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Recent research in an old quarry uncovered tracks from several Stegosaurus dinosaurs, and the tracks all headed in the same direction. A second set of tracks from the same quarry shows one instance of overlapping footprints, where a juvenile Stegosaurus footprint was stepped on by an adult Stegosaurus. From this one can infer that Stegosauruses most likely traveled in multiple-age herds and that adults of this species cared for their young.
Which of the following is an assumption on which the argument depends?
| Text from Passage | Analysis |
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| Recent research in an old quarry uncovered tracks from several Stegosaurus dinosaurs, and the tracks all headed in the same direction. |
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| A second set of tracks from the same quarry shows one instance of overlapping footprints, where a juvenile Stegosaurus footprint was stepped on by an adult Stegosaurus. |
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| From this one can infer that Stegosauruses most likely traveled in multiple-age herds and that adults of this species cared for their young. |
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The argument presents two pieces of track evidence and then jumps to conclusions about dinosaur social behavior. We start with tracks going the same direction, add evidence of adult-juvenile interaction, then conclude these dinosaurs lived in herds and cared for young.
Stegosauruses most likely traveled in multiple-age herds and adults cared for their young.
The author uses physical evidence (directional tracks + overlapping footprints) to make behavioral inferences about extinct animals. The logic assumes that these track patterns can only be explained by herd behavior and parental care, but this is a big leap from limited physical evidence.
Assumption - We need to find a statement that must be true for the argument's conclusion to hold. If we deny this statement, the conclusion should fall apart.
The conclusion makes specific claims about behavior (traveling in herds) and relationships (adults caring for young) based on physical evidence (track patterns and overlapping footprints).
Look for ways the conclusion could be wrong while keeping the facts intact. The author jumps from 'tracks going same direction + overlapping footprints' to 'herd behavior + parental care.' What gaps exist in this logical leap? We need to identify what must be assumed to bridge these gaps.
Many modern herd animals care for their young. This isn't something the argument needs to assume. The author is making a specific claim about Stegosaurus behavior based on physical evidence, not drawing parallels to modern animals. Whether contemporary animals care for young doesn't affect whether these particular dinosaur tracks prove Stegosaurus parental care.
Male and female adult Stegosauruses traveled together in the herd. The argument doesn't make any distinction between male and female adults - it just claims 'adults' cared for young. The conclusion works fine even if we're only talking about one gender of adult, so this assumption isn't necessary.
No tracks from dinosaurs other than Stegosaurus were found in the vicinity of the Stegosaurus tracks. While this might strengthen the argument, it's not essential. Even if other dinosaur tracks were nearby, the specific evidence about Stegosaurus tracks heading in the same direction and the adult-juvenile overlap could still support the conclusion about Stegosaurus herd behavior.
The adult dinosaur print was made at the time the juvenile print was made. This is absolutely critical. If these prints were made at different times (maybe years apart), then the overlapping footprints tell us nothing about adults and juveniles traveling together or caring relationships. The entire conclusion about parental care depends on these prints representing simultaneous movement, not random overlap across time.
The existence of parental care has been established for other dinosaur species. Similar to choice A, this isn't necessary. The argument is making a claim specifically about Stegosaurus based on this particular evidence. What's been proven about other dinosaur species doesn't need to be assumed for this argument to work.