Further Thought

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Further Thought

Use the questions at the end of the chapter to explore concepts and connections in greater depth through application and synthesis.

1. Explain why Ruvolo (1995, 1997) thought it was important to look at several nuclear genes, and not just the mtDNA genes, to study the relationships of humans and the great apes. [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

2. The data in this chapter show that humans and the chimpanzees are each other's closest relatives. Is it accurate to say that humans evolved from chimpanzees? How about that chimpanzees evolved from humans? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

3. In a study of the phylogeny of Old World monkeys (Hayasaka et al. 1996), the three individual rhesus macaques that were studied did not form a monophyletic group. Instead, the mtDNA of one of the rhesus macaques was more similar to the mtDNA of Japanese and Taiwanese macaques (which are different species) than it was to the other rhesus macaques. How might this have happened? (There are at least two possibilities.) With this as background, explain why it is useful that the phylogeny in Figure 19.4 (page 731 in your textbook) includes several individuals from each species. [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

4. What's in a name? Jared Diamond (1992), suggests that if we follow the naming traditions of cladistic taxonomy, then humans, chimpanzees, and bonobos should all be considered members of a single genus. Diamond proposes calling these species, respectively, Homo sapiens, Homo troglodytes, and Homo paniscus. Jonathan Marks (1994) objects to Diamond's taxonomic reasoning. Concerning the nature of humans and apes, Marks asserts that

Popular works tell us that we are not merely genetically apes, but that we are literally apes (e.g., Diamond 1992). Sometimes there is profundity in absurdity, but I don't think this is one of those times. It merely reflects the paraphyletic nature of the category "apes"—humans are apes, but only in the same sense that pigeons are reptiles and horses are fish. Focusing on the genetic relations obscures biologically significant patterns of phenotypic divergence.

Do you think humans, chimpanzees, and bonobos should all be classified as members of the same genus? Is there more at stake in the disagreement between Diamond and Marks than just Latin names? If so, what? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

5. Jared Diamond finds ethical dilemmas in the close kinship between humans and chimpanzees:

It's considered acceptable to exhibit caged apes in zoos, but it's not acceptable to do the same with humans. I wonder how the public will feel when the identifying label on the chimp cage in the zoo reads "Homo troglodytes" (Diamond 1992, p. 29).

Diamond finds the use of chimpanzees in medical research even more problematic. The scientific justification for the use of chimpanzees is that chimpanzee physiology is extremely similar to human physiology, so chimpanzees are the best substitute for human subjects. Diamond notes that jails are a very rough analogue to zoos, in the sense that they represent conditions under which we do consider it acceptable to keep people in cages without their consent (if not to display them). But there is no human analogue to research on chimpanzees: There are no conditions under which we consider it acceptable to do medical experiments on humans without their consent. Is it ethically justified to keep animals in zoos? To use animals in medical research? Does the phylogenetic relationship between ourselves and the animals in question matter? If so, how and why? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

6. We mentioned in Section 19.2 that there is debate over the evolutionary affinities of Sahelanthropus tchadensis. Given the age and appearance of the skull in Figure 19.9 (page 750 in your textbook), there are many possibilities: It could be our common ancestor with the chimpanzees; it could be a species more closely related to us than to the chimpanzees; it could be a species more closely related to the chimpanzees than to us; it could even be a species more closely related to gorillas than to either the chimpanzees or us. Suppose you are a paleoanthropologist who wants to figure out which of these possibilities is correct. What strata would you choose to search for more fossils? If you are lucky enough to find a skull, what features would tell you which hypothesis is closest to the truth? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

7. One of the most heated aspects of human racial politics is the contention that human races are genetically distinct. How do the African replacement versus multiregional evolution models address this issue? That is, which model predicts that human races are more genetically different from each other? How different are people from different geographic regions? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

8. We reviewed genetic studies showing that non-African human populations are descended from African populations. Some people might conclude from this data that modern African people are in some sense "primitive." What is the logical flaw in this thinking? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

9. Different ethnic groups within Africa are more diverse than are the ethnic groups on all other continents taken together. What does this imply about the common U.S. practice of categorizing people into "African," "Caucasian," "Asian," and "Native American"? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

10. Work by C. Swisher and colleagues (1996) indicates that Homo erectus may have persisted in Java until 53,000 years ago at Sambungmachan and until 27,000 years ago at Ngandong. If correct, these dates imply that H. erectus and H. sapiens coexisted in Java. Will this finding help settle the debate over the out-of-Africa model versus the multiregional origin model? Why or why not? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

11. For the sake of argument, adopt the proposition implied by Wood (1997) that early species of Homo did not participate in the production of Oldowan stone tools. What other puzzles must we now solve? Note that after the invention of Oldowan tools, the next advance in toolmaking is marked in the archaeological record by the appearance of Acheulean tools, which are substantially more sophisticated than Oldowan tools (Johanson et al. 1996). Acheulean tools appear about 1.4 million years ago and persist until less than 200,000 years ago. [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.

12. Derek Bickerton (1995) and Charles Catania (1995) object to the suggestion that Homo habilis had language. Bickerton writes, "If H habilis already had all the necessary ingredients for language, what happened during the next million years?" And Catania writes, "I [deduce] that our hominid ancestors should have taken over the world 950,000 years ago if a million years ago they were really like us in their language competence. But they did not, so they were not; if they had been, those years would have been historic instead of prehistoric." How do you think Phillip Tobias would respond to Bickerton and Catania? Who do you think is right? [Hint]
To create paragraphs in your essay response, type at the beginning of the paragraph, and at the end.




1.	Explain why Ruvolo (1995, 1997) thought it was important to look at several nuclear genes, and not just the mtDNA genes, to study the relationships of humans and the great apes. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



2.	The data in this chapter show that humans and the chimpanzees are each other's closest relatives. Is it accurate to say that humans evolved from chimpanzees? How about that chimpanzees evolved from humans? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



3.	In a study of the phylogeny of Old World monkeys (Hayasaka et al. 1996), the three individual rhesus macaques that were studied did not form a monophyletic group. Instead, the mtDNA of one of the rhesus macaques was more similar to the mtDNA of Japanese and Taiwanese macaques (which are different species) than it was to the other rhesus macaques. How might this have happened? (There are at least two possibilities.) With this as background, explain why it is useful that the phylogeny in Figure 19.4 (page 731 in your textbook) includes several individuals from each species. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



4.	What's in a name? Jared Diamond (1992), suggests that if we follow the naming traditions of cladistic taxonomy, then humans, chimpanzees, and bonobos should all be considered members of a single genus. Diamond proposes calling these species, respectively, Homo sapiens, Homo troglodytes, and Homo paniscus. Jonathan Marks (1994) objects to Diamond's taxonomic reasoning. Concerning the nature of humans and apes, Marks asserts that Popular works tell us that we are not merely genetically apes, but that we are literally apes (e.g., Diamond 1992). Sometimes there is profundity in absurdity, but I don't think this is one of those times. It merely reflects the paraphyletic nature of the category "apes"—humans are apes, but only in the same sense that pigeons are reptiles and horses are fish. Focusing on the genetic relations obscures biologically significant patterns of phenotypic divergence. Do you think humans, chimpanzees, and bonobos should all be classified as members of the same genus? Is there more at stake in the disagreement between Diamond and Marks than just Latin names? If so, what? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



5.	Jared Diamond finds ethical dilemmas in the close kinship between humans and chimpanzees: It's considered acceptable to exhibit caged apes in zoos, but it's not acceptable to do the same with humans. I wonder how the public will feel when the identifying label on the chimp cage in the zoo reads "Homo troglodytes" (Diamond 1992, p. 29). Diamond finds the use of chimpanzees in medical research even more problematic. The scientific justification for the use of chimpanzees is that chimpanzee physiology is extremely similar to human physiology, so chimpanzees are the best substitute for human subjects. Diamond notes that jails are a very rough analogue to zoos, in the sense that they represent conditions under which we do consider it acceptable to keep people in cages without their consent (if not to display them). But there is no human analogue to research on chimpanzees: There are no conditions under which we consider it acceptable to do medical experiments on humans without their consent. Is it ethically justified to keep animals in zoos? To use animals in medical research? Does the phylogenetic relationship between ourselves and the animals in question matter? If so, how and why? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



6.	We mentioned in Section 19.2 that there is debate over the evolutionary affinities of Sahelanthropus tchadensis. Given the age and appearance of the skull in Figure 19.9 (page 750 in your textbook), there are many possibilities: It could be our common ancestor with the chimpanzees; it could be a species more closely related to us than to the chimpanzees; it could be a species more closely related to the chimpanzees than to us; it could even be a species more closely related to gorillas than to either the chimpanzees or us. Suppose you are a paleoanthropologist who wants to figure out which of these possibilities is correct. What strata would you choose to search for more fossils? If you are lucky enough to find a skull, what features would tell you which hypothesis is closest to the truth? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



7.	One of the most heated aspects of human racial politics is the contention that human races are genetically distinct. How do the African replacement versus multiregional evolution models address this issue? That is, which model predicts that human races are more genetically different from each other? How different are people from different geographic regions? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



8.	We reviewed genetic studies showing that non-African human populations are descended from African populations. Some people might conclude from this data that modern African people are in some sense "primitive." What is the logical flaw in this thinking? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



9.	Different ethnic groups within Africa are more diverse than are the ethnic groups on all other continents taken together. What does this imply about the common U.S. practice of categorizing people into "African," "Caucasian," "Asian," and "Native American"? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



10.	Work by C. Swisher and colleagues (1996) indicates that Homo erectus may have persisted in Java until 53,000 years ago at Sambungmachan and until 27,000 years ago at Ngandong. If correct, these dates imply that H. erectus and H. sapiens coexisted in Java. Will this finding help settle the debate over the out-of-Africa model versus the multiregional origin model? Why or why not? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



11.	For the sake of argument, adopt the proposition implied by Wood (1997) that early species of Homo did not participate in the production of Oldowan stone tools. What other puzzles must we now solve? Note that after the invention of Oldowan tools, the next advance in toolmaking is marked in the archaeological record by the appearance of Acheulean tools, which are substantially more sophisticated than Oldowan tools (Johanson et al. 1996). Acheulean tools appear about 1.4 million years ago and persist until less than 200,000 years ago. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.



12.	Derek Bickerton (1995) and Charles Catania (1995) object to the suggestion that Homo habilis had language. Bickerton writes, "If H habilis already had all the necessary ingredients for language, what happened during the next million years?" And Catania writes, "I [deduce] that our hominid ancestors should have taken over the world 950,000 years ago if a million years ago they were really like us in their language competence. But they did not, so they were not; if they had been, those years would have been historic instead of prehistoric." How do you think Phillip Tobias would respond to Bickerton and Catania? Who do you think is right? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

Chapter 19: Human Evolution

Further Thought