Question

Difficulty: Very hardEvaluating Counterarguments and Rebuttals

Consider the following passage:

In evolutionary biology, the rapid adaptation of urban-dwelling wildlife to anthropogenic stressors has sparked intense debate over the underlying mechanisms. Classical neo-Darwinian theory posits that such adaptation relies exclusively on the selection of pre-existing genetic variants or novel beneficial mutations over successive generations. However, a growing cohort of epigeneticists contends that environmentally induced DNA methylation and histone modifications allow organisms to dynamically alter gene expression within a single generation, offering a far more rapid adaptive response to urban pollution and habitat fragmentation. Critics of the epigenetic framework push back strongly against this assertion. They argue that most environmentally induced epigenetic marks are developmentally transient or erased during germline reprogramming, rendering them incapable of serving as stable units of transgenerational inheritance. Furthermore, skepticism deepens because phenotypic plasticity driven by transient epigenetic changes can shield deleterious genetic variants from natural selection, potentially relaxing selective pressure and compromising long-term population fitness. Nevertheless, recent studies on urban populations of the white-footed mouse (Peromyscus leucopus) provide a nuanced rebuttal to these skepticism-driven critiques. Researchers demonstrated that specific methylation patterns in metabolic genes persist across multiple unexposed generations in laboratory settings, directly counteracting the germline-erasure argument. Moreover, modeling indicates that initial non-genetic epigenetic shifts can buy time for populations, facilitating survival in novel toxic environments until hardwired genetic adaptations catch up—a phenomenon known as the Baldwin effect. Thus, while epigenetic inheritance may not supersede traditional genetic mechanisms, discounting its role as an immediate evolutionary buffer oversimplifies the dynamics of urban adaptation.

Evaluate the following statement based on the passage above:

Statement: According to the passage, the empirical research on the white-footed mouse serves exclusively to refute the critics' claim regarding germline erasure, without offering any logical counter to the objection that epigenetic plasticity shields deleterious mutations from natural selection.

Answer: Answer

Answer

False. The passage explicitly addresses both objections raised by critics: the mouse study counters the germline-erasure argument, while the associated modeling counters the natural-selection argument by explaining the Baldwin effect.
The statement is false because the passage does not limit its rebuttal to the germline erasure claim. After presenting empirical evidence from the white-footed mouse study to counter germline erasure, the author explicitly extends the rebuttal using modeling of the Baldwin effect to explain how initial epigenetic shifts buy time for hardwired genetic adaptations to catch up, directly addressing the critics' concern regarding natural selection.

Step-by-Step Solution

1
Identify the specific counterarguments raised by critics in the passage.
The critics raise two distinct objections: (1) epigenetic marks are erased during germline reprogramming, and (2) epigenetic plasticity shields deleterious variants from natural selection, compromising long-term fitness.
Evaluating whether a rebuttal is complete requires first identifying all objections raised by the opposing viewpoint.
2
Analyze the components of the author's rebuttal in response to these objections.
The author provides a two-part rebuttal: first, empirical evidence from white-footed mice showing multi-generational methylation persistence (countering erasure); second, modeling demonstrating the Baldwin effect (countering the selection objection by showing how temporary buffering leads to genetic adaptation).
Tracking structural pivot words like 'Moreover' reveals how the author extends the rebuttal to cover both objections.
3
Determine the validity of the statement based on the scope of the passage's rebuttal.
Because the passage explicitly provides a logical and theoretical response to the second objection as well as empirical evidence for the first, claiming the passage offers no logical counter to the second objection is incorrect.
A statement asserting that an argument fails to address a specific objection is false if the text contains a direct counter-explanation to that exact objection.

Key Concept

Evaluating the Scope and Completeness of Rebuttals to Counterarguments
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