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A Mini-Lesson

 

CHRONOLOGY LAB

by Larry Flammer

 

 

EVOLUTION

Geological & Paleontological Patterns: Human

 SYNOPSIS

Students plot the times of existence for the several species of hominins (formerly "hominids") on a two-dimensional time line chart. Can be expanded to include new discoveries, and relative divergence of ape lines.

 CONCEPTS

1. Different hominin species came and went over different periods of time over the past 4-5 million years, often with 2-3 species living at the same period of time and in the same general part of the world.

2. A provisional evolutionary tree of hominins may be constructed easily from the array, but still with areas of considerable uncertainty.

3. When used with the matching array of skulls, the gradual changes toward modern humans is inescapable.

4. In concert with other, independent lines of evidence of human evolution, this shows how science can build confidence in a particular explanation (namely: humans have clearly evolved).

 MATERIALS

1. Directions sheet, with list of species and their ages
2. Time scale sheet
3. Key for overhead projection (completed Time Scale sheet)

 STUDENT HANDOUTS
 

 (see end of lesson for the formatted handouts).

1. Directions sheet, with list of species and their ages
2. Time scale sheet

 

 

TEACHING STRATEGY

1. This is best done as an adjunct to the "Skulls" lab (Hominoid Cranium Comparison), probably as a homework assignment during or after the skulls have been studied and discussed.

2. It helps greatly if you can briefly show how to start marking the time ranges on the time line (using overhead) as per directions, and even give them a quick glance at the finished product, just to give them the idea.

3. When the students have finished (next day?), have them check their work by looking at the projected image of a completed chart. Then, show them how the "existence" range lines can be connected with gently curving dashed lines (see key, part 2), using an overhead marking pen, producing a provisional evolutionary tree.

THE CHANGING CHRONOLOGY: The data provided on the Directions sheet were essentially accurate prior to 2001, taking the chronology back nearly 5 million years. However, "science marches on." Don't miss this opportunity to show how more recent data have changed the picture, that even fossil studies are very dynamic! After showing and discussing the results, show what the results would look like with more recent data, taking us back to around 6 million years ago, plus new fossils and new interpretations of those data. Use the "2002 results chart, #1" and then some of the provisional connections shown on the "2002 results chart #2". If you want your students to actually DO the "2002" version, provide them with the more recent discoveries (along with the original table) and the "2002 - 6mya blank chart". Furthermore, you may want to have them check to see what has been discovered more recently, and to add those discoveries to the chart.

NEW 2007 DATA: CLICK HERE For an updated Directions page, including the latest Table listing of key fossil discoveries and their revised time-ranges. No key is provided, but you should use the 6 mya blank timeline for this. A nice graphic showing the chronology of this latest collection can be found (near the bottom end) of the Talk Origins site, which also lists helpful information about each fossil hominin species, providing clues for which species are closest in features and time, suggesting how they may be connected.

SPELLING QUESTIONS: Neandertal vs Neanderthal: Which is it? Also, is Neandertal a species of Homo, or a subspecies of Homo sapiens? Check this out on the Talk Origins site.

NEW TAXONOMY: In addition to new fossils being added to the collection (with corresponding revisions), molecular studies have also made it increasingly clear that apes are biologically much closer to humans than their traditional taxonomy would indicate (if classified by the same criteria used for other species). As a result, a taxonomy that reflects that relationship much more accurately has been adopted. The main changes: the family Hominidae ("hominids") now includes the African apes along with humans, and all humans (including all their extinct bipedal predecessors and cousins) are now placed in the subfamily Hoimininae ("hominins"). Click here for more details.

 VISUAL ENHANCEMENT: A suggestion by 6th grade science teacher Karen Maor was to paste or tape little pictures of the skulls next to the names of each hominin. Such pictures are available from various sources online, including the collection of scale photos on our site of a sampling of six hominin skulls, each shown in 4 different views. The side (profile) view would probably be best to use. If you do use these, you should reduce them considerably to about 2x3 or smaller size. Or, if you make a classroom-size Chronology, you could use the larger photos.

4. As an example of the uncertainty in science, be sure to show a few alternative "pathways" to connect some of the fossil ranges, using additional dashed/dotted lines, and some question marks. You can also ask what differences we might expect to find in the hominin fossils which could be found between the selected ones we have (intermediate or transitional features), and where we might look for such fossils to test those hypotheses (in sediments or ash deposits of that particular age, in that part of the world). Doing this provides an excellent example of how we can make testable predictions about events of the past, which could be reasonably confirmed by subsequent discoveries.

 UPDATE: For a very nice chronology which reflects several more recent finds, take a look at the article in The American Biology Teacher 65(5) May 2003, pages 333-339: "Teaching Human Evolution" by DL Alles and JC Stevenson. The article actually has virtually NO teaching ideas, but it does have a nice summary of the current state and interpretation of the subject, along with an excellent chronology diagram, suitable for use on an overhead, or for a class handout.

5. Point out (ask) "how many different species lived..." at selected periods of time. For example, at 1.8 mya, there were 4 different species of hominins living (all in Africa).

6. It is interesting to point out that ALL of the fossils older than about 20,000 years were found ONLY in the old world (Africa, Europe, and Asia), never in the Americas. Furthermore, it is critical to emphasize that we have NO fossils of strictly modern humans that are older than about 100,000 years.

7. Take a look at the very nice online interactive chronology, "The Origins of Humankind", with built in details of specific fossils, and a plausible "tree" can be found on the PBS/WGBH-Evolution web site. This was developed in mid 2001, so it has a number of the new fossils and species found since the present lesson was posted (1998).

8. Early Human Phylogeny: Click on the branches of this family tree to learn more about different species of hominins and the scientists who discovered their fossils. If you click on the red question marks, you can find out why some branches of the family tree are still debated.

9. Becoming Human: This interactive documentary about human origins is worth an hour of your time, but if you're in class and you're looking for specific information, jump to "Becoming Human: The Documentary." Then select "Lineages" from the menu at the top. Move your cursor to the bottom of the screen, and a menu will pop up. Click on "The Human Family Tree" (or go directly to "The Human Family Tree") and then on the three theories to see alternative versions of the human family tree. You also may want to read the hominin profiles.

10. Since this lesson was developed and placed on this site, hundreds of new hominin fossils of these and several new species have been found. Take a look at the summary commentary of these Major Recent Developments (based on an article in the 6 March 2002 Science), along with a revised chronology diagram reflecting this new material.

11. See a very nice new provisional phylogeny which includes the recent discoveries along with profile drawings of the skulls of each species. It also shows the time spans for the main artifact traditions. This is a one-page PDF file, posted here 10 March 2003, with the kind permission of its source, Dr. Richard Klein, Prof. of Anthropology at Stanford University.

12. A very useful extension and/or alternative to the Chronology Lab or the Skulls Lab is the approach developed by Jeremy DeSilva at the Boston Museum of Natural History:
HUMAN EVOLUTION: INTERPRETING THE EVIDENCE. This was featured in the American Biology Teacher journal, April 2004. It is structured around the comparison of three different interpretations by 3 different anthropologists in how known hominin fossils are related to each other. Students become involved in reviewing their criteria and assumptions, and defending their own interpretations. An excellent experience in the process of science, including uncertainty, bias, assumptions, and controversy amongst scientists. Website includes full text of article and diagrams (3 full page provisional phylogenies, easily compared as transparencies, or handouts for students.)

13. Return to the "Skulls" lab (Hominoid Cranium Comparison) for further discussion and integration of the chronology info with the array of skulls.

 ATTRIBUTIONS

This lesson was developed by Larry Flammer in the 1970s, updated for the ENSI site in 1998 and updated again in March 2006.

 The two pages below show the Directions and Worksheet. These and the 2 keys are available in PDF format (retaining the intended structure) at the END of this lesson.

Page 1: Directions ("Chronology Lab: Directions & Data")
Page 2: Scale/Timeline Worksheet ("Chronology of Fossil Hominins")
Page 3: Key, part 1;
Page 4: Key, part 2.

The Key is for teacher use (on overhead), and/or for use by students as a self-check. Notice that this key is in two parts (or phases). Part 1 is what the students' worksheet should look like when done properly. Make a transparency of this one, then, when showing and discussing it in class, use erasable marking pen to draw in the dotted lines suggesting likely evolutionary pathways from species to species, according to the Part 2 Key. You will note that the A. robustus and A. boisei groups are not connected to the others. Current thinking suggests they may have evolved from A. africanus, so you can insert that curved dotted line yourself.

CHRONOLOGY LAB: DIRECTIONS & DATA

DIRECTIONS: READ ALL DIRECTIONS BEFORE STARTING! Using the list below, indicate (on the CHRONOLOGY OF FOSSIL HOMININS chart) the range of existence for each group (species or sub-species). Do this by marking on the chart the times for the earliest fossils and the most recent fossils known for a group (the maximum-minimum range, indicated in "years ago" below), then connect those marks with a vertical line. Add the name of the group just to the left or right of the line. Do this for each group.

BEST RESULT will be obtained if you start with the oldest known hominin (A. ramidus), and plot its vertical line near the lower left third of the chart (and at the proper vertical position on the page, near the bottom). Then, for each of the remaining species, shift about a centimeter to the right, and plot its vertical position. [Exception: when you get to A. robustus and A. boisei, plot their vertical lines about a cm to the left of A. africanus]. Continue the Homo groups to the right of A. africanus, shifting about 1 cm further to the right for each one in turn.

ON THE CHART..."MYA" = Millions of Years Ago; so 0.2 MYA = 200,000 years ago; 1.4 MYA = 1,400,000 years ago, etc. The dotted lines represent the time levels indicated; you should estimate as closely as possible the positions to plot which fall between the lines.

BONUS: If you are interested and have the time, tape some extra sheets of paper to the bottom of the CHRONOLOGY sheet, and continue the time scale (using the same dimensions and distances) so that you can include the points where the different apes apparently branched off and began to evolve towards their modern forms. Likewise, for the earliest hominoids (Proconsul and Aegyptopithecus). Be sure to label each identified time or range of time.

 SPECIES/SUB-SPECIES  LIVED...YEARS AGO
 Homo sapiens:
.....................Modern H. sapiens..................
.....................Neandertal...............................
.....................Archaic H. sapiens..................

120,000 - present
125,000 - 30,000
700,000 - 250,000
 Homo erectus / (H. ergaster?)  1.8 mya - 300,000
 Homo habilis  2.5 mya - 1.8 mya ?
 Australopithecus boisei  1.8 mya - 1.4 mya
 Australopithecus robustus  2 mya - 1.5 mya
 Australopithecus africanus  3 mya - 2.3 mya
 Australopithecus afarensis  3.9 mya - 3 mya
 Australopithecus anamensis  4.5 mya - 3.9 mya
 Ardipithecus ramidus ?  4.6 mya - 4.2 mya ?

EXTENDED CHART (BONUS)
 Chimpanzee (Pan)  line branched off about 7 mya
 Gorilla (Gorilla)  line branched off about 10 mya
 Ramapithecus (in orangutan line)  lived about 8 mya
 Orangutan (Pongo)  line branched off about 16 mya
 Proconsul (very early hominoid)  lived about 20-18 mya
 Aegyptopithecus (an early hominoid) lived about 33 mya

Name_________________________________________________ S.N._____ Date_____________ Per.____
CHRONOLOGY OF FOSSIL HOMININS

MYA

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PDF FILES

 Chronology Lesson

2001 - Directions, Data, 5my Blank Chart,
and 2 Results Charts

2002 - 6my Results bars only

2002 - 6my Results bars + connections

2002 - 6my Blank Chart

 IF YOU HAVE ANY PROBLEMS DOWNLOADING PDF FILES,
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THE WEBMASTER

 The following pages are in Adobe Acrobat pdf format in order to maintain their intended layout for easy printing of handouts. Only a "thumbnail" reduced size image of the first page is showing (if more than one page is in that file). For enlarging and copying, (and seeing other pages in that file), you will need to download the free Acrobat Reader from Adobe (unless it's already installed in your system). Then just click on the blue file name above, below, or next to the first page. You may see the "Acrobat Exchange" (Reader application) loading, then the pages will display. You might need to shift-click and drag the lower left corner of the page to enlarge it, or click the magnifying glass on the menu bar.

If this doesn't seem to work, you might need to load and/or enable the PDFViewer plug-in by following one of these protocols:

For Netscape Communicator: EDIT>Preferences>Navigator>Applications (then scroll down to "Portable Document Format (PDFViewer)", click on it, then click OK; if it's not there, click on "New", and add it in).

For Netscape Navigator: OPTIONS>General Preferences>Helpers (scroll to check for PDF on list, add it if it isn't, then click OK to activate it.

For other browsers, or problems with this, check with your browser tech support, Adobe tech support, or, in dire frustration, e-mail me. If nothing else, I will mail you hard copy of the formatted pages desired.

 


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