Spearman's methods were incredibly flawed.
He measure intelligence like it was a physical quality and not a broad spectrum based on many, MANY factors, then plotted them along two points. Even in the examples given here, two of the tests done are reaction time (A test that was just as reliant on physical qualities as on intellectual) and "common sense" (despite the fact that this is ANOTHER spectrum, that varies based on culture, upbringing, traditions, and personal experience).