 All of the heads are realistic , <unk> and <unk> descriptions of the men . It is likely that they were portraits of living ( or recently deceased ) rulers well known to the <unk> . Each head is distinct and <unk> , displaying <unk> features . They were once thought to represent <unk> although this theory is no longer widely held ; it is possible , however , that they represent rulers equipped for the <unk> <unk> . <unk> expressions depicted on the heads vary from stern through placid to smiling . The most <unk> <unk> art is the earliest , appearing suddenly without surviving <unk> , with a tendency towards more stylised sculpture as time progressed . Some surviving examples of wooden sculpture recovered from El <unk> demonstrate that the <unk> are likely to have created many more <unk> sculptures than works sculpted from stone . 
