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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 6-7 million years, often with 2 or more 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, (e.g., the Skulls Lab and the Chromosome Fusion lesson, this shows how science can build confidence in a particular explanation (namely: humans have clearly evolved).

 MATERIALS for
TEACHER

NOTE:To print any PDF file, first DOWNLOAD the file, THEN print it. Do NOT print it directly when just opened.
1. Key for overhead projection (completed Chronology)
2. Key showing provisional connections and
asterisked species known prior to 1970

 STUDENT HANDOUTS

1. Chronology Lab Directions
2. Hominin Chron Table 2013 (ages of key fossil)
3. Chronology of Fossil Hominins 2013 (blank chart)
(with horizontal time marker lines)

 

 

TEACHING STRATEGY

1. This lab is best done as an adjunct to the "Skulls" lab (Hominoid Cranium Comparison). Start when they finish the Skulls Lab, and finish as a homework assignment.

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 #2), using an overhead marking pen, producing a provisional evolutionary tree. Emphasize that this "tree" is only one hypothesis about how the vertical lines might be connected. Show a few other possible connections ("hypotheses"), further highlighting how scientists deal with uncertainty.

4. Ask your students "How many species of hominins apparently existed about 1.8 million years ago?" (6, all living in Africa); "How many about 100,000 years ago?" (2).

EXTENSIONS

& VARIATIONS

1. THE CHANGING CHRONOLOGY: If time, point out that the shaded species (with asterisks) were about all we knew about in 1960, when this lesson was first developed. Most of the other species were discovered (or new and better fossils of certain species) were discovered since 1960. In addition, fossils are still being discovered. Australopithecus sediba fossils were discovered in 2008 by the 9 year old son of paleoanthropologist, Dr. Lee Berger. Then, in 2015, in the same general area of South Africa, some cavers discovered the cave and fossils that they reported to Dr. Berger, who launched a major project with small women paleoanthropologists (small enough to enter the cave) and other scientists to carefully record, remove, and examine the 1550 fossils belonging to at least 15 individual hominins of different ages. Dr. Berger called the new species Homo naledi. The fossils showed an unusual mix of early (Autralopithecus) features and more modern (Homo) features. A useful beginning source for the recent (2015) H. naledi announcement can be found HERE. So far, the age of these fossils has not been established with clarity - something they are still working on. Estimates range from 2.5 my to less than 1 my old. In the July 5, 2016 issue of Science News magazine, pg. 12, is an excellent article that discusses the dating problems: "New dating suggests younger age fro Homo naledi." And, for a "peek" into the creationist views of Homo naldi (and a creationist-turned-evolutionist's view), see article in the Panda's Thumb blog.

2. 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.

3. 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.


 4. 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.

5. A nice graphic showing the chronology of the current 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.

6. 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.


 7. 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. Ironically, 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.

8. 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 200,000 years.

9. 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).

10. Human Family Tree: The Smithsonian National Museum of Natural History has a new website: "What Does it Mean to be Human?" Click on the many hotlinks to explore the many features of this site. This Human Family Tree shows the groupings of the many hominin fossils found, and their approximate relative ages. There is also a Human Evolution Interactive Timeline at this site. Take some time to explore

11. 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 to the three "theories" (actallly hypotheses) to see three of the several alternative versions of the human family tree. You also may want to read the hominin profiles. BTW, if you happen to watch the short "Documentary" and hear the conclusion that Neandertals never mixed with modern humans, be aware that more recent studies of DNA in Neandertals and certain groups of modern humans have clearly shown that modern humans do indeed posess around 2-3% Neandertal DNA in their own DNA, showing that modern humans (during their co-existence with Neandertals) did interbreed with them.

12. For a closer look at selected species (as of early 2002), see the summary commentary of those Major Recent Developments (based on an article in the 6 March 2002 Science), along with a revised chronology diagram reflecting this new material.

13. See the "new provisional phylogeny" (as of 2003) which includes 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.

14. 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.). If you are a member of NABT, you can download this article from their archives. if not, contact the the Webmaster about this article, asking for "Human Evo Interp Evid.pdf."

The article mentions related resources, but they are no longer available at the Boston Muserum. The author, Dr. Jeremy DeSilva says, "They could easily be reproduced from the ABT article, but ..., they are quite incomplete. The finds since 2004 (Au. sediba, H. naledi, H. floresiensis, Au. deyiremeda) have been extraordinary and support the point in the article. I still think it would be valuable to use the family trees in the ABT article as templates and add the new fossils, but I would not presume to know what Tim, Ian, or Meave would do with the new finds." If you do decide to use the article when you teach evolution, please share your experience and any resources that you develop with the Webmaster, so he can add them to the lesson on the ENSI website

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

16. Since the last update of this lesson, there have been many new discoveries of hominins, and new interpretations about their relationships. Ask you students to search for information about Ardipithecus ("Ardi") ramidus, the Denisovans, and about Homo naledi, for example. For more Homo naledi information, see HERE.

 ATTRIBUTIONS

This lesson was developed by Larry Flammer in the 1970s, updated for the ENSI site in 1998 and updated again in March 2006. And again April 2016.

A Major updating of all materials in this lesson was done in January, 2017 by Larry Flammer. It incorporates nearly all of the known hominin fossils as of that date.



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