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Intelligence & EvolutionIntelligence & Evolution

Part 1Part 1

Aim: To introduce and discuss Aim: To introduce and discuss intelligenceintelligence

O1) Students will be able to Define O1) Students will be able to Define IntelligenceIntelligence

O2) Describe evidence that humans O2) Describe evidence that humans are more intelligent than animalsare more intelligent than animals

RecapRecap

You have 10 minutes to in groups to You have 10 minutes to in groups to summarise the process of Evolution summarise the process of Evolution which you will then report back to which you will then report back to the class.the class.

Question

Why does an animal which stands still when there is a predator better adapted to survive than one who doesn’t?

What is Evolutionary What is Evolutionary Psychology?Psychology?

Tooby and Cosmides (1992) define Tooby and Cosmides (1992) define evolutionary psychology as informed by the evolutionary psychology as informed by the fact that the inherited structure of the fact that the inherited structure of the human mind is the product of evolutionary human mind is the product of evolutionary processes (!)processes (!)

They claim this can explain contemporary They claim this can explain contemporary behaviour.behaviour.

It seeks a FUNCTIONAL EXPLANATION of It seeks a FUNCTIONAL EXPLANATION of human behaviour – one that focuses on human behaviour – one that focuses on origins eg why a behaviour has evolved.origins eg why a behaviour has evolved.

This is opposite to causal explanations as This is opposite to causal explanations as they only focus on the immediate they only focus on the immediate precursors or causes of behaviour.precursors or causes of behaviour.

The Elements of Evolution - TimeThe Elements of Evolution - Time

TimeTime• Crucial element of evolutionCrucial element of evolution• Earth is about 5,000,000,000 years oldEarth is about 5,000,000,000 years old• Primitive life forms are dated to about Primitive life forms are dated to about

3,300,000,000 years ago!3,300,000,000 years ago!• Mammals appeared in the last Mammals appeared in the last

70,000,000 years70,000,000 years• Great Apes (our close ancestors) about Great Apes (our close ancestors) about

15,000,000 years ago.15,000,000 years ago.

The Elements of Evolution – The Elements of Evolution – Genetic Transmission and DiversityGenetic Transmission and Diversity Genetic Transmission and DiversityGenetic Transmission and Diversity

• Genes are passed from one generation Genes are passed from one generation to anotherto another

• Genes are mixed from both parentsGenes are mixed from both parents• This causes genetic diversity and that This causes genetic diversity and that

allows for changes to occur and is the allows for changes to occur and is the basis for evolutionbasis for evolution

• Some changes may be due to mutation Some changes may be due to mutation as well.as well.

The Elements of Evolution – The Elements of Evolution – Natural SelectionNatural Selection

Natural SelectionNatural Selection• Charles Darwin stated that some forms of Charles Darwin stated that some forms of

diversity are more adaptive (likely to promote diversity are more adaptive (likely to promote survival and reproduction) than others.survival and reproduction) than others.

• Natural Selection refers to the fact that an Natural Selection refers to the fact that an animal that inherits structures or behavioural animal that inherits structures or behavioural patterns that are well adapted to its particular patterns that are well adapted to its particular environment is more likely to survive and pass environment is more likely to survive and pass on its genes to the next generation.on its genes to the next generation.

• Those individuals less well adapted may die Those individuals less well adapted may die sooner and therefore their genes will gradually sooner and therefore their genes will gradually reduce in the population.reduce in the population.

The Elements of Evolution – The Elements of Evolution – Sexual SelectionSexual Selection

The process whereby physical and The process whereby physical and behavioural characteristics which promote behavioural characteristics which promote reproductive success (and the genes which reproductive success (and the genes which code for these) are passed on to descendantscode for these) are passed on to descendants• Differences between individuals’ reproductive Differences between individuals’ reproductive

capacity are crucialcapacity are crucial• Number of genes passed on to future generations Number of genes passed on to future generations

depend on having more offspring who survive to depend on having more offspring who survive to adulthood and sexual maturity.adulthood and sexual maturity.

• Any genetically inherited attribute that ensures Any genetically inherited attribute that ensures reproductive success (eg being attractive to reproductive success (eg being attractive to potential mates or helps you to win where there is potential mates or helps you to win where there is competition) would be more adaptive.competition) would be more adaptive.

Human EvolutionHuman Evolution

Imagine that the period between the Imagine that the period between the beginning of life on this planet and beginning of life on this planet and the present were represented as 24 the present were represented as 24 hours running from midnight to hours running from midnight to midnight. At what time do you think midnight. At what time do you think the earliest humans, our direct the earliest humans, our direct ancestors, initially appeared?ancestors, initially appeared?

Answer?Answer?

About 50 seconds before midnight…About 50 seconds before midnight… That’s about 2 million years ago.That’s about 2 million years ago. Homo sapiens – our own species – Homo sapiens – our own species –

would be about 4 seconds to would be about 4 seconds to midnight…midnight…

That’s about 150,000 years ago!That’s about 150,000 years ago!

DNADNA When life first appeared on earth, the structure of When life first appeared on earth, the structure of

DNA was pretty common to all life forms.DNA was pretty common to all life forms. Over long periods of time, DNA underwent subtle Over long periods of time, DNA underwent subtle

changes and different species emerged.changes and different species emerged. The shorter the time lapse since one species has The shorter the time lapse since one species has

split in two, the closer in structure their DNA will split in two, the closer in structure their DNA will be.be.

Since the structure of DNA evolves at a consistent Since the structure of DNA evolves at a consistent rate, we can work out mathematically when two rate, we can work out mathematically when two species diverged.species diverged.

Branching of Monkeys, Apes and Branching of Monkeys, Apes and Humans.Humans.

Humans and Chimps diverged about 5 million years ago.

In terms of DNA we are closer to chimps than they are to gorillas!

We’re the new kids on the block because homo sapiens is only 100 to 150,000 years old!

What is Intelligence?What is Intelligence?

10 Minutes- to discuss with group 10 Minutes- to discuss with group members and try and come to an members and try and come to an agreementagreement

15 minutes class discussion to look 15 minutes class discussion to look at your definitions and concepts of at your definitions and concepts of intelligenceintelligence

Charles SpearmanCharles Spearman Spearman noticed a trend, a correlation Spearman noticed a trend, a correlation

even between peoples abilities on one even between peoples abilities on one task and on another.task and on another.

He set about testing and analysing these He set about testing and analysing these and decided upon looking at his results and decided upon looking at his results everyone has a general and overaching everyone has a general and overaching intelligence (g)intelligence (g)

We also have specialised intelligence (s) We also have specialised intelligence (s) which is our abilities in a different area but which is our abilities in a different area but to top this up we have to take away from to top this up we have to take away from g.g.

‘‘g’ represents a singular intelligenceg’ represents a singular intelligence

L.L. ThurstoneL.L. Thurstone

Disagreed!Disagreed! He believed that indeed there was a ‘g’ it He believed that indeed there was a ‘g’ it

was no where near as important and was no where near as important and Spearman though. His work discoveredSpearman though. His work discovered

Primary Mental AbilitiesPrimary Mental Abilities Verbal, numerical, Spatial, Reasoning, Verbal, numerical, Spatial, Reasoning,

Verbal comprehension, memory etcVerbal comprehension, memory etc Intelligence is not one thing but an Intelligence is not one thing but an

interplay of severalinterplay of several

Horn & Cattell (1966)Horn & Cattell (1966)

These guys believed in fluid (gf) and These guys believed in fluid (gf) and crystallised (gc) intelligencecrystallised (gc) intelligence

gf= the ability to think logically and gf= the ability to think logically and relate concepts through reasoningrelate concepts through reasoning

gc= A specific set of knowledge e.g. gc= A specific set of knowledge e.g. multiplication, verbal fluencymultiplication, verbal fluency

Given what we know…Given what we know… On a scale of 1-7, how likely is it you think On a scale of 1-7, how likely is it you think

the following people are geniuses:-the following people are geniuses:- Albert EinsteinAlbert Einstein David BeckhamDavid Beckham Stephen HawkingStephen Hawking MadonnaMadonna Tony BlairTony Blair JordanJordan Stephen KingStephen King You?You?

Howard Gardener (1983)Howard Gardener (1983)

Given what we know…Given what we know… On a scale of 1-7, how likely is it you think On a scale of 1-7, how likely is it you think

the following people are geniuses:-the following people are geniuses:- Albert EinsteinAlbert Einstein David BeckhamDavid Beckham Stephen HawkingStephen Hawking MadonnaMadonna Tony BlairTony Blair JordanJordan Stephen KingStephen King You?You?

Individuals with AutismIndividuals with Autism Albert Einstein?Albert Einstein? Bill Gates?Bill Gates? Gary MckinnonGary Mckinnon Stephen WiltshireStephen Wiltshire

Autistic SavantsAutistic Savants Autistic savants are individuals diagnosed with autism who appear Autistic savants are individuals diagnosed with autism who appear

to have a particular skill or gift.to have a particular skill or gift.

There are only thought to be about 100 savants across the world.There are only thought to be about 100 savants across the world.

‘Islet of ability’

Mathematics Art Music

Logic, Reasoning and Logic, Reasoning and Problem SolvingProblem Solving

Just a few problems for funJust a few problems for fun

Adams 1979Adams 1979

Join all 9 dots with 1 line where you Join all 9 dots with 1 line where you don’t go back on yourselfdon’t go back on yourself

Inductive Reasoning Inductive Reasoning

2-4-62-4-6

Linda is 31 years old, single, outspoken Linda is 31 years old, single, outspoken and very bright. She has a degree in and very bright. She has a degree in Philosophy. As a student she was deeply Philosophy. As a student she was deeply concerned with issues of discrimination concerned with issues of discrimination and social justice, and also participated in and social justice, and also participated in anti-nuclear war demonstrationsanti-nuclear war demonstrations

Rank in order these following possibilities:-Rank in order these following possibilities:-

Linda is now a…Linda is now a…

Bank TellerBank Teller WriterWriter Stay at home motherStay at home mother FeministFeminist TeacherTeacher Feminist Bank TellerFeminist Bank Teller Taxi DriverTaxi Driver DoctorDoctor

If a word of three letters or more is If a word of three letters or more is sampled at random from an English sampled at random from an English text, is it more likely that the word text, is it more likely that the word starts with ‘r’ or has ‘r’ as it’s third starts with ‘r’ or has ‘r’ as it’s third letter?letter?

COMPARATIVE PSYCHOLOGYCOMPARATIVE PSYCHOLOGYEvolutionary explanations of human behaviourEvolutionary explanations of human behaviour

EVOLUTION OF INTELLIGENCEEVOLUTION OF INTELLIGENCE

1.Chimpanzee2.Cat3.Spiny Anteater

4.Dolphin5.Capybara6.Squirrel Monkey

7.Manatee8.Least Weasel 9.Beaver

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EncephalizationEncephalization — — ‘Bigger is better’ or ‘Bigger is better’ or something more?something more?

Relative brain sizesRelative brain sizes

Old World monkey89.1 cc

Lesser ape97.5 cc

Great ape316.7 cc

Human1251.8 cc

New world Monkey34.1 cc

Strepsirhines12.6 cc

Source: James K. Rilling. 2006. Human and NonHuman Primate Brains: Are They Allometrically Scaled Versions of the Same Design? Evolutionary Anthropology 15: 65-77.

Most formulae based on body size suggest

human should be 600 cc.

Comparative studiesComparative studies

Comparative studies of brain size and intelligence.

The human brain is a metabolically expensive organ.

Although it accounts for only 2% of total body mass, it uses about 10% of the basic metabolic rate in rhesus monkeys and about 20% in humans.

Large brains would not have evolved if it did not give humans a significant advantage.

EVOLUTIONARY OF INTELLIGENCEEVOLUTIONARY OF INTELLIGENCE

Comparative studies of brain size and intelligence.

Brain quantity – IfIntelligence were determined by brain size, the sperm whale would be at the top (see table right).

Approx. brain & body weight of Approx. brain & body weight of selected mammals (Klinowska, selected mammals (Klinowska, 1994)1994)SpeciesSpecies Brain Brain

weight weight (KG)(KG)

Body weight Body weight (tonnes)(tonnes)

Sperm WhaleSperm Whale 7.87.8 37.0037.00

DolphinDolphin 1.61.6 0.170.17

HumanHuman 1.51.5 0.070.07

CowCow 0.50.5 0.600.60

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Encephalization: ‘expected’ Encephalization: ‘expected’ brain sizebrain size


Comparative studies of brain size and intelligence cont…

We a get better indication of the intelligence of a particular species by considering brain size relative to body size.

Jerison (1978) developed the encephalizationquotient (EQ), in which the actual brain mass of a speciesIs divided by its ‘expected’ brain size for that body size…


Comparative studies of brain size and intelligence cont…

…Higher quotients indicate species withlarger-than-expected brains.

An EQ greater than 1 indicates a brain size greaterthan predicated (which could be an indicator of intelligence) and visa versa.

Using this scale, humans have the highest EQ (7) ofany animal (Jerison 1978).

Stephan (1972) looked at EQ in Stephan (1972) looked at EQ in Primates and found humans Primates and found humans waaaaaay higher than any of our waaaaaay higher than any of our close relativesclose relatives

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EncephalizationEncephalization

Evolutionary trendsEvolutionary trends

Graphic from Getty Images

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Encephalization among Encephalization among homininshominins

Brain growth over Brain growth over evolutionevolution

Time, in millions of years ago

Rela

tive

bra

in s

ize

http://www.talkorigins.org/faqs/homs/a_brains.html

Hominin doesn’t just get bigger, it spikes upward.

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How big does a brain have to be?

750cc - Author Keith.

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The first of our genus: Early The first of our genus: Early HomoHomo

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Homo habilisHomo habilis ((Australopithecus Australopithecus habilishabilis?)?)

‘‘Habilis’ because of ‘handy man’ Habilis’ because of ‘handy man’

(discovered 1960). (discovered 1960).

Remains 2.3-1.6 mya.Remains 2.3-1.6 mya.Overlaps Australopithecenes & Overlaps Australopithecenes & Paranthropus.Paranthropus.

Ape-like bodyApe-like body. .

Skeletal traits variable.Skeletal traits variable.H. rudolfensisH. rudolfensis for robust variant. for robust variant.

600-700 cc. brain.600-700 cc. brain.Is the big jump with Is the big jump with H./A. habilisH./A. habilis or or with with H. erectusH. erectus??

MayMay have made stone tools. have made stone tools.

Homo habilis (skull OH 24)

Source: http://www.mnh.si.edu/anthro/humanorigins/ha/a_tree.html

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Homo ergasterHomo ergaster ‘‘Work man’ (1976).Work man’ (1976).

1.8 mya to .6 mya.1.8 mya to .6 mya.

Larger body than earlier hominins with Larger body than earlier hominins with modern proportions (savanna modern proportions (savanna populations).populations).

Human-like traits:Human-like traits:Left Africa for Eurasia (range).Left Africa for Eurasia (range).Diet included meat (cooking?).Diet included meat (cooking?).Tool use.Tool use.Brain size around 800 cc.Brain size around 800 cc.

Used to be called Used to be called H. erectusH. erectus, but now , but now name is reserved for East Asian name is reserved for East Asian remains.remains.

‘Nariokotome Boy’

KNM-WT 15000Remains found at Lake

TurkanaPhoto by Kenneth Garrett/National

Geographic

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Comparative Comparative neurologyneurology

Human brain not simply Human brain not simply quantitativelyquantitatively different different (bigger).(bigger).

QualitativeQualitative differences differences are crucial.are crucial.

Terrence Deacon: Terrence Deacon: searching for special searching for special ‘language’ part of ‘language’ part of human brainhuman brain..

Relative brain sizes Relative brain sizes

Cerebral cortex much larger.Cerebral cortex much larger.

Rat’s cortex = postage stamp

Monkey’s = post card

Chimpanzee’s = page of printer paper

Human’s = four pages

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Relative brain sizeRelative brain sizeor... the neocortex is about the size of two

large pizzas.

Thanks to Paul Mason for this slide!

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Neocortex shape (sulchi, Neocortex shape (sulchi, fissures, gyri)fissures, gyri)

http://www.nature.com/nature/journal/v437/n7055/fig_tab/nature04103_F1.html — see also www.brainmuseum.org

Primordial plexiform layer (first & oldest); becomes I & subplate (SP) in human.

Cortical plate divides PPL & forms II-VI.

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Frontal lobe, associated with Frontal lobe, associated with synthesizing information from other synthesizing information from other areas and inhibiting action.areas and inhibiting action.

Volume of white matterVolume of white matter, brain , brain interconnections, grows faster than interconnections, grows faster than neocortex, eventually constituting neocortex, eventually constituting 34% of human brain.34% of human brain.

DifferentiationDifferentiation of tissue (but only of tissue (but only through development).through development).

Brain areas that grewBrain areas that grew


EvaluationEvaluation

Ok this may be hard but were going to try Ok this may be hard but were going to try and do some evaluation in groups-and do some evaluation in groups-

Can you think of any problems with Can you think of any problems with comparing out intelligence to animals?comparing out intelligence to animals?

Do you think brain size is really correlated Do you think brain size is really correlated with intelligence?with intelligence?

What other than head size do you think What other than head size do you think can influence our intelligence?can influence our intelligence?

EVOLUTIONARY OF INTELLIGENCEEVOLUTIONARY OF INTELLIGENCE Comparative studies of brain size and intelligence cont…

The idea of an EQ is appealing but has unfortunatelynot been supported by research – relative brain sizeis not necessarily related to intelligence.

Macphail (1982) found that rats and squirrels performed at about the same level on a learning task, but rats had an EQ of only 0.40, whereas that of squirrels was 1.10.


The relationship of brain size and intelligence

Head size and IQ – Sir Francis Galton (1888) found that head size and intelligence to be low and insignificant.

Wickett et al. (1994) looked at 25 separate studies, comprising over 50,000 individual samples, the majority of studies fell between 0.10 and 0.30, with a mean of just under 0.20.


The relationship of brain size and intelligence cont…

Andreasen et al. (1993) have found (using MRI scans) significant correlations of around 0.40 between brain size and intelligence.

Haug (1987) estimated a correlation of 0.48 between brain size and number of cortical neurones…



…A person with a brain size of 1400cm3 would have an average 600 million fewer cortical neurones than a person with a brain size of 1500cm3.

The difference between the low end of the normal distribution for brain size (1000cm3) and the high end (1700cm3) is a fact a staggering 4.2 billion neurones (Haug, 1987)…



…It seems reasonable to assume that such a difference would have a pronounced effect on cognitive ability.

• Human intellectual abilities, however, are Human intellectual abilities, however, are not carried entirely by genesnot carried entirely by genes..– ““Feral children,” for example…Feral children,” for example…

• Human companyHuman company influences intellect. influences intellect.– Other primates raised in Other primates raised in human environmentshuman environments

develop greater intelligence.develop greater intelligence.

– E.g. E.g. tool usetool use in “encultured” chimps & orangutans. in “encultured” chimps & orangutans.

– Carel van Schaik: Carel van Schaik: gregarious adult social lifegregarious adult social life key. key.

• ““Human” is especially Human” is especially immatureimmature at birth. at birth.– Brain less developed at same age to Brain less developed at same age to open wider open wider

learning windowlearning window..

Is intelligence all ‘in the brain’?Is intelligence all ‘in the brain’?

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‘‘Extended brain’Extended brain’

• Won’t deal with it todayWon’t deal with it today

• Language, culture, symbolic systems and other Language, culture, symbolic systems and other devices both create devices both create external supports for external supports for cognitive abilitiescognitive abilities, and..., and...

• Generate developmental environments that Generate developmental environments that shape the biological unfoldingshape the biological unfolding of humans. of humans.

• Human brains areHuman brains are shot through with shot through with cultureculture..

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Problems with a big brainProblems with a big brain

Why doesn’t every animal want one?Why doesn’t every animal want one?Graphic from Getty Images

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‘‘Expensive Expensive tissue’ tissue’

hypothesishypothesisLarge brain is Large brain is energy hungryenergy hungry — human brain consumes 25% — human brain consumes 25% of our energy when resting.of our energy when resting.

Brain tissue expends Brain tissue expends 9x body 9x body tissue averagetissue average..

In infants, In infants, 75%75% of body’s of body’s energy!energy!

Need for Need for energy-rich foodenergy-rich food..


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Human dietHuman diet Richard Wrangham argued that Richard Wrangham argued that

human could not eat enough human could not eat enough food on ‘chimp diet’ to survive.food on ‘chimp diet’ to survive.(Besides, he found the fruit (Besides, he found the fruit ‘very unpleasant.’)‘very unpleasant.’)

H. ergasterH. ergaster brain size brain size increasing while teeth are increasing while teeth are growing smaller.growing smaller.Would need more than 5 Would need more than 5 kilos/day in raw plant food.kilos/day in raw plant food.Around Around 6 hours/day chewing6 hours/day chewing..

Wrangham argues that cooking Wrangham argues that cooking would be necessary.would be necessary.

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Cost of Cost of bigger brainbigger brain

Examining Examining energy energy demanding organsdemanding organs..

Human gut, especially, Human gut, especially, is is significantly smallersignificantly smaller than predicted by than predicted by patterns in other species.patterns in other species.

Makes digestive tract Makes digestive tract

less efficientless efficient..

Intelligence & EvolutionIntelligence & Evolution

Part 2Part 2

Aim: To introduce and discuss two Aim: To introduce and discuss two theories of evolution of intelligencetheories of evolution of intelligence

1) Describe and evaluate theories of 1) Describe and evaluate theories of evolution and intelligence evolution and intelligence

2) Describe and evaluate evidence 2) Describe and evaluate evidence for the theory for the theory

3) Compare and Contrast the 3) Compare and Contrast the theoriestheories

10 minutes- you have 10 minutes in groups to recap what you learned last lesson about Evolution and Intelligence

So the important part is So the important part is why?why?

Some theories about human Some theories about human evolution of Intelligenceevolution of Intelligence

Food Theories!Food Theories!

You have 5 minutes, why would not You have 5 minutes, why would not eating grass and having a more eating grass and having a more varied diet cause someone to be varied diet cause someone to be more intelligent?more intelligent?

What about nutrition?What about nutrition? Think about what skills would be Think about what skills would be

required?required?

Grazing animals can gather their Grazing animals can gather their food without very many demands on food without very many demands on their intellect.their intellect.

They however need large guts, They however need large guts, animals which eat meat and eat a animals which eat meat and eat a more varied diets (as found in more varied diets (as found in primates) have smaller onesprimates) have smaller ones

Travelling-Travelling- Finding specific foods Finding specific foods can involve travelling over very long can involve travelling over very long distances in order to locate a distances in order to locate a balanced diet. They develop the balanced diet. They develop the abilities of cognitive mapping abilities of cognitive mapping (animals which store food such as (animals which store food such as squirrels have been shown to have squirrels have been shown to have larger brain areas than say rats)larger brain areas than say rats)

Identification Identification – the more varied the – the more varied the diet of the animal the better it has to diet of the animal the better it has to be at identifying its food.be at identifying its food.

This is even more true with primates This is even more true with primates and other fruit eaters who have and other fruit eaters who have evolved trichromatic vision.evolved trichromatic vision.

ExtractionExtraction- Obtaining food can also be - Obtaining food can also be taxing. Think about it, ripe fruit only taxing. Think about it, ripe fruit only appears in certain trees and certain parts appears in certain trees and certain parts of the year.of the year.

We and other primates (and some other We and other primates (and some other animals) use tools to obtain food (Boesch animals) use tools to obtain food (Boesch & Boesch, 1984)& Boesch, 1984)

Hunting also requires complex strategies Hunting also requires complex strategies like planning and co-ordinationlike planning and co-ordination

Ecological demandsEcological demands Foraging demands – Finding food.

Dunbar (1992) suggests that intelligence evolved because of an increased cognitive demand on fruit-eaters to monitor a food supply that was spatially and temporally dispersed.

Fruit-eaters must remember the location of their food supply, evaluate ripeness, develop a harvesting plan and decide how they will survive in the interim.

Foraging demands – Extracting food: tool use.

Mercader et al. (2002) studied chimpanzees in a remote West African rain forest where they used stones and branches as hammers to crack open nuts when foraging. Mercader et al. claimed that many of the stone by-products of chimps nut cracking are similar to those found in early human archaeological sites in East Africa.

Cont…

Foraging demands – Extracting food: tool use.

Some of the most successful human hunter-gatherers, such as the !Kung San, use highly elaborate tools.

Some less successful groups like the Tasmanian Aborigines, used only very simple tools.

Tool use is thus an indication of intelligence in both human and non-human species.

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‘‘Man the hunter’ Man the hunter’ hypothesishypothesis

Did Did huntinghunting drive human drive human evolution by fueling hungry brain?evolution by fueling hungry brain?

Evidence of Evidence of butcheringbutchering in stone in stone marks on bones & refuse piles.marks on bones & refuse piles.

Modern foragers get Modern foragers get 50% of 50% of caloriescalories from meat. from meat.

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‘‘Man the hunter’ hypothesisMan the hunter’ hypothesisMight seek especially Might seek especially rich foodsrich foods (like brains or marrow).(like brains or marrow).

Would also help explain Would also help explain expanding rangeexpanding range of of H. ergasterH. ergaster (out of Africa).(out of Africa).

But data and jaw suggests But data and jaw suggests small small animal huntinganimal hunting (not romantic (not romantic image of big game hunting).image of big game hunting).


Battle of the sexesBattle of the sexes

At birth a boy’s brain is 15% larger than a At birth a boy’s brain is 15% larger than a girls of the same size/weight. A similar girls of the same size/weight. A similar statistic can be found in adults (remember statistic can be found in adults (remember though it’s cortex complexity which is truly though it’s cortex complexity which is truly important)important)

This is inline with the hunting hypothesis This is inline with the hunting hypothesis (Washburn, 1968) as the men did the (Washburn, 1968) as the men did the hunting they needed bigger brains.hunting they needed bigger brains.

(They then dragged the women along with (They then dragged the women along with them…though it probably happened the them…though it probably happened the same the other way too)same the other way too)

Milton (1988) compared the EQ of Milton (1988) compared the EQ of Howler monkeys (leaf eaters) and the Howler monkeys (leaf eaters) and the fruit eating Spider-Monkeys (who fruit eating Spider-Monkeys (who have a living range 25X that of the have a living range 25X that of the Howler.) Their brain size was over Howler.) Their brain size was over twice as big.twice as big.


Foley and Lee (1991) point out the Foley and Lee (1991) point out the difficulty of seperating cause and difficulty of seperating cause and effect. ‘increased returns for foraging effect. ‘increased returns for foraging effort and food processing may have effort and food processing may have been an important prerequisite for been an important prerequisite for encephalization and in turn a large encephalization and in turn a large brain is needed for these skills’brain is needed for these skills’

Chicken or egg?Chicken or egg?

Creating a different hypothesis:-Creating a different hypothesis:-

Look back at the EQ chart from last week, do Look back at the EQ chart from last week, do the animals who are above the line fit the the animals who are above the line fit the trend we’ve just seen?trend we’ve just seen?

Elephants, Vampire Bats, Wolves, Baboons, Elephants, Vampire Bats, Wolves, Baboons, Humans, crows and PorpoisesHumans, crows and Porpoises

Can you think of anything else they all have Can you think of anything else they all have in common? (10 mins)in common? (10 mins)

Social ComplexitySocial Complexity

The Machiavellian HypothesisThe Machiavellian Hypothesis

It is not our food demands but the It is not our food demands but the social demands which have caused social demands which have caused us to develop more intelligence!us to develop more intelligence!

3 million years ago it’s estimated 3 million years ago it’s estimated australoapithecine lived in groups of australoapithecine lived in groups of 7070

150,000 years ago we lived in groups 150,000 years ago we lived in groups of about 150.of about 150.

The more people we live with the The more people we live with the more complex our lives becomemore complex our lives become

Alliances within the groups had to be Alliances within the groups had to be made (and remembered)made (and remembered)

Social reasoning developedSocial reasoning developed A Theory of MindA Theory of Mind

It’s named after Italian politician Niccolo It’s named after Italian politician Niccolo Machiavelli (1469-1527) who outlined a Machiavelli (1469-1527) who outlined a whole host of dirty tricks politicians used whole host of dirty tricks politicians used (and still do) to remain in power(and still do) to remain in power

We use such cunning and deceit in We use such cunning and deceit in everyday life.everyday life.

Those who were better at it and could, lie, Those who were better at it and could, lie, twist and con the others to their will got to twist and con the others to their will got to live longer and reproduce more!live longer and reproduce more!

If there were any out there however who If there were any out there however who were very good at spotting these tricks…were very good at spotting these tricks…they could also live longer.they could also live longer.

So….So…. ……The liars got even better!The liars got even better!

Social theories.

Theorists such as Humphrey (1976) argue that social objects (members of the same sex) offer a completely different order of complexity from the relatively stable word of physical objects.

Individuals who best dealt with these demands to their advantage would be more successful at increasing their reproductive fitness.


Social theories – Machiavellian intelligence .

Whiten and Byrne (1988) Human intelligence may be an adaptation not just to social life, but to social problem – solving.

Individuals able to use and exploit others in their social group without causing aggression would be favoured (Byrne, 1995). This Machiavellian intelligence may appear cooperative but ultimately selfish.


Social theories – Machiavellian intelligence …cont

Forming alliances – Power in complex social groups is often determined more by having the right allies than by physical strength.

Harcourt (1992) suggests that although other animals form alliances, only catarrhine primates (e.g. baboons, apes and humans) cultivate alliances based on individual’s ability.



Manipulation and deception – Among social-living animals, individual can use behavioural tactics to manipulate those who are not allies or relatives into unwitting help.

The ability to understand and plan deception appears to be restricted to great apes, although other primates seem to be able to learn such tactics by watching.

Theory of MindTheory of Mind

……ability to attribute mental ability to attribute mental states (feelings, beliefs etc) to states (feelings, beliefs etc) to oneself and others; develops oneself and others; develops from 12-18 mths to 4yrsfrom 12-18 mths to 4yrs

‘‘mind reading’, knowing what mind reading’, knowing what another person is thinking another person is thinking by looking at themby looking at them

Autistic children lack this and Autistic children lack this and are sometimes refered to are sometimes refered to as ‘mind blind’as ‘mind blind’



Byrne (1995) Manipulative ‘tricks’ include the management of attention, in which the target’s attention is diverted towards or away from something to profit the agent of the deceit. Deception also serves to change how other animals view the agent.

Byrne and Whiten (1988) report Byrne and Whiten (1988) report evidence of a young baboon who evidence of a young baboon who screamed out when a nearby adult screamed out when a nearby adult found some food. The baby’s mother found some food. The baby’s mother became alerted by the scream and became alerted by the scream and arriving at the scene thinking the arriving at the scene thinking the food had been taken from her baby food had been taken from her baby (the baby didn’t show the behaviour (the baby didn’t show the behaviour when his mother was present) stole it when his mother was present) stole it ‘back’‘back’


Social theories – The meat-sharing hypothesis

The importance of meat – Our ancestors and modern day chimpanzees, meat was important source of saturated fat – vital for survival.

Stanford (1999) studied chimps in Tanzania’s Gombe National Park and found for a few months they starved themselves, when they did kill, the chimps went straight for the fattiest fleshy parts instead of the most nutritious.


Social theories – The meat-sharing hypothesis cont…

Meat sharing – Because the importance of meat, Stanford believes that the strategies sharing of meat paved the way for human intelligence.

Meat could be used to forge alliances and persuade females to mate…



…Stanford observed a number of instances supporting this ‘meat for sex hypothesis’:

[1] Males chimpanzees used meat to entice females, often withholding it until mating.

[2] Hunting was more prevalent in the months when females chimps were sexually receptive.

[3] When begging for meat, swollen (sexual receptive) females had more success than non-swollen females.



Stanford believed that strategic meat-sharing required considerable cognitive abilities as males had to recognize individuals and keep a ‘running score’ of debts, credits and relationships.


The Cortex (grey matter) is The Cortex (grey matter) is responsible for higher order responsible for higher order intelligence. In many non-primates intelligence. In many non-primates it’s about 35%. 50% in primates and it’s about 35%. 50% in primates and 80% in humans80% in humans

Dubar (1993) found a correlation Dubar (1993) found a correlation between the complexity of animal between the complexity of animal groups and their % of grey matter.groups and their % of grey matter.

Larger group size does not Larger group size does not necessarily mean a greater social necessarily mean a greater social complexity (think about birds, fish, complexity (think about birds, fish, insects etc) who can swarm in their insects etc) who can swarm in their millions.millions.

What would this predict about other What would this predict about other great apes? Gorilla’s and Orang-great apes? Gorilla’s and Orang-utans (the most intelligent of the utans (the most intelligent of the great apes)great apes)

Out of AfricaOut of Africa

East Asian’s have a greater brain size than East Asian’s have a greater brain size than Europeans and Europeans a greater brain Europeans and Europeans a greater brain size than Africans (Beales, 1984)size than Africans (Beales, 1984)

Rushton & Ankney, 1996 support this with Rushton & Ankney, 1996 support this with a positive correlation when looking at MRI a positive correlation when looking at MRI scans (correlated with IQ)scans (correlated with IQ)

The Out of Africa hypothesis explains The Out of Africa hypothesis explains this…this…

Humans as we know them began in Humans as we know them began in africa about 200,000 years agoafrica about 200,000 years ago

110,000 years ago many migrated 110,000 years ago many migrated north to live in Europenorth to live in Europe

40,000 years ago some left Europe to 40,000 years ago some left Europe to go live in East Asia (Stringer & go live in East Asia (Stringer & andrews, 1988)andrews, 1988)

The further north the populations The further north the populations migrated the more they encountered migrated the more they encountered ‘demanding situations’ (where all of ‘demanding situations’ (where all of their instincts on how to hunt, make their instincts on how to hunt, make clothes, store food, protect children clothes, store food, protect children etc became useless)etc became useless)

So they developed larger brains, So they developed larger brains, greater intelligence etcgreater intelligence etc

Diamond (1997) dismisses all such Diamond (1997) dismisses all such research as ‘loathsome’ and ‘wrong’research as ‘loathsome’ and ‘wrong’

There is still massive problems with There is still massive problems with equating IQ and brain sizeequating IQ and brain size

In testing IQ at all.In testing IQ at all.

The theory however has been refined over The theory however has been refined over the years (not simply because of political the years (not simply because of political correctness) into something which makes correctness) into something which makes more sensemore sense

Others…Others…

Sexual Selection- Women picked the Sexual Selection- Women picked the most intelligent males to breed with most intelligent males to breed with (miller, 2000) which meant they had (miller, 2000) which meant they had intelligent offspring (both more intelligent offspring (both more intelligent boys and girls…who were intelligent boys and girls…who were better at choosing for intelligence better at choosing for intelligence etc)etc)

Co-Evolution of hardware and software- Co-Evolution of hardware and software- Dawkins (1998)Dawkins (1998)

A positive feedback loop develops A positive feedback loop develops between our brain and our bodies pushing between our brain and our bodies pushing both on.both on.

What’s the point in evolving apposable What’s the point in evolving apposable thumbs without the brain to control them? thumbs without the brain to control them? What’s the point of developing the brain What’s the point of developing the brain without the thumb?without the thumb?

Ditto for speechDitto for speech

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Recent changes in the brainRecent changes in the brainIn last 35,000 years, brain size has In last 35,000 years, brain size has shrunk 11%.shrunk 11%.In last 10,000 years, brain size has In last 10,000 years, brain size has shrunk 8%. :Sshrunk 8%. :SAre domesticated food sources Are domesticated food sources adequate?adequate?

Ruff, Trinkaus & Holliday 1997.

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