Paleoclimatic analysis has generated a claim that there is a possible correlation between an extinction event around 29 million years ago that allowed grasslands to become abundant and the adaptive radiation of several groups of butterflies.

Which of the following proposes the best alternative hypothesis for the claim?

Question

Paleoclimatic analysis has generated a claim that there is a possible correlation between an extinction event around 29 million years ago that allowed grasslands to become abundant and the adaptive radiation of several groups of butterflies.

Which of the following proposes the best alternative hypothesis for the claim?

BlackTom AI · Accepted Answer

A valid alternative hypothesis should directly challenge the proposed causal link by showing that the presumed driver (increase in grasslands) did not coincide with a change in the butterfly response (speciation or richness).

1. Relevant knowledge points and concepts
- Correlation vs. causation: demonstrating a temporal correlation does not prove that one event caused the other.  
- Alternative hypothesis in hypothesis testing: an alternative that can falsify the original causal claim should be plausible and testable.  
- Paleoproxies: pollen preserved in amber can indicate vegetation change (grass expansion).  
- Speciation rate and species richness: metrics to evaluate adaptive radiation in butterflies.

2. Step-by-step reasoning process
- The claim: grassland expansion ~29 Ma caused adaptive radiation in butterflies (implies butterfly speciation increased after 29 Ma).  
- A strong alternative should either (a) show the vegetation change did not occur, (b) show butterflies did not exhibit increased speciation, or (c) show another factor better explains the pattern.  
- Option analysis: we evaluate each answer option versus these criteria.

3. Intermediate considerations (no numerical calculations required)
- Evidence that grass pollen increases supports vegetation change, so the alternative that negates vegetation change is weaker if pollen data exist.  
- The most direct refutation is to accept the vegetation change but show no corresponding change in butterfly speciation—this directly undermines causation.

4. Why the correct answer is correct
- The chosen option states: pollen data show increased grass 29 Ma, but butterfly speciation rate and species richness show no significant difference before vs. after 29 Ma. This is the clearest alternative because it preserves the vegetation evidence while denying the expected biological response, thus falsifying the causal claim.

5. Why the other options are incorrect
- Option 1 posits a decrease in insect richness concurrently, which does not directly refute that butterflies specifically radiated; it is inconsistent and less direct.  
- Option 3 simply restates the original causal claim (grass increase correlates with increased butterfly speciation), so it is not an alternative.  
- Option 4 claims speciation was evenly distributed among environments; this could be an alternative but is weaker because it does not address whether speciation rate changed with grassland expansion—option 2 more directly contradicts the causal link.

6. Conclusion
The correct alternative hypothesis is that pollen shows increased grass 29 Ma but butterfly speciation and richness did not significantly change—this matches the provided answer.

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