In addition to normal serialization Yahgan also exhibits complex verb stems of a type relatively common in western North America, where the main verb is flanked by instrument/body part manner of action prefixes and pathway/position suffixes. The prefixes are part of a larger, more open system of elements marking various kinds of causes or motivations, grading off into more grammaticalized voice marking. Many of the path/position suffixes (especially posture verbs) do double duty as sources for more grammaticalized aspectual morphology. Tense suffixes seem to derive historically from horizontal motion verbs, and together with the more vertical postural aspect forms, make an interesting Cartesian-style coordinate system for dealing with the temporal dimension.