TOEFL inference and rhetorical purpose questions on scientific passages
Hello everyone! Today, we will show you how to answer TOEFL inference and rhetorical purpose questions that ask you what’s going on in terms of scientific activities.
Many TOEFL reading passages are about scientific activities, such as proposing a hypothesis to explain a phenomenon. Examples of TOEFL passages of these types include topics like why dinosaurs disappeared, why large mammals no longer roam North America, how the Hawaiian Islands formed, or who the first people were that lived in the Pacific Islands. In these passages, you'll often find a series of scientific activities: describing a puzzling fact, presenting a hypothesis to explain the fact, and providing confirming evidence for the hypothesis. But the activities don't stop there! You'll also encounter detractors – those who reject the hypothesis. They will present counterexamples to the hypothesis and offer alternative explanations, presenting an alternative hypothesis that can equally explain the puzzling phenomena. The plot thickens with the rebuttal by those who presented the hypothesis in the first place. In their effort to buttress their hypothesis, they will counter the counterexamples and explain why they are not actually counterexamples and why the alternative hypothesis is defective.
When the TOEFL passage describes these scientific activities, many of its inference and rhetorical purpose questions will be about the hypothesis, evidence, counterexamples, alternative explanations, and countering counterexamples. So, understanding which activity the author of the passage is describing is crucial. If you're familiar with this type of discourse, by taking college courses on critical thinking, scientific research methods, or the design of experiments, these questions will be a breeze. If not, they can be quite challenging.
Today, Dr. Byrnes will teach you strategies for identifying these activities using a TOEFL passage that involves these scientific discussions. After learning the strategies, you must practice how to use them with similar questions that require using the same strategies and questions that are exceptions to the strategies. Only with this practice can you master the strategies. You can find all the strategies and practice questions necessary to master the strategies to ace TOEFL reading in Dr. Byrnes’ TOEFL reading course. Find the course at www.nanheebyrnes.com.
Paragraph Analysis
OK, let’s get the party started. Since we want to know how a passage about scientific activities is presented, we will first read the passage, paying attention to clue words that tell us which scientific activities the author is presenting, and then solve related inference and rhetorical purpose questions. The passage we will work on today is about the Pleistocene overkill hypothesis. Let's begin by reading each paragraph.
https://toefl.kmf.com/detail/read/21m4tj.html
This is the first paragraph. It begins with a puzzling fact: large mammals disappeared in North America thousands of years ago, and it aims to explain why this happened. One theory suggests that when people living in Asia migrated to America, they hunted the large mammals to extinction. The next sentence provides details about these first Americans, known as the Clovis society.
The word "yet" indicates a contrast, so we should pay attention. It states, “Yet many scientists argue against this 'Pleistocene overkill' hypothesis.” From this sentence, we learn two things: first, the hypothesis that the first Americans hunted the large mammals to extinction is called the Pleistocene overkill hypothesis, and second, that some scholars reject the hypothesis. The following sentence explains why some scholars disagree with the hypothesis: it is hard to believe that ancient people with their primitive weapons had the capacity to kill all the large mammals. The rest of the paragraph contains numbers, which are too detailed, so we can skip them. We can see that the passage is about scientific activities that aim to explain how the large mammals disappeared in North America.
Second Paragraph
The next paragraph is short and begins with a fact. So let’s skim to look for the big idea, which comes at the end of the paragraph: “Was this coincidence or cause-and-effect?” Since the sentence contains a pronoun, we should look for the antecedent to understand the sentence, which is “The only apparently significant difference in the Americas 11,000 years ago was the presence of human hunters of these large mammals.” So, difference = human existence 11,000 years ago. "This" = difference. So the question raised is whether human existence and mammal extinction is accidental or causational.
Third Paragraph
Moving on to the third paragraph: “We do not know. Ecologist Paul S. Martin has championed the model that associates the extinction of large mammals at the end of the Pleistocene with human predation. With researcher J. E. Mosimann, he has co-authored a work in which a computer model…” The rest are minor details. As Dr. Byrnes emphasizes, wherever you see numbers, you can just skip them. Of course, nobody knows as it happened 11,000 years ago. With “championed” and “co-authored” we know that Martin and Mosimann support the Pleistocene overkill hypothesis.
Fourth Paragraph
The next paragraph continues the previous idea as it states, “The researchers ran the model.” The researchers = Martin and Mosimann. The rest are minor details. Anyway, we know that Martin and Mosimann support the hypothesis with computer model evidence.
Fifth Paragraph
Moving on to the next paragraph. It states, “Many scholars continue to support this scenario. For example, geologist Larry Agenbroad has mapped….” So we know that Agenbroad also supports the Pleistocene overkill hypothesis, and his evidence for the hypothesis is based on some mapping method.
Sixth Paragraph
Moving on to the next paragraph. It begins with, “There are, however, many problems with this model. Significantly, though a few sites are quite impressive, there really is very little archaeological evidence to support it.” So we know that a refutation of the hypothesis is happening in this paragraph. Since it says “many problems” we can expect to see some list of problems with the Pleistocene hypothesis. The first problem is that “there really is very little archaeological evidence to support it.” That is, there isn’t much evidence to support the hypothesis.
Seventh Paragraph
Moving on to the final paragraph, let’s read the first few sentences to see where the discussion is going. “Though Martin claims the lack of evidence actually supports his model—the evidence is sparse because the spread of humans and the extinction of animals occurred so quickly—this argument seems weak. And how could we ever disprove it?” It begins with Martin’s argument being unconvincing. And what is Martin’s argument? The lack of evidence actually supports the overkill hypothesis since the event of human killing the mammals happened so quickly.
“And” continues the same line of thought. So we know that the paragraph continues the previous paragraph about problems with the Pleistocene overkill hypothesis. With “As archaeologist Donald Grayson points out,” we know that Grayson is an objector to the hypothesis. What is his criticism of the hypothesis? The author states,
“As archaeologist Donald Grayson points out, in other cases where extinction resulted from the quick spread of human hunters—for example, the extinction of the moa, the large flightless bird of New Zealand—archaeological evidence in the form of remains is abundant.
Grayson has also shown that the evidence is not so clear that all or even most of the large herbivores in late Pleistocene America became extinct after the appearance of Clovis.” So we know that Grayson has two objections to the overkill hypothesis. One is that if Martin is right on his claim that the event of human killing the mammals happened so quickly, then there should actually be an abundance of evidence, not a lack of evidence, as evidenced by the moa disappearance in New Zealand. So the moa case is used as a counterexample to the overkill hypothesis.
Grayson’s second objection is that it is possible that the mammals did not disappear after the Clovis human hunters appeared. The passage ends with, “Many of the older genera, Grayson argues, may have succumbed before 12,000 B.C., at least half a century before the Clovis showed up in the American West.” If mammals died before the human hunters were in America, humans could not have killed the mammals.
Passage organization
So how is the passage organized? It begins with a puzzling event: there are no large mammals in America, and it provides an explanation, the Pleistocene overkill hypothesis. It presents the supporters of the hypothesis, Martin, Mosimann, and Agenbroad, with different pieces of evidence. The passage then moves to the objections to the hypothesis and presents two problems: one is that the lack of evidence weakens the hypothesis since if the disappearance happened quickly, then there should be abundant evidence as with the moa example. The second objection is that it is possible that the mammals disappeared before the hunters appeared. With that, let’s examine the following seven questions that ask about scientific activities.
puzzling event
explanation = the Pleistocene overkill hypothesis
Evidence =
Martin and Mosimann’s computer models
Agenbroad’s mapping
Objections to the hypothesis by Grayson
about lack of evidence: moa extinction as counterexample)
large mammals disappeared before the human hunters
Question 1
Why does the author compare “Modern humans” with “ancient people”? The author compares the two groups to raise a doubt that ancient people could have killed all the mammals.
A. To argue that modern people have continued to have drastic effects on animal species. Option A is not the point. B. To illustrate how people from different historical times treated animals differently. Option B is not the point. C. To question the idea that ancient people could have hunted the megafauna to extinction. Option C is what we are looking for. D. To emphasize that modern people are more successful hunters than ancient people were. Option D is not the point. The passage mentions that modern humans are capable of causing animal extinctions but does not specify how. So the answer is C.
Question 2
Let's look at this question. It asks what suggests that human activity played a role in the extinction of mammals about 11,000 years ago? This clearly asks us to infer under what conditions we can conclude that humans killed the mammals. Since this is a short paragraph and each part has a role in the argument, let’s read the relevant paragraph first.
Although the climate changed at the end of the Pleistocene, warming trends had happened before. A period of massive extinction of large mammals like that seen about 11,000 years ago had not occurred during the previous 400,000 years, despite these changes. The only apparently significant difference in the Americas 11,000 years ago was the presence of human hunters of these large mammals. Was this coincidence or cause-and-effect?
“These changes” refer to climate changes. So to recap, climate changes that happened 11,000 years ago also happened in previous times between 400,000 and 11,000 years ago. But animal extinction happened only during the period 11,000 years ago, and the only difference among these climate changes is that 11,000 years ago, human hunters were present.
To arrive at the conclusion that humans killed all the mammals, the paragraph uses this reasoning:
Either climate change 11,000 years ago killed the mammals, or the first Americans killed the mammals.
Climate change could not have killed the animals since mammals didn't die during climate changes before 11,000 years ago.
Therefore, the first Americans must have killed the mammals.
In logic, this inference is called disjunctive elimination. It follows this pattern: Either P or Q. Not P, therefore Q. For example, "Either you are lying or telling the truth. You are not lying. Therefore, you are telling the truth."
The main idea is that there are two possible theories that can explain why something happened. If one theory is not plausible, the other must be the correct theory. Many TOEFL inference questions rely on this disjunction elimination rule, so make sure you understand it. To arrive at the conclusion that humans killed all the mammals, we need to eliminate the rival hypothesis, which is climate change.
A. Climate changes that would have favored human population expansion occurred at the time of the extinctions. Option A is not it. B. The presence of human hunters had caused animal extinctions in other time periods. Option B is not it. C. There was a pattern of climate change earlier than 11,000 years ago that had not caused animal extinctions. Option C is what we are looking for. D. Harmful climate changes 11,000 years ago would have required humans to hunt larger numbers of animals for food. Option D is not it. So the answer is C.
Question 3
Which of the following best describes the results of the research discussed in paragraph 4? The result is that Mosimann and Martin found that it takes about 1,000 years for the first Americans to kill all the mammoths. Now let's look at the question which asks what the result of the research is. The result is that it takes just 1,000 years for 100 humans to kill all the mammals in North America.
A. Scientists used mathematical models to show that most of the extinctions occurred in areas where humans had recently arrived. A is not the point. B. Scientists established that the main population of North Americans who hunted lived in Canada during the time of the megafauna extinctions. B is incorrect; Canada was the starting location and they migrated to the US. C. Scientists used numerical models to confirm that a small population of humans could have caused big-game extinctions in a relatively short period of time. C is what we are looking for. 100 people killing megafauna in 1,000 years is quite a short period of time in human history. You can see that C is a good choice by the word choice like "confirm" as it is a perfect word for empirical science. D. Scientists used statistics to prove beyond doubt the currently accepted view that human hunters were the main cause of the megafauna extinctions. Words like "prove beyond doubt" are inappropriate for empirical science. Here, the best thing is an educated guess. D has to be false. The answer is C.
Question4
Let's look at the question. Which of the following statements about Larry Agenbroad’s work is implied in the discussion in paragraph 5? This is the relevant text: "Geologist Larry Agenbroad has mapped the locations of dated Clovis sites alongside the distribution of dated sites where the remains of woolly mammoths have been found in both archaeological and purely paleontological contexts. These distributions show remarkable synchronicity (occurrence at the same time)." From examining the passage we already know that Agenbroad supports the Pleistocene overkill hypothesis and what he did to support the hypothesis is map out the locations of Clovis sites and mammoth bone sites to show that the two happened at the same time period. Let's consider the options.
Agenbroad confirms the hypothesis by mapping out the locations of Clovis sites and mammoth bone sites and found that the two happened at the same time period
A. Agenbroad showed that Mosimann and Martin’s estimates of the amount of time needed to drive big-game to extinction were correct. No. Agenbroad's evidence for the hypothesis is mapping out the Clovis sites and mammoth sites and showed that the two happened at the same time. B. Agenbroad’s maps were the first to indicate the ages of the Clovis sites. No such remark is mentioned. C. Agenbroad reinforced the idea that humans could have caused the extinctions. C is what we are looking for and is the answer. D. Agenbroad’s studies of woolly mammoths led to his discovery of Clovis sites. No mention, so the answer is C.
Question 5
Which of the following statements challenges the view that hunting by humans caused the extinctions of North American megafauna? The question basically asks what are the objections to the Pleistocene overkill hypothesis. The objection was mainly presented by Grayson in two ways: there should have been abundant evidence and the mammals could have disappeared before the Clovis people existed in America. Let's first see whether that is enough info to answer the question.
A. The Clovis sites that contain the remains of mammoths were settled by humans long after the extinctions occurred. A is not what we are looking for. B. Only a few of the Clovis sites are located near known mammoth habitats.
B is tricky as it has some relevant ideas that we are looking for, which is not much evidence. So we need to read the details in the passage to evaluate this sentence. This is the passage: “…there really is very little archaeological evidence to support it. Writing in 1982, Martin himself admitted the paucity of evidence; for example, at that point, the remains of only 38 individual mammoths had been found at Clovis sites. In the years since, few additional mammoths have been added to the list; there are still fewer than 20 Clovis sites where the remains of one or more mammoths have been recovered, a minuscule proportion of the millions that necessarily would have had to have been slaughtered within the overkill scenario.”
There’s only 38 mammoths found at Clovis sites in 1982, and it didn't change much. And there are fewer than 20 Clovis sites where the remains of mammoths have been recovered, this idea is quite different from option B, which talks about not many Clovis sites are near mammoth’s habitat. The passage only talks about Clovis sites and the numbers of mammoths found on the sites, never mentioning mammoth sites. So B is not what we are looking for. Remember Dr. Byrnes’s tip when evaluating options that repeat some of the keywords in the passage. This looks like an attractive choice, but in fact it is a siren’s song and a trap. B contains keywords like “only, few, Clovis sites, mammoth,” but it connects ideas incorrectly.
C. No archaeological evidence of extinctions has been found at Clovis sites since 1982. The absoluteness in citing the word "No" is inappropriate and incorrect. The passage says "few" which means at least one. Remember to use Dr. Byrnes’s tip that any absoluteness indication words are candidates for elimination. D. The number of mammoth remains found at Clovis sites is smaller than would be expected if hunting by humans had caused the extinctions. If the Clovis people hunted the mammals for food then many Clovis sites should contain many mammoth bones, but not many sites have mammoth bones, only 20 sites and only 38 mammoths. D is what we are looking for and is the answer.
Question 6
Let's consider the question. Why does the author mention that there is abundant archaeological evidence for the moa extinction? The moa example by Grayson was mentioned to respond to Martin’s claim that there is not much evidence of mammoth bones in the Clovis sites because it happened so fast. So the moa evidence is to refute Martin's claim.
A. To show that extinctions occurred in areas other than North America. This is not the purpose. B. To challenge Martin’s claim that the lack of megafauna remains supports his model of the megafauna extinctions. B is precisely what we are looking for. C. To identify a country where humans were highly skilled as hunters. C is not relevant. D. To help explain why it is unclear whether all large herbivores of late Pleistocene America became extinct after the appearance of Clovis. D has two problems. First, it is incorrect since Grayson believes that large mammals could have disappeared before not after the Clovis people. Also, the moa extinction is not used to make this point.
Question 7
This is the last question of the day: Donald Grayson believes which of the following about the remains at Clovis sites and megafaunal extinctions? What is Grayson's view? With the moa example, his view is that if humans ate the mammals, there has to be abundant evidence, not lack of evidence, as exemplified with the moa extinction case where there's abundant evidence.
A. The rapid rate of the spread of humans explains why the extinctions also occurred at a rapid rate. A is Martin’s idea. B. The lack of evidence of human-caused extinctions is not surprising in view of the speed with which the extinctions occurred. B is also Martin's idea. C. It is likely that more evidence will be found as dating methods improve. C is the opposite of what is mentioned in the passage: “In the years since, few additional mammoths have been added to the list.” In fact, Grayson does not believe that more evidence would be found since he rejects the overkill hypothesis. D. If humans did contribute to the extinctions, much more evidence of that would have been found by now. D is what we are looking for. The answer is D.
Conclusion:
OK, I hope this lecture was helpful. Let me know if you have any difficult TOEFL passages that you want us to analyze. Thank you for listening. Have a great day!