EVOLUTION and RITUALIZATION

1. EVOLUTION and RITUALIZATION Neil Greenberg

2. Evolution: natural selection NATURAL SELECTION • Overproduction[individuals tend to produce as many offspring as possible] • Stability[population size seems to remain stable from generation to generation in stable environments] • Limited resources[there is not enough for everyone] • Struggle for existence inferred • Variability [offspring manifest varying traits] • Heritability[traits are to some extent inherited] • Differential survival (=Natural selection) inferred[some traits allow their bearers to produce more offspring than other individuals = be more fit] • Evolution- Over many generations lead to changes in the frequencies of genes and thus the traits they code for (=evolution)

3. Evolution: sexual selection “preferences” of opposite sex is principal “selection pressure” • Runaway sexual selection - positive feedback between an ornamental trait in a male and the female preference for the trait -- can lead to very elaborate ornaments. (Fisher) • Good genes – e.g., Nuptial crest of male newts and tail height increase with nutrition; brightness of fin or feather is affected by diet thus reflecting foraging ability • Handicap hypothesis –apparently harmful traits in males become attractive to females because they indicate the male's capacity to cope with them.

4. Evolution: speciation • gradual accumulation of changes • geographical isolation - barriers to gene mixing; key ideas:a. ethological isolationb. sibling speciesc. character displacement

5. Evolution • Blind variation, selective retention • Traits are often polygenic, able to “multitask,” and the specific function maximizing fitness at a given developmental or evolutionary moment (the EEA) is the one that will selectively retained

6. Gradualism in Mental Powers If no organic being excepting man had possessed any mental power, or if his powers had been of a wholly different nature from those of the lower animals, then we should never have been able to convince ourselves that our high faculties had been gradually developed. But it can be shewn that there is no fundamental difference of this kind. We must also admit that there is a much wider interval in mental power between one of the lowest fishes, as a lamprey or lancelet, and one of the higher apes, than between an ape and a man; yet this interval is filled up by numberless gradations.” --Charles Darwin, 1871:445.

7. EVOLUTION of BEHAVIOR “In animals, almost invariably, a change in behavior is the crucial factor initiating evolutionary innovation” (Ernst Mayr 1988). Behavior creates new selective pressures (Mark Baldwin via Deacon 1998)

8. Evolution: ritualization There is often “selection pressure” for social signals to become more precise, less ambiguous . . . “ritualization” it is of great intrinsic interest to the student of social behavior and the processes observed also exemplify the ways in which units of behavior can be transformed in function. Any behavioral pattern is a candidate for ritualization if it can communicate information

9. RITUALIZATION • A fragment of a somatic (muscle) or autonomic (homeostatic) reflex may be detectable by other organisms and thereby communicate an organism’s inner state. • If the communicative function serves fitness, it may come under the control of new pathways in the nervous system

10. Evolution: ritualization MOTOR PATTERNS (“somatic”) • Intention movement of (e.g.) body, limbs, ears, tail • Ambivalent Posture or movement . . . raising or lowering head (e.g., dominance) AUTONOMIC REFLEXES • Alimentary: Increase or decrease in salivation. Sphincter control, urination, defecation. (e.g., territorial marking) • Circulatory: Pallor, flushing, vasodilation of sex organs. Fainting.(e.g., skin patches) • Respiratory: Changes in respiratory rate or amplitude. Gasping, sighing, panting. (e.g., inflation displays, hissing, speech (?) • Thermoregulatory: Sweating, pilomotor responses. (e.g., hair or feather erection, scent signals) Electrodermal response • Lacrimatory: weeping.

11. Evolution: ritualization Ways in which the displays can become elaborated(Morris 1966): 1. Development of conspicuous structures 2. Schematization("simplification") by means of (e.g.) • Lowering of threshold changes • Rhythmic repetition • Exaggeration or omission of specific components of a movement • Change in speed or vigor of a movement When the movement comes to be governed by causal factors other than those that governed the source of the display it is said to be emancipated.

12. RITUALIZATION Autonomic reflexes that various species have built on to serve as communications often originate as part of the stress response and have been derived from • Alimentary systems (copes with ingestions, digestion, excretion); • Circulatory system (distributes blood,); • Respiratory system (copes with need for oxygen); • Thermoregulatory system (coping with temperature); • Lacrimatory system (tears)

13. The Peacock’s Tail • raised by feather pilomotor muscles • an ancient autonomic theromregulatory mechanism • Ordinarily hidden • displayed when aroused

14. The Lizard’s Flag • Effected by the hyoid apparatus • An ancient mechanism activated by stress • Ordinarily hidden • displayed when aroused

15. “BRICOLAGE” – the utilization of a structure or process that serves one adaptive function to meet another need • A structure that has been utilized is the HYOID apparatus -- a part of the gill arches that serves to enhance respiration in ancestral organisms which changed in the process of vertebrate evolution. • In mammals “The muscles of the tongue also derive from the hyoid bone. ... play a large role in swallowing and sound production.” • A sight or sound that is emitted because of a respiratory reflex may communicate an organism’s sudden need for more oxygen

16. BRICOLAGE: the transformation of the hyoid: from STRESS to cultured CONVERSATION • “The hyoid apparatus is a vestige of the gill arches of crossopterygians, which changed in the process of vertebrate evolution.” • In mammals “The muscles of the tongue also derive from the hyoid bone. ... play a large role in swallowing and sound production.” • Throughout vertebrate history, the hyoid has been involved in the expression of communicative reflexes associated with stress-evoked changes in respiration

17. STRESS and the EVOLUTION of BEHAVIOR The “Ritualization” of signals a model: fragments of motor patterns or autonomic reflexes that partucipate in the stress responsebecome temporally or spatially associated as an ensemble (Morris 1956, Hinde and Tinbergen 1958) The “Central Adaptation Syndrome”(Huether 1996). Controllable stressors lead to a “go and specialize” strategy (e.g., earlier recognition and avoidance, improved fighting strategies, refined submission behavior) Uncontrollable stressors lead to a “wait and reorganize” strategy (e.g., CS reorganization of neural circuits; tuning of learning, motivation, and emotional states)

18. STRESS and the EVOLUTION of BEHAVIOR Stress can selectively affect many systems: input, integration, and output . . . where these involve motivation, affect, and cognition, adaptive behavioral change can occur and be selected for. Valence of affect can be positive(involves cortical-limbic areas) or negative (involves subcortical-limbic areas)(Paradiso et al. 1999) Active versus passive coping (involves parallel autonomic strategies correlated with activity in discrete columns of periaquaductal gray (Bandler et al. 2000)

19. My Own Work . . . Clarifying function of the striatal complex in reptiles . . . • Specific lesions profoundly impair species-typical responses to very precise stimuli • Stress endocrine dynamics is an important variable