Anthropology 130 Research Simulation 5 Hominin Skeletal Anatomy

50 points maximum

Instructions This fifth and last Research Simulation combines what we have learned about humans

and modern primates to view fossil evidence of our species’ ancestors.

Paleoanthropologists have to play detective and piece together what happened over a

geologic time scale with a small amount of fossils and stone tools.

Type your answers into the separate report sheet. Make sure that your name is at the

top of the report sheet as well. When you are done, upload the report sheet to Canvas

or in class by the due date.

Assignment Start Your reputation for solid work in the Philippine tarsier research team and other projects

has traveled across social media to reach the ears of other physical anthropologists! A

few email exchanges with paleoanthropologists later, you find yourself on a plane to

Ethiopia to join a team that is studying Australopithecines. Your role in this research

project is to examine the skeleton of Lucy, an Australopithecus afarensis, with a fresh

pair of eyes. In particular, you will be comparing Lucy’s skeleton with that of a

chimpanzee and a modern human.

Download and open the report sheet to record your answers.

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Part One – Moonlit Wings The airport is just as busy as last time, which seems like ages ago. You look around for

any unattended children and see none. Despite yourself, you doze off waiting for your

flight to the whispered conversations around you.

“BZZ RFH BRDDN AMN. Thank you.”

The unintelligible words weave among the background noise that lulled you to sleep.

The telltale chime of the public service announcement has you worried. You check the

time and sit up in shock as it is time to board. Was that announcement for your flight?

For you?

You quickly grab your personal items and rush towards your gate. You stop an old man

along the way as panic rises. He senses that you hoping to find those forgotten words

before the airport melody.

“Where is your flight headed to?” the nice man asks, trying to help. You tell him that you

are going to Ethiopia, and volunteer the detail that you are studying fossils.

“Indeed. Amazing how past traces of life can be found embedded in solid rock. How

does fossilization start so long ago? Could you explain how an organism could avoid

decomposition through natural processes?”

1. In at least a complete sentence, explain an example of how natural geological forces

could preserve a dead organism and keep it from decomposing. (2 points)

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“How fascinating. Scientists are always going to the driest, most barren places to look

for fossils. Montana, the Gobi Desert, Ethiopia… why do you think scientists look in

these places?”

2. In at least a complete sentence, explain why researchers look for fossils in places

that are now dry and barren instead of other places like forests or grasslands. (2

points)

“That is remarkable. The sheer odds that must be defied for fossilization to happen. You

know, I have been to Ethiopia myself. I learned that there are deposits of volcanic ash in

the earth that help scientists date the layers of rock. Do you happen to know anything

about them?” You assemble your thoughts without complete sentences.

3. What kind of dating from the lecture or textbook would be the best method for finding

the number of years ago when a volcanic rock was formed? (1 points)

4. Is this method absolute or relative dating? (1 points)

The man nods slowly, pleased with the conversation. “She’s coming in, your 12:30 flight.

Don’t want to miss the plane down to Africa.” You smile at the good news and bid him

farewell. With a warm smile, he turns to you as if to say: “Hurry now it’s waiting there for

you.”

The flight is long but uneventful. The headphones warded off any conversation as you

looked out the window in solitary company. Exhausted from the flight, finding your way

to your hostel was a blur. After a day of acclimatizing to the arid Ethiopian weather

(definitely some sweating and vasodilation going on), you travel to the National Museum

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of Ethiopia in Addis Ababa. You are still a little jet-lagged, but the site of the laboratory

jolts you awake: the priceless skeleton of Lucy is right there for you to examine!

As you handle the bones of a chimpanzee, a human, and the fossilized bones of Lucy,

you take detailed photographs from standard anatomical angles for reference. These

will be useful when you make your analysis.

{ Your new workplace (not really). }

Part Two – Foot Notes 1. Download and open the skeletal photographs PDF, or go to this Google Photos

gallery: https://goo.gl/photos/r1HDetrZt5tdKrz98

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2. Complete the next parts of the assignment by referencing the photographs and

answering the question using the report sheet. Be sure to keep focused on which

organism’s bones you are looking at in each photograph.

The modern human skeleton has many refined bipedal traits. The chimpanzee, though

its lineage is the same age as our own after splitting from our common ancestor, has

kept more of the primitive quadrupedal traits. We will go on a short tour of Lucy’s

skeleton to see whether her skeleton is closer to a humans’ or a chimpanzees’. Many

parts of the skeleton are different when comparing quadrupedal (four-legged) and

bipedal (two-legged) animals since the bones of each have to be adapted to different

functions. The lower limb (or rear legs) are a good place to start your examination.

In the photos, look in the first section, which as photographs of the pelvis as viewed

from the front (Pelvis – Anterior (Front) View). Each set of two photos has Lucy’s pelvis

on the left. On the right is either the same bone of a modern human (H. sapiens) or

chimpanzee (P. troglodytes). Look at the human and chimpanzee pelvises, comparing

each of them with Lucys’. Then answer the following questions in the boxes using the

report sheet. The photos are to scale. Complete sentences are not necessary for this

section.

5. According to the lecture and textbook, why is the pelvis of a quadruped taller and

narrower than the pelvis of a biped? (2 points)

6. Does the overall shape of Lucy’s pelvis resemble the human pelvis or the

chimpanzee pelvis more? Not thinking of the size, compare the outlines of each

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bone. For questions that do not specifically mention the textbook or lecture, try to

use your own observations to form an answer. (2 points)

7. Does the shape of Lucy’s pelvis suggest that she was bipedal or quadrupedal? (2

points)

The sacrum forms the back structure of the pelvic girdle. Like the pelvic bones, the

sacrum is also different between quadrupeds and bipeds due to the different physical

forces that they experience.

Look at the “Sacrum – Superior (Top-Down) View” section of the photos. This will give us

a view of the surface of the sacrum that joins with the last lumbar vertebrae. On a biped,

this would be a top-down view. For a quadruped, imagine looking through the spine

from the front to back of the organism.

8. Why would the sacrum of a biped be wider than the sacrum of a quadruped? (2

points)

9. Who has the wider sacrum, Lucy or a chimpanzee? (2 points)

It seems pretty clear that Lucy’s pelvic girdle was geared towards one type of

locomotion over the other. You move on to view another bone for more clues.

Move on to the “Femur – Anterior (Front) View” section to compare the thigh bones of

these three species. Compare Lucy’s femur with the humans’, then with the

chimpanzees’.

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10.What feature of Lucy’s femur suggests that she was bipedal? You can refer to the

textbook or lecture sections on skeletal changes for bipedalism for clues. (2 points)

11. Based on the length of these femurs, was Lucy’s standing height closer to a

standing chimpanzee or a modern human? (2 points)

Part Three – Armed and Ready The lower limbs of both quadrupeds and bipeds have the role of locomotion. The upper

limbs, on the other hand (!), do not contribute much to locomotion in bipeds. This leads

to structural differences between the upper limbs of these groups of animals.

Go to the “Scapula – Anterior View” section of photos to view the shoulder blade from

the front. As before, look at the fragments of Lucy’s scapula, as well as the bones of a

human and chimpanzee. Chimpanzees are quadrupedal, either knuckle-walking on the

ground or practicing suspensory climbing in trees with all four limbs. The glenoid fossa

of the chimpanzee’s scapula, where the humerus (upper-arm bone) connects to the

body, is adapted for both of these modes of locomotion by being angled cranially

(upwards when standing up, or forward when on all fours). The human glenoid fossa is

angled horizontally instead.

12. It is hard to see in the photo of Lucy’s scapula, but her glenoid fossa is angled

cranially, as with the chimpanzees’. Based on these observations of the glenoid

fossa, was Lucy’s scapula more adapted for bipedalism or quadrupedal/arboreal

locomotion? (2 points)

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You move down to the distal (farthest) end of the upper limb. We are now at the “Manual

Proximal Phalanx – Palmar (Palm) View” of the photo gallery. This is one of the hand

finger bones that attaches to your palm. We are also looking at the bone from the

direction of the palm, like looking at your open hand. Compare this view among Lucy,

human, and chimpanzee bones. Arboreal primates, such as chimpanzees, have thick

and curved phalanges for gripping tree branches. Humans have thin and straight

phalanges that are better for fine control of objects.

13.Based on your observation of palmar (palm-side) view, does Lucy have thick

chimpanzee-shaped phalanges, or thin human-shaped phalanges? Do not spend

too much time overthinking the answer, but come to your own conclusion. (2 points)

Now go to the “Manual Proximal Phalanx – Lateral (Outside)” view. This is the view of

the bone from the anatomical outside edge of the hand – the edge along the outside of

the pointer finger.

14.Based on your observation of the lateral (outside) view, does Lucy have curved

chimpanzee-shaped phalanges, or straight human-shaped phalanges? Again, do not

spend too much time overthinking the answer, but come to your own conclusion. (2

points)

15.Based on your comparisons of Lucy’s finger bone in the previous two questions, do

you think that Lucy’s hands are more adapted for gripping branches or fine control of

objects? (2 points)

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You are now done with the reference photo gallery. The rest of the questions do not

depend on these photos.

Part Four – Looking at Larsen Back in your hostel in Addis Ababa, you reflect on your study of Lucy’s fossils. You think

back to what you learned about hominin bipedalism from your anthropology class. Out

of the corner of your eye, you see the Larsen textbook peeking out from your luggage

(at least, the primate eyes on the cover are). You must have packed it out of habit after

studying Tibetan adaptation! Since you are now doing research in paleoanthropology,

you open the book to Chapter 8. You go over the information that was not mentioned in

lecture.

16.What dating method did Dragutin Gorjanović Kramberger use to show that human

and animal bones were from the same time period? (1 point)

You then turn the textbook to Chapter 9 to reread the information on prehistoric

primates.

17.Eosimias, a human thumb-sized primate from China, is a member of what prehistoric

primate lineage? (1 point)

18. What are the names of two of the apes that used to live in tropical Europe? They’re

not listed together in the chapter (thanks, Larsen). (2 points)

The chapter makes you ponder the prehistoric primates of millions of years ago, and all

the variety that have already been discovered by researchers. You flip a few more

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pages to Chapter 10, which is on the very early hominins you flew to Ethiopia to study.

Near the start of the chapter, you read about several experts’ theories on how

bipedalism evolved in hominins.

19.Which of the theories, by Darwin, Rodman and McHenry, and Lovejoy, do you think

is the strongest in explaining hominin bipedalism? Why did you choose this theory

over the others? Answer in a few sentences. (2 points)

Part Five – Thinking About Brains One day, you are about to get to work in the museum laboratory when you run into an

old friend: it is Lhindsay, from the tarsier research project! “Hey, funny seeing you here!”

she exclaims. “I didn’t know that you are here too. I’ve been collecting data to see if

Australopithecines’ brains were closer to a chimpanzees’ or humans’. I just got this table

done by finding real estimates of cranial capacity (brain size) and body mass for each

species in published scientific papers. By dividing these numbers, I can correct for body

mass, since modern humans are simply larger than the other two species. That number

is in the column to the far right. A higher number there means more relative brain matter

and more intelligence.”

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20.Looking at Lhindsay’s table, does the amount of brains in Australopithecus afarensis

resemble the amount in chimpanzees or modern humans more? (2 points)

You give Lindsay your conclusion and continue to work. From your analysis of Lucy’s

lower and upper limb bones, you find that her legs were adapted to one type of

locomotion while her arms were adapted to another type (if not, it may be good to revisit

the previous questions!).

21.From Lucy’s dual-specialization to both bipedal and arboreal types of locomotion,

what do you think her natural environment was like? (2 points)

Part Six – The Evolution of Homo Work at the museum has involved Lucy, but it is important to remember that she was

one individual within millions of years of hominin evolution. You recall from class that

one lineage of australopithecines kept evolving new traits beyond how the other

lineages were changing. They became the earliest members of our own genus.

22.What is the big difference between Homo habilis and the australopithecines? (2

points)

Lhindsay’s Table of Brain Size Versus Body Mass

Cranial Capacity (cc)

Body Mass (kg) Cranial Capacity Over Body Mass

(cc/kg)

A. afarensis 430 42 10.23

Chimpanzee 395 50 7.9

Modern Human 1260 65 19.38

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23.What part of Homo habilis’s skeleton is very similar to the australopithecines? (2

points)

24.Homo erectus was even more specialized than Homo habilis. What are two derived

traits that H. erectus evolved? (2 points)

25.The Homo erectus traits mentioned in the previous question are adaptations for what

type of environment and lifestyle? (2 points)

Your mental review of early Homo evolution allowed you to put your work on Lucy into

perspective. Tracking the evolution of hominins, the traits we see today in our species

evolved separately instead of all at once. You put those thoughts aside as you wrap up

your time in Addis Ababa. Your research journey is winding down, but you feel like a

clear ending is missing.

Part Seven – The Final Boss It is very early, too early, as you give your lab space one more look before starting the

journey back home with stories of your experience. As you get up to leave, Donald

Johanson himself enters the laboratory! He was the paleoanthropologist who

discovered Lucy in 1974. His reputation is Kilimanjaro rising like Olympus above the

Serengeti. “Great work,” he says in a warm fatherly tone as he shakes your hand.

“You’ve done more than a hundred men or more could ever do. Before you head back

home, I have would like your expertise on a matter…”

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26.“Based on what you have seen in Lucy’s

skeleton compared to a human’s skeleton,

and how the genus Homo evolved their own

traits beyond what Lucy had, did bipedalism

or high intelligence evolve first in hominins?

Also, how do you know?” Please treat me to

a few sentences that mentions the evidence

you saw in this research project. (4 points)

Conclusion You say goodbye to Lhindsay and Dr. Johanson

and head to the airport. The experience has been challenging but rewarding. “It would

take a lot to drag me away from Ethiopia,” you think. Still, you have to go home and take

some time to do even more things you never have.

Your detailed analysis of Lucy has really shown you how Australopithecines differed

from the common ancestor between chimpanzees and hominins. Still, Lucy’s skeleton

showed clear differences from modern humans. You wonder what led past hominins

after Lucy to gain the definitive human traits of efficient bipedal long-distance running

and extremely high intelligence.

The assignment is done! You have completed the ANTH 101 Research Simulations.

Please upload to Canvas or turn in during class.

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