There is evidence to suggest that our cave-dwelling ancestors polished many of their flints to a degree far surpassing what was necessary for hunting purposes. It seems, ttherefore, that early humans possessed an aesthetic sense. Which one of the following statements, if true, most seriously weakens the argument? ['Most flints used by our cave-dwelling ancestors were not highly polished.', 'The caves in which the highly polished flints were found are unadorned by cave paintings.', 'Flints were often used by early humans for everyday chores other than hunting.', 'Any benefits that an aesthetic sense would have given to cave-dwelling humans are poorly understood.']