Yawning: An Evolutionary Perspective

Evolutionary analyses of human behavior have illuminated a number of fundamental questions (i.e., foraging, mating systems, communication, etc.), and a wide array of behaviors have been targeted for investigation (infanticide, polygyny, child abuse, homicide, etc.). In general, investigation has centered on complex behaviors organized into broader functional units based on their context, or in some cases, their outcome. Little attention has been given te, more basic behavioral units (Scott, 1950) (e.g., ingestive, eliminative) that serve as the foundation for all more complicated patterns. The ubiquity of these basic patterns across animal species may have contributed to their perceived lack of importance in understanding higher order and more complex behavior patterns. On the other hand, the systematic analysis of basic motor/behavior patterns [e.g., fixed action pattern (Lorenz, 1954; Lorenz & Tinbergen, 1938) or modal action pattern (Barlow, 1968)], characterized by: (1) being species typical (within classes of animals the behavior is typically found in all individuals); (2) consisting of movements that occur simultaneously or sequentially with a high degree of predictability; and (3) being repeatedly recognizable (Slater, 1978, p. 14) may be quite productive.