Rock surfaces on the Mediterranean island of Malta show extensive ruts of seemingly ancient origin, always found in parallel pairs. Many geomorphologists agree that the ruts were probably caused by vehicles and may have originated in the
later Bronze Age. But questions remain concerning their origins. The ruts are 0.04 meters to 0.10 meters wide and up to 0.675 meters deep. Were they deliberately cut to facilitate vehicle movement, or did they arise from erosion caused, at
least in part, by vehicle movement? If the latter, what kind of vehicles were involved? For example, the vehicles might have moved on wheels, traveled on sled runners, or slid along on inclined shafts (travois) strapped to a draught animal.
Researchers Mottershead and collaborators investigated samples of rutted rock from three locations, using measurements of rock density, hardness, and resistance to compressive stresses. A two-wheeled cart was then reverse-engineered to
fit the ruts. The researcher’s findings indicated that two-wheeled carts could, given certain laden weights, have generated forces sufficient to indent the rock surfaces and, through frequent passage, help cause ruts deeper than 0.5 m. Nothing
in the ruts’ morphological features was found to contradict this hypothesis.
The researchers considered possibilities other than wheeled vehicles. They note that tracks resulting from sled runners would necessarily be wider on curves than on straights because of some lateral rotation of the runners. Also, such runners
would have tended to wear away the higher portions of uneven rock surfaces while missing hollows. But the morphology of the ruts in Malta shows no evidence of these features. As regards the travois possibility, the researchers concede that,
in theory, the sliding movement of a loaded travois could abrade the rock surfaces, especially if the weight-bearing point of each wooden shaft were tipped with stone. But they point out that another researcher, Pike, found no evidence of
travois use anywhere in the Mediterranean region.
A further finding of the research was that the rut walls had no markings other than those expected to result from erosion (natural or vehicular) and the weathering of the rock. Thus there was nothing, such as the presence of pick marks, to
indicate that the ruts were created by design.
The research, as described in the passage, most clearly indicates that the paired ruts found in Malta are

Question

Examsnet · Accepted Answer

Correct Answer is :  the result of vehicular traffic that occurred over a period of thousands of years

GMAT Verbal Reasoning Practice Test 1