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Quick Essays on Evolution

A Drama of Evidence & Interpretation

Outline, Introduction, Dramatis Personae, Charts


Outline of Topics

Introduction: A Drama of Evidence & Interpretation (This page)
Essay 1: Imagining Prehistoric Behavior (T .D. Carter) (Not assigned in 2018)
Essay 2: The Idea of Evolution (D. K. Jordan) (Not assigned in 2018)
Essay 3: The Evolution of Early Evolutionary Theory
Essay 4: Genes That Mutate, Flow, & Drift
Essay 5: Bipedalism: Hallmark of the Hominid Family (Not assigned in 2018)
Essay 6: Human Birth and Bipedalism (D.K. Jordan)
Essay 7: Evolutionary Selection for Bipedalism
Essay 8: Mysteries of the Last Common Ancestor
Essay 9: Our Hallmark Traits (Not assigned in 2018)
Essay 10: Mitochondrial Eve (D.K. Jordan)
Appendix 1: Reviewing High School Genetics (Not assigned in 2018)
Appendix 2: Primate Cousins: A Case Study (Not assigned in 2018)
Appendix 3: Evolving Methods: A Case Study (Not assigned in 2018)

Introduction: A Drama of Evidence & Interpretation

MMW-11 is a five-quarter course sequence primarily intended to introduce students to written history and, increasingly, to world literature. It is also intended to introduce the kinds of evidence and reasoning involved in the study of these topics.

However humans did not first appear with the first writing —most of our time on this planet occurred before writing existed. Nor are we unaffected by our biological traits or the environments around us.

This first section of the course makes a brief nod to our human biological heritage as seen through human paleontology, including the fossil record and DNA research. Probably no field of study provides clearer exemplification of scholarly argumentation about evidence than human paleontology. Unfortunately, given the number of other topics to be covered in MMW-11, paleontology must be given extremely short shrift, and no published textbook of this complex field is suited to accommodate such brevity, at least if we exclude accounts intended for children.

The essays making up this extremely brief introduction were written specifically for MMW. The goal was to provide an overview of the data and arguments that now prevail among mainstream scholars studying our evolutionary past. The essays were not written to be a single work. Each essay is a stand-alone discussion of its topic, and therefore you will notice some overlaps as well as a few gaps to be filled in during class lectures. Some of the essays prepared for to this purpose are not part of this year's printed Sourcebook and will not be assigned, but are included here for those who may be interested in them. To avoid confusion, the original numbering is retained. (That is why the assigned essays begin with Essay 3.)

The essays are designed to be used in conjunction with some on-line materials, in particular “Essential Fossils: A Portfolio.” The portfolio is a group of pages that provide both pictures and summary facts about nearly all of the fossil hominid forms discussed in the essays. The essays have been edited to refer to that portfolio rather than to repeat the information in it.

For the convenience of readers of the paper Sourcebook, all of the web links mentioned in the evolution essays have been consolidated at http://dkjordan.net/mmwplus/evolution.html, which is the only link used in the printed Sourcebook. In HTML versions of these essays, the links have, of course, been integrated directly into the text.

We wish to express our gratitude to Dr. Nancy Friedlander, a biological anthropologist, former MMW instructor, and former Dean of Academic Advising at Eleanor Roosevelt College, for her careful and insightful comments as these essays reached their final versions.


Dramatis Personae:
The Major Players and Why They Are Not Frightening

photo by DKJ
Skeleton of Cro-Magnon of La Madeleine
(Musée de Préhistoire, Les Eyzies)

These essays full of people’s names, technical terms and exotic Latin specimen names. It is not as bad as it seems. In the end, there are only eight major “players”:

  1. Carolus Linnaeus, the XVIIIth-century scholar who saw the world as orderly, but static.
  2. Charles Darwin, the XIXth-century scholar who saw the world as orderly, but constantly changing.
  3. LCA or “Last Common Ancestor,” the shadowy last member of our family tree who was ancestral both to humans and to chimpanzees before we went our separate evolutionary ways.
  4. Early Hominids, a ragtag bunch of unsavory creatures, descendants of LCA, most of whom were probably bipedal.
  5. Australopithecus, another ragtag bunch, a single genus (divided into several species) that was bipedal and eventually may or may not have learned to make stone tools —it’s not easy to make stone tools. Some of them may have been capable of language, but it seems kind of doubtful.
  6. Homo, yet another ragtag bunch —our line is pretty ragtag, on the whole— divided into several species, including ourselves, Homo sapiens, who are pretty much as good as it gets … at least so far.
  7. Neanderthals and Denisovans, other Homo species that seem to have exchanged a small amount of DNA with Homo sapiens. (Denisovans are the Next Big Thing. There is not much evidence yet, but what there is already makes things more complicated than before.)
  8. Mitochondrial Eve, the title —not really name— of a real Homo sapiens lady who, DNA evidence convinces us, was the ancestress of every human on earth today, all other descent lines having died out.


Potentially Useful Charts

The two charts below are far more simplified than the real situation, and imply far more clarity than available fossil specimens justify. For one thing, hundreds of forms are left out. For another, the arrows were made up by me. But you may find them helpful as you read the following chapters.

To help you remember them, try finding three kinds Australopithecus in Chart 1. We don’t know how many different species of Australopithecus there were. The ones shown are the most often discussed. Notice the line leading from Australopithecus africanus to Homo naledi. I made that up, and I can think of lots of reasons why it is probably wrong. Nobody actually knows where Homo naledi came from. Notice the inclusion of Paranthropus. That is a “robust” kind of Australopithecus, and in fact some people still regard Paranthropus forms as robust kinds of Australopithcus. Trying Googling and see what you find.

The second chart is devoted entirely to various kinds of Homo. They probably all descended from H. habilis, but beyond that nothing is very clear, and the arrows are gross simplifications. H. erectus and H. ergaster are regarded by many scholars as the same animal, differing only in age and location. Once again, Homo naledi is inscrutable.

Homo heidelbergensis was merely a sturdy-looking jaw named “Mauer” when I went to graduate school. The category has been expanded, for better or worse, to include a vast range of miscellaneous fossils that used to be lumped together as simply “early homo” or “early modern” forms.

Denisovans are the new kids on the block. Known almost entirely from central Siberian DNA, they seem to be most closely related to Neanderthals. Neanderthals, and Denisovans seem to have been inter-fertile, at least some of the time, and unless you are of purely African descent, you probably have some Neanderthal and Denisovan DNA in you. (Like most diversification, from Neolithic crops to modern investment portfolios, DNA diversification is also probably also generally beneficial.)

Chart 1: Tentative Human Family Tree (Early)
graphic

Chart 2: Tentative Human Family Tree (Late)
graphic


A review quiz is available for these charts. Link.

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