ANHB1102 Lecture Notes - Lecture 28: Human Behaviour, Gestation, Australopithecus

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Human Behaviour Notes
1. Why study behaviour
2. Levels of control of behaviour
3. Variation in human behaviour
4. Evolutionary perspective on behaviour: many behaviours are adaptations (result from natural
selection in particular environments)
Behaviour is the interface of the organism with its environment and as such precedes the evolution
of many anatomical and physiological features
E.g locomotion and changes in femur and pelves in Australopithecus & Homo
Behaviour is part of our interactions with one another
-We are constantly behaving and interpreting the behaviour of others
Human behaviour: Function & Evolution:
-Proximate explanations: what controls, elicits or modifies the expression of a behaviour and
what is the outcome within the life time of an individual?
-Genetics, physiology, development, ecology
-Ultimate explanations: How does a behaviour increase survival and reproduction? What is the
selective advantage that has resulted in the evolution of this behaviour?
-Comparative analyses of behaviour use naturally occurring variations and measure survival
and reproductive success
-Correlations of behaviour with environmental variables
Ultimate and Proximate explanations are NOT alternatives:
1. There will be ultimate AND proximate explanations possible for every behaviour
-How does it work?
-How could it have evolved to work that way?
2. The mechanisms of control and expression of a behaviour can tell us something about its
evolution
-Eg courtship rituals (feed intended mate)
Behaviour occurs in a context:
-Physical environment (forest canopy, woodland floor…)
-Biological environment (food substances, predators, conspecifics)
Proximate: what triggers the behaviour within the individual?
-E.g hunger = food search and ingestion
Ultimate: what was the selective pressure that resulted in this variant predominating?
-E.g If nutrients (energy) too low, organisms dies or can’t reproduce
-Empty gut = hunger = food search behaviour = energy intake
How did the behaviour further survival and reproduction in the individual actor?
Selective advantage of a behaviour is context dependent
Controls of behaviour:
Proximate:
-Immediate (fast response)
-Neuronal
-CNS
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-Reflexes
-Intermediate (expression, thresholds, liklihood)
-Development (early psychosocial stress changes repro patterns)
-Hormonal
-CNS
-Cognitive/Learning
Ultimate:
-Environment through natural selection shapes level of control as well as the behaviour itself
How fast must the response occur to increase p(survival)?
General questions about human behaviour:
-Human universals: what is true of all humans and different from other species (derives species
trait)
-Human diversity: what is true of some humans and not others? (population, sex, culture)
-Human plasticity: how does developing context shape human behaviours?
-Physical environment (e.g altitude)
-Social environment (e.g father absence, number of siblings)
Reflex Behaviours: Involuntary
-Primative reflexes (low plasticity): behaviour that is not volutional (that is automatic)
-Rooting (turns cheek side stimulation)
-Plantar (curl of foot at stimulation)
-Grasping
-Startle
-“Fight to flight” adrenaline response
-E.g Pupil dilation
-Low light
-Pleasing sight
-These are behaviours with little plasticity
-Unlike many species, much of human behaviour has MUCH plasticity
Natural Selection (= individual selection)
-Trait/behaviour that increases survival and reproduction of an individual
-How did individuals with that behaviour survive and reproduce better than other individuals in
same population (same time and in same environment) without that behaviour?
Individual Selection of Behaviour:
Survival:
-Recognising and avoiding predators, parasites
-Efficient foraging (obtaining energy)
Cooperating and competing with conspecifics
Reproduction:
-Recognising ans accessing mates
-Appropriate levels of care of offspring selection for investment, infanticide, neglect?
Reproduction: Contributions to offspring differ between sexes:
-Shows some different selection pressures on males and females
Females
Males
Genetic material
Genetic material
Gestation
Resources (some mammals)
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Sexual Selection:
-Increased individual fitness through obtaining a larger number of mates or better quality mates
-Different roles and time commitments by males and females to offspring = different selection
pressures acting on 2 sexes of one species
-Behaviour
-Morphology
-Psychology
Mammalian males and females:
General mammalian case:
-Mammalian females invest more in offspring (gestation and lactation) and so usually increase
their fitness more by obtaining better quality mates
-Mammalian males invest less in offspring and so usually increase their fitness more by obtaining
a greater number of mates
Selection for: Human mate preferences:
Reproductive Value of Human Females:
Lactation
Protection (some mammals)
Care of juveniles
Care (very few mammals)
Min time per surviving human offspring
~ 5 years
Min time per surviving human offspring
~ 2 hours?
Selection on MALE to prefer females who are:
Selection on FEMALE to prefer males who are:
Fertile
-reproductive age
-not already pregnant
-high probability of achieving pregnancy
Fertile:
-mature (can survive)
-healthy (good immune, low disease risk)
Waist to hip ratio
Good genes (symmetry)
Healthy
Investment:
-resources
-willing to share resources
-protection
Good genes (symmetry)
Able mother
-lactate
-care for young
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Document Summary

Human behaviour notes: why study behaviour, levels of control of behaviour, variation in human behaviour, evolutionary perspective on behaviour: many behaviours are adaptations (result from natural selection in particular environments) Behaviour is the interface of the organism with its environment and as such precedes the evolution of many anatomical and physiological features. E. g locomotion and changes in femur and pelves in australopithecus & homo. Behaviour is part of our interactions with one another. We are constantly behaving and interpreting the behaviour of others. Comparative analyses of behaviour use naturally occurring variations and measure survival and reproductive success. Ultimate and proximate explanations are not alternatives: there will be ultimate and proximate explanations possible for every behaviour. How could it have evolved to work that way: the mechanisms of control and expression of a behaviour can tell us something about its evolution. E. g hunger = food search and ingestion. E. g if nutrients (energy) too low, organisms dies or can"t reproduce.

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