The controls are not "normally hydraulic, but manual fallback" - the pitch controls and ailerons are cable and pulley systems, with hydraulic assistance. Manual reversion simply means the hydraulic (or electrical for stab trim) assistance is removed. The controls can split between the two columns, the captains column connected to left elevator and ailerons, the fo's connected to right elevator and spoilers. They split in case one jams, as Olasek said.
Amazing how many people are commenting here without proper knowledge.