Walking bipedally is efficient for covering long distances
     e. Bipedalism is heat efficient in hot climates

13.  Darwin believed that bipedalism evolved after big brains.  What adaptive advantage did he believe bipedalism gave early hominids?
     a. It left the hands free to manipulate tools and weapons
     b. It allowed males to carry food back to females
     c. It allowed hominids to more easily spot predators
     d. It helped hominids to maintain dominance in their social groups
     e. It enabled hominids to remain stable while feeding in or near small trees

14.  What were the first human fossils to be widely accepted?
     a. Piltdown Man
     b. Pithecanthropus erectus
     c. Taung child
     d. Neandertal (original find from Neander valley)
     e. Cro-Magnon

15. Which of the following is the earliest widely accepted hominid species?
     a. Aegyptopithecus zeuxis
     b. Orrorin tugenensis
     c. Australopithecus afarensis
     d. Ardipithecus ramidus
     e. Australopithecus anamensis
This is one of the questions where I gave credit for multiple answers -- though D is the correct answer, B and C also counted.  Although Orrorin is the earliest possible hominid, and A. afarensis is the earliest hominid that we have lots of specimens described, ramidus is the earliest hominid widely accepted as being a hominid.

16.  Which is the most recently extinct of the following species (i.e., which one lived closest to the present)?
     a. Proconsul africanus
     b. Australopithecus aethiopicus
     c. Australopithecus boisei
    d. Australopithecus africanus
    e. Australopithecus afarensis
Responses were fairly evenly split among A, C, and D.  Note that Proconsul is a Miocene ape; all others are Pliocene or Pleistocene hominids.  It may help to remember that boisei went extinct at 1 mya or even a little after; it's the latest surviving australopithecine.

17.  The Taung fossil
     a. Is an example of Australopithecus afarensis
     b. Is an example of Australopithecus africanus
     c. Was not immediately accepted as a hominid fossil
     d. A and C
     e. B and C
Careful -- Taung is the type specimen of A. africanus!

18.  Which anatomical feature of Australopithecus afarensis is the most unusual (and challenging to explain) when compared to both humans and chimpanzees?
     a. Curved fingers
     b. Width of pelvis
     c. Shape of scapula
     d. Size of heel bone
     e. Torso shape

19.  How was the bipedalism of Australopithecus afarensis different from that found in modern humans?
     a. It used more energy for the distance walked than moderns do
     b. It was more efficient than modern bipedalism
     c. It included some anatomical features that allowed for more use of trees
     d. A. afarensis could carry heavier objects
     e. A and C only

20.  Which anatomical feature of Australopithecus afarensis may suggest that the species retained a substantial amount of arm-hanging in its behavior?
     a. Angled glenoid fossa on scapula
     b. Extremely wide pelvis
     c. Valgus femur
     d. Large calcaneus
     e. Position of foramen magnum

21.  Based on the evidence of sexual dimorphism, what would be the most likely social system for Australopithecus afarensis?
     a. Female bonded
     b. Female choice
     c. Community/fission-fusion 
     d. Monogamy
     e. Solitary

22. How does Australopithecus africanus differ from Australopithecus afarensis?
     a. A. africanus has much more humanlike postcrania
     b. Brain size has increased in A. africanus
     c. Molars are larger in A. africanus but incisors are smaller
     d. All of the above
     e. B and C only
The most popular answer here was D.  It has been suggested that the postcrania of A. africanus may be even more chimplike than those of A. afarensis; it definitely looks no more human than afarensis.

23.  The robust australopithecines are considered to have gone extinct with no descendants alive today.  Based on what you know about their adaptation/lifeway, which of these would be the best explanation for their extinction?
     a. Their very small brains indicate they lacked the intelligence to survive
     b. They were anatomically unable to make stone tools
     c. They were hunted to extinction by early Homo
     d. Their “chewing machine” adaptation was not flexible enough for 
         them to adjust successfully to changing conditions (including 
         appearance of Homo)
     e. They succumbed to massive dental infections after attempting to make 
         stone tools with their giant molars

24.  Many morphological features differ between early Homo (habilis, rudolfensis) and the gracile australopithecines (i.e., A. africanus).  What IS NOT one such difference?
     a. Brain size increases in Homo
     b. Zygomatics begin to recede backward in some early Homo specimens
     c. All early Homo postcrania are completely modern
     d. Some early Homo specimens have less prognathic faces
     e. Molar size begins to decrease substantially in some early Homo specimens

25. Boucher de Perthes was one of the first prehistoric archaeologists.  What did he believe about the stone tools he found?
     a. They were the work of elves
     b. They were caused when lightning struck rock formations
     c. They were formed by geological processes, not human activity
     d. They were the work of ancient humans, being found with extinct 
         animal bones
     e. They were hoaxes, made to confuse archaeologists

26.  Which site has yielded the oldest stone tools?
     a. Sterkfontein
     b. Gona
     c. Olduvai
     d. Koobi Fora
     e. Kromdraai
I also gave credit for C (Olduvai), because something like 85% of you chose that answer.  You will almost certainly be tested on this information again on the final...

27.  If you were excavating an Oldowan site, which of these tools would you NOT expect to find?
    a. Spheroids
    b. Cores
    c. Sharp flakes
    d. Handaxes and cleavers
    e. All of these would be expected to be present

28.  Based on present evidence, which of these hominids IS NOT considered a possible candidate to have made the earliest stone tools?
     a. Australopithecus garhi
     b. Australopithecus robustus
     c. Australopithecus boisei
     d. Australopithecus afarensis
     e. Early Homo
I actually intended this question to be much easier than it turned out to be (only about 25% got it) -- A. afarensis went extinct (by 3 mya) before the earliest stone tools appear (at 2.5-2.6 mya).  All the others could have been toolmakers based on their dates; where available, hand anatomy would not rule any of them out as stone toolmakers.

29.  Many of the animal bones at Olduvai sites such as FLK Zinj have stone tool cutmarks in various locations on the bones.  Which ones have been interpreted as indicating disarticulation of carcasses (i.e., limb removal)?
     a. The ones near the joints
     b. Those at midshaft
     c. Those on the skulls
     d. The ones on vertebrae
     e. The ones on animals’ horns

30.  Which of the following is a conclusion reached from analysis of Oldowan stone tools?
     a. Only early Homo was capable of making these tools
     b. The toolmakers were about equally right- and left-handed
     c. The toolmakers did not fully understand the fracture properties of rock
     d. Only “core tools” like choppers were actually used
     e. The toolmakers were trying to produce sharp edges, not necessarily 
         specific tool shapes

II.  Short Answer.  Answer any FIVE (5) of the following seven questions. 2 points each.

1.  Choose one aspect of hominid behavior/lifeway that we discussed in class.  What does the anatomy of Australopithecus afarensis suggest about its behavior?  You may choose any aspect of behavior to focus on (locomotion, social system, diet, etc.) but be sure to back up your behavioral inference with evidence.

For this question, you could have answered that the extreme sexual dimorphism (greater than seen in gorillas) may indicate that A. afarensis lived in a female choice type social system.  You might also have mentioned A. afarensis' omnivorous diet; evidence for this includes the large incisors and nuchal area (for biting fruits/stripping) and the relatively large, thick enameled molars (indicating a hard item component like nuts).  Another option would be to describe some feature of A. afarensis' locomotor adaptation -- bipedalism and/or some climbing of trees.  Evidence for bipedalism would include the valgus femur, wide pelvis, enlarged calcaneus, and the Laetoli footprints; evidence for some arboreal behavior would include the relief on the elbow joint, the angled glenoid fossa on the scapula, the long, curved fingers, and the long arms in relation to legs (for details, see the lecture outlines or your notes).
 

2.  Name the two South African australopithecines we’ve discussed in class.

The two australopithecines found in South Africa are Australopithecus robustus and Australopithecus africanus.

Almost nobody remembered poor Australopithecus africanus!  And many of you placed A. boisei and/or A. afarensis in South Africa as well.

3.  We discussed the controversy regarding whether early Homo (habilis, rudolfensis) is one species or two.  Assume they are two separate species, and give two pieces of evidence that support this conclusion. (Recall, H. habilis is represented mainly by KNM-ER 1813 and OH 62, while H. rudolfensis includes KNM-ER 1470 and 1472.)

Some evidence that these are two species includes:
    Brain size difference (600 vs. 770 cc) is beyond normal dimorphism in modern single species; the difference in overall size is also extreme
    The putative female (1813) has a larger brow ridge and nose than the putative male, the opposite of what would be expected in a dimorphic species
    Dental differences suggest different dietary adaptations (larger incisors and smaller molars in 1813; very large molars in 1470), not expected for a single species
    Postcrania also suggest different adaptations: the 1472 femur suggests a modern stance and height; the OH 62 skeleton has long arms and short legs (more apelike than 1472), which would not be expected for a single species.  Also, in this case the female would have shorter legs for her overall height than the male, which is reversed in modern primates.
 

4.  Hunt’s postural feeding hypothesis for the evolution of bipedalism asserts that bipedalism began as a postural (not locomotor) adaptation for feeding in small trees.  Choose one anatomical feature of A. afarensis we discussed in class (i.e., pelvis shape, knee joint, elbow joint, scapula, torso shape, feet/hands).  Briefly describe A. afarensis for that feature, and explain how Hunt’s hypothesis accounts for that feature.

Elbow: Relief on the distal humerus is chimplike -- more pronounced projections, giving the joint more stability and suggesting an arboreal component to the adaptation; Hunt's theory suggests this was related to climbing small trees and engaging in arm-hanging bipedal feeding.

Scapula: The glenoid fossa is angled up toward the head, as seen in chimps, indicating arm hanging behavior; Hunt's theory suggests that arm hanging for support while feeding bipedally was part of their behavior

Torso: Cone shaped, as seen in chimps.  This allows for more even distribution of force when hanging by an arm than would be possible with a barrel shaped chest (like ours). Again, this relates to Hunt's idea that arm hanging was part of the bipedalism used by A. afarensis.

Hands/feet: The fingers are long and curved, with flexor sheath ridges, indicating a strong grip.  Hunt's theory suggests they were gripping small branches while feeding bipedally.  The large calcaneus suggests the feet were used to bear weight more than in chimps, suggesting the bipedal standing to feed of the theory.

Pelvis: Pelvis is narrow front to back but wider side to side than necessary for childbirth, suggesting that bipedal walking was less efficient than in modern people. Hunt's theory suggests that this width would allow the organs to ride lower in the body, lowering the center of gravity and improving stability when the hominids fed bipedally in small trees.

Knee: The femur angles from the hip toward the midline of the body, creating a valgus angle; the proximal tibia is thicker than in chimps (suggesting more weight bearing).  This is an indicator of habitual bipedalism; it places the support (feet) beneath the center of mass.  Hunt's theory simply suggests that this adaptation occurred for postural feeding and was later refined for locomotion.

The main problem in answers to this question was not making clear the connection to Hunt's hypothesis.

5.  We discussed a number of primate social systems.  Describe one of these systems (name, basic group composition, etc.) and give an example of a modern nonhuman primate that exhibits that system.

I won't give a detailed description of the systems here, since that should be in the outlines and your notes.  However, here are some primate examples for each system:
    Monogamy: Gibbon, siamang, marmoset, tamarin
    Female choice: Gorilla
    Female bonded: Many Old World monkeys like langur, vervet
    Solitary: Orangutan; also some loris species
    Community: Chimpanzee, bonobo, spider monkey
 

6.  Wild chimpanzees have been observed to use a variety of tools.  Name and briefly describe two of these tools.

Again, these should be in your notes.  Some of the most common answers included nut-cracking stones, ant and termite fishing sticks, leaf sponges, and the use of clubs and branches for display.

Several people mentioned stone tools such as choppers and flakes.  Although captive bonobos have made these tools, wild chimpanzees are not known to flake stone.

7.  Robust and gracile australopithecines are inferred to have had different dietary adaptations based on their teeth and crania.  What is this difference, and what evidence (at least one piece of evidence) shows this?

Robust australopithecines are inferred to have eaten a hard, rough diet based on their dental proportions (very large molars and smaller incisors suggest the eating of small foods requiring lots of grinding) and the presence of a sagittal crest (for large chewing muscles to attach).  Microwear (pits and scratches) on their tooth enamel also resembles microwear experimentally determined to be caused by such foods.

Gracile australopithecines probably ate a more omnivorous diet.  Their molars are fairly large, but their incisors are larger than seen in the robust australopithecines, indicating that they included some softer foods such as fruits that had to be processed using the incisors; they also lack a sagittal crest, showing that they had smaller chewing muscles and thus probably less emphasis on grinding hard foods than seen in the robust australopithecines.

The problems here were either describing the diets but leaving out the evidence, or covering only one kind of australopithecine.

III.  Short Essay.  5 points.

1.  Which theory concerning the evolution of bipedalism do you find the most convincing?  Describe that theory, and back up your answer with evidence discussed in class (anatomy of early bipeds, inferred social behavior, probable environment of the first bipeds).

2.  FLK Zinj has been a very important site for reconstructing hominid behavior.  Specifically, it has been used to make inferences about hominid food-getting practices.  Some researchers interpret the faunal and cutmark evidence as indicating both hunting and scavenging, while others interpret this evidence as indicating only very marginal scavenging.  Which of these interpretations do you favor?  Make an argument for either mostly hunting or mostly scavenging being practiced by the FLK Zinj hominids.  Use evidence from readings and lecture in your answer.

For both of these questions I was primarily looking for you to take a clear position and back it up with evidence and a reasoned argument; overall, you did quite well.  The main problem with both essays was a lack of details in terms of the evidence -- I don't expect you to remember every detail presented in class or provided in the text/outlines, but you should be able to go beyond broad generalizations.  In other words, don't just say "The environment changed, making hominids become bipeds," say how it changed, and why this would select for bipedalism; instead of "anatomy shows that A. afarensis was bipedal," include a feature or two that supports this conclusion.  However, most of you did a very good job of explaining your reasoning and why you chose your explanations.