Passage Summary: Since prehistoric skeletons have the same types of broken bones as rodeo riders, scientists assume those ancient people were doing the same dangerous animal-handling activities.

Conclusion: Ancient cave dwellers probably participated in activities like chasing and tackling animals, much like modern rodeo riders do.

Reasoning: The patterns and types of bone fractures found in prehistoric skeletons are nearly identical to those found in the skeletons of rodeo riders.

Analysis: This argument relies on a 'Principle Justify' structure, moving from a physical effect (fractures) to a behavioral cause (tackling animals). The gap here is the assumption that similar injuries must result from similar activities. To justify this conclusion, we need a principle that solidifies this link—essentially stating that skeletal damage is a reliable indicator of specific past behaviors. Look for a rule that bridges the gap between the physical evidence and the inferred lifestyle.