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1:​ ​INTRODUCTION

2

2:​ ​STUDYING​ ​BEHAVIOUR​ ​SCIENTIFICALLY

2

3:​ ​PRIMATE​ ​DIVERSITY​ ​AND​ ​ECOLOGY

3

4:​ ​PRIMATE​ ​MATING​ ​SYSTEMS

9

5:​ ​PRIMATES​ ​TO​ ​HOMININS

11

6:​ ​THE​ ​RISE​ ​OF​ ​MODERN​ ​HUMANS

17

7:​ ​ORIGINS​ ​OF​ ​MODERN​ ​HUMAN​ ​BEHAVIOUR

20

8:​ ​HUMAN​ ​VARIATION​ ​AND​ ​“UNIVERSALS”

24

9:​ ​RECIPROCITY​ ​AND​ ​SHARING

29

10:​ ​COOPERATION​ ​AND​ ​KIN

33

11:​ ​SEXUAL​ ​SELECTION​ ​AND​ ​HUMANS

36

12:​ ​HUMAN​ ​MATE​ ​CHOICE

40

13:​ ​HUMAN​ ​PARENTAL​ ​CARE

42

14:​ ​HUMAN​ ​LIFE​ ​HISTORIES

44

15:​ ​THE​ ​EVOLUTION​ ​OF​ ​HUMAN​ ​INTELLIGENCE

49

16:​ ​COGNITION​ ​AND​ ​THE​ ​MODULAR​ ​MIND

54

17:​ ​EVOLUTION​ ​OF​ ​LANGUAGE

58

18:​ ​EVOLUTION​ ​AND​ ​CULTURE

62

19:​ ​EVOLUTIONARY​ ​MEDICINE

64

Joanna​ ​Griffith​ ​(2017)

1:​ ​INTRODUCTION
Studying​ ​humans
● Social​ ​sciences/humanities​ ​perspective​ ​vs
...
​ ​With​ ​birds,​ ​between​ ​size
and​ ​flight​ ​manoeuvrability)
○ Darwinian​ ​evolution
■ Living​ ​individuals​ ​are​ ​descendants​ ​of​ ​other​ ​individuals​ ​that​ ​lived​ ​in​ ​the
past
■ Evolution​ ​occurs​ ​through​ ​cumulative​ ​change​ ​over​ ​a​ ​long​ ​period​ ​of​ ​time
■ New​ ​forms​ ​occur​ ​via​ ​splitting​ ​of​ ​lineages
■ Natural​ ​selection​ ​is​ ​an​ ​engine​ ​of​ ​change
Challenging​ ​the​ ​model
● Genealogies
○ Fossils
○ Living​ ​forms
○ Biogeography
● Pattern​ ​of​ ​inheritance​ ​+​ ​the​ ​strength​ ​of​ ​selection​ ​should​ ​=​ ​different​ ​degrees​ ​of
evolutionary​ ​change
● Differences​ ​between​ ​organisms​ ​should​ ​reflect​ ​their​ ​niches
○ Eg
...
​ ​Optimality​ ​(utility)​ ​theory
○ Eg
...
​ ​Thorndike,​ ​Watson,​ ​Skinner)
○ Based​ ​studies​ ​on​ ​controlled​ ​laboratory​ ​experiments​ ​on​ ​a​ ​small​ ​range​ ​of
animals
● Ethologists​ ​(eg
...
​ ​Studies​ ​of​ ​animal​ ​intelligence
● Ethology
● Behavioural​ ​ecology
● Applied
○ For​ ​purposes​ ​of​ ​welfare​ ​research​ ​and​ ​animal​ ​welfare​ ​(studious)
● Behavioural​ ​biology​ ​is​ ​the​ ​term​ ​commonly​ ​used​ ​now
Tinbergen’s​ ​4​ ​Whys
● Proximate:​ ​explanations​ ​for​ ​the​ ​existence​ ​of​ ​behaviours​ ​over​ ​an​ ​animal’s​ ​lifetime
○ Development​ ​(ontogeny)
■ How​ ​did​ ​the​ ​behaviour​ ​develop​ ​in​ ​the​ ​organism’s​ ​lifetime?
● Eg
...
​ ​While​ ​hunting​ ​or​ ​grooming
● Growth​ ​rate
● Reproductive​ ​effort
○ Primates​ ​require:
■ Carbohydrates​ ​(produced​ ​by​ ​plants)
■ Amino​ ​acids​ ​(protein)
■ Fats​ ​and​ ​oils​ ​(from​ ​seeds,​ ​insects,​ ​and​ ​animal​ ​prey)
■ Vitamins​ ​and​ ​minerals
■ Water
○ Primates​ ​must​ ​avoid​ ​toxins​ ​such​ ​as​ ​those​ ​found​ ​in​ ​adult​ ​leaves
○ Insectivores:
■ Small​ ​body​ ​size
■ High,​ ​sharp​ ​cusps​ ​on​ ​molar​ ​teeth
■ Many​ ​undifferentiated​ ​teeth
■ Simple​ ​digestive​ ​system
○ Foliovores:
■ Large​ ​body​ ​size
■ Small​ ​incisors
■ Sharp,​ ​shearing​ ​crests​ ​on​ ​molars
■ Enlarged,​ ​well-developed​ ​digestive​ ​system
○ Frugivores:
■ Medium​ ​body​ ​size
■ Large,​ ​broad​ ​incisors
■ Low-cusped,​ ​relatively​ ​flat​ ​molars
■ Relatively​ ​large​ ​digestive​ ​system,​ ​but​ ​not​ ​specialised​ ​like​ ​that​ ​found​ ​in
foliovores
○ Gummivores:
■ Relatively​ ​small​ ​body​ ​size
■ Long,​ ​robust​ ​incisors​ ​to​ ​tap​ ​directly​ ​into​ ​the​ ​phloem​ ​of​ ​plants
■ Some​ ​have​ ​claws​ ​(Callitrichids)
○ Diets​ ​and​ ​home​ ​ranges
■ How​ ​does​ ​the​ ​diet​ ​of​ ​a​ ​primate​ ​impact​ ​its​ ​home​ ​range?
● Availability​ ​of​ ​food
Joanna​ ​Griffith​ ​(2017)

●
●

●

●

○ Leaves​ ​and​ ​seeds​ ​are​ ​often​ ​more​ ​plentiful​ ​than​ ​fruit
Seasonality​ ​of​ ​food
○ Ripe​ ​fruit​ ​and​ ​leaves​ ​are​ ​not​ ​always​ ​present

Primate​ ​territoriality
○ Some​ ​primates​ ​are​ ​territorial
■ Home​ ​ranges​ ​do​ ​not​ ​overlap,​ ​and​ ​territories​ ​are​ ​defended
aggressively
■ Territorial​ ​in​ ​order​ ​to​ ​defend​ ​mates​ ​(primarily​ ​males)​ ​and​ ​resources
(primarily​ ​females)
○ Some​ ​primates​ ​are​ ​not​ ​territorial
■ Home​ ​ranges​ ​overlap
○ Whether​ ​a​ ​primate​ ​is​ ​territorial​ ​or​ ​not​ ​depends​ ​on​ ​the​ ​cost​ ​of​ ​defending​ ​an
area​ ​and​ ​the​ ​benefits​ ​of​ ​protecting​ ​limited​ ​resources/mates
Predation
○ Threats​ ​from:
■ Big​ ​cats
■ Snakes
■ Birds​ ​of​ ​prey
■ Crocodiles​ ​and​ ​alligators
○ Defences​ ​against​ ​predation
■ Interspecific​ ​associations,​ ​eg
...
​ ​In​ ​South​ ​American​ ​forests),​ ​and​ ​in​ ​areas
with​ ​few​ ​felids​ ​or​ ​raptors,​ ​primates​ ​evolve​ ​larger​ ​body​ ​size​ ​and
group​ ​size​ ​(eg
...
​ ​Vervet​ ​monkeys)
■ Increased​ ​group​ ​size
● Detection:​ ​more​ ​eyes​ ​to​ ​spot​ ​a​ ​predator
● Deterrence:​ ​mobbing​ ​behaviour
● Dilution:​ ​individual​ ​risk​ ​of​ ​death​ ​is​ ​lower
Primate​ ​sociality
○ Why​ ​are​ ​primates​ ​social?
■ Predator​ ​avoidance
■ Feeding​ ​competition
● Can​ ​defend​ ​food​ ​patches
● Female​ ​distribution​ ​is​ ​related​ ​to​ ​resource​ ​distribution​ ​=​ ​female
social​ ​groups
■ Can​ ​be​ ​costly​ ​as​ ​there​ ​is​ ​more​ ​competition​ ​for​ ​food​ ​and​ ​mates,​ ​and
disease​ ​transmission​ ​is​ ​more​ ​of​ ​a​ ​risk
○ Social​ ​groups
■ Solitary
■ Polygynous​ ​(one​ ​male,​ ​multiple​ ​females)
■ Monogamous/pair-bonded
■ Polyandrous​ ​(multiple​ ​males,​ ​one​ ​female)
■ Polygynandrous​ ​(multiple​ ​males,​ ​multiple​ ​females)
Joanna​ ​Griffith​ ​(2017)

--------------------------------------------------------------------------------------------------------------------------4:​ ​PRIMATE​ ​MATING​ ​SYSTEMS
Mating​ ​systems:​ ​the​ ​ways​ ​animals​ ​find​ ​mates​ ​and​ ​care​ ​for​ ​offspring
Basic​ ​rules​ ​for​ ​mammals​ ​(though​ ​there​ ​can​ ​be​ ​different​ ​variations​ ​among​ ​primates):
○ Sexual​ ​reproduction
○ Female​ ​gestation
○ Female​ ​lactation
● Language​ ​of​ ​adaptive​ ​explanations:
○ Strategy:​ ​evolved​ ​behaviours​ ​that​ ​are​ ​a​ ​product​ ​of​ ​natural​ ​selection
○ Costs​ ​and​ ​benefits:​ ​trade-offs​ ​in​ ​reproductive​ ​success
Evolution​ ​of​ ​female​ ​reproductive​ ​strategies
● Variation​ ​in​ ​parental​ ​care​ ​in​ ​animals​ ​(eg
...
​ ​Female​ ​baboons​ ​with​ ​strong​ ​social​ ​bonds​ ​have​ ​greater
reproductive​ ​success​ ​and​ ​live​ ​longer​ ​overall
● Reproductive​ ​trade-offs
○ Resources​ ​are​ ​limited
■ Allocation​ ​of​ ​energy​ ​to​ ​one​ ​offspring​ ​comes​ ​at​ ​the​ ​expense​ ​of​ ​others
■ There​ ​is​ ​a​ ​trade-off​ ​between​ ​quantity​ ​and​ ​quality​ ​of​ ​offspring
■ Eg
...
​ ​The​ ​tail​ ​feathers​ ​of​ ​a​ ​male​ ​peacock
○ Pair-bonds​ ​have​ ​little​ ​male-male​ ​competition,​ ​so​ ​there​ ​is​ ​little​ ​dimorphism
○ Polygynous​ ​groups​ ​have​ ​huge​ ​body​ ​and​ ​canine​ ​dimorphism
○ Polyandrous​ ​groups​ ​have​ ​large​ ​dimorphism
● Sexual​ ​selection
○ Because​ ​of​ ​high​ ​sexual​ ​selection​ ​in​ ​some​ ​species,​ ​a​ ​lot​ ​of​ ​resources​ ​go
towards​ ​increasing​ ​a​ ​male’s​ ​mating​ ​success​ ​rather​ ​than​ ​going​ ​to​ ​females​ ​to
increase​ ​reproductive​ ​success
○ Arguably​ ​stronger​ ​than​ ​natural​ ​selection,​ ​but​ ​both​ ​may​ ​balance​ ​out​ ​over​ ​time
■ Eg
...
​ ​Stags​ ​during​ ​the​ ​rut
● Dominant​ ​males​ ​gain​ ​access​ ​to​ ​females
■ Behavioural​ ​flexibility​ ​in​ ​primates
● In​ ​polygynandrous​ ​groups,​ ​males​ ​establish​ ​a​ ​dominance
hierarchy

Joanna​ ​Griffith​ ​(2017)

Higher​ ​ranking​ ​individuals​ ​have​ ​greater​ ​reproductive
success
● Infanticide
○ Death​ ​of​ ​an​ ​infant​ ​accelerates​ ​the​ ​return​ ​of​ ​a​ ​female​ ​to
sexual​ ​receptivity​ ​(lactational​ ​amenorrhea​ ​no​ ​longer
has​ ​an​ ​effect​ ​on​ ​ability​ ​to​ ​become​ ​pregnant)
○ 85%​ ​of​ ​deaths​ ​follow​ ​takeover​ ​by​ ​a​ ​new​ ​male
○ Unweaned​ ​infants​ ​primarily​ ​targeted
○ Rarely​ ​done​ ​by​ ​sexually​ ​active​ ​males​ ​in​ ​the​ ​group
○ In​ ​45-70%​ ​of​ ​cases,​ ​males​ ​mated​ ​with​ ​the​ ​same​ ​female
○ Infanticide​ ​is​ ​not​ ​reproductively​ ​beneficial​ ​for​ ​females,
therefore​ ​they​ ​have​ ​evolved​ ​counterstrategies
■ Paternity​ ​confusion
■ Male​ ​friendships
● Male​ ​protects​ ​female​ ​in​ ​return​ ​for
grooming
● Studies​ ​show​ ​that​ ​female​ ​stress​ ​rises​ ​if
the​ ​female​ ​does​ ​not​ ​have​ ​a​ ​male​ ​friend
during​ ​a​ ​takeover
○ Intersexual​ ​selection
■ Female​ ​choice
● The​ ​female​ ​selects​ ​the​ ​most​ ​attractive​ ​male
● Sperm​ ​competition
○ Polygynandrous​ ​groups
■ Oestrous​ ​females​ ​mate​ ​with​ ​many​ ​males,​ ​therefore​ ​males​ ​with​ ​larger
sperm​ ​volume​ ​have​ ​a​ ​greater​ ​chance​ ​of​ ​fathering​ ​offspring
● Selects​ ​for​ ​testes​ ​size
● Investing​ ​males
○ Pair-bonding
■ Mate​ ​guarding​ ​(mates​ ​may​ ​cheat),​ ​eg
...
​ ​Marmosets​ ​and​ ​tamarins​ ​often​ ​have​ ​twins,​ ​so​ ​the​ ​mother
can​ ​increase​ ​fertility/survival​ ​rate​ ​by​ ​having​ ​helpers
■ Humans​ ​are​ ​cooperative​ ​breeders
Naturalistic​ ​fallacy
● What​ ​we​ ​see​ ​in​ ​nature​ ​is​ ​not​ ​necessarily​ ​“correct”
○ Explanations​ ​do​ ​not​ ​equal​ ​justifications
--------------------------------------------------------------------------------------------------------------------------○

5:​ ​PRIMATES​ ​TO​ ​HOMININS
Origin​ ​and​ ​evolution​ ​of​ ​mammals
● Early​ ​Triassic​ ​period
○ Therapsids
Joanna​ ​Griffith​ ​(2017)

225​ ​million​ ​years​ ​ago
● Overlapped​ ​with​ ​the​ ​dinosaurs’
■ Warm-blooded,​ ​fur-covered​ ​reptiles
■ Egg-layers,​ ​did​ ​not​ ​produce​ ​milk
■ Around​ ​for​ ​30-40​ ​million​ ​years
● Late​ ​Triassic,​ ​early​ ​Jurassic​ ​period
○ First​ ​mammals
■ Dinosaurs​ ​ruled
■ Oviparous​ ​(laid​ ​eggs)
● End​ ​of​ ​Cretaceous
○ Dinosaurs​ ​went​ ​extinct,​ ​mammals​ ​radiated​ ​into​ ​new​ ​niches
Origin​ ​of​ ​primates
● Angiosperm​ ​hypothesis
○ The​ ​adaptive​ ​radiation​ ​of​ ​primates​ ​occurred​ ​with​ ​the​ ​radiation​ ​of​ ​angiosperms
(flowering​ ​plants)​ ​that​ ​offered​ ​new​ ​opportunities​ ​and​ ​an​ ​unexploited​ ​niche
■ Omnivores​ ​adapted​ ​more​ ​flexible​ ​hands​ ​to​ ​handle​ ​fruit
● Visual​ ​predation​ ​hypothesis
○ Omnivores​ ​adapted​ ​orbital​ ​convergence​ ​(eyes​ ​moved​ ​from​ ​sides​ ​of​ ​the​ ​head
to​ ​the​ ​front)​ ​in​ ​order​ ​to​ ​forage​ ​for​ ​fruit​ ​nocturnally
● Leaping​ ​hypothesis
○ Primate​ ​biomechanics​ ​for​ ​leaping​ ​and​ ​grasping​ ​were​ ​favoured
● Generalised​ ​nocturnal​ ​characteristics​ ​(large​ ​forward-facing​ ​eyes,​ ​grasping​ ​hands​ ​and
feet)​ ​were​ ​favoured
● Terminal​ ​branch​ ​hypothesis
○ Primates​ ​evolved​ ​to​ ​better​ ​meet​ ​the​ ​needs​ ​of​ ​an​ ​arboreal​ ​lifestyle​ ​(vision,
leaping,​ ​grasping​ ​hands​ ​and​ ​feet)
Evolution​ ​of​ ​early​ ​primates
● Plesiadapiformes
○ Frugivorous
○ No​ ​opposable​ ​thumbs
○ Nail​ ​on​ ​one​ ​toe,​ ​claws​ ​on​ ​the​ ​others
○ Long,​ ​narrow​ ​snout
○ Small​ ​brain
○ Large​ ​incisors
● Eocene​ ​period
○ Earth​ ​was​ ​warm​ ​and​ ​wet
■ Tropical​ ​forests​ ​spread​ ​into​ ​North​ ​America​ ​and​ ​Europe
○ Evolution​ ​of​ ​two​ ​types​ ​of​ ​primates​ ​(it​ ​is​ ​not​ ​possible​ ​to​ ​say​ ​which​ ​came​ ​first)
■ Adapids
● Possible​ ​Strepsirrhine​ ​ancestor​ ​(wet-nosed​ ​primates)
● Larger​ ​than​ ​Omomyids
● Diurnal​ ​and​ ​quadrupedal
■ Omomyids
● Possible​ ​Haplorhine​ ​ancestor​ ​(dry-nosed​ ​primates)
○ Possible​ ​tarsier​ ​ancestor
● Nocturnal
■

Joanna​ ​Griffith​ ​(2017)

● Some​ ​leapers
Evolution​ ​of​ ​Haplorhines​ ​and​ ​Anthropoids
● Evolved​ ​in​ ​Fayum,​ ​Egypt,​ ​during​ ​the​ ​Eocene/Oligocene​ ​boundary​ ​(33-36​ ​million
years​ ​ago)
○ Oligopithecids​ ​(anthropoid/ape​ ​dentition,​ ​2-1-2-3)
○ Parapithecids​ ​(new​ ​world​ ​monkey​ ​dentition,​ ​2-1-3-3)
● Propliopithecids​ ​(group​ ​with​ ​many​ ​genera)
○ Propliopithecus
○ Aegyptopithecus
■ 2-1-2-3​ ​(new​ ​world​ ​monkey​ ​dentition)
■ Frugivorous
■ Sexually​ ​dimorphic,​ ​suggests​ ​sexual​ ​selection
■ Arboreal​ ​quadrupeds
■ Diurnal
■ Relatively​ ​small​ ​brain
Evolution​ ​of​ ​the​ ​Platyrrhines​ ​(New​ ​World​ ​monkeys)
● Little​ ​evidence​ ​of​ ​NW​ ​monkeys​ ​during​ ​the​ ​Eocene
○ Possibly​ ​just​ ​due​ ​to​ ​a​ ​misleading​ ​fossil​ ​record
● We​ ​do​ ​not​ ​know​ ​how​ ​primates​ ​moved​ ​from​ ​Africa​ ​to​ ​the​ ​Americas
Origin​ ​and​ ​evolution​ ​of​ ​the​ ​apes
● Evolved​ ​during​ ​the​ ​Miocene​ ​(5-23​ ​million​ ​years​ ​ago)
● “Hominoids”
● Changed​ ​from​ ​a​ ​warm​ ​and​ ​wet​ ​climate​ ​to​ ​dry​ ​and​ ​cool
● Apes​ ​vs
...
8​ ​million​ ​years​ ​ago,​ ​Kenya)
From​ ​hominoid​ ​to​ ​hominin
● What​ ​is​ ​unique​ ​about​ ​humans?
○ Bipedal​ ​(walk​ ​on​ ​two​ ​legs)
○ Small​ ​canines​ ​and​ ​large​ ​molars​ ​with​ ​thick​ ​enamel
○ Large​ ​brains
○ Very​ ​slow​ ​life​ ​histories,​ ​long​ ​juvenile​ ​period
○ Language,​ ​symbolic​ ​culture
○ These​ ​human​ ​characteristics​ ​did​ ​not​ ​all​ ​develop​ ​at​ ​once
● Sahelanthropus
○ Evolved​ ​in​ ​Chad,​ ​Africa,​ ​6-7​ ​million​ ​years​ ​ago
○ Hominin​ ​characteristics?
■ Foramen​ ​magnum​ ​(where​ ​the​ ​spine​ ​joins/goes​ ​into​ ​the​ ​skull)​ ​suggests
bipedalism
■ Chimpanzee-sized​ ​brain
■ Small​ ​canines
■ Flat​ ​face,​ ​large​ ​brow​ ​ridge
● Orrorin
○ Evolved​ ​in​ ​Kenya,​ ​Africa,​ ​6​ ​million​ ​years​ ​ago
○ Preferred​ ​a​ ​mix​ ​of​ ​woodland​ ​and​ ​savannah
○ Hominin​ ​characteristics?
■ Femur​ ​suggest​ ​bipedalism
■ Chimpanzee-like​ ​teeth
● Ardipithecus​ ​kadabba
○ Evolved​ ​in​ ​Ethiopia,​ ​Africa,​ ​5
...
8​ ​million​ ​years​ ​ago
○ Hominin​ ​characteristics?
■ Toe​ ​bone​ ​suggest​ ​bipedalism
■ Canines​ ​sharpen​ ​against​ ​lower​ ​premolars
● Ardipithecus​ ​ramidus
○ Evolved​ ​in​ ​Ethiopia,​ ​Africa,​ ​4
...
9-4
...
​ ​anamensis
○ Evolved​ ​in​ ​Ethiopia​ ​and​ ​Tanzania,​ ​3-3
...
​ ​anamensis
○ Bipedal
○ Body​ ​size​ ​dimorphism
○ Partial​ ​skeletons​ ​found​ ​(Lucy)​ ​and​ ​Dikika​ ​child​ ​(Selam)
■ Dikika​ ​child
● Found​ ​in​ ​Dikika,​ ​Ethiopia,​ ​3
...
2-3​ ​million​ ​years​ ​ago
○ Preferred​ ​wooded​ ​grassland
○ Similar​ ​cranium​ ​to​ ​A
...
5​ ​million​ ​years​ ​ago
○ Cranium
■ Small​ ​brain​ ​(450cc)
■ Sagittal​ ​crest
■ Large​ ​teeth
○ Longer​ ​legs
○ May​ ​have​ ​used​ ​stone​ ​tools
Australopithecus​ ​sediba
○ Found​ ​in​ ​Malapa​ ​Cave​ ​in​ ​South​ ​Africa,​ ​evolved​ ​1
...

sediba
Paranthropus
○ “The​ ​robust​ ​Australopiths”
○ Cranial​ ​adaptations
■ Enormous​ ​back​ ​teeth​ ​(made​ ​for​ ​hard-to-chew​ ​food?)
■ Sagittal​ ​crest,​ ​linked​ ​to​ ​large​ ​temporalis​ ​muscles​ ​(linked​ ​to​ ​stronger
chewing)
■ Huge​ ​cheek​ ​bones​ ​(linked​ ​to​ ​stronger​ ​chewing)
○ Bipedal
○ Paranthropus​ ​aethiopicus
■ Evolved​ ​in​ ​Kenya,​ ​2
...
8​ ​million​ ​years​ ​ago
■ Cranial​ ​and​ ​dental​ ​adaptations​ ​for​ ​heavy​ ​chewing
■ Bipedal
■ Extended​ ​periods​ ​of​ ​growth​ ​in​ ​males
○ Kenyanthropus
■
■

●

●

●

Joanna​ ​Griffith​ ​(2017)

Evolved​ ​in​ ​Kenya,​ ​3
...
5​ ​million​ ​years​ ​ago
Cranial​ ​adaptations
● Small​ ​brain
● Flat​ ​face
● Small​ ​molars
■ Possible​ ​alternatives​ ​to​ ​hominids​ ​evolving​ ​from​ ​Australopiths
Hominin​ ​phylogenies
● There​ ​are​ ​two​ ​common​ ​theories
○ Either​ ​theory​ ​could​ ​be​ ​correct​ ​with​ ​current​ ​evidence
--------------------------------------------------------------------------------------------------------------------------■
■

6:​ ​THE​ ​RISE​ ​OF​ ​MODERN​ ​HUMANS
Early​ ​Homo
● Evolved​ ​in​ ​Africa,​ ​about​ ​2
...
4-2
...
6-1
...
8​ ​million​ ​years​ ​old
Joanna​ ​Griffith​ ​(2017)

●
●
●

4​ ​skulls​ ​found​ ​(600-775cc​ ​brains)
Homo-like​ ​postcrania
Oldowan​ ​stone​ ​tools

Homo​ ​erectus
○ Discovered​ ​in​ ​the​ ​late​ ​1800s​ ​by​ ​Eugene​ ​Dubois
○ First​ ​fossil​ ​evidence​ ​for​ ​an​ ​ape-human​ ​transitional​ ​species
○ Cranial​ ​differences​ ​with​ ​H
...
​ ​ergaster​ ​and​ ​H
...
​ ​ergaster​ ​in​ ​Africa​ ​and​ ​western​ ​Eurasia​ ​evolved​ ​into​ ​H
...
​ ​floresiensis?
■ Ancestral​ ​lineage​ ​of​ ​early​ ​Homo?
■ Island​ ​dwarfism​ ​of​ ​H
...
​ ​sapiens​ ​and
modern​ ​humans)
○ Oblong​ ​skulls
●

Joanna​ ​Griffith​ ​(2017)

■ Occipital​ ​bun
■ Thin-walled
○ Unique​ ​teeth
■ Taurodont​ ​roots​ ​(extra​ ​pulp,​ ​enabled​ ​them​ ​to​ ​repair​ ​themselves)
■ Heavily​ ​worn​ ​incisors
● Suggests​ ​extensive​ ​use​ ​of​ ​teeth
○ Possible​ ​increase​ ​in​ ​meat​ ​consumption,​ ​use​ ​of​ ​tools
held​ ​between​ ​teeth
○ Short​ ​and​ ​stocky​ ​(helped​ ​to​ ​reduce​ ​heat​ ​loss)
○ More​ ​robust​ ​limbs​ ​with​ ​more​ ​developed​ ​muscle​ ​attachments
○ Wide​ ​torso
○ Short​ ​arms​ ​and​ ​legs
The​ ​road​ ​to​ ​Homo​ ​sapiens
● H
...
​ ​sapiens​ ​about​ ​200,000​ ​years​ ​ago
○ There​ ​are​ ​many​ ​alternative​ ​theories​ ​as​ ​to​ ​how​ ​this​ ​happened,​ ​any​ ​proposed
theory​ ​could​ ​be​ ​correct​ ​with​ ​current​ ​evidence
● Morphological​ ​features​ ​of​ ​modern​ ​Homo​ ​sapiens
○ Large,​ ​round​ ​skull​ ​with​ ​high​ ​forehead
○ Small​ ​face​ ​and​ ​teeth
○ Protruding​ ​chin
○ Less​ ​robust​ ​postcranial​ ​skeleton
○ Long​ ​limbs
● Genetic​ ​features​ ​of​ ​modern​ ​Homo​ ​sapiens
○ Only​ ​a​ ​1
...
2​ ​million​ ​years​ ​ago
● Apes​ ​use​ ​tools​ ​(suggests​ ​a​ ​common​ ​tool-using​ ​ancestor)
○ Sticks​ ​used​ ​to​ ​extract​ ​insects
○ Sticks​ ​used​ ​to​ ​test​ ​water​ ​depth
○ Stones​ ​used​ ​to​ ​crack​ ​open​ ​nuts​ ​and​ ​shells
● Oldowan​ ​tools
○ Model
○ Use​ ​of​ ​a​ ​hammer​ ​stone​ ​to​ ​produce​ ​flakes​ ​from​ ​a​ ​core​ ​stone,​ ​which​ ​are​ ​then
used​ ​as​ ​tools
○ Earliest​ ​evidence​ ​may​ ​have​ ​been​ ​among​ ​Homo​ ​habilis
■ Tools​ ​found​ ​at​ ​Dikika​ ​from​ ​3
...
5
million​ ​years​ ​ago
○ Oldowan​ ​toolmakers​ ​were​ ​likely​ ​all​ ​right-handed
Complex​ ​foraging​ ​strategies​ ​in​ ​humans
● studies​ ​of​ ​aboriginal​ ​tribes
● food​ ​resources
○ collected​ ​food
■ fruit,​ ​leaves
○ extracted​ ​food
■ termites,​ ​honey,​ ​tubers
○ hunted​ ​food
■ vertebrate​ ​prey
○ extracted​ ​and​ ​hunted​ ​food​ ​tend​ ​to​ ​be​ ​calorie​ ​rich​ ​but​ ​high​ ​risk​ ​or​ ​hard​ ​to​ ​find
■ very​ ​important​ ​sources​ ​of​ ​energy​ ​for​ ​a​ ​species​ ​with​ ​a​ ​demanding,
long,​ ​slow​ ​life​ ​history
● human​ ​foraging
○ Hunting
○ tuber​ ​extraction
○ hard-to-acquire​ ​food
■ require​ ​hard-to-learn​ ​skills,​ ​promoting​ ​a​ ​long​ ​juvenile​ ​period
● division​ ​of​ ​labour
○ by​ ​sex
■ men​ ​tend​ ​to​ ​be​ ​more​ ​involved​ ​in​ ​hunting
■ women​ ​tend​ ​to​ ​be​ ​involved​ ​in​ ​extractive​ ​foraging
● as​ ​soon​ ​as​ ​women​ ​become​ ​sexually​ ​mature,​ ​they​ ​are​ ​pregnant
or​ ​nursing​ ​for​ ​pretty​ ​much​ ​the​ ​rest​ ​of​ ​their​ ​sexual​ ​lives
○ extractive​ ​foraging​ ​allows​ ​pregnant/nursing​ ​women​ ​to
contribute​ ​to​ ​subsistence​ ​in​ ​a​ ​lower​ ​risk​ ​environment
● food​ ​sharing
●

Joanna​ ​Griffith​ ​(2017)

in​ ​chimpanzees
■ mothers​ ​share​ ​with​ ​infants
■ males​ ​share​ ​with​ ​females​ ​that​ ​they​ ​have​ ​recently​ ​been​ ​associated​ ​with
■ dominant​ ​chimps​ ​share​ ​with​ ​subordinates
■ chimps​ ​share​ ​with​ ​individuals​ ​who​ ​have​ ​shared​ ​with​ ​them​ ​in​ ​the​ ​past
■ small​ ​prey​ ​is​ ​usually​ ​not​ ​shared
■ large​ ​prey​ ​is​ ​shared​ ​with​ ​other​ ​members​ ​of​ ​the​ ​group
○ in​ ​humans
■ juveniles​ ​tend​ ​to​ ​be​ ​more​ ​consumers​ ​than​ ​producers
■ middle-aged​ ​men​ ​and​ ​postmenopausal​ ​women​ ​tend​ ​to​ ​be​ ​the​ ​most
productive
Evolution​ ​of​ ​a​ ​slow​ ​life​ ​history
● Humans​ ​are​ ​socially​ ​and​ ​technologically​ ​specialised​ ​for​ ​collection​ ​of​ ​high-gain,
high-risk​ ​food
● Extractive​ ​foraging​ ​and​ ​hunting​ ​require​ ​intelligence​ ​and​ ​learning
○ Large​ ​brain
○ Long​ ​juvenile​ ​period
○ Increased​ ​longevity
○ Paternal​ ​investment
○ Reduced​ ​dimorphism
Complex​ ​foraging​ ​in​ ​Oldowan​ ​toolmakers
● Used​ ​mode​ ​1​ ​stone​ ​tool​ ​technology​ ​for:
○ Carcass​ ​butchering
○ Digging
● Bone​ ​tools​ ​found​ ​in​ ​Swartkrans,​ ​South​ ​Africa,​ ​were​ ​most​ ​likely​ ​used​ ​for​ ​termite
extractions
Evidence​ ​for​ ​meat​ ​eating
● Concentrations​ ​of​ ​butchered​ ​bones​ ​and​ ​tools
○ Bovid​ ​bones​ ​outnumber​ ​others
■ Homo​ ​habilis​ ​focused​ ​on​ ​bovids
● Taphonomy
○ Study​ ​of​ ​what​ ​happens​ ​to​ ​bone​ ​after​ ​death
■ Eg
...
9​ ​million​ ​years​ ​ago​ ​due​ ​to​ ​evidence​ ​from​ ​the
Olduvai​ ​Gorge​ ​(a​ ​stone​ ​circle)
■ However,​ ​Olduvai​ ​was​ ​unlikely​ ​to​ ​have​ ​been​ ​a​ ​home​ ​base
● Carnivore​ ​activity
● Limited​ ​processing​ ​of​ ​bone
● Very​ ​little​ ​weathering​ ​of​ ​bone
● May​ ​have​ ​been​ ​a​ ​meat​ ​processing​ ​site​ ​instead
Homo​ ​ergaster:​ ​tools​ ​and​ ​subsistence
● Acheulean​ ​industry
○ Mode​ ​2​ ​tools
■ Used​ ​the​ ​core​ ​stone​ ​as​ ​a​ ​tool​ ​rather​ ​than​ ​just​ ​flakes
○ Bifacial​ ​tools,​ ​eg
...
​ ​For​ ​carcass​ ​processing
○ Unchanged​ ​for​ ​about​ ​1​ ​million​ ​years
● Meat​ ​eating
○ KNM-ER​ ​1808​ ​bones​ ​had​ ​evidence​ ​of​ ​vitamin​ ​A​ ​poisoning
○ Hand​ ​axes​ ​were​ ​plentiful
○ Cut​ ​marks​ ​on​ ​animal​ ​bones
○ Pronounced​ ​incisors,​ ​may​ ​have​ ​been​ ​more​ ​beneficial​ ​for​ ​meat​ ​eating
○ May​ ​have​ ​been​ ​able​ ​to​ ​use​ ​fire,​ ​allowing​ ​them​ ​to​ ​get​ ​more​ ​nutrients​ ​from
meat,​ ​and​ ​thus​ ​enabling​ ​the​ ​development​ ​of​ ​larger​ ​brains
Homo​ ​erectus:​ ​tools​ ​and​ ​subsistence
● mode​ ​1​ ​in​ ​most​ ​areas
● mode​ ​2​ ​present​ ​in​ ​rare​ ​circumstances
● may​ ​have​ ​used​ ​bamboo​ ​mode​ ​2​ ​tools​ ​instead,​ ​which​ ​are​ ​not​ ​preserved
○ mode​ ​2​ ​stone​ ​tools​ ​may​ ​only​ ​have​ ​been​ ​useful​ ​during​ ​glacial​ ​periods
Homo​ ​heidelbergensis:​ ​tools​ ​and​ ​subsistence
● focused​ ​on​ ​hunting​ ​large​ ​game,​ ​so​ ​created​ ​spears​ ​and​ ​new​ ​butchering​ ​tools
● diversity​ ​of​ ​food​ ​resources
● mode​ ​3​ ​technology
○ used​ ​Levallois​ ​prepared​ ​core​ ​technique
Neanderthal​ ​intelligence
● use​ ​of​ ​language?
○ Had​ ​a​ ​hyoid​ ​bone​ ​that​ ​enabled​ ​speech,​ ​but​ ​skull​ ​was​ ​a​ ​different​ ​shape​ ​so
sounds​ ​may​ ​have​ ​been​ ​different
● Mode​ ​3​ ​tools​ ​(Mousterian,​ ​predominantly​ ​flint)
● Hunted​ ​large​ ​game,​ ​eg
...
​ ​To​ ​keep​ ​scavengers​ ​or​ ​disease
away​ ​from​ ​camp
Joanna​ ​Griffith​ ​(2017)

Produced​ ​personal​ ​ornaments,​ ​such​ ​as​ ​necklaces,​ ​and​ ​may​ ​have​ ​used​ ​natural
pigments​ ​to​ ​paint​ ​their​ ​bodies
● Life​ ​of​ ​a​ ​Neanderthal
○ Short​ ​life​ ​span​ ​(maximum​ ​of​ ​about​ ​45​ ​years)
○ Difficult​ ​lives
■ Arthritis
■ Gum​ ​disease
■ Injuries
■ Evidence​ ​of​ ​the​ ​injured​ ​being​ ​cared​ ​for​ ​by​ ​the​ ​group,​ ​eg
...
​ ​Tools)
○ increased​ ​social​ ​organisation
■ not​ ​just​ ​by​ ​sex/age
○ growth​ ​of​ ​symbolic​ ​expression​ ​(eg
...
​ ​Ivory,​ ​bone,​ ​horn​ ​and​ ​stone
○ variation​ ​in​ ​tool​ ​kits​ ​between​ ​different​ ​populations
○ raw​ ​materials​ ​transported​ ​long​ ​distances
■ shows​ ​that​ ​they​ ​knew​ ​the​ ​properties​ ​of​ ​different​ ​materials
● big-game​ ​hunters
● diverse​ ​diet
○ range​ ​of​ ​vegetation
○ not​ ​just​ ​carnivorous
● evidence​ ​of​ ​shelters
○ eg
...
​ ​Sculptures,​ ​cave​ ​paintings
More​ ​efficient​ ​foraging​ ​and​ ​hunting​ ​techniques​ ​may​ ​have​ ​meant​ ​that
people​ ​had​ ​more​ ​time​ ​for​ ​art
The​ ​origin​ ​and​ ​spread​ ​of​ ​modern​ ​humans
● Tools
○ evidence​ ​of​ ​Neanderthals​ ​copying​ ​Homo​ ​sapiens,​ ​led​ ​to​ ​mode​ ​hybrids
● revolution​ ​or​ ​evolution?
○ Some​ ​scientists​ ​thought​ ​that​ ​the​ ​explosion​ ​of​ ​art​ ​40,000​ ​years​ ​ago​ ​may​ ​have
been​ ​the​ ​result​ ​of​ ​a​ ​revolution​ ​accompanied​ ​by​ ​a​ ​modern​ ​language​ ​and
culture
■ However,​ ​art​ ​has​ ​been​ ​found​ ​in​ ​sites​ ​dating​ ​from​ ​the​ ​Middle​ ​Stone
Age​ ​that​ ​suggests​ ​that​ ​art​ ​may​ ​have​ ​just​ ​been​ ​slowly​ ​evolving​ ​over
time
The​ ​African​ ​archaeological​ ​record
● mode​ ​3​ ​tool​ ​technology​ ​developed​ ​in​ ​Africa​ ​during​ ​the​ ​Middle​ ​Stone​ ​Age
● mode​ ​5​ ​tool​ ​technology​ ​developed​ ​in​ ​the​ ​Later​ ​Stone​ ​Age
○ about​ ​40,000​ ​years​ ​ago
○ much​ ​more​ ​sophisticated​ ​tools,​ ​such​ ​as​ ​microliths
● Middle​ ​Stone​ ​Age
○ Blades
○ Bone​ ​tools
○ Composite​ ​tools
■ Eg
...
​ ​nurture​ ​debate,​ ​as​ ​both​ ​have​ ​an​ ​influence
■ It​ ​is​ ​difficult​ ​to​ ​determine​ ​the​ ​relative​ ​contributions​ ​of​ ​each
○ There​ ​is​ ​variation​ ​both​ ​within​ ​and​ ​between​ ​groups
Variation​ ​in​ ​traits​ ​is​ ​influenced​ ​by​ ​single​ ​genes
○ When​ ​things​ ​go​ ​wrong,​ ​they​ ​can​ ​almost​ ​always​ ​be​ ​attributed​ ​to​ ​a​ ​single​ ​gene
■ Normal​ ​characteristics​ ​are​ ​coded​ ​for​ ​by​ ​a​ ​huge​ ​complex​ ​of​ ​genes
○ Genetic​ ​variation
■ Eg
...
​ ​Non-insulin-dependent​ ​diabetes​ ​(type​ ​2)
■ genetic​ ​basis
■ in​ ​normal​ ​systems,​ ​insulin​ ​regulates​ ​the​ ​uptake​ ​of​ ​sugar​ ​into​ ​cells,​ ​but
in​ ​NIDD​ ​individuals,​ ​their​ ​pancreas​ ​does​ ​not​ ​produce​ ​enough/any
insulin
● leads​ ​to​ ​the​ ​buildup​ ​of​ ​fat​ ​deposits
■ adaptive​ ​gene​ ​for​ ​fat​ ​deposits​ ​in​ ​Micronesia
● Micronesians​ ​would​ ​have​ ​been​ ​able​ ​to​ ​build​ ​up​ ​their​ ​fat
reserves​ ​before​ ​long​ ​boat​ ​trips
○ Those​ ​with​ ​the​ ​gene​ ​were​ ​better​ ​able​ ​to​ ​survive,​ ​so
they​ ​went​ ​on​ ​to​ ​found​ ​new​ ​populations​ ​(eg
...
​ ​High​ ​rates​ ​of​ ​carriers​ ​of​ ​sickle​ ​cell​ ​anaemia​ ​in​ ​countries​ ​affected
by​ ​malaria
● The​ ​shape​ ​of​ ​the​ ​red​ ​blood​ ​cells​ ​prevents​ ​malaria​ ​from​ ​taking​ ​a
hold
● Carriers​ ​are​ ​protected​ ​from​ ​malaria,​ ​those​ ​homozygous​ ​for
sickle​ ​cell​ ​anaemia​ ​die​ ​before​ ​they​ ​can​ ​reproduce,​ ​and​ ​those
without​ ​the​ ​gene​ ​are​ ​likely​ ​to​ ​die​ ​from​ ​malaria
○ Maintains​ ​a​ ​high​ ​frequency​ ​of​ ​heterozygotes​ ​in​ ​the
population
■ Eg
...
​ ​The​ ​Amish,​ ​200​ ​founders
■ Eg
...
​ ​Height
■ Leads​ ​to​ ​a​ ​normal​ ​distribution​ ​(bell​ ​curve)​ ​in​ ​a​ ​population
■ Heritability​ ​(estimation​ ​of​ ​how​ ​much​ ​variation​ ​in​ ​a​ ​phenotypic​ ​trait​ ​in​ ​a
population​ ​is​ ​due​ ​to​ ​genetic​ ​variation​ ​among​ ​individuals​ ​in​ ​that
population)
■ Environmental​ ​covariation​ ​(two​ ​individuals​ ​become​ ​alike​ ​due​ ​to​ ​them
living​ ​in​ ​the​ ​same​ ​environment)
○ Twin​ ​studies
■ Monozygotic​ ​(identical)​ ​vs
...
​ ​Factory​ ​workers​ ​vs
...
​ ​Rat​ ​diets
■ Rats​ ​have​ ​all​ ​evolved​ ​the​ ​ability​ ​to​ ​eat​ ​basically
anything,​ ​but​ ​individual​ ​rats​ ​learn​ ​what​ ​foods​ ​in
their​ ​environment​ ​are​ ​safe​ ​to​ ​eat​ ​over​ ​time
■ Evolutionary​ ​psychology
● Environment​ ​of​ ​evolutionary​ ​adaptedness​ ​(the​ ​environment​ ​in
which​ ​a​ ​given​ ​adaptation​ ​is​ ​said​ ​to​ ​have​ ​evolved)
●

Joanna​ ​Griffith​ ​(2017)

Humans​ ​have​ ​lived​ ​in​ ​small​ ​foraging​ ​groups​ ​for​ ​much​ ​of​ ​their
existence
● Explains​ ​strong​ ​cheater​ ​detection​ ​abilities​ ​(ensuring​ ​fitness)
and​ ​common​ ​phobias
Is​ ​inbreeding​ ​avoidance​ ​an​ ​evolved​ ​human​ ​universal?
○ Many​ ​diseases​ ​are​ ​homozygous​ ​recessive
● Each​ ​person​ ​has​ ​2-5​ ​fatal​ ​alleles,​ ​and​ ​relatives​ ​are​ ​likely​ ​to
share​ ​these​ ​alleles
● Inbreeding​ ​reduces​ ​fitness
■ Many​ ​primates​ ​leave​ ​their​ ​natal​ ​group​ ​once​ ​they​ ​reach​ ​sexual​ ​maturity
● Females​ ​leave​ ​in​ ​chimps,​ ​males​ ​leave​ ​in​ ​old​ ​world​ ​monkeys
(closer​ ​to​ ​apes)
■ Inbreeding​ ​avoidance​ ​may​ ​be​ ​a​ ​psychological​ ​mechanism​ ​in​ ​humans
● The​ ​Westermarck​ ​effect
○ People​ ​are​ ​not​ ​attracted​ ​to​ ​the​ ​people​ ​that​ ​they​ ​grew​ ​up
with
○ Eg
...
​ ​When​ ​listening​ ​to​ ​a​ ​foreign​ ​language,​ ​words​ ​cannot
be​ ​distinguished
● Grammar​ ​rules​ ​are​ ​deeply​ ​ingrained
■ Language​ ​has​ ​evolved
■ Not​ ​just​ ​a​ ​byproduct​ ​of​ ​having​ ​a​ ​complex​ ​brain
● Humans​ ​are​ ​born​ ​with​ ​fundamental​ ​rules​ ​of​ ​grammar
● Vervet​ ​monkeys​ ​can​ ​associate​ ​sounds​ ​with​ ​meaning
● Koko​ ​the​ ​gorilla​ ​learned​ ​American​ ​sign​ ​language​ ​and​ ​could
associate​ ​movements​ ​with​ ​meaning​ ​and​ ​associate​ ​different
signs​ ​together​ ​to​ ​explain​ ​the​ ​unknown
● Kanzi​ ​the​ ​bonobo​ ​can​ ​use​ ​lexigrams​ ​to​ ​communicate
● Primates​ ​can​ ​associate​ ​things​ ​with​ ​symbols​ ​but​ ​have​ ​no
concept​ ​of​ ​time​ ​or​ ​intention
Human​ ​society​ ​and​ ​the​ ​free​ ​rider​ ​problem
○ Society
■ Hunting​ ​and​ ​gathering​ ​societies
● Relied​ ​on​ ​readily​ ​available​ ​plants​ ​and​ ​hunted​ ​game​ ​for
subsistence
● Small​ ​(about​ ​40​ ​members)
● Nomadic
● Little/no​ ​division​ ​of​ ​labour
■ The​ ​domestication​ ​revolution
●

●

●

●

Joanna​ ​Griffith​ ​(2017)

Domestication​ ​of​ ​plants​ ​and​ ​animals​ ​for​ ​food​ ​purpose,​ ​resulted
in​ ​horticultural​ ​and​ ​pastoral​ ​societies
■ Social​ ​organisation
● Domestication​ ​allowed​ ​people​ ​to:
○ Gain​ ​greater​ ​control​ ​over​ ​the​ ​production​ ​of​ ​food
○ Improve​ ​their​ ​lives
■ Dependable​ ​food​ ​supply​ ​changed​ ​the​ ​structure​ ​of​ ​human​ ​society
○ Free​ ​riders​ ​and​ ​the​ ​tragedy​ ​of​ ​the​ ​commons
■ Overexploitation​ ​for​ ​own​ ​benefit
● Lack​ ​of​ ​trust​ ​that​ ​they​ ​will​ ​get​ ​their​ ​fair​ ​share
● Nature​ ​vs
...
​ ​Mating​ ​behaviours​ ​of​ ​soapberry​ ​bugs​ ​changes​ ​depending
on​ ​how​ ​often​ ​their​ ​habitat​ ​is​ ​disturbed
--------------------------------------------------------------------------------------------------------------------------●

9:​ ​RECIPROCITY​ ​AND​ ​SHARING
a​ ​human​ ​universal​ ​is​ ​the​ ​presence​ ​of​ ​societies
○ creates​ ​problems​ ​of​ ​public​ ​good
The​ ​prisoner’s​ ​dilemma
● two​ ​people​ ​(accomplices)​ ​are​ ​arrested​ ​and​ ​interrogated
○ Assuming​ ​that​ ​they​ ​are​ ​the​ ​same​ ​in​ ​character​ ​and​ ​relationship,​ ​they​ ​have​ ​two
choices:
■ Cooperate​ ​and​ ​take​ ​the​ ​blame
■ Defect​ ​and​ ​blame​ ​the​ ​other​ ​person​ ​wholly
○ The​ ​payoff​ ​from​ ​their​ ​choice​ ​depends​ ​on​ ​what​ ​the​ ​other​ ​person​ ​has​ ​chosen
●

COOPERATE

DEFECT

COOPERATE

REWARD​ ​=​ ​3

SUCKER​ ​=​ ​0

DEFECT

TEMPTATION​ ​=​ ​5

PUNISHMENT​ ​=​ ​1

●

Payoff:
○ If​ ​they​ ​are​ ​unsure,​ ​(3+0)/2<(5+1)/2
■ More​ ​incentive​ ​to​ ​defect,​ ​0<1
○ If​ ​everyone​ ​is​ ​known​ ​to​ ​defect,​ ​0<1
■ No​ ​incentive​ ​to​ ​cooperate
■ Suggests​ ​that​ ​there​ ​should​ ​be​ ​a​ ​greater​ ​proportion​ ​of​ ​defectors​ ​in​ ​the
population,​ ​as​ ​defecting​ ​is​ ​evolutionarily​ ​stable
● There​ ​is​ ​no​ ​incentive​ ​to​ ​cooperate​ ​in​ ​a​ ​defect​ ​world,​ ​but​ ​a​ ​high
incentive​ ​to​ ​defect​ ​in​ ​a​ ​cooperative​ ​world
○ Even​ ​if​ ​everyone​ ​is​ ​cooperative,​ ​3<5
■ Incentive​ ​to​ ​defect​ ​in​ ​a​ ​cooperative​ ​world

Joanna​ ​Griffith​ ​(2017)

Model​ ​assumes​ ​that​ ​two​ ​people​ ​only​ ​meet​ ​once,​ ​so​ ​defectors​ ​do​ ​not​ ​have​ ​to​ ​face
shame
○ Titt-for-tatt​ ​vs
...
​ ​all​ ​cooperate
■ T4T​ ​involves​ ​cooperating,​ ​then​ ​do​ ​what​ ​your​ ​opponent​ ​did​ ​to​ ​you
● Requires​ ​a​ ​substantial​ ​probability​ ​of​ ​interaction
● Drifts​ ​into​ ​the​ ​population,​ ​maintains​ ​evolutionary​ ​stability
● Reciprocal​ ​altruism
○ Altruism:​ ​doing​ ​something​ ​nice​ ​for​ ​someone,​ ​but​ ​not​ ​expecting​ ​an​ ​immediate
reward
○ Extended​ ​relationships​ ​between​ ​individuals
○ Memory
○ Conditional​ ​punishment​ ​(even​ ​at​ ​own​ ​cost)
Reciprocal​ ​altruism
● “I’ll​ ​scratch​ ​your​ ​back​ ​if​ ​you​ ​scratch​ ​mine”
○ Individuals​ ​balance​ ​reciprocal​ ​acts
○ Use​ ​many​ ​different​ ​currencies
■ Grooming
■ Food​ ​sharing
■ Coalitionary​ ​support
■ Sexual​ ​favours
● Criteria​ ​for​ ​reciprocal​ ​altruism
○ Frequent​ ​interactions
○ Ability​ ​to​ ​keep​ ​track​ ​of​ ​actions​ ​given​ ​and​ ​received
○ Support​ ​those​ ​who​ ​supported​ ​you
○ Conditions​ ​may​ ​have​ ​applied​ ​to​ ​humans​ ​in​ ​early​ ​smaller-scale​ ​societies
● Eg
...
​ ​vervet​ ​monkeys​ ​and​ ​baboons
○ Nonkin​ ​individuals​ ​provide​ ​greater​ ​assistance​ ​after​ ​grooming
Conditions​ ​under​ ​which​ ​reciprocation​ ​flourishes
● Individuals​ ​must​ ​associate​ ​for​ ​long-enough​ ​periods​ ​of​ ​time​ ​to​ ​develop​ ​reciprocal
interactions
● The​ ​likelihood​ ​of​ ​one​ ​individual​ ​performing​ ​some​ ​social​ ​exchange​ ​with​ ​another
should​ ​be​ ​predicted​ ​on​ ​the​ ​basis​ ​of​ ​their​ ​past​ ​associations
● The​ ​roles​ ​of​ ​giver​ ​and​ ​receiver​ ​should​ ​reverse​ ​at​ ​least​ ​once
● The​ ​short-term​ ​benefits​ ​to​ ​the​ ​recipient​ ​are​ ​greater​ ​than​ ​the​ ​costs​ ​to​ ​the​ ​donor
● Givers​ ​should​ ​be​ ​able​ ​to​ ​recognise​ ​and​ ​expel​ ​cheaters​ ​from​ ​the​ ​system
Indirect​ ​reciprocation
● Trivers​ ​(1974)
○ Argued​ ​that​ ​an​ ​altruistic​ ​act​ ​need​ ​not​ ​necessarily​ ​be​ ​reciprocated​ ​by​ ​the
person​ ​directly​ ​assisted​ ​but​ ​can​ ​be​ ​returned​ ​indirectly​ ​by​ ​other​ ​individuals
■ Eg
...
​ ​by​ ​a​ ​sticker​ ​or​ ​badge​ ​indicating​ ​their
actions)
○ Many​ ​of​ ​the​ ​classic​ ​studies​ ​used​ ​as​ ​evidence​ ​are​ ​eurocentric,​ ​and​ ​focus​ ​on
students
■ Possible​ ​bias​ ​and​ ​lack​ ​of​ ​validity
○ Low​ ​and​ ​Heinen​ ​(cited​ ​in​ ​Alcock,​ ​1993)
■ Reported​ ​that​ ​students​ ​are​ ​significantly​ ​more​ ​likely​ ​to​ ​give​ ​to​ ​charity​ ​if
they​ ​receive​ ​a​ ​pin​ ​or​ ​tag​ ​that​ ​advertises​ ​their​ ​participation
○ Mulcahy​ ​(1999)
■ Observed​ ​who​ ​gave​ ​money​ ​to​ ​beggars,​ ​then​ ​interviewed​ ​mixed-sex
couples​ ​after​ ​the​ ​male​ ​had​ ​donated​ ​money
● Males​ ​at​ ​the​ ​early​ ​stage​ ​of​ ​a​ ​relationship​ ​were​ ​more​ ​likely​ ​to
give​ ​that​ ​those​ ​in​ ​a​ ​long-established​ ​relationship
○ The​ ​act​ ​of​ ​giving​ ​when​ ​accompanied​ ​by​ ​a​ ​female​ ​is​ ​to
do​ ​with​ ​demonstrating​ ​one’s​ ​generosity​ ​to​ ​a​ ​potential
partner
An​ ​alternative​ ​theory
● Gintis​ ​et​ ​al​ ​(2003)
○ Argues​ ​that​ ​kin​ ​selection​ ​and​ ​reciprocity​ ​theories​ ​do​ ​not​ ​explain​ ​why
cooperation​ ​is​ ​frequent​ ​amongst​ ​unrelated​ ​individuals​ ​in​ ​non-repeated
interactions​ ​when​ ​gains​ ​are​ ​small
● Strong​ ​reciprocity:​ ​the​ ​predisposition​ ​to​ ​cooperate​ ​with​ ​others,​ ​and​ ​to​ ​punish​ ​those
who​ ​violate​ ​the​ ​norms​ ​of​ ​cooperation,​ ​at​ ​some​ ​personal​ ​cost,​ ​even​ ​when​ ​such​ ​costs
may​ ​not​ ​be​ ​repaid
○ Fehr​ ​and​ ​Gachter​ ​(2002)
■ When​ ​asked​ ​to​ ​play​ ​a​ ​game​ ​for​ ​monetary​ ​reward​ ​under​ ​‘no
punishment’​ ​or​ ​‘punishment’​ ​conditions,​ ​punishment​ ​of
non-cooperators​ ​substantially​ ​increased​ ​the​ ​amount​ ​that​ ​individuals
invested​ ​for​ ​the​ ​good​ ​of​ ​the​ ​group
○ The​ ​concept​ ​of​ ​fairness​ ​lies​ ​at​ ​the​ ​heart​ ​of​ ​many​ ​human​ ​social​ ​interactions
and​ ​can​ ​be​ ​modelled​ ​using​ ​the​ ​‘ultimatum​ ​game’
■ A​ ​participant​ ​is​ ​given​ ​a​ ​sum​ ​of​ ​money​ ​and​ ​told​ ​they​ ​can​ ​keep​ ​it
provided​ ​that​ ​they​ ​split​ ​the​ ​sum​ ​with​ ​another​ ​individual
● The​ ​participant​ ​has​ ​to​ ​make​ ​a​ ​one-off​ ​offer​ ​between​ ​0-100%​ ​of
the​ ​total​ ​sum​ ​to​ ​the​ ​other​ ​person,​ ​no​ ​haggling​ ​is​ ​allowed
●

Joanna​ ​Griffith​ ​(2017)

If​ ​the​ ​second​ ​person​ ​agrees​ ​to​ ​the​ ​offered​ ​sum,​ ​both​ ​keep
these​ ​amounts;​ ​if​ ​they​ ​reject​ ​the​ ​offer,​ ​both​ ​receive​ ​nothing
■ According​ ​to​ ​one-off​ ​game​ ​theory​ ​exchanges,​ ​we​ ​would​ ​expect​ ​that
the​ ​first​ ​participant​ ​would​ ​offer​ ​a​ ​sum​ ​of​ ​well​ ​below​ ​50%,​ ​and​ ​that​ ​the
receiver​ ​would​ ​accept​ ​any​ ​sum​ ​as​ ​anything​ ​is​ ​better​ ​than​ ​nothing
● However,​ ​when​ ​the​ ​game​ ​is​ ​played,​ ​it​ ​is​ ​typically​ ​found​ ​that
individuals​ ​offer​ ​around​ ​50%,​ ​and​ ​more​ ​than​ ​half​ ​of​ ​receivers
do​ ​not​ ​accept​ ​offers​ ​of​ ​less​ ​that​ ​20%​ ​(Sigmund​ ​et​ ​al,​ ​2002)
○ Individuals​ ​do​ ​not​ ​behave​ ​completely​ ​selfishly​ ​but​ ​place
a​ ​high​ ​value​ ​on​ ​fair​ ​outcomes
○ Receivers​ ​are​ ​prepared​ ​to​ ​accept​ ​smaller​ ​‘gifts’​ ​under
the​ ​following​ ​conditions:
■ The​ ​giver​ ​is​ ​chosen​ ​by​ ​better​ ​performance​ ​on​ ​a
quiz
■ The​ ​giver’s​ ​offer​ ​is​ ​randomly​ ​selected​ ​by​ ​a
computer
■ Several​ ​responders​ ​compete​ ​to​ ​accept​ ​a​ ​giver’s
offer
● Sigmund​ ​et​ ​al​ ​(2002)
○ Proposed​ ​that​ ​our​ ​emotional​ ​apparatus​ ​has​ ​been
shaped​ ​over​ ​millions​ ​of​ ​years​ ​of​ ​small​ ​group​ ​living​ ​in
which​ ​it​ ​is​ ​hard​ ​to​ ​cheat​ ​more​ ​than​ ​once​ ​and​ ​where​ ​we
expect​ ​conspecifics​ ​to​ ​notice​ ​and​ ​remember​ ​our​ ​actions
Hunter-gatherer​ ​reciprocity
● Reciprocity:​ ​an​ ​exchange​ ​between​ ​social​ ​equals
○ Common​ ​in​ ​egalitarian​ ​societies
○ Three​ ​types:
■ Generalised:​ ​someone​ ​gives​ ​with​ ​no​ ​explicit​ ​expectation​ ​of​ ​a​ ​like​ ​gift
■ Balanced:​ ​giving​ ​and​ ​expecting​ ​something​ ​in​ ​return
■ Negative:​ ​giving​ ​with​ ​the​ ​expectation​ ​of​ ​immediate​ ​return
● Generalised​ ​reciprocity
○ Occurs​ ​to​ ​some​ ​extent​ ​in​ ​all​ ​societies​ ​(eg
...
​ ​study​ ​of​ ​return​ ​rates​ ​of​ ​exploited​ ​food​ ​resources​ ​among​ ​the
Ache
--------------------------------------------------------------------------------------------------------------------------10:​ ​COOPERATION​ ​AND​ ​KIN
Types​ ​of​ ​social​ ​interaction
ACT​ ​BENEFITS​ ​THE
RECIPIENT​ ​(+)

ACT​ ​COSTS​ ​THE
RECIPIENT​ ​(-)

ACT​ ​BENEFITS​ ​THE
ACTOR​ ​(+)

MUTUALISM​ ​(+/+)

SELFISH​ ​(+/-)

ACT​ ​COSTS​ ​THE​ ​ACTOR
(-)

ALTRUISM​ ​(-/+)

SPITEFUL​ ​(-/-)

The​ ​top​ ​two​ ​behaviours​ ​are​ ​predictable,​ ​as​ ​they​ ​are​ ​positive​ ​for​ ​the​ ​actor​ ​so​ ​help​ ​to
improve​ ​fitness​ ​and​ ​therefore​ ​ability​ ​to​ ​survive
○ The​ ​bottom​ ​two​ ​behaviours​ ​make​ ​no​ ​evolutionary​ ​sense​ ​and​ ​so​ ​are​ ​harder​ ​to
explain
Altruism
● Altruism:​ ​helping​ ​other​ ​in​ ​a​ ​way​ ​that​ ​benefits​ ​them​ ​but​ ​at​ ​a​ ​personal​ ​cost​ ​to​ ​yourself
○ Eg
...
​ ​males​ ​sharing​ ​food,​ ​may​ ​eventually​ ​allow​ ​them​ ​to​ ​show​ ​off
● There​ ​is​ ​a​ ​problem​ ​with​ ​group-level​ ​explanations​ ​of​ ​altruism
○ Altruism​ ​must​ ​ultimately​ ​favour​ ​the​ ​individual,​ ​not​ ​the​ ​group,​ ​for​ ​the​ ​tendency
to​ ​behave​ ​altruistically​ ​to​ ​persist​ ​in​ ​the​ ​group
○ Group-level​ ​explanations​ ​do​ ​not​ ​fit​ ​our​ ​understanding​ ​of​ ​evolutionary​ ​theory
■ Eg
...
​ ​a​ ​marking
Green​ ​beards​ ​(Dawkins)
● A​ ​gene​ ​has​ ​two​ ​effects:
○ Produces​ ​a​ ​green​ ​beard
○ Motivates​ ​helping​ ​behaviour​ ​towards​ ​those​ ​who​ ​have​ ​a​ ​green​ ​beard
● May​ ​lead​ ​to​ ​a​ ​mutation​ ​where​ ​an​ ​individual​ ​grows​ ​a​ ​green​ ​beard​ ​but​ ​does​ ​not​ ​help
other​ ​with​ ​green​ ​beards
● Shows​ ​that​ ​the​ ​evolution​ ​of​ ​altruism​ ​is​ ​not​ ​straightforward
○ How​ ​can​ ​a​ ​gene​ ​increase​ ​its​ ​own​ ​frequency,​ ​and​ ​is​ ​there​ ​a​ ​way​ ​of​ ​knowing
who​ ​has​ ​a​ ​probability​ ​of​ ​sharing​ ​the​ ​same​ ​gene?
■ Can​ ​make​ ​copies​ ​of​ ​itself
■ Can​ ​help​ ​copies​ ​of​ ​itself​ ​make​ ​copies​ ​of​ ​itself
Kin​ ​selection/inclusive​ ​fitness​ ​theory
● Hamilton​ ​(1964)
○ An​ ​allele​ ​may​ ​spread​ ​because​ ​it​ ​causes​ ​its​ ​bearer​ ​to​ ​reproduce​ ​or​ ​because​ ​it
causes​ ​its​ ​bearer​ ​to​ ​help​ ​others​ ​to​ ​reproduce​ ​who​ ​are​ ​likely​ ​to​ ​carry​ ​the​ ​same
gene
■ Individuals​ ​who​ ​are​ ​likely​ ​to​ ​carry​ ​the​ ​same​ ​genes​ ​are​ ​genetic
relatives​ ​(have​ ​common​ ​ancestors)
● Direct​ ​(individual)​ ​fitness:​ ​the​ ​ability​ ​for​ ​a​ ​heritable​ ​design​ ​feature​ ​to​ ​reproduce​ ​itself
by​ ​promoting​ ​the​ ​survival​ ​and​ ​reproduction​ ​of​ ​its​ ​bearer
● Inclusive​ ​fitness:​ ​the​ ​ability​ ​of​ ​a​ ​gene​ ​(design​ ​feature)​ ​to​ ​cause​ ​its​ ​own​ ​spread​ ​either
through​ ​its​ ​bearer​ ​or​ ​those​ ​having​ ​a​ ​high​ ​probability​ ​of​ ​sharing​ ​the​ ​gene,​ ​close
genetic​ ​relatives
○
○
○

Joanna​ ​Griffith​ ​(2017)

Technically,​ ​we​ ​all​ ​share​ ​genes,​ ​but​ ​the​ ​variation​ ​in​ ​the​ ​few​ ​genes​ ​that​ ​we​ ​don’t
share​ ​allows​ ​for​ ​the​ ​evolution​ ​of​ ​kin​ ​selection
● Degree​ ​of​ ​relatedness​ ​(r)
○ The​ ​probability​ ​that​ ​an​ ​allele​ ​present​ ​in​ ​one​ ​individual​ ​is​ ​present​ ​in​ ​another
individual,​ ​over​ ​and​ ​above​ ​the​ ​population​ ​average​ ​frequency​ ​of​ ​the​ ​allele
○ The​ ​probability​ ​that​ ​alleles​ ​sampled​ ​from​ ​two​ ​individuals​ ​are​ ​identical​ ​by
descent
○ Events​ ​of​ ​mating​ ​organise​ ​relatedness​ ​between​ ​individuals
● Hamilton’s​ ​rule
○ rb>c
■ R​ ​=​ ​coefficient​ ​of​ ​relatedness​ ​between​ ​actor​ ​and​ ​recipients
■ B​ ​=​ ​sum​ ​of​ ​benefits​ ​to​ ​individuals​ ​impacted​ ​by​ ​behaviour
■ C​ ​=​ ​fitness​ ​cost​ ​to​ ​individual​ ​performing​ ​behaviour
○ If​ ​rb​ ​is​ ​greater​ ​than​ ​c,​ ​the​ ​behaviour​ ​will​ ​spread/evolve
○ Altruism​ ​is​ ​limited​ ​to​ ​kin,​ ​as​ ​the​ ​r​ ​of​ ​nonkin​ ​is​ ​0
○ More​ ​closely​ ​related​ ​individuals​ ​(higher​ ​r)​ ​can​ ​afford​ ​more​ ​costly​ ​acts​ ​of
altruism
Kin​ ​biases​ ​in​ ​behaviour
● Grooming
○ Benefits
■ Hygiene
■ Reinforces​ ​social​ ​relationship
■ Conflict​ ​resolution
○ Costs
■ Time
■ Energy
○ Most​ ​instances​ ​are​ ​between​ ​mother​ ​and​ ​infant​ ​(r​ ​=​ ​½)
○ Occurs​ ​more​ ​often​ ​between​ ​kin​ ​than​ ​distant​ ​kin​ ​or​ ​nonkin
Kin​ ​selection​ ​in​ ​humans
● Food​ ​sharing​ ​is​ ​more​ ​common​ ​among​ ​close​ ​relatives
● Political​ ​alliances​ ​between​ ​kin​ ​are​ ​more​ ​stable​ ​than​ ​those​ ​formed​ ​between​ ​distantly
related,​ ​or​ ​unrelated​ ​individuals
● The​ ​passing​ ​on​ ​of​ ​wealth​ ​to​ ​lineal​ ​descendants​ ​(excluding​ ​spouses)​ ​is​ ​far​ ​more
common​ ​than​ ​giving​ ​to​ ​less​ ​closely​ ​related​ ​or​ ​unrelated​ ​individuals
● Close​ ​relatives​ ​are​ ​preferentially​ ​sought​ ​out​ ​in​ ​times​ ​of​ ​need​ ​and​ ​such​ ​help​ ​is​ ​less
likely​ ​to​ ​be​ ​reciprocal
● Relatives​ ​typically​ ​receive​ ​more​ ​expensive​ ​presents
● Fieldman​ ​et​ ​al
○ Asked​ ​participants​ ​to​ ​hold​ ​a​ ​painful​ ​position
■ The​ ​longer​ ​they​ ​held​ ​the​ ​position,​ ​the​ ​more​ ​money​ ​they​ ​would​ ​receive
○ Participants​ ​could​ ​earn​ ​money​ ​for​ ​individuals​ ​differing​ ​in​ ​relatedness
■ Themselves​ ​(r​ ​=​ ​1)
■ Parent​ ​or​ ​sibling​ ​(r​ ​=​ ​½)
■ grandparent/niece/nephew/cousin​ ​(r​ ​=​ ​⅛)
■ Unrelated​ ​friend​ ​(r​ ​=​ ​0)
○ Length​ ​of​ ​time​ ​holding​ ​painful​ ​position​ ​increased​ ​with​ ​increasing​ ​relatedness
●

Joanna​ ​Griffith​ ​(2017)

DeBruine​ ​(2002)
○ Argued​ ​that​ ​animals​ ​should​ ​be​ ​sensitive​ ​to​ ​cues​ ​of​ ​genetic​ ​relatedness​ ​when
making​ ​altruistic​ ​decisions
■ In​ ​humans,​ ​these​ ​decisions​ ​may​ ​be​ ​based​ ​around​ ​facial​ ​similarity
○ Participants​ ​played​ ​a​ ​computer​ ​game​ ​where​ ​they​ ​had​ ​to​ ​choose​ ​whether​ ​or
not​ ​they​ ​would​ ​share​ ​money​ ​with​ ​an​ ​individual
■ Opponents​ ​were​ ​either​ ​facially​ ​different​ ​or​ ​manipulated​ ​to​ ​resemble
their​ ​own
■ Showed​ ​more​ ​trusting​ ​behaviour​ ​towards​ ​opponents​ ​who​ ​resembled
them
● Human​ ​adoption
○ The​ ​adoption​ ​of​ ​unrelated​ ​children​ ​has​ ​been​ ​used​ ​as​ ​evidence​ ​against​ ​kin
selection,​ ​as​ ​raising​ ​unrelated​ ​children​ ​will​ ​not​ ​provide​ ​genetic​ ​benefits​ ​to​ ​the
giver
○ Silk​ ​(1990)
■ Observed​ ​that​ ​among​ ​Polynesian​ ​cultures,​ ​a​ ​substantial​ ​number​ ​of
adopters​ ​cared​ ​for​ ​children​ ​who​ ​were​ ​cousin​ ​equivalents​ ​or​ ​closer
● Families​ ​who​ ​adopted​ ​unrelated​ ​children​ ​tended​ ​to​ ​be
agricultural​ ​families​ ​who​ ​needed​ ​an​ ​extra​ ​hand
○ Stack​ ​(1974)
■ In​ ​Chicago,​ ​found​ ​that​ ​the​ ​majority​ ​of​ ​foster​ ​children​ ​were​ ​adopted​ ​by
kin
○ Adopting​ ​unrelated​ ​children​ ​is​ ​a​ ​recent​ ​Western​ ​phenomenon
■ Alcock​ ​(1993)
● Argues​ ​that​ ​the​ ​urge​ ​to​ ​produce​ ​children​ ​and​ ​look​ ​after​ ​them​ ​is
so​ ​beneficial​ ​in​ ​reproductive​ ​terms​ ​that​ ​it​ ​has​ ​become​ ​deeply
ingrained
Problems​ ​for​ ​kin​ ​selection
- Kin​ ​selection​ ​does​ ​not​ ​explain​ ​observed​ ​incidents​ ​of​ ​animals​ ​helping​ ​non-relatives
- Eg
...
​ ​vampire​ ​bats​ ​will​ ​feed​ ​non-relatives​ ​(Wilkinson,​ ​1990)
- Humans​ ​will​ ​often​ ​engage​ ​in​ ​apparently​ ​altruistic​ ​acts​ ​such​ ​as:
- Giving​ ​blood
- Donating​ ​to​ ​charity
- Forgoing​ ​reproduction
- Rescuing​ ​unrelated​ ​individuals​ ​(and​ ​even​ ​animals)
- Sacrificing​ ​their​ ​lives​ ​for​ ​moral​ ​or​ ​ethical​ ​principles
--------------------------------------------------------------------------------------------------------------------------●

11:​ ​SEXUAL​ ​SELECTION​ ​AND​ ​HUMANS
●

Sexual​ ​selection:​ ​Darwin’s​ ​attempt​ ​to​ ​explain​ ​traits​ ​that​ ​defied​ ​natural​ ​(viability)
selection
○ Traits​ ​that​ ​negatively​ ​impact​ ​fitness​ ​rather​ ​than​ ​improving​ ​it

Joanna​ ​Griffith​ ​(2017)

Form​ ​of​ ​selection​ ​that​ ​accounts​ ​for​ ​many​ ​elaborate​ ​traits​ ​and​ ​behaviours​ ​in
organisms
■ Arises​ ​from​ ​differences​ ​in​ ​the​ ​ability​ ​to​ ​find​ ​and​ ​mate​ ​with​ ​members​ ​of
the​ ​opposite​ ​sex
■ Only​ ​occurs​ ​when​ ​access​ ​to​ ​the​ ​other​ ​sex​ ​is​ ​limiting​ ​(ie
...
​ ​peacocks,
irish​ ​elk)
● Sexual​ ​dimorphism​ ​in​ ​body​ ​characteristics​ ​can​ ​indicate​ ​that​ ​sexual​ ​selection​ ​is​ ​going
on
○ Eg
...
​ ​many​ ​female​ ​insects​ ​(such​ ​as​ ​the​ ​female​ ​bush​ ​cricket)
gain​ ​direct​ ​benefits​ ​by​ ​consuming​ ​a​ ​portion​ ​of​ ​the
spermatophore​ ​presented​ ​to​ ​them​ ​by​ ​males
○

Joanna​ ​Griffith​ ​(2017)

○

More​ ​spermatophores​ ​eaten​ ​=​ ​more​ ​eggs​ ​laid

Indirect​ ​benefits
■ Good​ ​genes​ ​hypothesis:​ ​genetically​ ​superior​ ​mates​ ​produce​ ​fitter
offspring)
■ Sexy​ ​son​ ​hypothesis:​ ​females​ ​that​ ​mate​ ​with​ ​preferred​ ​fathers
produce​ ​sons​ ​that​ ​will​ ​have​ ​high​ ​mating​ ​success​ ​(not​ ​necessarily
genes​ ​that​ ​improve​ ​fitness)
● Good​ ​genes​ ​model
○ Elaborated​ ​male​ ​traits​ ​may​ ​be​ ​indicators​ ​of​ ​heritable​ ​genetic​ ​fitness
○ The​ ​handicap​ ​principle​ ​(Zahavi,​ ​1975)
■ Males​ ​have​ ​a​ ​heritable​ ​trait​ ​to​ ​show​ ​off​ ​that​ ​reduces​ ​fitness,​ ​so​ ​only
the​ ​males​ ​with​ ​the​ ​best​ ​genes​ ​can​ ​survive​ ​despite​ ​the​ ​handicap
● Females​ ​that​ ​mate​ ​with​ ​these​ ​males​ ​will​ ​have​ ​offspring​ ​with
higher​ ​fitness
● Eg
...
​ ​Trinidad​ ​guppies
● Female​ ​guppies​ ​are​ ​attracted​ ​to​ ​orange,​ ​a​ ​response​ ​that​ ​may
be​ ​due​ ​to​ ​feeding​ ​behaviour​ ​selecting​ ​for​ ​the​ ​ability​ ​to​ ​locate
ripe​ ​fruit
○ Sexual​ ​selection​ ​then​ ​favours​ ​males​ ​with​ ​a​ ​lot​ ​of
orange​ ​on​ ​them
Intrasexual​ ​selection
● Usually​ ​male-male​ ​competition
○ Strategies​ ​used​ ​to​ ​compete​ ​with​ ​members​ ​of​ ​the​ ​same​ ​sex​ ​for​ ​access​ ​to
members​ ​of​ ​the​ ​opposite​ ​sex
○

Joanna​ ​Griffith​ ​(2017)

Not​ ​often​ ​female-female​ ​competition​ ​as​ ​female​ ​ornamentation​ ​is​ ​produced​ ​at
the​ ​expense​ ​of​ ​their​ ​offspring,​ ​which​ ​makes​ ​them​ ​lose​ ​fitness
● Eg
...
​ ​irish​ ​elk
○ Male-male​ ​competition​ ​can​ ​explain​ ​the​ ​evolution​ ​of​ ​many​ ​morphological​ ​and
behavioural​ ​traits
■ Eg
...
​ ​small​ ​“jack”​ ​salmon
■ Female​ ​mimicry:​ ​to​ ​distract​ ​or​ ​interrupt​ ​a​ ​competitor
● Eg
...
​ ​male​ ​dendrobatid​ ​frogs,​ ​male​ ​giant​ ​water​ ​bugs
● Stronger​ ​sexual​ ​selection​ ​on​ ​females​ ​leads​ ​to​ ​the​ ​expression​ ​of​ ​secondary​ ​sexual
characteristics​ ​in​ ​females
○ Eg
...
​ ​DNA
fingerprinting​ ​and​ ​microsatellites)​ ​allow​ ​the​ ​direct​ ​assessment
of​ ​paternity
○ Evidence​ ​suggests​ ​that​ ​polyandry​ ​(females​ ​mating​ ​with
more​ ​than​ ​one​ ​male)​ ​is​ ​far​ ​more​ ​common​ ​in​ ​nature
than​ ​was​ ​assumed​ ​based​ ​on​ ​behavioural​ ​observations
○

Joanna​ ​Griffith​ ​(2017)

Eg
...
​ ​in​ ​China,​ ​both​ ​male​ ​and​ ​female​ ​chastity​ ​is​ ​important,​ ​and​ ​in
Nigeria,​ ​female​ ​chastity​ ​is​ ​extremely​ ​important​ ​to​ ​males
○ Good​ ​financial​ ​prospects​ ​is​ ​uniform​ ​across​ ​all​ ​cultures
Male​ ​mate​ ​preferences
●

Joanna​ ​Griffith​ ​(2017)

●

Youth
○ Female​ ​maximum​ ​fecundity​ ​is​ ​at​ ​about​ ​26​ ​years​ ​old
● Waist-to-hip​ ​ratio​ ​of​ ​0
...
​ ​Hadza,​ ​Tanzania
■ Males​ ​bring​ ​back​ ​more​ ​food​ ​if​ ​only​ ​their​ ​biological​ ​children​ ​are​ ​home,
and​ ​less​ ​food​ ​if​ ​stepchildren​ ​are​ ​home
Grandparental​ ​care
● Grandparents​ ​can​ ​provide​ ​dramatic​ ​fitness​ ​benefits​ ​to​ ​offspring
● Certainty​ ​of​ ​parenthood​ ​affects​ ​amount​ ​of​ ​grandparental​ ​investment
○ Mother’s​ ​mother​ ​has​ ​greatest​ ​certainty​ ​of​ ​parenthood
○ Father’s​ ​mother​ ​and​ ​mother’s​ ​father​ ​are​ ​intermediate
○ Father’s​ ​father​ ​has​ ​least​ ​certainty​ ​of​ ​parenthood
■ 3%​ ​possibility​ ​that​ ​their​ ​son​ ​is​ ​not​ ​the​ ​father​ ​of​ ​their​ ​grandchild
● Mothers​ ​with​ ​their​ ​mothers​ ​alive​ ​and​ ​living​ ​nearby​ ​have​ ​children​ ​earlier,​ ​and​ ​have
more​ ​overall
○ Menopause​ ​may​ ​stop​ ​mothers​ ​from​ ​reproducing​ ​so​ ​that​ ​they​ ​are​ ​free​ ​to
improve​ ​the​ ​fitness​ ​of​ ​their​ ​lineage​ ​by​ ​helping​ ​to​ ​care​ ​for​ ​their​ ​grandchildren
■ Competition​ ​of​ ​their​ ​own​ ​new​ ​offspring​ ​may​ ​interfere​ ​with​ ​the​ ​fitness​ ​of
the​ ​offspring​ ​of​ ​their​ ​previous​ ​offspring
Discriminative​ ​parental​ ​solicitude
● quality/quantity​ ​trade-off
○ Pregnancy​ ​is​ ​terminated​ ​if:
■ Mother​ ​is​ ​in​ ​poor​ ​health
● Pregnancy​ ​and​ ​lactation​ ​are​ ​costly
● Gambling​ ​perspective
○ Mothers​ ​will​ ​choose​ ​to​ ​protect​ ​themselves​ ​(thus
ensuring​ ​the​ ​possibility​ ​of​ ​future​ ​offspring)​ ​over​ ​current
attempts
■ Fetus​ ​has​ ​a​ ​genetic​ ​defect
■ 78%​ ​of​ ​pregnancies​ ​miscarry
○ Mothers​ ​are​ ​always​ ​thinking​ ​about​ ​future​ ​returns
Parental​ ​resource​ ​allocation
● Males​ ​must​ ​often​ ​compete​ ​for​ ​limited​ ​numbers​ ​of​ ​females
○ Bridewealth:​ ​male​ ​giving​ ​resources​ ​to​ ​the​ ​female’s​ ​family
○ Dowry:​ ​female​ ​giving​ ​resources​ ​to​ ​the​ ​male’s​ ​family
○ Bridewealth​ ​is​ ​much​ ​more​ ​common,​ ​particularly​ ​in​ ​polygynous​ ​cultures
● In​ ​times​ ​of​ ​limited​ ​resources,​ ​some​ ​species,​ ​eg
...
​ ​nonbiological​ ​parents
● Stepchildren​ ​are​ ​usually​ ​not​ ​given​ ​as​ ​much​ ​parental​ ​investment​ ​as​ ​biological​ ​children
○ Eg
...
25​ ​degree​ ​of
relatedness​ ​(cousins,​ ​nieces,​ ​nephews)
● Is​ ​adoption​ ​contrary​ ​to​ ​evolutionary​ ​theory?
○ In​ ​Oceania,​ ​most​ ​adoptions​ ​are​ ​by​ ​close​ ​kin
● Proximate​ ​mechanisms​ ​for​ ​adoption
○ Parental​ ​instinct​ ​tends​ ​to​ ​be​ ​aroused​ ​in​ ​childless​ ​couples
■ Inability​ ​to​ ​have​ ​children​ ​is​ ​the​ ​most​ ​common​ ​reason​ ​for​ ​seeking
adoption
■ Many​ ​childless​ ​couples​ ​treat​ ​pets​ ​like​ ​children
○ Some​ ​animals,​ ​eg
...
​ ​testosterone
● Correlated​ ​traits
○ Fast​ ​life​ ​history
■ Reproduce​ ​early
■ Small​ ​body,​ ​small​ ​brain
■ Short​ ​gestation
■ Large​ ​litters
■ High​ ​mortality​ ​rate
■ Short​ ​life​ ​span
○ Slow​ ​life​ ​history
■ Reproduce​ ​late
■ Large​ ​body,​ ​large​ ​brain
■ Long​ ​gestation
■ Small​ ​litters
■ Low​ ​mortality​ ​rate
Joanna​ ​Griffith​ ​(2017)

■ Long​ ​life​ ​span
● Other​ ​fundamental​ ​life​ ​history​ ​trade-offs:
○ Investment​ ​per​ ​offspring​ ​vs
...
​ ​future​ ​survival​ ​and​ ​reproduction
○ Reproduction​ ​vs
...
​ ​producing​ ​sons​ ​reduces​ ​lifetime​ ​reproductive​ ​success​ ​of
subsequent​ ​offspring​ ​in​ ​pre-industrial​ ​Finns)
The​ ​expression​ ​of​ ​trade-offs​ ​may​ ​depend​ ​upon​ ​overall​ ​levels​ ​of​ ​available​ ​resources
● Car-house​ ​paradox
○ With​ ​monetary​ ​trade-offs,​ ​why​ ​do​ ​people​ ​either​ ​have​ ​a​ ​fancy​ ​car​ ​AND​ ​a​ ​big
house​ ​or​ ​neither?
■ Because​ ​people​ ​vary​ ​in​ ​levels​ ​of​ ​overall​ ​resources,​ ​and​ ​people​ ​lower
in​ ​overall​ ​resources​ ​are​ ​subject​ ​to​ ​stronger​ ​trade-offs
■ Only​ ​people​ ​with​ ​a​ ​large​ ​amount​ ​of​ ​resources​ ​ever​ ​bother​ ​to​ ​get​ ​both
the​ ​car​ ​and​ ​the​ ​house
○ Implications​ ​for​ ​health
■ Individuals​ ​with​ ​fewer​ ​resources​ ​are​ ​affected​ ​by​ ​stronger​ ​trade-offs,
which​ ​affect​ ​health​ ​more,​ ​and​ ​the​ ​individuals​ ​are​ ​more​ ​subject​ ​to
resource​ ​stress
Resource​ ​allocation​ ​in​ ​different​ ​environments
● General​ ​principle:
○ In​ ​an​ ​unstable​ ​environment​ ​(population​ ​is​ ​below​ ​carrying​ ​capacity​ ​(K)),
organisms​ ​invest​ ​in​ ​breeding​ ​early​ ​and​ ​producing​ ​small​ ​offspring,​ ​thus
maximising​ ​growth​ ​rate​ ​(r)
■ “Weeds”
○ in​ ​a​ ​stable​ ​environment​ ​(population​ ​is​ ​at​ ​carrying​ ​capacity​ ​(K)),​ ​organisms
invest​ ​in​ ​provisioning​ ​for​ ​their​ ​offspring,​ ​at​ ​the​ ​cost​ ​of​ ​producing​ ​fewer
offspring,​ ​thus​ ​maximising​ ​competitive​ ​ability
■ “Trees”
○ These​ ​strategies​ ​are​ ​called​ ​r-selected​ ​(weeds,​ ​selected​ ​by​ ​growth​ ​rate)​ ​vs
...
​ ​pygmy​ ​elephants​ ​(Borneo),​ ​pygmy​ ​hippos​ ​(West​ ​Africa),​ ​pygmy​ ​possums
(Australia),​ ​Baka​ ​pygmies​ ​(Africa),​ ​Batak​ ​pygmies​ ​(Philippines)
○ Why​ ​are​ ​pygmies​ ​small?
■ Live​ ​in​ ​a​ ​dangerous​ ​environment​ ​(life​ ​expectancy​ ​is​ ​between​ ​16​ ​and
24,​ ​compared​ ​with​ ​34-48​ ​in​ ​non-pygmy​ ​hunter-gatherer​ ​environments)
● To​ ​ensure​ ​that​ ​enough​ ​individuals​ ​survive​ ​to​ ​reproduce,
pygmies​ ​reach​ ​sexual​ ​maturity​ ​earlier​ ​(fertility​ ​peaks​ ​at​ ​20-24
compared​ ​with​ ​30-34​ ​in​ ​non-pygmy​ ​hunter-gatherer
communities)​ ​at​ ​the​ ​cost​ ​of​ ​reduced​ ​allocation​ ​of​ ​limited
resources​ ​to​ ​growth​ ​(determinate​ ​growth​ ​-​ ​pygmies​ ​stop
growing​ ​at​ ​the​ ​age​ ​of​ ​14​ ​rather​ ​than​ ​18,​ ​but​ ​grow​ ​at​ ​a​ ​similar
rate​ ​to​ ​non-pygmies)
■ R-selected
■ Hastened​ ​maturity​ ​is​ ​the​ ​goal​ ​of​ ​adaptive​ ​evolution,​ ​short​ ​stature​ ​is​ ​the
price​ ​paid
Proximate​ ​and​ ​ultimate​ ​causes​ ​of​ ​trade-offs​ ​in​ ​human​ ​health​ ​and​ ​disease
● Central​ ​role​ ​of​ ​hormones
○ Hormones​ ​mediate​ ​flow,​ ​distribution,​ ​rate​ ​of​ ​consumption​ ​of​ ​glucose​ ​and​ ​fat,
among​ ​competing​ ​physiological​ ​functions
○ Hormones​ ​implement​ ​trade-offs​ ​between​ ​growth,​ ​reproduction,​ ​and​ ​survival
○ Eg
...
​ ​future
offspring,​ ​mediated​ ​by:
● Nursing​ ​and​ ​mother’s​ ​condition​ ​via​ ​lactational​ ​amenorrhea
(affecting​ ​prolactin​ ​levels)​ ​and​ ​by​ ​the​ ​timing​ ​of​ ​the​ ​introduction
of​ ​supplementary​ ​foods
○ Influences​ ​the​ ​timing​ ​of​ ​the​ ​start​ ​of​ ​the​ ​next​ ​menstrual
cycle
● Fecundity​ ​during​ ​waiting​ ​time​ ​to​ ​next​ ​conception
○ Poor​ ​energetic​ ​condition​ ​(and​ ​low​ ​ovarian​ ​steroid
levels)​ ​are​ ​associated​ ​with​ ​reduced​ ​ovulation​ ​frequency
■ May​ ​produce​ ​male-female​ ​and​ ​mother-offspring
conflict​ ​over​ ​next​ ​conception,​ ​with​ ​mechanisms
that​ ​may​ ​become​ ​dysregulated
■ Trade-off​ ​between​ ​offspring​ ​number​ ​and​ ​quality
● Mothers​ ​may​ ​also​ ​benefit​ ​from​ ​a​ ​faster​ ​reproductive​ ​rate​ ​and
shorter​ ​interbirth​ ​intervals,​ ​even​ ​when​ ​doing​ ​so​ ​involves​ ​higher
offspring​ ​mortality
■ Three​ ​stages​ ​of​ ​fecundity
● Rise​ ​over​ ​the​ ​first​ ​decade​ ​after​ ​menarche​ ​(slow​ ​climb​ ​to​ ​full
fertility)
○ May​ ​be​ ​due​ ​to​ ​selection​ ​against​ ​high​ ​potential
survivorship​ ​costs​ ​of​ ​childbearing​ ​for​ ​younger​ ​females
● Fairly​ ​stable​ ​from​ ​mid-20s​ ​to​ ​mid-30s
● Decline​ ​to​ ​menopause​ ​at​ ​about​ ​50
○ Proximately​ ​due​ ​to​ ​depletion​ ​of​ ​follicles​ ​(number​ ​fixed
at​ ​birth)
■ Disorders​ ​of​ ​this​ ​process​ ​are​ ​premature​ ​ovarian
failure​ ​and​ ​polycystic​ ​ovary​ ​syndrome
○ Ultimately​ ​may​ ​be​ ​due​ ​to​ ​some​ ​combination​ ​of:
■ Higher​ ​risks​ ​of​ ​childbearing​ ​with​ ​increased​ ​age
■ Higher​ ​risk​ ​of​ ​death​ ​from​ ​other​ ​causes​ ​with
increased​ ​age​ ​(for​ ​self​ ​and​ ​mate)
Joanna​ ​Griffith​ ​(2017)

Benefits​ ​from​ ​enhancing​ ​the​ ​reproduction​ ​of
one’s​ ​children​ ​and​ ​grandchildren
○ Trade-off​ ​between​ ​existing​ ​and​ ​future​ ​children,​ ​and
future​ ​reproduction​ ​and​ ​survival
● Medical​ ​implications​ ​of​ ​trade-offs​ ​in​ ​human​ ​life​ ​history
○ Declines​ ​in​ ​testosterone​ ​with​ ​age​ ​lead​ ​to​ ​increased​ ​risk​ ​of​ ​obesity,​ ​insulin
resistance,​ ​and​ ​cardiovascular​ ​disease
■ Testosterone​ ​supplementation​ ​may​ ​increase​ ​mortality​ ​in​ ​individuals
under​ ​energy​ ​limitation
○ Exposure​ ​to​ ​reproductive​ ​hormones​ ​(including​ ​contraceptives)​ ​and​ ​older​ ​age
at​ ​first​ ​birth​ ​in​ ​women​ ​can​ ​increase​ ​the​ ​risk​ ​of​ ​some​ ​reproductive​ ​cancers
(breast,​ ​ovarian,​ ​testicular,​ ​prostate,​ ​uterine,​ ​cervical)
○ Hormone​ ​physiology​ ​and​ ​trade-offs​ ​may​ ​differ​ ​between​ ​human​ ​populations
historically​ ​exposed​ ​to​ ​different​ ​selective​ ​pressures​ ​affecting​ ​life​ ​history​ ​(eg
...
​ ​reproduction
--------------------------------------------------------------------------------------------------------------------------■

15:​ ​THE​ ​EVOLUTION​ ​OF​ ​HUMAN​ ​INTELLIGENCE
Big​ ​brains​ ​and​ ​long​ ​lives
● Longevity​ ​via​ ​selection​ ​on​ ​brains
○ Primates​ ​are​ ​able​ ​to​ ​learn,​ ​but​ ​there​ ​is​ ​no​ ​point​ ​learning​ ​if​ ​there​ ​is​ ​no​ ​time​ ​to
apply​ ​the​ ​knowledge
● Primate​ ​characteristics
○ Large​ ​brains
○ Long​ ​childhood
○ Learned​ ​behaviours
○ Behavioural​ ​flexibility
○ Long​ ​lives
● Life​ ​history​ ​theory
○ Primates​ ​have​ ​long​ ​life​ ​histories
■ Slow​ ​maturation
■ Large​ ​brain
■ Long​ ​gestation
■ Small​ ​litters
■ Long​ ​lifespan
■ Variation​ ​within​ ​primates
● Monkeys​ ​have​ ​slower​ ​life​ ​histories​ ​than​ ​strepsirrhines
● Apes​ ​have​ ​slower​ ​life​ ​histories​ ​than​ ​monkeys
● Orangutans​ ​have​ ​the​ ​slowest​ ​life​ ​histories
○ Humans​ ​are​ ​still​ ​brainier

Joanna​ ​Griffith​ ​(2017)

■

Suggests​ ​that​ ​the​ ​correlation​ ​between​ ​brain​ ​size
and​ ​longevity​ ​is​ ​not​ ​simple

Evolution​ ​of​ ​the​ ​large​ ​primate​ ​brain
● Hypotheses
○ Social​ ​intelligence​ ​hypothesis
■ Social​ ​intelligence:​ ​the​ ​ability​ ​to​ ​effectively​ ​navigate​ ​and​ ​negotiate
complex​ ​social​ ​relationships​ ​and​ ​environments
■ Sociability​ ​requires​ ​greater​ ​awareness​ ​for​ ​individuals​ ​around​ ​you​ ​and
relationships,​ ​therefore​ ​brain​ ​size​ ​increases​ ​to​ ​enable​ ​individuals​ ​to
process​ ​this​ ​wider​ ​dimensional​ ​world
○ Ecological​ ​challenges​ ​hypothesis
■ Mental​ ​mapping​ ​of​ ​fruit
● Frugivorous​ ​primates​ ​can​ ​remember​ ​where​ ​trees​ ​are​ ​and​ ​how
productive​ ​they​ ​are,​ ​allowing​ ​them​ ​to​ ​consume​ ​more​ ​fruit
○ Primates​ ​who​ ​evolved​ ​this​ ​ability​ ​had​ ​larger​ ​brains,​ ​and
they​ ​were​ ​better​ ​equipped​ ​to​ ​survive
■ Extractive​ ​foraging
● Exploiting​ ​foods​ ​that​ ​are​ ​difficult​ ​to​ ​get​ ​to​ ​and​ ​process​ ​requires
special​ ​cognitive​ ​skills​ ​in​ ​primates
○ Behavioural​ ​flexibility​ ​hypothesis
■ Primates​ ​can​ ​learn​ ​new​ ​solutions​ ​to​ ​problems​ ​from​ ​others
○ A​ ​large​ ​brain​ ​would​ ​allow​ ​primates​ ​to​ ​better​ ​cope​ ​with​ ​both​ ​ecological​ ​and
social​ ​problems
■ Ecological​ ​problems
● Processing​ ​inaccessible​ ​food​ ​items
● Locating​ ​and​ ​remembering​ ​food​ ​sources
● Navigating​ ​between​ ​food​ ​sources
■ Social​ ​problems
● Keeping​ ​track​ ​of​ ​kin
● Keeping​ ​track​ ​of​ ​relative​ ​rank
● Remembering​ ​benefits​ ​given​ ​and​ ​received
● Manipulating​ ​rivals
● Managing​ ​coalitions
● Brain​ ​structure
○ Frontal​ ​lobe
■ Reasoning
■ Decision-making
■ Emotions
■ Personality
○ Temporal​ ​lobe
■ Memory
■ Auditory​ ​information
○ Cerebellum
■ Posture​ ​and​ ​balance
■ Coordination​ ​of​ ​movement
○ Occipital​ ​lobe

Joanna​ ​Griffith​ ​(2017)

■ Colour​ ​vision
■ Shape​ ​recognition
■ Perspective
○ Parietal​ ​lobe
■ Memory​ ​and​ ​recognition
■ Movement,​ ​sensation,​ ​orientation
○ Hypothalamus
■ Thermoregulation
■ Controls​ ​the​ ​pituitary​ ​gland
■ Autonomic​ ​nervous​ ​system
■ Controls​ ​the​ ​basics​ ​(eg
...
​ ​controls​ ​the​ ​heartbeat)
○ Human​ ​brains​ ​are​ ​larger​ ​and​ ​more​ ​“wrinkly”​ ​than​ ​primate​ ​brains
■ Wrinkliness​ ​increases​ ​volume
○ Body​ ​size​ ​affects​ ​the​ ​size​ ​of​ ​the​ ​brain,​ ​so​ ​ratios​ ​are​ ​used
○ Neocortex​ ​ratio
■ Neocortex:​ ​most​ ​recently​ ​evolved​ ​part​ ​of​ ​the​ ​brain,​ ​involved​ ​in​ ​sight
and​ ​hearing​ ​in​ ​mammals
■ Correlated​ ​with​ ​group​ ​size​ ​in​ ​primates​ ​(although​ ​apes​ ​are​ ​more
intelligent​ ​despite​ ​smaller​ ​group​ ​size)
● Supports​ ​the​ ​social​ ​intelligence​ ​hypothesis
■ Higher​ ​in​ ​fruit-eating​ ​primates​ ​with​ ​larger​ ​home​ ​ranges
● Supports​ ​the​ ​ecological​ ​hypothesis
■ Not​ ​all​ ​primates​ ​are​ ​good​ ​at​ ​everything
● Eg
...
​ ​adult​ ​apes
■ Equal​ ​ability​ ​in​ ​physical​ ​tasks
■ Humans​ ​outperform​ ​apes​ ​in​ ​social​ ​tasks
Human​ ​uniqueness
○ Large​ ​brain
■ Huge​ ​cerebral​ ​hemisphere​ ​(frontal​ ​lobe)​ ​compared​ ​to​ ​most​ ​mammals
(Deacon,​ ​1997)
○ Brain​ ​is​ ​functionally​ ​lateralized​ ​(tasks​ ​are​ ​performed​ ​by​ ​one​ ​side​ ​of​ ​the​ ​brain
or​ ​the​ ​other)​ ​in​ ​a​ ​way​ ​which​ ​differs​ ​from​ ​chimpanzees
○ Brain​ ​may​ ​be​ ​metabolically​ ​enhanced​ ​(Cacares​ ​et​ ​al,​ ​2003)
■ May​ ​include​ ​different​ ​physiological​ ​components​ ​(Allman​ ​et​ ​al,​ ​2005)
○ Humans​ ​have​ ​10​14​​ ​neurons​ ​in​ ​the​ ​nervous​ ​system,​ ​over​ ​2x​ ​the​ ​number​ ​that
chimpanzees​ ​have
Brain​ ​reorganisation:​ ​expansion​ ​of​ ​the​ ​frontal​ ​lobes
○ Schoenemann​ ​et​ ​al​ ​(2005)
■ Suggested​ ​that​ ​prefrontal​ ​white​ ​matter​ ​is​ ​disproportionately​ ​larger​ ​in
humans​ ​than​ ​in​ ​other​ ​primates
○ Allman​ ​et​ ​al​ ​(2005)
■ Von​ ​Economo​ ​neurons​ ​(VENs)
● Recently​ ​evolved​ ​cell​ ​type
● May​ ​be​ ​involved​ ​in​ ​the​ ​fast​ ​intuitive​ ​assessment​ ​of​ ​complex
situations
○ Could​ ​be​ ​part​ ​of​ ​the​ ​circuitry​ ​supporting​ ​human​ ​social
networks
● Humans​ ​shown​ ​to​ ​have​ ​a​ ​large​ ​number​ ​of​ ​these
○ Very​ ​interconnected​ ​throughout​ ​the​ ​brain
Functional​ ​differences:​ ​cultural​ ​learning​ ​and​ ​invention
○ Tomasello​ ​and​ ​Rakoczy​ ​(2003)
■ Argue​ ​that​ ​there​ ​are​ ​two​ ​(initial)​ ​stages​ ​of​ ​uniquely​ ​human​ ​social
cognition
● First​ ​stage​ ​is​ ​observable​ ​in​ ​one-year-olds
○ Have​ ​an​ ​understanding​ ​of​ ​others​ ​as​ ​intentional​ ​agents
■ Allows​ ​them​ ​to​ ​take​ ​part​ ​in​ ​pretend​ ​play
■ Important​ ​as​ ​a​ ​prerequisite​ ​for​ ​shared​ ​attention
and​ ​early​ ​social​ ​and​ ​linguistic​ ​learning
● Second​ ​stage​ ​is​ ​‘theory​ ​of​ ​mind’​ ​belief-desire​ ​psychology
which​ ​normally​ ​starts​ ​around​ ​four​ ​years​ ​of​ ​age
○ Dependent​ ​on​ ​several​ ​years​ ​of​ ​linguistic
communication
■ Early​ ​stages​ ​of​ ​uniquely​ ​human​ ​social​ ​cognition​ ​enable​ ​the​ ​cultural
“ratchet”​ ​of​ ​social​ ​and​ ​technological​ ​innovation
Understanding​ ​and​ ​sharing​ ​intentions
○ A​ ​species-unique​ ​motivation​ ​to​ ​share​ ​emotions,​ ​experiences,​ ​and​ ​activities
with​ ​other​ ​people
■ Leads​ ​to​ ​a​ ​“species-unique​ ​form​ ​of​ ​cultural​ ​cognition​ ​and​ ​evolution”
○ Especially​ ​important​ ​when​ ​manufacturing​ ​of​ ​tools​ ​became​ ​more​ ​common
○

●

●

●

●

Joanna​ ​Griffith​ ​(2017)

--------------------------------------------------------------------------------------------------------------------------16:​ ​COGNITION​ ​AND​ ​THE​ ​MODULAR​ ​MIND
Swiss​ ​army​ ​knife​ ​analogy
○ Evolutionary​ ​psychology
■ The​ ​swiss​ ​army​ ​knife​ ​is​ ​a​ ​flexible​ ​tool,​ ​as​ ​it​ ​has​ ​a​ ​bundle​ ​of​ ​tools,​ ​and
each​ ​is​ ​well-designed​ ​for​ ​solving​ ​a​ ​particular​ ​problem
● Similarly,​ ​different​ ​parts​ ​of​ ​the​ ​brain​ ​all​ ​have​ ​different​ ​functions
to​ ​handle​ ​a​ ​range​ ​of​ ​situations
A​ ​modular​ ​mind
● Modules​ ​of​ ​the​ ​brain​ ​are​ ​organised​ ​by​ ​function
● Modules​ ​have​ ​been​ ​generated​ ​by​ ​evolutionary​ ​processes​ ​throughout​ ​human​ ​history
○ Assumed​ ​that​ ​they​ ​mainly​ ​developed​ ​during​ ​the​ ​Pleistocene​ ​(2​ ​million​ ​years
ago​ ​to​ ​10,000​ ​years​ ​ago),​ ​when​ ​our​ ​ancestors​ ​lived​ ​in​ ​small​ ​kin-based
hunter-gatherer​ ​societies
● There​ ​are​ ​cross-cultural​ ​differences
○ Evolutionary​ ​psychology​ ​predicts​ ​that​ ​the​ ​evolved​ ​cognitive​ ​mechanisms
(modules)​ ​should​ ​be​ ​context-dependent,​ ​as​ ​differential​ ​inputs​ ​(provided​ ​by
different​ ​environments)​ ​should​ ​evoke​ ​different​ ​representational​ ​and
behavioural​ ​outputs
■ Eg
...
)
○ Few​ ​lifestyle​ ​options
○ However,​ ​it​ ​must​ ​be​ ​considered​ ​that​ ​there​ ​is​ ​no​ ​concrete​ ​evidence​ ​that​ ​shows
exactly​ ​what​ ​the​ ​EEA​ ​was​ ​like​ ​(Badcock,​ ​2000)
Impact​ ​on​ ​modern​ ​life
● Adaptations​ ​to​ ​the​ ​EEA​ ​may​ ​now​ ​affect​ ​modern​ ​life
○ Humans​ ​have​ ​developed​ ​psychological​ ​mechanisms​ ​(and​ ​later,​ ​culture)​ ​to
solve​ ​problems​ ​related​ ​to​ ​the​ ​lifestyle​ ​of​ ​a​ ​hunter-gatherer
○ Some​ ​of​ ​these​ ​adaptations​ ​are​ ​not​ ​necessarily​ ​adaptive​ ​to​ ​modern​ ​humans,
eg
...
​ ​lactose​ ​tolerance)
● Different​ ​populations​ ​may​ ​lead​ ​very​ ​different​ ​lives​ ​depending​ ​on​ ​their​ ​environments
● Tooby​ ​and​ ​Cosmides​ ​(1992)
○ Stated​ ​that​ ​there​ ​is​ ​no​ ​single​ ​EEA,​ ​but​ ​that​ ​each​ ​adaptation​ ​can​ ​be​ ​viewed​ ​as
a​ ​statistical​ ​aggregate​ ​of​ ​selection​ ​pressures​ ​over​ ​a​ ​particular​ ​time​ ​period
Domain​ ​specificity
● The​ ​more​ ​important​ ​the​ ​adaptive​ ​problem,​ ​the​ ​more​ ​intensely​ ​natural​ ​selection​ ​will
improve​ ​and​ ​specialise​ ​the​ ​mechanism​ ​for​ ​solving​ ​it
○ Therefore,​ ​Darwinian​ ​algorithms​ ​become​ ​domain-specific​ ​-​ ​they​ ​are​ ​designed
to​ ​solve​ ​specific​ ​rather​ ​than​ ​general​ ​problems
■ Eg
...
​ ​swiss​ ​army​ ​knife​ ​analogy,​ ​Cosmides)
● Example:​ ​algorithms​ ​for​ ​social​ ​exchange
○ Social​ ​exchange​ ​behaviour​ ​is​ ​universal​ ​and​ ​highly​ ​elaborated​ ​in​ ​present
human​ ​cultures
■ Must​ ​have​ ​been​ ​an​ ​important​ ​feature​ ​of​ ​our​ ​evolutionary​ ​history
● Trading​ ​tools
● Sharing​ ​food
● Making​ ​and​ ​swapping​ ​alliances
● Soliciting​ ​help​ ​when​ ​faced​ ​with​ ​aggression
● Cooperation​ ​in​ ​hunting
● Gaining​ ​access​ ​to​ ​mates
● Sharing​ ​information​ ​about​ ​resources
● Sharing​ ​social​ ​information
■ Chimpanzees​ ​engage​ ​in​ ​similar​ ​forms​ ​of​ ​social​ ​exchange​ ​and
reciprocation
○ Spotting​ ​a​ ​cheater
■ The​ ​key​ ​to​ ​success​ ​in​ ​social​ ​exchange​ ​is​ ​the​ ​ability​ ​to​ ​recognise​ ​and
expel​ ​a​ ​cheater​ ​from​ ​the​ ​system
● Traditional​ ​psychology​ ​argues​ ​that​ ​we​ ​learn​ ​such​ ​abilities
through​ ​the​ ​general​ ​purpose​ ​process​ ​of​ ​cultural​ ​transmission
○ Suggests​ ​that​ ​the​ ​logic​ ​underpinning​ ​such​ ​behaviour​ ​is
generalised
● Evolutionary​ ​psychology​ ​instead​ ​argues​ ​that​ ​we​ ​should​ ​have
developed​ ​specialised​ ​cognitive​ ​mechanisms​ ​for​ ​spotting
cheaters​ ​in​ ​such​ ​exchange​ ​situations
○ These​ ​skills​ ​are​ ​not​ ​generalised​ ​-​ ​they​ ​are​ ​domain
specific
○ Human​ ​social​ ​exchanges
■ Social​ ​exchanges​ ​can​ ​be​ ​viewed​ ​in​ ​terms​ ​of​ ​formal​ ​logic
■

Joanna​ ​Griffith​ ​(2017)

If​ ​the​ ​traditional​ ​psychology​ ​model​ ​is​ ​correct,​ ​we​ ​should​ ​be
equally​ ​skilled​ ​at​ ​all​ ​types​ ​of​ ​formal​ ​logic
■ The​ ​Wason​ ​selection​ ​task​ ​(Wason,​ ​1966)
● Measure​ ​of​ ​conditional​ ​hypotheses
○ ‘If​ ​P​ ​then​ ​Q’,​ ​the​ ​logically​ ​correct​ ​response​ ​is​ ​‘P​ ​and
not-Q’
● In​ ​a​ ​typical​ ​paradigm,​ ​students​ ​chose​ ​the​ ​correct​ ​solution​ ​less
than​ ​25%​ ​of​ ​the​ ​time
○ Most​ ​pick​ ​P,​ ​and​ ​then​ ​wrongly​ ​select​ ​Q​ ​instead​ ​of​ ​not-Q
● Performance​ ​is​ ​always​ ​poor​ ​on​ ​traditional​ ​logic​ ​versions​ ​of​ ​the
task
■ Social​ ​contract​ ​versions​ ​of​ ​the​ ​Wason​ ​selection​ ​task
● Cosmides​ ​(1985)​ ​argued​ ​that​ ​individuals​ ​will​ ​be​ ​able​ ​to​ ​detect
violations​ ​of​ ​conditional​ ​rules​ ​when​ ​such​ ​rules​ ​represent
cheating​ ​on​ ​a​ ​social​ ​contract
○ Eg
...
​ ​history​ ​of​ ​cheating/trustworthiness​ ​and
irrelevant​ ​information)
● One​ ​week​ ​later,​ ​the​ ​same​ ​participants​ ​recognised​ ​the​ ​faces​ ​of
the​ ​cheaters​ ​more
■ Stone​ ​et​ ​al​ ​(2002)
● Reported​ ​a​ ​case​ ​of​ ​a​ ​patient​ ​with​ ​extensive​ ​brain​ ​damage
○ Performed​ ​as​ ​expected​ ​on​ ​Watson​ ​traditional​ ​logic
problems,​ ​but​ ​was​ ​severely​ ​impaired​ ​in​ ​Watson​ ​social
contract​ ​logic​ ​problems
■ Suggests​ ​that​ ​reasoning​ ​about​ ​social​ ​exchange
can​ ​be​ ​neurologically​ ​impaired
Can​ ​we​ ​judge​ ​a​ ​book​ ​by​ ​its​ ​cover?
○ Yamagishi​ ​et​ ​al​ ​(2003)
■ Identified​ ​people​ ​who​ ​either​ ​cooperated​ ​or​ ​cheated​ ​on​ ​a​ ​game
● Showed​ ​their​ ​pictures​ ​to​ ​participants​ ​with​ ​no​ ​knowledge​ ​of​ ​their
honesty
●

●

Joanna​ ​Griffith​ ​(2017)

Later​ ​asked​ ​to​ ​recognise​ ​the​ ​pictures​ ​amongst​ ​other
unseen​ ​pictures
■ Pictures​ ​of​ ​cheaters​ ​recognised​ ​significantly
better
Argued​ ​that​ ​cheaters​ ​may​ ​look​ ​different​ ​to​ ​non-cheaters,​ ​and​ ​that
people​ ​may​ ​be​ ​able​ ​to​ ​pick​ ​up​ ​on​ ​subtle​ ​facial​ ​cues
○

■

Interactionism
● Critics​ ​often​ ​state​ ​that​ ​evolutionary​ ​psychologists​ ​are​ ​deterministic​ ​because​ ​they
ignore​ ​the​ ​role​ ​of​ ​the​ ​environment​ ​in​ ​shaping​ ​human​ ​behaviour
○ This​ ​is​ ​not​ ​true,​ ​a​ ​key​ ​assumption​ ​underlying​ ​evolutionary​ ​psychology​ ​is​ ​that
behaviour​ ​is​ ​created​ ​by​ ​gene-environment​ ​interactions
■ Eg
...
​ ​because​ ​we​ ​possess
psychological​ ​and​ ​physiological​ ​mechanisms​ ​that​ ​make​ ​us​ ​want​ ​to​ ​do​ ​these
things
■ “Feelings”​ ​are​ ​a​ ​mechanism​ ​designed​ ​by​ ​evolution​ ​to​ ​ensure​ ​that​ ​the
individual​ ​attends​ ​to​ ​beneficial​ ​or​ ​harmful​ ​stimuli
Domain​ ​general​ ​and​ ​domain​ ​specific
● The​ ​swiss​ ​army​ ​knife​ ​analogy​ ​is​ ​more​ ​formally​ ​expressed​ ​in​ ​terms​ ​of​ ​modular
capacities​ ​or​ ​domain​ ​specific
○ It​ ​is​ ​also​ ​possible​ ​that​ ​general​ ​intelligence​ ​is​ ​also​ ​domain-specific
■ Opens​ ​the​ ​door​ ​to​ ​the​ ​idea​ ​that​ ​human​ ​evolution​ ​ended​ ​up​ ​by
providing​ ​us​ ​with​ ​very​ ​open-ended​ ​and​ ​general​ ​purpose​ ​physiological
capacities
● General​ ​intelligence​ ​as​ ​a​ ​domain-specific​ ​adaptation​ ​(Kanzawa,​ ​2004)
○ General​ ​intelligence​ ​creates​ ​a​ ​problem​ ​for​ ​the​ ​modular​ ​view​ ​of​ ​the​ ​human
brain
○ Argues​ ​that​ ​general​ ​intelligence​ ​evolved​ ​as​ ​a​ ​domain-specific​ ​adaptation​ ​for
the​ ​originally​ ​limited​ ​sphere​ ​of​ ​evolutionary​ ​novelty​ ​in​ ​the​ ​ancestral
environment
■ Has​ ​accidentally​ ​become​ ​universally​ ​important​ ​because​ ​we​ ​now​ ​live​ ​in
an​ ​evolutionary​ ​novel​ ​world
--------------------------------------------------------------------------------------------------------------------------Joanna​ ​Griffith​ ​(2017)

17:​ ​EVOLUTION​ ​OF​ ​LANGUAGE
Human​ ​language
● Phonemes
○ The​ ​human​ ​brain​ ​splits​ ​sounds​ ​into​ ​meaningful​ ​sections​ ​(words)
■ Discrete​ ​words​ ​are​ ​an​ ​illusion
○ Infants​ ​are​ ​born​ ​with​ ​the​ ​ability​ ​to​ ​distinguish​ ​all​ ​phonemes
○ Humans​ ​can​ ​decode​ ​10-25​ ​phonemes​ ​a​ ​second
○ Humans​ ​inherently​ ​understand​ ​grammar​ ​rules
● The​ ​major​ ​transitions​ ​(JMS​ ​and​ ​ES,​ ​1995)
○ Replicating​ ​molecules​ ​to​ ​populations​ ​of​ ​molecules​ ​in​ ​protocells
○ Independently​ ​replicating​ ​genes​ ​to​ ​chromosomes
○ RNA​ ​as​ ​genes​ ​and​ ​enzymes​ ​to​ ​DNA​ ​genes,​ ​protein​ ​enzymes
○ Bacterial​ ​cells​ ​(prokaryotes)​ ​to​ ​cells​ ​with​ ​nuclei​ ​and​ ​organelles​ ​(eukaryotes)
○ Asexual​ ​clones​ ​to​ ​sexual​ ​populations
○ Single-celled​ ​organisms​ ​to​ ​animals,​ ​plants,​ ​and​ ​fungi
○ Solitary​ ​individuals​ ​to​ ​colonies​ ​with​ ​non-reproductive​ ​castes
○ Prelinguistic​ ​societies​ ​to​ ​human​ ​societies​ ​with​ ​language
● What​ ​is​ ​language​ ​for?
○ Helps​ ​us​ ​to​ ​pass​ ​on​ ​and​ ​develop​ ​technologies​ ​(eg
...
​ ​hunting)
○ Allows​ ​humans​ ​to​ ​communicate​ ​knowledge​ ​about​ ​relevant​ ​aspects​ ​of​ ​the
environment
○ Helps​ ​humans​ ​to​ ​identify​ ​things​ ​with​ ​names​ ​and​ ​description
○ Allows​ ​expression​ ​of​ ​emotions
○ Allows​ ​us​ ​to​ ​remember​ ​and​ ​use​ ​the​ ​past,​ ​to​ ​plan​ ​for​ ​the​ ​future
○ Could​ ​we​ ​achieve​ ​or​ ​even​ ​think​ ​any​ ​of​ ​these​ ​things​ ​without​ ​language?
○ Language​ ​is​ ​open-ended,​ ​allows​ ​for​ ​potentially​ ​infinite​ ​communication
Speech​ ​and​ ​symbolic​ ​language
● Investigation​ ​comparing​ ​an​ ​adult​ ​chimpanzee​ ​and​ ​a​ ​21-month-old​ ​child
○ Chimp​ ​more​ ​advanced​ ​in​ ​language
○ Six​ ​months​ ​later,​ ​the​ ​vocabulary​ ​of​ ​the​ ​child​ ​far​ ​exceeded​ ​that​ ​of​ ​the
chimpanzee
● Can​ ​non-humans​ ​develop​ ​languages?
○ Washoe​ ​the​ ​chimpanzee
■ Learned​ ​160​ ​words​ ​of​ ​ASL
○ Nim​ ​Chimpsky​ ​the​ ​chimpanzee
■ Demonstrated​ ​that​ ​while​ ​primates​ ​could​ ​learn​ ​individual​ ​words,​ ​they
struggled​ ​with​ ​grammar​ ​rules
■ Criticised​ ​for​ ​using​ ​operant​ ​conditioning​ ​(rewarding​ ​desired​ ​behaviour,
punishing​ ​undesired​ ​behaviour)
○ Koko​ ​the​ ​gorilla​ ​(1971)
■ Understands​ ​1,000​ ​ASl​ ​signs​ ​and​ ​about​ ​2,000​ ​spoken​ ​English​ ​words
○ Alex​ ​the​ ​African​ ​Grey​ ​parrot​ ​(1975-2007)
Joanna​ ​Griffith​ ​(2017)

Could​ ​identify​ ​50​ ​objects,​ ​count​ ​to​ ​6,​ ​distinguish​ ​7​ ​colours​ ​and​ ​5
shapes,​ ​vocabulary​ ​of​ ​about​ ​150​ ​words
● Probably​ ​operant​ ​conditioning
○ Kanzi​ ​the​ ​bonobo
■ Used​ ​symbols​ ​that​ ​represented​ ​language,​ ​could​ ​respond​ ​to​ ​72%​ ​of
660​ ​requests
○ Chaser​ ​the​ ​dog
■ Can​ ​identify​ ​1,022​ ​words​ ​(names​ ​of​ ​toys)
When​ ​did​ ​language​ ​evolve?
● Language​ ​doesn’t​ ​leave​ ​a​ ​trace​ ​in​ ​the​ ​fossil​ ​record,​ ​so​ ​we​ ​can’t​ ​say​ ​exactly​ ​when​ ​it
evolved
○ Must​ ​be​ ​after​ ​divergence​ ​of​ ​gorillas,​ ​chimpanzees,​ ​etc
...
​ ​car​ ​is​ ​a​ ​class​ ​of​ ​objects​ ​with​ ​certain​ ​properties
○ Generative:​ ​a​ ​limited​ ​number​ ​of​ ​symbols​ ​can​ ​generate​ ​an​ ​infinite​ ​array​ ​of
novel​ ​messages
○ Structured:​ ​rules​ ​govern​ ​the​ ​arrangement​ ​of​ ​words​ ​into​ ​phrases​ ​and
sentences​ ​(infinite​ ​variety​ ​is​ ​structured​ ​in​ ​a​ ​limited​ ​number​ ​of​ ​ways)
Understanding​ ​language​ ​evolution​ ​is​ ​complex
● Language​ ​acquisition/breakdown
○ Developmental​ ​psychology,​ ​neuropsychology
● Language​ ​structure
○ Linguistics,​ ​psycholinguistics
■

Joanna​ ​Griffith​ ​(2017)

Language​ ​change,​ ​universals
○ Linguistics
● Models
○ Computer​ ​science,​ ​robotics,​ ​population​ ​biology
● Genetic​ ​correlates
○ Behavioural​ ​genetics
● Animal​ ​communication
○ Primatology,​ ​comparative​ ​psychology
● Fossils,​ ​endocasts,​ ​artefacts
○ Archaeology,​ ​anthropology
● Articulatory​ ​physiology
○ Speech​ ​sciences
● Neural​ ​correlates
○ neuroscience
Gossiping​ ​hypothesis
● 2/3s​ ​of​ ​all​ ​conversation​ ​is​ ​about​ ​social​ ​relationships
○ Both​ ​in​ ​developed​ ​and​ ​hunter-gatherer​ ​societies
● Does​ ​this​ ​kind​ ​of​ ​language​ ​use​ ​have​ ​any​ ​effect​ ​on​ ​our​ ​fitness?
● Does​ ​it​ ​help​ ​our​ ​survival​ ​rate?
● Does​ ​it​ ​increase​ ​our​ ​reproductive​ ​rate?
Substitute​ ​for​ ​grooming​ ​hypothesis
● Monkeys​ ​and​ ​apes​ ​are​ ​very​ ​social​ ​and​ ​maintain​ ​complex​ ​relationships​ ​through
grooming​ ​as​ ​a​ ​main​ ​social​ ​interaction
○ Maybe​ ​humans​ ​have​ ​substituted​ ​grooming​ ​with​ ​language​ ​to​ ​maintain​ ​complex
social​ ​relationships
Increasing​ ​group​ ​size​ ​hypothesis
● The​ ​largest​ ​group​ ​size​ ​for​ ​non-human​ ​primates​ ​is​ ​50-55​ ​in​ ​chimps​ ​and​ ​baboons,​ ​and
about​ ​150​ ​for​ ​modern​ ​hunter-gatherers
○ Primates​ ​spend​ ​up​ ​to​ ​20%​ ​of​ ​their​ ​days​ ​grooming,​ ​humans​ ​would​ ​need​ ​to
spend​ ​40%​ ​of​ ​their​ ​time​ ​to​ ​cover​ ​such​ ​a​ ​large​ ​group
○ Humans​ ​may​ ​use​ ​language​ ​as​ ​‘vocal​ ​grooming’
● However,​ ​social​ ​insects​ ​can​ ​live​ ​in​ ​colonies​ ​of​ ​30,000​ ​insects​ ​and​ ​have​ ​not​ ​evolved
language​ ​or​ ​grooming
The​ ​genetic​ ​origin​ ​of​ ​language
● Early​ ​hominids​ ​probably​ ​began​ ​using​ ​gestures​ ​to​ ​communicate​ ​intentions​ ​within​ ​a
social​ ​setting
● FOXP2​ ​gene
○ Language​ ​or​ ​speech​ ​gene​ ​responsible​ ​for​ ​a​ ​major​ ​inherited​ ​speech​ ​disorder
○ Study​ ​of​ ​the​ ​KE​ ​family
■ Over​ ​3​ ​generations,​ ​half​ ​of​ ​the​ ​family​ ​was​ ​affected
■ Inability​ ​to​ ​form​ ​intelligible​ ​speech,​ ​defects​ ​in​ ​processing​ ​words
according​ ​to​ ​rules
○ Caused​ ​by​ ​a​ ​single​ ​nucleotide​ ​mutation​ ​on​ ​exon​ ​14​ ​of​ ​chromosome​ ​7
(10,000-100,000​ ​years​ ​ago)
○ Very​ ​conserved​ ​gene
●

Joanna​ ​Griffith​ ​(2017)

1​ ​change​ ​in​ ​75​ ​million​ ​years​ ​before​ ​the​ ​divergence​ ​of​ ​chimps​ ​and
humans,​ ​and​ ​2​ ​changes​ ​in​ ​the​ ​6​ ​million​ ​years​ ​since​ ​that​ ​divergence
○ May​ ​be​ ​critical​ ​for​ ​the​ ​development​ ​of​ ​modern​ ​human​ ​speech
● Neanderthals​ ​may​ ​have​ ​been​ ​able​ ​to​ ​do​ ​the​ ​basics​ ​of​ ​language
● Vocal​ ​anatomy​ ​gradually​ ​evolved
○ Oral​ ​cavity​ ​increased​ ​in​ ​size,​ ​giving​ ​the​ ​tongue​ ​more​ ​room​ ​to​ ​move​ ​around
○ In​ ​chimpanzees​ ​and​ ​Australopithecines,​ ​the​ ​pharynx​ ​is​ ​short,​ ​and​ ​the​ ​soft
palate​ ​and​ ​epiglottis​ ​meet​ ​to​ ​separate​ ​the​ ​oral​ ​cavity​ ​from​ ​the​ ​pharynx​ ​while
breathing
○ In​ ​humans,​ ​the​ ​pharynx​ ​is​ ​longer,​ ​the​ ​oral​ ​cavity​ ​is​ ​taller​ ​and​ ​the​ ​tongue​ ​is
shorter
■ Longer​ ​necks
■ Humans​ ​also​ ​have​ ​a​ ​distinct​ ​chin,​ ​which​ ​allows​ ​for​ ​more​ ​varied​ ​tongue
movements​ ​necessary​ ​to​ ​articulate​ ​the​ ​sounds​ ​of​ ​speech,​ ​and
paranasal​ ​sinuses,​ ​which​ ​act​ ​as​ ​resonating​ ​chambers
● Coevolution​ ​of​ ​language​ ​and​ ​the​ ​brain
○ Wilson
■ Increased​ ​brain​ ​size​ ​=​ ​more​ ​complex​ ​behaviour,​ ​which​ ​in​ ​turn,​ ​due​ ​to
increased​ ​environmental​ ​complexity,​ ​selects​ ​for​ ​increased​ ​brain​ ​size
■ Feedback​ ​loops
○ Genetic​ ​assimilation:​ ​process​ ​by​ ​which​ ​a​ ​phenotype​ ​originally​ ​produced​ ​in
response​ ​to​ ​an​ ​environmental​ ​condition​ ​becomes​ ​genetically​ ​encoded​ ​due​ ​to
artificial​ ​or​ ​natural​ ​selection
● Evolution​ ​of​ ​language
○ Gene​ ​evolved​ ​120,000​ ​years​ ​ago,​ ​recorded​ ​culture​ ​appeared​ ​50,000​ ​years
ago
○ Incremental​ ​language​ ​‘strategies’​ ​produced​ ​by​ ​different​ ​hunter-gatherer
groups​ ​may​ ​have​ ​led​ ​to​ ​the​ ​development​ ​of​ ​different​ ​languages
○ May​ ​be​ ​the​ ​most​ ​important​ ​synapomorphy​ ​in​ ​all​ ​of​ ​human​ ​evolutionary​ ​history
■ Synapomorphy:​ ​a​ ​characteristic​ ​present​ ​in​ ​an​ ​ancestral​ ​species​ ​and
shared​ ​exclusively​ ​by​ ​its​ ​evolutionary​ ​descendants
Human​ ​language​ ​families
● There​ ​are​ ​currently​ ​12​ ​extant​ ​phyla​ ​of​ ​human​ ​languages
● All​ ​cultures​ ​have​ ​language
○ Currently​ ​over​ ​6,000​ ​languages,​ ​many​ ​are​ ​unwritten
● Competition​ ​among​ ​languages
○ 50-90%​ ​expec

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