Although many lines of evidence indicate that birds evolved from ground-dwelling theropod dinosaurs, some scientists remain unconvinced. They argue th...
GMAT Reading Comprehension : (RC) Questions
Although many lines of evidence indicate that birds evolved from ground-dwelling theropod dinosaurs, some scientists remain unconvinced. They argue that theropods appeared too late to have given rise to birds, noting that Archaeopteryx lithographica—the oldest known bird—appears in the fossil record about 150 million years ago, whereas the fossil remains of various nonavian maniraptor theropods—the closest known relatives of birds—date only to about 115 million years ago. But investigators have now uncovered bones that evidently belong to nonavian maniraptors dating to the time of Archaeopteryx. In any case, failure to find fossils of a predicted kind does not rule out their existence in an undiscovered deposit. Skeptics also argue that the fused clavicles (the "wishbone") of birds differ from the unfused clavicles of theropods. This objection was reasonable when only early theropod clavicles had been discovered, but fossilized theropod clavicles that look just like the wishbone of Archaeopteryx have now been unearthed. Finally, some scientists argue that the complex lungs of birds could not have evolved from theropod lungs, an assertion that cannot be supported or falsified at the moment, because no fossil lungs are preserved in the paleontological record.
The primary purpose of the passage is to
1. Passage Analysis
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| Although many lines of evidence indicate that birds evolved from ground-dwelling theropod dinosaurs, some scientists remain unconvinced. | What it says: Most evidence supports the theory that birds came from land dinosaurs, but some scientists disagree. What it does: Sets up the main debate - introduces competing viewpoints Source/Type: Author's overview of scientific consensus vs. opposition Connection to Previous Sentences: This is the opening - establishes the central debate we'll explore Visualization: Scientific Community Split:
Reading Strategy Insight: Notice the author's position is already clear - they say "many lines of evidence indicate" (supporting the theory) while skeptics "remain unconvinced" (weaker language). The author is on the side of the evolution theory. What We Know So Far: Main scientific debate about bird evolution What We Don't Know Yet: What specific arguments skeptics make, how these arguments are answered |
| They argue that theropods appeared too late to have given rise to birds, noting that Archaeopteryx lithographica—the oldest known bird—appears in the fossil record about 150 million years ago, whereas the fossil remains of various nonavian maniraptor theropods—the closest known relatives of birds—date only to about 115 million years ago. | What it says: Skeptics say timing doesn't work - oldest bird fossil is 150 million years old, but closest dinosaur relatives are only 115 million years old. What it does: Provides the first specific argument from skeptics Source/Type: Skeptical scientists' argument based on fossil dating Connection to Previous Sentences: This builds on "some scientists remain unconvinced" by giving us their first concrete reason - it provides the "why" behind their skepticism. Visualization: Timeline Problem (According to Skeptics):
Reading Strategy Insight: This seems like a reasonable objection - the timing does seem backwards. Don't worry about the complex dinosaur names; focus on the simple timing issue. What We Know So Far: Main debate + first skeptical argument (timing problem) What We Don't Know Yet: How supporters respond to this timing issue |
| But investigators have now uncovered bones that evidently belong to nonavian maniraptors dating to the time of Archaeopteryx. | What it says: Scientists found older dinosaur fossils that are the same age as the oldest bird. What it does: Directly refutes the timing argument with new evidence Source/Type: New fossil evidence from researchers Connection to Previous Sentences: This directly addresses the timing problem from the previous sentence. The "But" signals this contradicts the skeptics' argument. The 35-million-year gap is now closed. Visualization: Updated Timeline (New Evidence):
Reading Strategy Insight: Feel relieved here - the author is systematically dismantling the skeptics' arguments. The "But" tells us we're getting the counter-evidence. What We Know So Far: Timing objection has been resolved with new fossil finds What We Don't Know Yet: What other arguments skeptics make |
| In any case, failure to find fossils of a predicted kind does not rule out their existence in an undiscovered deposit. | What it says: Even if we hadn't found those fossils, just because we can't find something doesn't mean it never existed. What it does: Provides a general principle that reinforces the counter-argument Source/Type: Author's logical principle about fossil evidence Connection to Previous Sentences: This builds on the previous sentence's solution by adding a broader point. "In any case" means "even if the previous solution weren't true, here's another reason the skeptics are wrong." This is backup support. Visualization: Logic of Fossil Hunting:
Reading Strategy Insight: This is reinforcement, not new complexity. The author is giving us TWO ways the timing argument fails, making their case stronger. What We Know So Far: First skeptical argument defeated in two ways What We Don't Know Yet: Additional skeptical arguments |
| Skeptics also argue that the fused clavicles (the "wishbone") of birds differ from the unfused clavicles of theropods. | What it says: Skeptics have a second argument - bird bones are fused together while dinosaur bones are separate. What it does: Introduces the second specific skeptical argument Source/Type: Skeptical scientists' argument based on bone structure Connection to Previous Sentences: "Skeptics also argue" signals we're moving to their next argument. This follows the same pattern - state skeptical position, then (we expect) the response. Visualization: Bone Structure Difference:
Reading Strategy Insight: We're seeing a clear pattern: skeptical argument → response. Expect the author to address this bone issue next. What We Know So Far: Two skeptical arguments (timing + bone structure) What We Don't Know Yet: Response to bone structure argument |
| This objection was reasonable when only early theropod clavicles had been discovered, but fossilized theropod clavicles that look just like the wishbone of Archaeopteryx have now been unearthed. | What it says: The bone argument made sense before, but now scientists found dinosaur bones that look exactly like bird wishbones. What it does: Refutes the second skeptical argument with new fossil evidence Source/Type: Author's assessment + new fossil evidence Connection to Previous Sentences: Perfect parallel to the timing argument response. "But" again signals the counter-evidence. Same pattern: respectful acknowledgment ("reasonable") + new evidence that solves the problem. Visualization: Updated Bone Evidence:
Reading Strategy Insight: Identical pattern to timing argument - students should feel confident recognizing this structure. The author is systematically dismantling each objection. What We Know So Far: Two skeptical arguments, both defeated by new fossils What We Don't Know Yet: Whether there are more arguments |
| Finally, some scientists argue that the complex lungs of birds could not have evolved from theropod lungs, an assertion that cannot be supported or falsified at the moment, because no fossil lungs are preserved in the paleontological record. | What it says: The third skeptical argument is about lung complexity, but this can't be proven either way because soft tissues like lungs don't fossilize. What it does: Presents the third skeptical argument and immediately neutralizes it Source/Type: Skeptical scientists' argument + author's logical assessment Connection to Previous Sentences: "Finally" signals this is the last skeptical argument. Unlike the previous two, this one isn't refuted with new evidence but dismissed as unprovable. Visualization: The Lung Argument Problem:
Reading Strategy Insight: Third response strategy: if you can't prove it, it's not valid scientific evidence. The author has now systematically addressed ALL skeptical arguments. What We Know So Far: Complete picture - all three skeptical arguments have been effectively countered What We Don't Know Yet: Nothing major - the argument is complete |
2. Passage Summary
Author's Purpose
To defend the scientific theory that birds evolved from dinosaurs by systematically addressing and refuting the main arguments made by skeptical scientists.
Summary of Passage Structure
In this passage, the author builds their defense of bird evolution theory by methodically responding to each skeptical argument:
- First, the author sets up the debate by acknowledging that while most evidence supports birds evolving from ground-dwelling dinosaurs, some scientists remain unconvinced.
- Next, the author presents and refutes the timing objection by showing that new fossil discoveries have found dinosaur relatives that are the same age as the oldest known birds.
- Then, the author addresses and dismisses the bone structure argument by explaining that scientists have now discovered dinosaur bones that look exactly like bird wishbones.
- Finally, the author neutralizes the lung complexity argument by pointing out that it cannot be proven or disproven since soft tissues like lungs do not preserve in fossils.
Main Point
The scientific objections to the theory that birds evolved from dinosaurs have been effectively answered by new fossil discoveries and logical reasoning, leaving the evolutionary connection between birds and dinosaurs well-supported by evidence.
3. Question Analysis:
This question asks us to identify the primary purpose of the passage - the main reason the author wrote it and the overarching goal they wanted to accomplish. We need to look at the passage's overall structure and flow to determine what the author is fundamentally trying to do.
Connecting to Our Passage Analysis:
From our detailed analysis, we can see a clear pattern that reveals the author's purpose:
- The opening establishes that most evidence supports bird evolution from dinosaurs, but some scientists remain unconvinced
- The author then systematically presents each skeptical argument and provides counter-evidence or logical rebuttals
- The structure follows: skeptical argument → author's response that defends the theory
- This pattern repeats three times (timing, bone structure, lung complexity)
Our passage analysis revealed that the author consistently uses language that favors the evolutionary theory ("many lines of evidence indicate") while treating skeptics' views as less substantiated ("remain unconvinced").
Prethinking:
Based on our analysis, the author's primary purpose is clearly defensive - they are responding to criticisms of the bird evolution theory. The entire passage is structured around presenting skeptical arguments and then showing why those arguments don't hold up. The author isn't proposing new theories, comparing different hypotheses, or evaluating fossil evidence in general - they're specifically defending one established theory against its critics by systematically addressing each objection.
Why It's Wrong:
• The passage doesn't compare two competing hypotheses - it defends one established theory against criticism
• Only one hypothesis (bird evolution from dinosaurs) is being supported; skeptical arguments aren't alternative hypotheses but objections
• The structure is defense-oriented, not comparative
Common Student Mistakes:
1. Did the author present multiple theories as equally valid options?
→ No, the author clearly supports the dinosaur evolution theory and works to refute objections to it
2. Are skeptical objections the same as alternative hypotheses?
→ No, objections are criticisms of a theory, not competing theories with their own supporting evidence
Why It's Wrong:
• The author doesn't suggest revisions to the standard theory - they defend it as currently understood
• New fossil evidence is used to support the existing theory, not modify it
• The passage reinforces the standard theory rather than proposing changes
Common Student Mistakes:
1. Does presenting new fossil evidence mean revising the theory?
→ No, the new evidence supports and strengthens the existing theory without changing its fundamental claims
2. Is defending a theory the same as revising it?
→ No, defense maintains the theory as is, while revision would involve changing the theory itself
Why It's Wrong:
• The passage uses fossil evidence as a tool but doesn't evaluate the general usefulness of fossils
• The focus is on defending a specific theory, not on fossil methodology
• Fossil evidence is assumed to be useful - the debate is about specific interpretations
Common Student Mistakes:
1. Since the passage mentions fossil evidence extensively, is that the main focus?
→ No, fossils are the means to an end - the end goal is defending the evolution theory
2. Does discussing fossil limitations mean evaluating fossil usefulness?
→ No, the author only mentions limitations (like soft tissue preservation) to address specific objections
Why It's Wrong:
• This is the opposite of what the author does - they defend the theory, not challenge it
• The author consistently supports the dinosaur evolution theory throughout
• The skeptical challenges come from other scientists, not the author
Common Student Mistakes:
1. Since the passage discusses objections to the theory, is the author making those objections?
→ No, the author presents others' objections in order to refute them
2. Does presenting both sides mean the author opposes the theory?
→ No, the author's language and structure clearly show support for the evolution theory
Why It's Right:
• The entire passage structure follows the pattern: present criticism → provide response that defends the theory
• The author systematically addresses timing, bone structure, and lung complexity objections
• The language consistently favors the evolution theory while treating criticisms as answerable objections
Key Evidence: "Although many lines of evidence indicate that birds evolved from ground-dwelling theropod dinosaurs, some scientists remain unconvinced" - this opening establishes the author's defensive stance, followed by three detailed responses to specific criticisms.