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Dominance hierarchies

Refers to an ordering of the members of a social group

1. Some individuals are “higher” in rank than others and are constantly able to displace others from a resource

2. The rank is dynamic and can be challenged (by fighting) and reversed

3. Ranks in the hierarchy will depend on size, strength, age, coalition support


Social brain hypothesis

Refers to the idea that maintaining social relationships requires devoted brain mechanisms

--> social species will tend to have relatively larger brains than non social ones

=> a bigger brain size must therefore have developed as a result of bigger group size


There is fossil evidence for a series of intermediate forms between ourselves and the chimpanzees, which tend to have more human like characteristics over time and all of which are now extinct.

What are those major branches on the primate phylogeny ?

1. Haplorrhine

2. Strepsirrhine

3. Tarsier

4. Platyrrhine

5. Catarrhine

--> old world monkeys + apes



Are a type of ape that from longterm pair bonds + their territorial social groups consist of monogamous pair, including an offspring

--> specialized in their hand, arm, shoulder anatomy for brachiation



Refers to locomotion through trees by swiping from the arms, like a child in monkeys bars



Refers to a member of the group consisting of humans + their extinct relatives

--> human ancestors



Refer to extinct hominins found in africa who were more bipedal than chimpanzees, but had smaller brains

--> specialized in processing coarse plant foods



For which reasons is the early "Homo" significant ? (2.5m y ago)

1. First animals where the brain size begins to move clearly away from that of chimpanzees + towards human pattern

2. Around their time of appearance some tools start to appear

3. First hominins to appear outside of africa

--> begun to depend on meat to a greater extent



(800.000 y ago)

Refer to a more developed form of hominins that appeared in africa first

--> brain + body size were within the range of humans



(300.000 y ago)

I a branch of the archaics that first appeared in europe and lived until relatively recently


Out of africa model

The model proposes that

1. All living humans seem to have descended from a small population living in Africa within the last 200.000 years

--> morphology


2. AMH (anatomically modern human) is a new species that replaced the other living hominins without interbreeding

--> emphasis on the "single origin"



Refers to the "Ice Age", which is a geological epoch that included the world’s most recent period of glaciations

--> 1.8m to 10.000y ago



Refers to the current geological epoch, beginning 10.000 years ago

--> warm period


Compared to our closest relatives, humans show remarked changes in certain domains

What makes humans different ? What distinguishes them from the hominins ?

1. Great dependency on MEAT EATING (Diet)

  • reduced gut relative to apes, which are usually smaller in carnivores than herbivores
  • Moore metabolic energy left for brain


2. The extent of dependency on TOOLS

  •  related to meat eating


3. LARGE BRAIN SIZE relative to chimpanzees

  •  increase from australopithecine - homo - archaics


4. High skill foraging/SKILL LEARNING

  • ability to occupy an incredible breadth of different environments in many ingenious ways



  •  increased lifespan + longer childhood



  •  productive, meaningful, social learning


Humans belong to the primates.

More specifically to the ... ?

Haplorrhines, gibbons + great apes

--> their closest living relatives are the chimpanzees


Cultural intelligence hypothesis

Argues that the human’s unique cognitive skills stem mainly from the species-specific set of social-cognitive skills for participating and exchanging knowledge in cultural groups

--> supported as children + chimpanzees have very similar skills when it comes to dealing with the physical world but children use more sophisticated skills


General intelligence hypothesis

Predict that larger brains enable more efficient use of all cognitive operations


Ecological intelligence hypothesis 

Cognition evolved in response to challenging demands of foraging seasonal fruits & resources embedded in substrates


--> related to fruit hypothesis 


Adapted intelligence hypothesis

Cognitive abilities evolve in response to relatively specific environmental challenges


Machiavellian intelligence hypothesis

Proposed that what differentiates primates from all other species was the complexity of their social lives and environment

--> Since the term Machiavellian was misleading for many, it got replaced by the social brain hypothesis (SBH)


Expensive tissue hypothesis

States that increases in brain size of hominis must have been balanced by a reduction of demands of other organs

--> part of the ecological intelligence hypothesis 

ex.: gut reduction


Aboreal theory

Claims that primates evolved from their ancestors by adapting to arboreal life (living on trees)

  •  moving + feeding on land required stereoscopic vision and dextrous hands, both of which in turn required a large brain to coordinate and control


  •  criticized as carnivores need to kill too which requires the same abilities


Fruit hypothesis

States that fruit diet allowed rather than drove the evolution of big brains



Refers to the predictable relationship between brain and body size in mammals

ex.: if a mouse would grow as big as a human, its brain size would increase accordingly


FORMULA: C x (body size)^k

C= brain weight

W= body size

k= constant


Encephalisation quotient (EQ)

Refers to the departure of the brain size to the allometric line

--> comparable to the standard deviation


Chihuahua fallacy

(Criticism on EQ)

States that Brain size does not predict intelligence as  intelligence is way too complex to have such a simple relationship

ex.: Chihuahuas could become really small but keep their brain size

--> EQ shows that it is larger than expected/Predicted


Which ones are the great apes ?

1. Orang Utans

2. Gorillas

3. Chimpanzees


Which kinds of Hominins are there ?

1. Australopithecines

2. Early Homos

3. Archaics


How does the Gene "ARHGAP11B" make human brains more unique ?

It is a modified version of common DNA strand found in simple organisms that drives the expansion of the brain by increasing the number of neurons in the neocortex


Criticism on the gene "ARHGAP11B" ? Does it generally account for human intelligence ?

Gene is not sufficient enough to explain the phenomenon of intelligence

--> intelligence is polygenic, thus needs many genes to account for it