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NOVA scienceNOW: First Primates

Viewing Ideas

Before Watching

1. Identify the characteristics of a primate. Present the following list of animals to your students. Have them identify those that are primates and explain their reasoning. Consider displaying pictures of some of the less familiar animals.

   • Dogs (No)
   • Human beings (Yes)
   • Dolphins (No)
   • Lemurs (Yes)
   • Lions (No)
   • Rabbits (No)
   • Orangutans (Yes)
   • Deer (No)
   • Tree shrews (No, though they are close relatives)

   Next, explain that primates have the following characteristics: (1) forward-facing eyes with binocular vision allowing for depth perception; (2) thumb mobility for holding on; (3) precision grip for picking up small objects; (4) grasping hands (which aid in power grip) with nails rather than claws. With these characteristics in mind, have your students revisit their list and change answers if necessary, again explaining their reasoning. Where are they in agreement? Can any of the maybes be switched over to a yes or a no? Conclude the activity by watching the program segment, which details the characteristics of primates.

2. Examine the advantages of stereoscopic vision.

   A key primate characteristic that will be described in the segment is stereoscopic vision. It involves using two eyes located so both aid depth perception and the ability to see things three-dimensionally. Each eye takes in slightly different information about 3-D objects, which aids the brain in approximating distance.

   To help students understand the importance of stereoscopic vision, have them experience what the world is like without it. Before class, gather cups and small items, such as paper clips, coins, or buttons. Provide a ruler, four cups, and four items per team.

   Setup:

   • Student one: Sit in a chair several meters away from a desk or table with the surface just below eye level. Close both eyes.

   • Student two: Hold the paper clips or similar items and stand near the desk or table.

   • Student three: Place paper on the surface and set the four cups on top of the paper. Prepare to record data in a data table like the one below.

   Student Name	Number of Items Using One Eye	Number of Items Using Two Eyes	Notes

   
   

   Task:

   • Student one: Opening only one eye, direct student two to move his or her hand right/left and forward/back until you think it is directly over one of the cups. At that point, tell student two to drop the item. Mark on the paper where the item first dropped.

   • Students one and two: Repeat with the remaining items and cups.

   • Student three: Record how many items landed in the cups and measure how far off any misses were.

   • Student two: Pick up all the items that were dropped.

   • All three students: Repeat the above steps. This time, however, student one should use both eyes.

   • All three students: Switch roles and repeat the experiment, shifting the position of the cups on the desk.

   As a class, discuss stereoscopic vision, why it is important, and the difference in depth perception when we see with one eye vs. two eyes. (Seeing with two eyes improves depth perception and therefore should result in a higher success rate. However, 10–20 trials per team is a small sample, which may skew the data. Take a class average, if necessary.) What might be the evolutionary advantages of stereoscopic vision? (As will be mentioned in the program segment, stereoscopic vision "allows us to judge the world around us in three dimensions," meaning it provides greater depth perception. This trait could help primates judge leaps between branches, distance to prey, or position of fruit on a branch. The ability to focus on objects in three dimensions increases efficiency and success.)

3. Examine the advantages of hands with thumb mobility: A distinguishing primate characteristic is hands with thumb mobility. To understand one advantage of this, have your students experience what it's like without thumb mobility. Before class, gather masking tape, stopwatches, small items (e.g., paper clips, toothpicks, coins, marbles, or buttons), and cups. Supply about 20 items, one stopwatch, and one cup per pair. Calculators are optional.

   Have each student pair:

   1. Spread the items out on a desktop and set the cup about six inches away.

   2. Student one: Using just your dominant hand (the hand you write with), pick up all the items one at a time and drop them into the cup.

   3. Student two: Time and record how long it takes Student one to pick up and drop all the items into the cup.

   Student Name	Trial	Dominant Hand and Free Thumb (time in seconds)	Dominant Hand and Taped Thumb (time in seconds)
   	1.
   	2.
   	Average Time

   
   

   4. Repeat Steps a–c for a second trial.

   5. Calculate the average time: Average Time = (Time 1 + Time 2) / 2

   6. Student two: Using masking tape, bind Student one's thumb to the side of her/his hand, being careful not to impair circulation.

   7. Repeat Steps a–e with a taped thumb.

   8. Switch roles and repeat the experiment.

   Lead a class discussion on the differences between picking up small items using a free thumb and attempting the task with one's thumb taped. What was the average time for picking up the items with the dominant hand and a free thumb? With the dominant hand and a taped thumb? What do students think contributed to the time differences? (A movable thumb aids in precision gripping or picking up small objects.) Why are movable thumbs important?

After Watching

Safety Warning: Wear goggles, and have students wear goggles, when performing the activities and handling the materials below.

1. Dissolve limestone with acid. In the program segment, Jonathan Bloch and his graduate student, Doug Boyer, extract delicate bones from limestone. Limestone (e.g., calcium carbonate—CaCO₃) reacts chemically with acid, forming carbon dioxide (CO₂) and lime (e.g., calcium hydroxide—Ca(OH)₂). By using a strong acid to remove the limestone, Bloch and Boyer are able to expose the trapped, ancient bones little by little. Your students also can use acid to remove limestone. Before class, gather goggles, vinegar, clear glass cups, and small pieces of rocks containing calcium carbonate, such as chalk, limestone, or marble. Then, in class, place the chalk and the rocks in separate cups and pour vinegar into each. Within a few minutes, students should see tiny bubbles appear. The gas is carbon dioxide, which is released as the acid reacts chemically with the calcium carbonate. It may require several acid baths, but students should see that the smooth surface of the chalk becomes pockmarked and rough as the acid dissolves it.

   Extension: Before class, purchase some plaster of paris, available at your local craft or hardware store. Prepare a small amount, and encase a paperclip in a small block of the plaster. Plaster of paris is largely a calcium sulfate hemihydrate and will react with vinegar the same way limestone does. Place the small block of plaster of paris in a glass, add vinegar, and let it sit for a while. Pour out the old vinegar and add new. Repeat several times. You will gradually be removing the plaster of paris from the paperclip, just as Jonathan and Doug removed the limestone from around the delicate bones of their early primate fossil.

2. Document a fossil, archeological, or forensic site. In the segment, graduate student Doug Boyer devised a method to "meticulously document the relationship between each and every bone exposed in the limestone." Such documentation is a vital part of many scientific disciplines, including archeology, paleontology, and forensics. Test your students' ability to document a scene. The activity steps can apply to individuals or to pairs of students:

   1. Gather small objects that can form a pile (e.g., pens, pencils, rulers, straws, paper clips, etc.) Students will need a writing implement separate from any in the collection.

   2. Give each student or pair eight objects. Have them make a pile where the objects overlap, cross over, pile on top of, and lean against each other.

   3. Have students draw a map of or otherwise document their pile. (Set a time limit of 5–10 minutes.) NOTE: If a digital camera is available, have students also take a photograph of their original pile and for sharing at the end of the activity.

   4. Then have each student or pair disassemble their pile and exchange their objects and map/documentation with another student or pair.

   5. Have the second group try to recreate the original pile based on the objects and documentation they've received. Compare this to the photograph, if applicable. How accurate was the documentation? Was the second group able to reconstruct the pile using the documentation?

   Lead a class discussion on documentation and why it is important. How easy or difficult was it to document the piles? To recreate the piles? What might have made the process easier? (More time, agreed-upon notation, graph paper, photographs, practice documenting items.) In what situations might documentation be crucial? (Whenever the relationship between items, and between items and their location, is important, such as fossil bones in a piece of limestone, fragments of a pot at an archeological site, or evidence at a crime scene.) Why was it important for Bloch and Boyer to create a map of the delicate bones, as shown in the segment? (They weren't sure which bones went with which animal. The careful process of documenting the bones took months, but it allowed them to recreate the skeletons of the three separate animals.)

3. Examine the nature of evidence. Astronomer Carl Sagan (1934–1996) popularized the phrase, "Extraordinary claims require extraordinary evidence." Thus, if someone makes an extraordinary claim, such as that he has found the earliest primate, then there must be some extraordinary evidence to back up that claim. The story of identifying the first primate is an example of evidence that converges from a variety of sources: Jonathan Bloch found the nail; Mary Silcox found the tiny ear tube; and Eric Sargis provided anatomy data.

   Present your students with a (not so extraordinary) claim and related pieces of evidence, and have them consider how convincing they find the evidence, individually and as a whole. Start by holding up a sealed envelope in front of the class. Make the claim that there's an ace of spades in the envelope. Tell students you will supply them with different pieces of evidence, and that their job is to determine how well your claim—that the envelope contains an ace of spades—is supported by the evidence. Present the sets of evidence to your class orally, and have small groups discuss each set.

   Evidence Set 1: Look at the shadow of the envelope's contents. Tell students that:

   • When the envelope is held up to the light, one and only one dark area can be seen.

   • The dark area appears to be about the size of a playing card. (So a visual inspection looks roughly correct for the envelope to contain a playing card.)

   • The dark area is a rectangle with slightly rounded corners.

   • A set of sample playing cards from various decks all have slightly rounded corners. (So the shape is right for a playing card.)

   Discussion: Ask, "Based solely on this shadow inspection, can there be a playing card in the envelope?" (Yes.) Do your students think that there is a playing card in the envelope? (Possibly. It at least looks reasonable.) Are your students convinced that there is an ace of spades in this envelope? (They definitely should not be convinced that the envelope contains the ace of spades.)

   Evidence Set 2: Consider the weight of the envelope's contents. Tell students that:

   • The weight of this sealed envelope is 7.9 grams.

   • A similar, empty envelope weighs 4.9 grams. (So this envelope's contents weigh about 3 grams.)

   • The sample playing cards each weigh between 1.3 and 2.0 grams. (So, a single playing card can't account for the weight in the envelope.)

   Discussion: Ask, "Can there be a playing card in the envelope?" (Yes, but not just one.) Based only on the weight evidence, do students think that there is a playing card in the envelope? (Probably not.) Based on both the shadow and weight evidence together, do they think that there is a playing card in the envelope? (Possibly. The contents could be a playing card plus something else.) Are your students convinced that there is an ace of spades in this envelope? (They definitely should not be convinced.)

   Evidence Set 3: Consider the dimensions of the envelope's contents. Tell students that:

   • The dimensions of the dark area are 8.8 centimeters by 6.5 centimeters.

   • The sample playing cards are all 8.8 centimeters by 6.3 centimeters.

   Discussion: Based strictly on this evidence, can students say that the envelope contains a playing card? (Opinion will probably be split; the dimensions are close but not a perfect match.) Based on all the evidence, do they think that there is a playing card in the envelope? (Possibly.) Are your students convinced that there is an ace of spades in this envelope? (Again, they definitely should not be convinced that the envelope contains the ace of spades.)

   Evidence Set 4: Shake the envelope's contents. Tell students that:

   • When the envelope is shaken, the dark area moves around.

   • After several shakes, the shape of the dark area changes.

   • With some manipulation, the dark area can be separated into two dark areas, both 8.8 by 6.3 centimeters with rounded corners.

   Discussion: Based on all the evidence, do students think there is a playing card in the envelope? (Probably yes; the dimensions and shape of the dark areas are exactly those of a playing card, and two playing cards weighing 1.5 grams each could combine to weigh the 3 grams difference between the empty envelope and its contents.) Are your students convinced that there is an ace of spades in this envelope? (Again, they definitely should not be convinced that the envelope contains the ace of spades, though with the strong evidence that the envelope contains playing cards, they are justified in turning their attention to this part of the claim.

   Evidence Set 5: Closely inspect the contents of the envelope. Tell students that:

   • A close visual inspection of the dark areas reveals patterns faintly visible through the envelope.

   • Under inspection through one side of the envelope, one of the dark areas appears to be largely covered by a slightly reddish pattern; the other appears to have a series of red diamonds, in two rows of three each, plus indistinct patterns in two opposite corners.

   • Under inspection through the other side of the envelope, one of the dark areas again appears to be largely covered by a slightly reddish pattern; the other appears to have a large spade shape in its middle, plus indistinct patterns in two opposite corners.

   Discussion: Based on all the evidence, are your students convinced that there is an ace of spades in this envelope? (Probably yes. The evidence is very strong (though not necessarily absolutely conclusive) that the envelope contains two playing cards, one of which is the ace of spades.

   This activity modeled one of the primary characteristics of science—the use of evidence to support or counter a claim or hypothesis . Researchers gather evidence, bit by bit, from different locations, sources, and lines of inquiry until a strong case can be made for a claim or until something is found that contradicts a claim and requires a new, different hypothesis. So far, Bloch and his colleagues have found evidence that the plesiadapiforms are indeed the earliest primates. Yet who knows what the next piece of evidence or line of inquiry will bring?

Web Sites

NOVA scienceNOW
www.pbs.org/nova/sciencenow/0303/02.html
Offers resources related to the earliest primates, including additional activities, streamed video, and reports by experts.

Florida Museum of Natural Science: Article
www.flmnh.ufl.edu/sciencestories/2007/bloch_primate.htm
Reports on the early primate discoveries of Jonathan Bloch and his colleagues.

NetVet: Primates
netvet.wustl.edu/primates.htm
Provides links to many Web sites on primates and primatology.

NOVA: The Last Great Ape
www.pbs.org/wgbh/nova/bonobos
Offers a variety of interesting readings, slide shows, and tools for learning about bonobos—one of the five great apes, along with humans.

PBS Evolution
www.pbs.org/wgbh/evolution
Presents the PBS miniseries on evolutionary science and related Web-based materials, including an interactive timeline (Deep Time).

Paleontologists discover most primitive primate skeleton
www.eurekalert.org/pub_releases/2007-01/yu-pdm012307.php
Reports on the study led by University of Florida paleontologist Jonathan Bloch, who is featured in the video, about the earliest known primates.

Scientific American Frontiers: Chimps R Us
www.pbs.org/saf/1108
Presents a Scientific American Frontiers episode and related Web-based materials on chimps.

Books

Our Inner Ape: A Leading Primatologist Explains Why We Are Who We Are
by Frans De Waal.
Riverhead Hardcover, October 2005.
Explores and compares three primates: chimps, bonobos, and human beings.

The Pictorial Guide to the Living Primates
by Noel Rowe.
Pogonias Press, 1996.
Offers a photographic field guide of primates.

Primate Adaptation and Evolution, 2nd edition
by John G. Fleagle.
San Diego: Academic Press, 1999.
Presents a detailed survey of living primates and a current synopsis of the primate fossil record.

Activity Author

Teon Edwards is a curriculum developer with a background in astrophysics, mathematics, and the use of technology and multimedia in teaching and learning. Since 1996, she has developed numerous science and mathematics education materials for school, home, and informal learning environments.