. . . 'She was full of reptiles.' --Joseph Conrad (Lord Jim)
Evolution. 1. Collectively, those early parts of the human brain which developed during the reptilian adaptation to life on land. 2. Of particular interest are modules of the forebrain which evolved to enable reptilian body movements, mating rituals, and signature displays.
Usage I: Many common gestures, postures, and nonverbal routines (expressive, e.g., of dominance, submission, and territoriality) elaborated ca. 280 m.y.a. in modules of the reptilian brain. The latter itself evolved from modules and paleocircuits of the amphibian brain.
Usage II: In the house of the reptile, it makes a difference whether one crouches or stands tall. Flexing the limbs to look small and submissive, or extending them to push-up and seem dominant, is a reptilian ploy used by human beings today. Size displays as encoded, e.g., in boots,business suits, and hands-on-hips postures, have deep, neural roots in the reptilian forebrain, specifically, in rounded masses of grey matter called basal ganglia.
Literature: "Of these the vigilance I dread, and to elude, thus wrapt in mist of midnight vapor, glide obscure, and pry in every bush and brake, where hap may find the serpent sleeping, in whose mazy folds to hide me, and the dark intent I bring." --John Milton (Paradise Lost, Book IX; 1667)
Reptilian ritual. In Nonverbal World, the meaning of persistence (e.g., repeated attempts to dominate) and repetition (e.g., of aggressivehead-nods or shakes of a fist) are found in underlying, reptilian-inspired rituals controlled by the habit-prone basal ganglia (a motor control area identified as the protoreptilian brain or R-complex by Paul D. MacLean ).
Reptilian routine. According to MacLean (1990), our nonverbal ruts start in the R-complex, which accounts for many unquestioned, ritualistic, and recurring patterns in our daily master routine. Like a fence lizard's day--which starts with a cautious commute from its rock shelter, and ends with a bask in the sun--our workday unfolds in a series of repetitive, nonverbal acts. Countless office rituals (from morning's coffee huddle, e.g., to the sacred lunch break) are performed in a set manner throughout the working days of our lives.
Prehistory. As reptiles adapted entirely to life on land, terrestrial legs grew longer and stronger than those of aquatic-buoyed amphibian ancestors. In the reptilian spinal cord and brain stem, antigravity reflexes worked to straighten limbs through extensor muscle contractions which lifted the body higher off the ground. Advances in the forebrain's basal ganglia enabled reptiles to walk more confidently than amphibians--and to raise and lower their bodies and broadsides in status displays. The reptile's high-stand display, e.g., presages our own pronated palm-down cues of emphasis while speaking.
Neuro-notes I. 1. The protoreptilian brain, as defined by MacLean, consists of systems a. in the upper spinal cord, b. in the midbrain, and c.in the forebrain's diencephalon and basal ganglia (Isaacson 1974). 2. "The major counterpart of the reptilian forebrain in mammals includes thecorpus striatum (caudate plus putamen), globus pallidus, and peripallidal structures [including the substantia innominata, basal nucleus of Meynert, nucleus of the ansa peduncularis, and entopeduncular nucleus]" (MacLean 1975:75).
Neuro-notes II. 1. As a footnote, the relatively high nonverbal IQ of the reptilian basal ganglia was recruited for the development of intelligence in birds, specifically, in the hyperstriatum and neostriatum (rather than, as with mammals, in the cerebral cortex). 2. "Within the avian telencephalon, the dorsal ventricular ridge (DVR) contains higher order and multimodal integration areas. Using multiple regressions on 17 avian taxa, we show that an operational estimate of behavioral flexibility, the frequency of feeding innovation reports in ornithology journals, is most closely predicted by relative size of one of these DVR areas, the hyperstriatum ventrale (Timmermansa et al. 2000:196).
Illustration detail from Getting There (copyright 1993 by William Howells)