Richard W. Byrne in 'Tree of Origin: What Primate Behaviour Can Tell Us about Human Social Evolution'
Notes by Georgina Holmes
BOOK CHAPTER SUMMARY
BOOK:
Tree of Origin: What Primate Behaviour Can Tell Us about Human Social Evolution
CHAPTER 6:
Social and Technical Forms of Primate Intelligence
by Richard W. Byrne
How did our cognition and intellectual capacities evolve?
Role of Comparative Biology
Behaviour of ancient ancestors hardly preserved archaeology
Behaviour of modern living species can provide an insight
We can look at:
What form does a particular behaviour take?
The functions of a particular behaviour now?
Under what conditions is a particular behaviour seen?
How is the behaviour related to the environment?
How does the behaviour vary?
Relatives have evolved as much as we have since divergence
Modern primates they are not perfect prehistoric ape replicas
Two popular but wrong theories of using comparative biology:
19th Century: Great Chain of Being
Belief that studying modern primate is direct way our ancestors were like
View that monkeys evolved into apes evolved into humans
Ontogeny recapitulates phylogeny
20th Century: Radical Behaviourism
Belief that all species equal so rat can be used to compare with humans rather than ape
But if all species equal why need comparison
Claims that language sets humans apart
BUT
Both theories are overly simplistic
Language cannot be acquired suddenly, it is so complex it must have roots in other animal cognition
Capacities of all animals are not equal:
Monkeys show more complex behaviour than most mammals
This ability results from an enlarged neocortex that allows rapid learning
Great apes demonstrate some understanding of intentions and causes.
This comprehension is based on an ability to perceive, and to build, complex novel behaviour
What do we need to consider to answer evolutionary questions?
1. Function of evolved trait
Selection pressure = environmental challenge
Environmental challenge met by aptitude
How challenge increased inclusive fitness in carriers of allele/trait
How did those with trait produce more offspring with trait than those without the trait
Example: Cognition
"What environmental challenge caused ancestors to gain a fitness advantage from the cognitive adaption?"
The challenge may not have related to the function of cognition at the time
Are the challenges which cognition helps with today the same as the ones which led to its evolution, or does intelligence have new functions?
2. Form of evolved trait
Specific abilities for one use?
Multiple uses?
If intelligence is modular its function may have been the same
3. Chronology of trait
a) Sociocultural variation
Modern: cross-cultural variation
Evolutionary variety between cultures
Understand modern human psychology - individual and social environments
Recent evolution of trait
b) Evolution since divergence
Ancient: Evolutionary changes since divergence from last ancestor
Change in biological potential seen via archaeology, knowledge modern humans and last common ancestor
Behaviour leaves little material trace so archaeology rooted in past environment is more accurate
c) Evolution before divergence
Adaptions in our last ancestor with the potential for intelligence
Roots of intelligence have own evolutionary origins (challenges in past)
Presence and cause of intellect of the common ancestor can only seen via comparative study
Overall:
As humans and chimpanzees/bonobos are more closely related to each other than any of them are to gorillas and orangutans, our last common ancestor is only 4.5m years old. This is too short a time span for any intellectual development. We need to look at its roots before our divergence. Modern comparative studies of animals shows wide intellectual differences, this provides evidence of the stages of intellectual development in human past.
Evolutionary Reconstruction
Evolutionary reconstruction uses comparative evidence to reconstruct the human past
The distribution of the characteristic in the living members is used to reconstruct its origin in the past
We can reconstruct the earliest phases of human behavioural evolution without fossil evidence
Similar to a family tree we use the phylogeny of primate relatives
Each biological branch on this family tree is a common ancestor
Existence of ancestors reliable from modern studies
Fossils/bones hard to attribute as lineage may have died out quickly
Phylogeny based on molecular and DNA similarities
Change occurs at constant rate overtime
So we can roughly calculate dates of ancestor
Traits shared with certain animals show its evolutionary origins:
All monkeys = early evolutionary origin (approx. 25-30m ya)
Great apes = trait evolves12-25m years ago
Chimpanzees = trait evolves 4.5-6m years ago
No species share trait = trait evolves after 4.5m years
Where trait is developed by convergent evolution (independently in different species) this cannot tell us how it evolved in humans but perhaps its function
Primate comparison allows time-frame for human behaviour
Complex Primate Behaviour
Social Support:
Monkeys and apes interact in third parties
Rely more on alliances to give power in competition
Alliances form among kin and non-kin
Grooming:
Important trade in alliances
Repaid by support in fights/tolerance at feeding site
Socially complex:
When major alliance threatened by minor argument, even opponents will reconcile
Obligation and influence of relationships key
Analysis of Social Rankings:
Socially knowledgable
Monkeys attacked by dominant animals react to assert their power
Attacked monkeys redirect aggression to weaker parties (like bullying)
Attack young relatives/subordinate females to gain power
Choice of victim shows awareness of social rank, opponents, dominant members and alliances
Calls and responses to monkeys shows they are aware of:
Other kinships
Dominance and social rank of other members
Membership of groups they were never part of
Deception and Dominance:
Monkeys and apes use social knowledge for manipulative tactics (deception to get what they want)
Example:
Dominant male stops female gorillas from mating with subordinates
So she 'gets left' to be out of site to copulate
Invite subordinates and copulate quietly
Whiten and Byrne Survey of Deception:
Primatologists rarely publish 'anecdotes' of deception
Survey done to see cases of deception
Results suggest tactics varied but deception is used by primates
Example:
Young baboon screamed as if hurt when saw adult with food
Mother scare off 'aggressor'
Young gets food
AND Young aware of:
Ensuring this is when mother out of sight
Mother's rank is higher than adult
Not reusing tactic often on same person
Why do primates have social complexity?
Quick at remembering socially relevant info
It is a species typical principle based on genetics
Trial and Error learning:
Because primates have fast social learning and connect social facts to environmental circumstances, they can quickly learn from situations
Example:
1. Event happens (Baboon attacked by adult)
2. Events follow (Mother protects young and gets food)
3. Application (Use situation is deceptive way next time)
OR
Learn based off observing others
Ability to Learn:
Based off size of neocortex
Ratio neocortex linked to larger brains
Dunbar: ratio also linked to size of group/social complexity
Size neocortex may also be related to recognition (social or environmental - such as fruits)
Apes have brain x2 size of mammal of same body mass
Feedback Loop:
Increasing social complexity may select for brain size
Increasing brain size affects behavioural complexity
(neocortex ratio affect frequency of deception)
Theory:
Larger brains evolved in response to a need for social skills, this increased brain size allowed for rapid learning which underlies the social sophistication of apes
Inability to understand mental state:
Tempting to assume animals using deception understand the situation
BUT comprehension of deceit and situation is not necessary
Rapid learning based off observation and application rather than understanding
Dorothy Cheney and Robert Seyfarth Experiment
Mother approached by "predator" when infant
a) can see threat
b) cannot see threat
In both circumstance mother alerted child of threat
Unaware of infants mental state of seeing or not
This explains why animals who are manipulated by deception do not understand what is happening
BUT Chimpanzees and apes show knowledge of intention:
Sarah Boysen Experiment
Chimpanzee approached by "predator" when friend
a) can see threat
b) cannot see threat
When chimpanzee realises its friend cannot see a call is raised and it acts to "protect"
When chimpanzee realises its friend can see there is no call raised
Chimpanzees can distinguish mental states
In the wild only chimpanzees teach offspring in a way that is aware of infants ignorance
Ability to understand mental state is unique to Great Apes:
Chimpanzees aware of when being deceived e.g. annoyed at a "look behind you" trick when there is nothing there
Cercopithecine monkeys use deceptive tactics more frequently than great apes
BUT the ways the apes use tactics imply awareness of what they were doing
Chimpanzees must have intentional social manoeuvring (e.g. switch allegiances)
Example:
Frans De Waal observe in Chimpanzee Politics:
Male who did not have qualities to become top ranked himself
Male used clever switches of allegiance to gain more effective power than held by either of the two males he supported
Once they began to solidify position with his support he defected to the other
Reasons behind social manoeuvring:
Males who require powerful ally to hold top rank were always vulnerable
A male who gradually built up a broad base of support among weaker males and females males was able to hold tenure far longer
Self-recognition:
Gordon Gallup notice chimpanzees, but not monkeys, show self-recognition
E.g. Looking in the mirror to examine hidden areas of their bodies such as teeth and gums, or making repeated, exaggerated gestures while watching their reflections
Complex understanding:
Few Old World monkeys regularly make/use tools
Chimpanzees in West Africa use two rocks as hammer and anvil to break nuts
Chimpanzees in East Africa use tools and bimanual coordination to capture ants
Manipulation of tools and techniques:
Capuchins use tools but in simplified situation - obvious visibility of hole of an open termite mound
Chimpanzees can termite fish with less clear mound, without a hole, and delicately guide tool - more abilities beyond use of tools
Planning:
Chimpanzees can plan their tactics driven by knowledge not immediate stimuli and show awareness of possible outcomes
Examples:
No suitable plant for fishing grows near termite mound, chimpanzees plan to make tools in advance to bring to site
No suitable rocks near nuts, chimpanzees carry a hammer-stone before they get to tree
Cultural Variation:
McGrew shows local traditions in chimpanzee tool use as in human cultures:
Some discard frayed tools
Some rotate tools to use less worn end
Some 'resharpen' tool
The use of inefficient methods shows social learning by imitation
Trial-and-error requires progression towards optimal technique and cannot pin point inefficiency if there is no more efficient method attempted to compare to
Elaborate series of actions:
Tool manipulation and planning is a great ape trait
Example:
Gorilla diet is mainly of plants which use stings/hard castings/mechanics which make it hard to it
Gorillas use techniques to minimise stings from nettles
Remove leaf blades in gathered bunch by using half-open hand to strip stem
Remove stems/petioles with worst stings
Folds leaf bundle so only one leaf sting side is exposed
Why are great apes cognitively superior?
Efficient Skill Learning Mechanism: Imitation
Gorilla: population consistent techniques and individual variation at detail
Chimps: inter-population tool use differences not explained by ecology
Orangutan: copy human traditions (e.g. building fire)
Comprehend objects and events - mental states and tool behaviour
Monkeys cannot acquire complex novel behaviour by observation and imitation
Great ape ancestor had cognitive potential to plan, imitate and understand others
Not due to further neocortex size (neocortex affects learning speed) so something else affect ape mental complexity (maybe structure?)
Selection Pressure:
Complex Social interaction
30m years ago: monkey and ape ancestor develop rapid learning and larger brain
Due to: Need for larger permanent groupings
Monkey vs Ape Competition
12m years ago: apes and human ancestor develop ability to take account of others' behaviour and understanding
Due to: Large size of apes adapted to brachiation (for trees) mean walk in awkward gait on knuckles
Old World monkeys have adv of eating unripe fruit
SO apes develop cognitive abilities such as foraging and planning to survive intense competition with monkeys
What cognitive skills were we left with?
A causal understanding of complex behaviour, enabling novel schedules of actions to be put together and allowing the behaviour of others to be used as a source of ideas for new action schedules; in other words, nonverbal planning and skill learning by imitation
A degree of understanding of the intentions of others-what they want, know, and think; in other words, possession of a theory of mind
Evolution of language would be impossible in a species in which individuals could not imagine that other individuals know things that they do not know themselves.
Language is acquired by imitation - not by direct copying
Children do not parrot our parents' words
Child "imitates" a word, the actual sounds are quite different and the use of the word is individual
An understanding of a novel behaviour is gained so an individual can express it in their way