Flashcards in Health & Disease Deck (19):
Classic Vs Inclusive fitness
Classic = individual reproduction success.
Inclusive = own and relatives reproduction success - genes survival matters.
Adaptation definition (Wilson, 1966)
Adaptations = evolved solutions to specific problems that contribute to successful reproduction (either directly or indirectly).
- eg. temp regulation, mate preferences.
Criteria of adaptations (Wilson, 1966)
Efficiency - solving problem in proficient manner.
Economy - solving in cost-effective manner.
Precision - are parts specialised for achieving a particular end.
Reliability - performing dependably in the context in which is was designed to operate.
Mechanisms of genetic adaptation spreading
Those with reproductive advantage more likely to be passed down in greater numbers.
Unfavourable mutations selected against.
Successful mutations spread over many generations to entire population.
Types/mechanisms of adaptations
- variability present on every time scale
Homeostasis, acclimation, habituation - seconds to days.
Acclimatisation - days, months, years.
Developmental acclimatisation and plasticity - months and years.
Transgenerational epigenetic effects - one of more generations.
Natural and sexual selection - many generations (thousands of years).
3 products of evolution
Adaptations - used before birth for survival - eg. feeding through umbilical cord.
By-product - belly buttons have no function but are carried on.
Noise - chance mutations - eg. belly button shape.
Evolved psychological mechanisms
There to solve a problem of survival or reproduction.
Just because previously advantageous, does not mean it will be now.
Input - narrow part of info (eg. human visual or auditory system tells the organisms about a specific adaptive problem).
Decision making - input transformed by decision rules into output.
Output - can be physiological activity, info for other psychological mechanisms or a behaviour. Directed towards the specific adaptive solution.
- Usually successful, not always.
Properties of evolved psychological mechanism
Adaptive problems require specific solutions which are implemented by evolved mechanisms.
Many psychological mechanisms linked to:
- problems of survival - eg. thermal regulation, avoiding predators.
- other problems - eg. mating, parenting etc.
Specificity, complexity and other mechanisms give humans flexibility.
- several specific response options for each mechanism = complexity.
- potential combination of many specific mechanisms = behavioural flexibility.
Some argue domain general mechanisms are useful when humans routinely solve ancient adaptive problems in unpredictable and variable ways (rapid changing environment) - eg. general intelligence, reasoning, working memory etc - work cohesively.
Specialised mechanisms (work independently, eg. problem solving, creating, curiosity, communicating) need to work together - potentially superordinate mechanisms regulate interaction between these.
- eg. walking through forest - spot wolves, berries, and mate.
- 1: avoid wolves (lose other two).
- 2: risk eating berries (solves starvation) before running from predator (risk being attacked, but lose mate).
Uses evolutionary ideas to understand why humans are vulnerable to disease.
Questions of ultimate causation - evolutionary explanation.
Only touches on preventive and therapeutic implications.
Basic ideas the evolution of health and medicine
Evolution concerned with shifting gene frequencies.
- not survival of a species or health/happiness of individuals.
Health submissive to inclusive fitness.
Disease is not an objective definition - socially and ecologically constructed.
- eg. lactose-intolerance only a disorder in milk drinking cultures.
Taxonomy: Human, cultural and pathogen evolution
NS is slow vs. cultural and environmental change, and the rate of pathogens.
- Mismatch between genotype and current environment: "out of Eden" genome lag (and evolutionary discordance theories). - eg. lifestyle diseases due to post neolythic diets - high fat/sugar leads to diabetes, heart disease etc.
- Preparedness theory: responses to phylogenetically relevant stimuli (eg. phobia of spiders).
- Bacteria, viruses and parasites rapidly mutate in comparison to hosts defence system: eg. antibiotic resistance.
- Adaptive development plasticity in unanticipated environments: epigenetic and foetal development processes suggest priming to expect a certain environment - if not as predicted this leads to illness.
Taxonomy: Natural selection is an iterative process
Faces constraint and makes compromises - no optimal adaptive solutions.
- life history theory and design compromises: what might seem maladaptive short term may be adaptive long time. Features must also be trade-offs between negative and positive effects - eg. human reproduction times vs lifespan.
- structural compromises: eg. trade off between bipedalism and large brains.
- pathway constraints: natural selection can only act on what is already there; difficult to reach another higher adaptive peak if means travelling down adaptive gradient (eg. human eye vs. elegantly designed mollusk eye).
Taxonomy: Health does not equal optimum reproductive fitness
Subservient - less important.
NS and SS do not operate to optimise health and longevity.
- antagonist pleiotropy: genes may code for unrelated traits that increase reproductive success even at the cost of disease vulnerability; diploid organisms may have heterozygote advantage but deleterious recessive genes maintained in gene pool (eg. Huntington's disease - increased fertility, reduced risk of cancer; sickle cell anaemia - protection against malaria etc).
- sexual selection: reproductive optimum in a trait may not be same for health (eg. high levels of testosterone = higher risk taking, reduced immune function).
- defence mechanisms taken as signs of ill health: eg. morning sickness = avoidance of toxins; fever = kill bacteria; anxiety = smoke detector? (predominantly plant based societies have fewer cases of pregnancy related vomiting).
Diagnosis of mental disorders
Based on diagnostic classification systems - agreed by clinicians, therapists and researchers.
Not discussed in evolutionary terms.
- many MDs not classified according to causes - alternatively, based on symptoms.
- not very theoretical/causal.
- sometimes difficult to distinguish between normal responses and genuine disorder - on a continuum.
APA definition of MD (VandenBos, 2007): "mental disorder characterised by psychological symptoms, abnormal behaviours, impaired functioning and any combination of these..."
Problems with definition:
- mental illness = "abnormal" or "maladaptive": delusions, phobias, depression.
- mental disorder as statistical deviance: eg. sadness vs depression (where is the boundary?) - same applies for low/high IQ, moods, personality traits.
- MD as deviance from societal norm: eg. victorians believed female orgasms were disorders; homosexuality - strong variation across time and cultures.
APA definition of MD (VandenBos, 2007): "such disorders may cause clinically significant distress and impairment in a variety of domains of functioning..."
- MD creates distress and suffering: not all MDs (eg. ASPD); some mental suffering/distress is normal and maybe an evolutionary advantage (eg. worry about kinship, empathetic pain).
- MD are linked to impaired (social, occupational, personal) functioning: people can function even with MDs; who defines this; cultural differences; individual differences vs. disorder.
APA definition of MD (VandenBos, 2007): "may be due to organic, social, chemical or psychological factors."
- mental illnesses arise from multiple interacting causes: many of which are not fully understood - genetics, environment, psychological experiences. Impact neuroanatomy and function; and mental functions (eg. attention, memory).
Biopsychosocial model of health and disease
Health is always about the interaction between genetics and the environment.