We present a simple, arithmetic-free, efficient scheme to compress trees maintaining the nearest common ancestor (NCA) information. We use this compression scheme to provide an O(n + q lg lg n) solution for solving the NCA problem on Pure Pointer Machines (PPMs) (i.e., pointer machines with no arithmetic capabilities) in both the static and dynamic case, where n is the number of add-leaf/delete operations and q is the number of NCA queries. This solution is optimal