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PSYC205 Evolutionary Psychology Hostile Forces of Nature Edison Tan Evolutionary Psychology Singapore Management University Anything can kill us Extreme Climates Each of these hostile forces created adaptive problems that have Harsh Weath...

PSYC205 Evolutionary Psychology Hostile Forces of Nature Edison Tan Evolutionary Psychology Singapore Management University Anything can kill us Extreme Climates Each of these hostile forces created adaptive problems that have Harsh Weather recurred over generations. Lack of food and food spoilage Act as a filter – those who succumb to these adaptive problems fail Toxin to reproduce. Disease Whoever possesses solutions to these adaptive problems survives Pathogens and reproduces. Predators Other Humans Ourselves Edison Tan Evolutionary Psychology Singapore Management University  01 Food Acquisition and Selection Edison Tan Evolutionary Psychology Singapore Management University Evolved Food Preferences Food preferences aid in solving the adaptive problems of food- seeking Preferences for sweet food – indicative of high caloric value Ranking of food preferences amongst hunter-gatherers positively correlates with caloric values (Berbesque & Marlowe, 2009) Honey is consistently favored over tubers. Preference for salty food – replenishing sodium in the body, which is necessary for neural activities. Sodium-depleted humans rated salty food as more appealing than unsalted food (Neauchamp et al, 1990). Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Hunting Hypothesis (Tooby & Devore, 1987) Global cooling a few million years ago marked a dramatic decrease in plant-based food sources, making animal hunting the more attractive food source. Physiological evidence The human digestive system appears to be better designed for processing meat in the small intestine (vs. fiber in the colon). Humans are unable to produce vitamins A and B12, found in abundance in meat, despite it being critical to human bodily function Paleontological evidence Not show wear and tear in teeth associated with fibrous plant diet in human fossil Cut marks on collections of bones – indicating early butchering attempts Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Provisioning Hypothesis Explains: (Tooby & Devore, 1987) Strong Male Coalition Meat from big-game hunting is a highly Large-game hunting requires coordinated action between male economical and concentrated food hunters resource. Reciprocal Altruism and Social Exchange Transporting meat calories is far more Excess perishable food has diminishing fitness returns for sated cost-effective than lower-caloric food individuals and family members. The benefits of sharing food and generating reciprocal debt are high over long distances. Sexual Division of Labor Allow for heavy investment and Men are biologically and physiologically better suited for hunting provisioning of resources to children Ancestral women, often preoccupied with pregnancy and children, supplement food sources by gathering to exchange with returning men Emergence of Stone Tools Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Show-Off Hypothesis Men who pursue risky hunting strategies would benefit from showing (Hawkes, 1991) off in several ways: Women are more likely to offer benefits Increased sexual access to women, higher odds of fathering more to men who can provide gifts of food, offspring particularly in times of shortage. High odds of offspring survival via better provision of care Siding with them during intragroup Gaining social status within the group conflict Providing care to their children Offering sexual favors Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution The Gathering Hypothesis (Tanner, 1983; Tanner & Zihlman, 1976; Zihlman, 1981) A competing hypothesis to the Hunting Hypothesis, which speculates that the emergence of tools was not driven by hunting but by digging and gathering plants – making gathering mode efficient and economical Posit that how much women spend on gathering food depends on how much men bring back from hunting to compensate for a poor provider Does not explain: Strong Male Coalition Sexual Division of Labor Human’s ability to live in an environment with poor plantation Social exchange between men and women Humanity's digestive anatomy seems designed to process meat rather than plants primarily Edison Tan Evolutionary Psychology Singapore Management University How Food Drives Human Evolution Sex Differences in Spatial Ability as Sex-Differentiated Adaptation to Specific Adaptive Problems Faced During Food Acquisition If men and women specialize in different means of acquiring food, we should expect sex differences in ability, wherein each sex is likely to outperform the other on specific skills required for gathering/hunting. Men Women Superior navigational ability Superior recognition and recall of spatial configuration and location of objects Abstract and Euclidian direction orientation Landmark-based direction orientation Aid navigation through unfamiliar terrain during hunting Aid location of plants and fruits during foraging Superior mental rotation Superior object perception and perceptual Facilitate tool and projectile use during memory hunting Facilitate identification of gatherable food (e.g., ripe fruits) Edison Tan Evolutionary Psychology Singapore Management University Evolved Food Preferences Preferences for spices aid in solving the adaptive problems of food contamination Antimicrobial Hypothesis (Billing & Sherman, 1998; Sherman & Flaxman, 2001) Spices are produced as chemicals by plants to deter organisms and pathogens from attacking them. Commonly used spiced in human diets, it often effectively kills foodborne bacteria Garlic, onion, allspice, oregano Sherman & Billing (2009) Climates where food spoils more quickly than to favor a spicier cuisine. Cuisine as an adaptive cultural practice Edison Tan Evolutionary Psychology Singapore Management University Evolved Food Aversion Food aversion aids in solving the adaptive problems of avoiding toxins and contaminated food. Neophobia – aversion to unfamiliar food Humans generally avoid bitterness, which usually indicates toxins (Krebs, 2009) It is possible that ancient human preference–aversion functions for acidic foods evolved to allow ancestral humans to appreciate certain ripe or rotting fruits that contained acids that inhibit harmful microbes Fermentation by lactic acid bacteria better food digestibility, hence increasing food calories In challenging nutritional environments, fruits rotted by yeasts or lactic acid bacteria likely represented a valuable food source that could increase the chances of survival. (Amato et al. 2021) Edison Tan Evolutionary Psychology Singapore Management University Alcohol Consumption Fruits are the mainstay of primate diet, including humans Ethanol plumes cue ripeness In palm fruit (Astrocaryum standleyanum), ripe fruit averages about 0.9% ethanol and up to 4.5% at overripe (Dudley, 2004) Humans have an adaptive preference for ripe fruit – and alcoholism may be a byproduct of this adaptation Edison Tan Evolutionary Psychology Singapore Management University  02 Disease Avoidance Edison Tan Evolutionary Psychology Singapore Management University The Behavioral Immune System A hypothesized set of adaptations that facilitate behavioral avoidance of infectious diseases. Pathogens cannot be detected directly but indirectly via their effect on food and infected organisms, which serve as inputs. Smell (e.g., odor) Look (e.g., pus, mold, slime, sore) Symptoms (e.g., sneeze, cough, lesions) Disgust as an affective output that motivates avoidance and withdrawal of offending stimuli. Edison Tan Evolutionary Psychology Singapore Management University The Behavioral Immune System Some predictions that can be made from the BIS hypothesis: 1. Disgust should be the most strongly evoked by disease-carrying substances Feces and other bodily waste 2. Given that all humans face the adaptive problem of avoiding diseases, the operation of BIS should be universal Cross-cultural studies suggest that disgust is universally evoked by spoilt food and feces (Rozin, 1996) 3. Disgust should trigger physiological response associated with immune responses Increased body temperature (Stevenson et al., 2012) 4. People should show a strong memory for potential sources of contamination (Fernandez et al. 2017) 5. Sex differences in disgust sensitivity – Women are more likely to be disgusted than men Edison Tan Evolutionary Psychology Singapore Management University  03 Shelter Edison Tan Evolutionary Psychology Singapore Management University Humanity’s Ancestral Home The Savanna Hypothesis (Orians, 1980) Humans face the adaptive problem of surviving hostile elements of nature; natural selection would favor preference for a living environment that: Provide an abundance of food and water resource Abundance of prey Vegetation for grazing Facilitates avoidance of environmental hazard Trees provide protection from weather and refuge during escape from danger The African savannas meet these requirements. Edison Tan Evolutionary Psychology Singapore Management University Habitat Selection Human chooses their habitat based on how well the environment aids survival. Orians and Heerwagen (1992) proposed three stages of habitat selection: 1. Selection On the first encounter, affective responses are invoked to influence the decision to stay or live. Places that are lacking over or restrict viewing and movement are abandoned. 2. Information Gathering Environment is explored for risk and benefit 3. Exploitation Decision is made to stay and exploit available resources or leave. Cost-benefit trades are weight Edison Tan Evolutionary Psychology Singapore Management University Departure from Ancestral Environment The Savanna Principle (Kanazawa, 2004) Humans tend to face great difficulty processing inputs that did not exist in ancestral environments, often generating maladaptive output as a response. For example: Individuals living in urban cities with high population density but with low levels of socialization with friends tend to report lower well-being than individuals living in rural environments. Ancestral humans live in small groups of 150 that split off if the population exceeds 150-200 (Dunbar 1992) Ancestral humans are often surrounded by life-long friends and allies that facilitate each other’s survival and reproductive success. (Lewis et al., 2015) Edison Tan Evolutionary Psychology Singapore Management University  04 Predators and other Environmental Hazards Edison Tan Evolutionary Psychology Singapore Management University Functions of Fear Fear and anxiety are danger signals that facilitate disengagement from sources of danger. Fear facilitates: Fear Responses Definition Functions Freezing Stopping, becoming alert, watchful, Assessment of situation, concealment vigilant, and on guard from threat Response Sequence Fleeing (Flight) Rapidly fleeing or running away Distancing away from threat from the threat Fighting Attacking the source of the threat Eliminating or neutralizing threats Submission/Appeasement Appease or yield to a member of Signaling non-competitive intentions one’s own species to prevent attack to avoid posing as a threat Fright Becoming muscularly immobile, or Creating opportunity for escape, “playing dead” especially when fight or flight is impossible Faint Losing consciousness to signal to an Losing consciousness to remove attacker that one is not a threat oneself as a source of threat Edison Tan Evolutionary Psychology Singapore Management University Functions of Fear Fear and anxiety are danger signals that facilitate disengagement from sources of danger. Fear solves survival adaptive problems Types of Fear Adaptive Problems Fear of snakes Receiving poisonous bite Fear of spiders Receiving poisonous bite Fear of heights Injury or death from falling Panic Imminent attack by predator or other humans Agoraphobia Crowded places which one cannot escape Small-Animal Phobias Dangerous small animals Disease Pathogen Avoidance Separation Anxiety Loss of Protection from Attachment Figure Stranger Anxiety Harm from unfamiliar males Social Anxiety Loss of status, social ostracism Mating Anxiety Public rejection of courtship attempts. Edison Tan Evolutionary Psychology Singapore Management University Functions of Fear Specific fears appear to emerge during development when dangers are most likely encountered. Fear of spiders – 5th months Fear of height and strangers – 6th months Separation anxiety, - 9 to 13th months Animal fears – Age 2 Agoraphobia – Home-leaving age Edison Tan Evolutionary Psychology Singapore Management University Functions of Fear Sex differences in fear are explainable by the sex difference in the likelihood of encounter and cost of encounter. Men are more likely to survive threat encounters than women; hence, women are more likely to harbor fear Fear interferes with risk-taking in men to obtain status, resources, and mating opportunities Alsharawy et al., (2021) Edison Tan Evolutionary Psychology Singapore Management University Adaptations to Environmental Hazards A human possesses information-process adaptations for over-estimating environmental danger to facilitate avoidance of danger. Jackson & Cormack (2007) Bias towards perceiving sounds of object approach (vs. receding) Descent illusion – overestimation of distance when viewing from top to bottom (vs. bottom to top) Edison Tan Evolutionary Psychology Singapore Management University  04 Death Why do we die? Edison Tan Evolutionary Psychology Singapore Management University Senescence Bodily mechanisms deteriorate as we grow older Telomere, region of genetic coding at the protective end of the chromosome, shortens with each cell replication Result in the gradual deterioration of functional characteristics in living organisms External factors may exacerbate the rate of aging UV radiation Stress etc. Vaiserman & Krasnienkov (2021) Edison Tan Evolutionary Psychology Singapore Management University Pleiotropic Theory of Senescence Certain genes may promote fitness-enhancing effects early in life but cause negative effects later. For example, testosterone facilitates status- enhancing behavior amongst men but increases the risk of prostate cancer later in life. Natural selection weakly affects the gene because the benefit it provides early in life outweighs the cost it imposes on the organism later in life. Flatt & Partridge (2018) Edison Tan Evolutionary Psychology Singapore Management University Suicide Evolved Suicide Adaptation Hypothesis Maladaptive By-Product Hypothesis Suicide will be most likely to occur when an Fitness-reducing events are usually individual has a dramatically reduced ability temporary; there are always future to contribute to their inclusive fitness. opportunities to enhance fitness The replication of an individual’s genes would Suicidal idealization may be an adaptive “call have a better chance without the suicidal for help” individual. Accidental death as a result is a by-product Evidence suggests that suicidal ideation positively correlates with fitness-reducing concerns. Damaged health Financial problems Relational and sexual failure Burden to family Both hypotheses can be partially correct. Edison Tan Evolutionary Psychology Singapore Management University Other Cause of Death Homicide Infanticide Rival killing Mate killing Warfare Accidental Death Edison Tan Evolutionary Psychology Singapore Management University  05 Transcending Death Edison Tan Evolutionary Psychology Singapore Management University Terror Management Theory (Greenberg et al., 1986; Pyszczynski et al., 2015) Humans face a unique adaptive problem: Existential Terror Like all animals, humans possess an inherent drive for self-preservation and survival Humans’ ability for abstract thoughts makes possible the awareness of one’s inevitable end This potential for existential terror can seriously interfere with goal-directed behavior and perhaps survival itself unless effectively managed. Solution: Cultural Worldviews Edison Tan Evolutionary Psychology Singapore Management University Terror Management Theory (Greenberg et al., 1986; Pyszczynski et al., 2015) Cultural Worldviews are: 1. A conceived theory of reality that gives life meaning, purpose, and significance 2. A standard by which human behavior can be assessed and have value 3. A hope of literal or symbolic immortality Literal Immortality – beliefs that one will continue to exist beyond bodily death e.g., heaven, hell, reincarnation Symbolic immortality – the belief that one is part of an entity greater than oneself, which will persist beyond one’s death e.g., contribution to society, social or ideological group, having children, Edison Tan Evolutionary Psychology Singapore Management University “What man really fears is not so much extinction, but extinction with insignificance.” ― Ernest Becker (1973), The Denial of Death Edison Tan Evolutionary Psychology Singapore Management University  Discussion Edison Tan Evolutionary Psychology Singapore Management University Individual/Cultural Differences in Disgust Elicitor and Response Diseases are adaptive problems universal to every human; therefore, all humans should possess evolved psychological mechanisms that tend to input potential disease sources to generate disgust as an output. However, there are clear cultural differences in disgust elicitors; some consider eating insects or certain meat to be a delicacy in some cultures, while others feel disgusted at the prospect of eating them in others. Other times, people feel disgusted purely as a response to an object, individual, or their actions. 1. Is disgust an affective response specific to dealing with adaptive problems uniquely associated with disease avoidance? What other adaptive problems can disgust play a role in solving? 2. What role would environment and culture play in shaping disgust? Edison Tan Evolutionary Psychology Singapore Management University The Multidimensional Output of Disgust In general, disgust is an output of evolved psychological mechanisms where avoidance is the adaptive solution. While we feel disgusted by unwanted sexual approaches, we can also feel disgusted by individuals we do not wish to be socially associated with because they impose fitness costs one way or another. Edison Tan Evolutionary Psychology Singapore Management University  Individual Differences in Propensity and Intensity of Pathogen Disgust Some of the variations in propensity and intensity of pathogen disgust will stem from individual differences in: The ability of perceptual mechanisms to detect pathogen threat cues (e.g., olfactory sensitivity) How feedback processes return to baseline after removal of the pathogen threat; How pathogen threat estimates are traded off against levels of nutrient depletion (hunger) and other states Immunocompetence These are contextual factors or inputs that change how disgust elicitors are processed, where the cost and benefit of disgust response vary. Edison Tan Evolutionary Psychology Singapore Management University  Cross-Cultural Variability Cultural variability in disgust reflects Cultural variability in disgust reflects adaptive responses to ecologically specific adaptive responses to deviation from conditions. adaptive cultural practices. Cultural differences in pathogen disgust A local may feel disgusted when propensity and intensity could thus vary due to foreigners violate cultural norms (e.g., food ecological differences in these inputs. preparation habits). For example: Ecology with a higher pathogen load experiences When we feel disgusted as we view other higher infection risk, prompting higher disgust cultural groups eating food unfamiliar to propensity and intensity us, we are applying our cultural lens, Population with higher genetic-relatedness share which evolved to tend to local adaptive immunity to local pathogens that reduces the problems that different cultural groups need for pathogen disgust as an output may not face. Edison Tan Evolutionary Psychology Singapore Management University Cross-Cultural Variability Edison Tan Evolutionary Psychology Singapore Management University  Discussion Open Floor Discussion Edison Tan Evolutionary Psychology Singapore Management University NEXT WEEK: Long-Term Sexual Strategies Edison Tan Evolutionary Psychology Singapore Management University