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Alien From Earth

Viewing Ideas


Before Watching

  1. Use a map to locate where scientists found the Homo floresiensis skeletons. Review map skills by asking students how they would locate Flores Island, Indonesia on the map. Using a world map, have them locate Indonesia (the island chain northwest of Australia). If the map has sufficient detail, have them locate Flores Island (at the southeastern end of the chain, next to the island of East Timor). Have them determine its latitude and longitude (120-124º East, 8.5º South). Tell students that people may have been able to reach Flores Island during the Pleistocene ice ages, when sea level was considerably lower and many landmasses were connected by land bridges. Ask them from which major landmass Flores Island's first hominids might have arrived. (From Asia)

  2. Review the system of scientific classification. Some scientists have proposed the idea that Homo floresiensis is a separate human species. To help students understand what 'species' means, review the system of scientific classification (i.e., kingdom, phylum, class, order, family, genus, species). Have students research the classification for humans (animalia, chordata, mammalia, primate, hominidae, homo, sapiens). As an extension, have students identify some of the animals found in each of the following categories: animalia (insect), chordata (alligator), mammalia (mouse), and primate (apes). Point out that this system goes from general to specific—more specific categories are subsumed by more general ones.

  3. Show that the body's bones grow in predictable ways. When the Flores skeletons were discovered, scientists had to determine whether they were from full-grown adults or from people who were afflicted with diseases that interfered with their growth. Comparing the lengths of certain bones yields predictable ratios, such as one's height being equal to the finger tip-to-finger tip distance between one's outstretched arms. If a skeleton's bone ratios differ greatly from what is expected, that individual may have had a disease or genetic condition that affected his or her growth. To investigate whether the body's bones show predictable ratios when measured, have student pairs use a measuring tape to compare the lengths of different bones. (They can use a length of string to determine the distance and then measure the string length.) You can help students calculate the ratios by providing the table below or by copying it on the board.

    Measurement #1

    Length #1

    Measurement #2

    Length #2

    Length #1 / Length #2

    Expected Quotient

    Ratio

    Arm span
    (measure finger tip to finger tip with arms outstretched)

    Height*

    1

    1:1

    Thigh
    (measure outer side, from hip to kneecap)

    Height*

    4

    4:1

    Forearm
    (measure elbow to wrist)

    Foot
    (measure heel to toe)

    1

    1:1

    Thumb Circumference (measure lowest part of thumb)

    Wrist Circumference

    2

    2:1

    Wrist Circumference

    Neck Circumference

    2

    2:1

    Head Circumference
    (measure around eyes)

    Height*

    7

    7:1

    * remove shoes before measuring height

    To process the activity, write the names of the pair of bones being compared on the board. Next to each pair, have students write the values they determined when dividing the length of Bone #1 by the length of Bone #2. Students' numbers will differ from the expected result due to measurement errors or because of variation in bone length. Thus, while the expected result may be 1.0, students may get results of 0.8 or 1.2. However, scientists do not expect a data set to contain identical values. Rather, they are interested in seeing where the data points cluster. As a class, see if the student values cluster around the expected result. Discuss whether, when taken together, the class's numbers support the idea that certain body dimensions are proportional. Students should find this to be the case. Scientists use the fact that an animal's bone sizes are proportional to reconstruct full skeletons from mere bone fragments. Ask students if they think the ratios would hold for both children and for adults. How could they test their prediction? (Choose a pair of bones listed in the table. Measure these bone lengths on a child and an adult and calculate the ratios. If the two ratios are close in value, one can conclude that a body's bones grow proportionally, irrespective of age. Note: Some ratios for babies and young children will differ from those of older children because their heads are proportionally larger.)

  4. Explore the debate about the hobbit's place in the evolutionary time line. This program focuses on where the hobbit fits in human evolution. The debate looks at whether fossils recently found on an Indonesian island represent a previously unknown primitive hominin species or are the remains of a modern human (hominins are a subgroup of hominids that include only humans and their ancestors). Prior to having students watch the program, review the following key information with them:

    • Hominin fossil remains have been discovered on the island of Flores in Indonesia (latitude 120-124° East, longitude 8.5° South).

    • The remains are from an organism that had a brain less than one-third the size of that of the average modern human.

    Inform students that they will be taking notes on the evidence relating to the two main, but contrary, ideas presented in the program:

    • the fossils represent a new species on the hominin family tree.

    • the fossils are the remains of a diseased modern human, possibly a pygmy.

    Play the program preview to introduce students to the topic and debate. Begin a discussion about what can be learned from fossils. What can body fossils, the preserved remains of a dead plant or animal, reveal? (Fossils offer a snapshot of what an organism was like during the time it lived. Such remains can sometimes reveal clues about the environment that the organism lived in. By collecting and comparing many fossils, scientists can gain a more complete picture of how organisms evolved.) What cannot be learned from such fossils? (It is difficult to learn anything about the DNA of an organism as fossils rarely still contain organic material that can analyzed.)

    Following the discussion, organize students into teams and assign each team one of the following types of evidence to track: skull and teeth, skeleton, brain, other fossils found on site, and dating techniques. Have each team use the Evidence Chart (PDF) to take notes on its assigned area, recording whether the facts presented:

    • support the idea that the fossils are from a new species on the hominin family tree

    • support the idea that the remains are from a diseased modern human

    • are inconclusive

    Have students watch "Alien From Earth." After watching the program, have each team meet and come to consensus on the information members collected before teams take turns presenting their conclusions to the rest of the class. (See Completed Evidence Chart for a filled-in table.)

    After all teams have shared their notes, conduct a poll about which of the two premises students think is best supported by the evidence. Which evidence did students have the most confidence in? Which evidence did they have the least confidence in? Why? Which chart entries are a result of direct analysis of the skeleton? Which entries are inferences drawn either from items found around the skeleton or from the differences in size between a skeleton and a modern human?

    If the fossils do represent a new species, do students think there is more evidence to support Homo erectus or Australopithecus, as the ancestor? And if the hobbit is a new species, what does do these findings potentially suggest regarding where humans may have originated?

    In the show, some scientists concluded the fossils were from a new species based on their findings from the examination of one skeleton. Theories about human evolution have been drawn from bone and bone fragments of thousands of individuals. How much evidence do scientists need before they draw conclusions?


  5. Evidence Chart

After Watching

  1. Brainstorm the advantages and disadvantages of being small. Evidence supports the idea that when animals migrate to remote islands, they can develop smaller body sizes over the span of generations. The segment mentions that the hippos, buffalo, elephants, elk, and deer found on remote islands are smaller than their mainland counterparts. Ask students to generate a list of ideas as to why being small might be an advantage on Flores Island. (Small animals require less food.) What might be some of the disadvantages for a species when this happens? (If larger animals reach the island, they may out-compete small animals for food and shelter. Also, they might eat the small animals.) Record students' ideas on the board.

  2. Use the H. floresiensis controversy to model the scientific process. When the first Homo floresiensis skeleton was found, some scientists claimed that it represented a new species. Others maintained that it was from a Homo sapiens (i.e., modern human) with developmental problems. Scientists on both sides of the question presented evidence to support their views, and debate stalled. Subsequently, nine skeletons, all of small stature, were found, supporting the idea that H. floresiensis was a miniature species distinct from H. sapiens. (Have students think of an example from the video that shows how the H. floresiensis controversy illustrates each part of the scientific method (formulate hypothesis, define procedure, collect data, analyze evidence, and draw conclusion). Discuss how the amount of data influences a debate. (As with any experiment, increased amounts of data make it easier to identify meaningful patterns.) Discuss the advantages and disadvantages to having scientists pose different explanations for the same evidence. (It may lead to more research, which provides additional insight. Alternatively, it can lead to biased testing and biased consideration of the results.)

  3. Research the human family tree. To help students better understand the human family tree, have the class create a 'time line of humans.' Ask student teams to research one or two groups of the 11 different hominids (see the Web sites in the Links & Books section below) and find when and where their groups lived and which hominids they are most closely related to. Have them put their information on an index card or a poster. Organize the class's work in a time line on a bulletin board. Draw connecting arrows to groups that are closely related. Is the family tree linear or branched? (Branched) What differences define each group? Where does Homo floresiensis fit in? How recently did H. floresiensis live? (18,000 years ago) How many hominids currently inhabit Earth? (One, just Homo sapiens.) Have students consider some of the reasons a species might become extinct. (Changing conditions alter the environment and make it uninhabitable; disease can devastate a species; other organisms can increase competition for food and shelter; major catastrophic events, such as an asteroid impact, can wipe out species or make the environment uninhabitable.)


Links and Books

Web Sites

Archaeology and Age of a New Hominid from Flores in Eastern Indonesia
http://www.nature.com/cgi-taf/DynaPage.taf?
file=/nature/journal/v431/n7012/full/nature02956_fs.html

Discusses archeological findings for H. floresiensis at Liang Bua cave on Flores Island, Indonesia. (Requires site license or subscription to Nature.)

Asia: Habitats and Faunal Barriers
http://www.loris-conservation.org/database/
distribution_maps/01_Asia_zoogeography.html

Maps Pleistocene land bridges in Asia.

Human Evolution
http://www.pbs.org/wgbh/aso/tryit/evolution/
Presents human evolution activity with an animated, interactive time line.

The Pleistocene: 1.8 million to 11,000 years ago
http://www.ucmp.berkeley.edu/quarternary/ple.html
Describes the Pleistocene Epoch, including the evolution and expansion of Homo sapiens.


Books

Gamlin, Linda. Eyewitness: Evolution. New York: Dorling Kindersley, 2000.
Traces discoveries that help explain life's diversity. Includes a section on human evolution.

Page, Martin, editor. Eyewitness Visual Dictionary: Animals. New York: Dorling Kindersley, 1991.
Describes animal classification.

Reid, Des, editor. Eyewitness Visual Dictionary: Human Anatomy. New York: Dorling Kindersley, 1996.
Presents annotated diagrams of human anatomy and the human skeleton.


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Alien From Earth
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