S292 Explaining the emergence of humans End of Course Assessment S292 02I




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S292 Explaining the emergence of humans

End of Course Assessment S292 02I


Cut-off date 31 October 2002

Before attempting this assessment, read the general instructions and advice on End of Course Assessments that is available as a separate file in the S292 Assessment folder in the course conference.

This assessment is your opportunity to take an overview of the sometimes very detailed information that was presented to you in Lewin’s book. Detailed discussion of fossils is all part of the process of trying to provide answers to much more general questions, such as where we came from, when humans appeared and what were our ancestors like. You are given one of these major themes below, and you are asked to answer four questions that relate to this theme. You should attempt to provide answers that fit in with the evidence that you have been given and with what you have read of the views of scientists working in the area. You will not be expected to give detailed descriptions of the evidence, and you should write each of the answers as if you were summarizing information for somebody who had not had the benefit of taking the S292 course. You will be expected to use information that you have gleaned from other sources, in addition to the course material that you were sent.

Louis Leakey spent much time in the 1950’s searching for fossils of human ancestors in Africa. He found fossil evidence for the origin 20–30 million years ago of apes and gibbons, and suggested that apes and humans evolved from a common ancestor.

The first discovery of an australopithecine had been made in 1924. Raymond Dart, an anatomist working at the University of the Witwatersrand, South Africa, had been given a part of a fossil face, a lower jaw and a brain endocast, found by quarry workers at Taung, Johannesburg. Dart suggested that the fossil remains were those of a ‘missing link’ midway between ape and human. He thought the brain was more human-like than ape-like, and noted the central position of the foramen magnum in the basicranium, a feature of human skulls. Dart named the fossils as Australopithecus africanus. By the late 1950’s South African researchers had collected a number of fossils identified as australopithecines, from a variety of cave sites. The gracile fossils were placed in the genus Australopithecus. The more robust australopithecine fossils were named as Paranthropus, a generic name which was initially unpopular, but is now accepted. Leakey first viewed fossil australopithecines in 1945 and did not believe that they were ancestral to Homo. He felt that australopithecines were so specialized that it was anatomically impossible for them to be ancestral to Homo. However, he agreed that australopithecines were close to Homo sapiens and felt that the term ‘near-men’ suited them well.

In 1959 Mary Leakey discovered the famous fossil skull, Zinjanthropus, (Zinj), at Olduvai Gorge. Initially, Leakey was not enthusiastic about Mary’s discovery of Zinj. His immediate reaction to Zinj was to say, “Oh dear, I think it’s an australopithecine”. In the late 1960’s, like his father, Richard Leakey also used the term ‘near men’ to describe australopithecines. However, most other researchers and scholars in the field of human evolution consider that australopithecines were ancestral to Homo.

The theme for this assessment is:

Who were the australopithecines and what is their relevance to the emergence of humans?

Lewin’s book contains much information about australopithecines and their evolutionary relationships in Units 15, 19, 20 and 22. Units 3 and 4 outline historical views and modern evolutionary theory, respectively, and provide useful background material. Evidence about the behaviour of extinct hominines is discussed in Units 14 and 17. Early Homo is described in Unit 21. In addition, use the web links on the course website to get more information and illustrations. There will also be additional guidance on the FirstClass computer conference, particularly in the ‘Skull of the Week’ section. You should select information as appropriate, as a basis for your assessment. In each of your answers, you will need to provide references to the sources of information that you use.



You should answer Part I and select three questions from Part II.

Whichever three of Questions 2–6 that you select, your combination of answers will address both aspects of the theme. In your answers, you need to set out and interpret the lines of evidence that you will be using to address each aspect of the question.

Part I

This part consists of one compulsory question that carries 25 marks. Your answer should be no more than 300 words.

Question 1


List the key features of the ‘single species’ hypothesis of human evolution. Select and describe one line of evidence derived from finds of australopithecine and Homo fossils and explain how your evidence refutes the single species hypothesis. Your evidence should describe specific fossil finds and quote the dates attributed to them to support your answer. What does the fossil evidence imply about the shape of the evolutionary tree for hominines?

Part II


This part contains five questions from which you should answer any three. Each question carries 20 marks and your answer to each question should be about 300 words.

Question 2


Who were the immediate ancestors of the australopithecines?

Lewin states in Unit 19 that the hominine clade arose between 5–6 million years ago, but points out that fossil evidence dated earlier than 4 million years ago is sparse. Describe specific fossil evidence for the earliest hominines known, including finds discovered recently and reported in News online and site reviews in the S292 website. To obtain full marks you need to describe two fossils and explain why these fossils are interpreted as being on the hominine line of evolution and even if not directly ancestral to australopithecines, at least close to the australopithecine line. Write about 300 words.


Question 3


Do the australopithecines form a real group?

To answer this question, begin by summarizing the main features of named australopithecines in a table of your own design. Select at least six examples, including both gracile and robust species. Write a brief summary of the key cranial and post-cranial features of the group in which you explain the distinction between gracile and robust forms. Draw together the evidence for your answer to the question. Write about 300 words for your summary and conclusion.


Question 4


Compare and contrast selected anatomical features of australopithecines and Homo presenting the information in a table of your own design. You should identify a total of at least 8 similarities and differences for full marks.

What clues are available from fossil and archaeological remains about similarities and differences in the behaviour of australopithecines and Homo? Describe evidence that relates to two aspects of behaviour in the australopithecines. Information about fossil and archaeological evidence for behaviour of australopithecines is available from Lewin (1999) and the S292 website.

Can it be concluded that australopithecines may be ancestral to Homo? Justify your view by referring to the evidence that you have included.

Write about 300 words for your summary of evidence about aspects of australopithecine behaviour and your conclusion.

Question 5


The recent find of Kenyanthropus resembles australopithecines superficially at least. Describe the key features of Kenyanthropus, and the dating of the fossil remains. What is the evidence for separating the Kenyanthropus line from the australopithecines? What can you conclude from the anatomical evidence and the dating of the fossils about the link between Kenyanthropus and the origin of Homo? Write about 300 words.

Question 6


Discuss the possibility that there is a single line from australopithecines to Homo or that there is more than one branch on the australopithecine tree, one of which leads to Homo. Which of the australopithecines do you think are unlikely and which may be likely to have been the ancestor of Homo? To answer the latter question, use only evidence from dates of early Homo and australopithecine fossils.

Discussion of which of the australopithecines is ancestral to Homo has centred specifically on anatomy of fossil jaws and teeth. Explain how interpretation of this evidence* can lead to inaccurate phylogenies. Justify or reject one suggestion for phylogeny of Homo from named Australopithecus species which is based on evidence from aspects of fossil anatomy* of australopithecines and early Homo. Draw one simplified evolutionary tree including australopithecines and early Homo, and annotated as necessary, to illustrate your answer.



Write about 300 words.

References


5 marks are available for the list of all of the references cited in your answers to the four questions. You may prefer to list the references at the end of each answer, or provide a list of all the references used at the end of the four answers.

Summary of marks available


Part I (Question 1) 25 marks

Part II (three of Questions 2–6 for 20 marks each) 60 marks

References 5 marks

For presentation of your answer 5 marks



For the use of sources other than Lewin 5 marks

*Detailed descriptions of fossil anatomy are not required — the issue here is whether it is appropriate to use the evidence to derive phylogeny.

*


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