Under the leadership of C. F. Marbut, the Russian concept was broadened and adapted to conditions in the United States. This concept emphasized individual soil profiles to the subordination of external soil features and surface geology. By emphasizing soil profiles, however, soil scientists at first tended to overlook the natural variability of soils which can be substantial even within a small area. Overlooking the variability of soils seriously reduced the value of the maps which showed the location of the soils.