Lecture 16 - Evolution of a social brain Flashcards
Outline of lecture
Outline:
The role of families, groups, tribes..
A.Humans take over the world
B.Why would I cooperate?
C. Natural selection: more concepts and counterintuitive cases
e.g. Mental health from an evolutionary perspective
Evolution of a social brain
Main linkages to other parts of course:
Social psychology
What is abnormal? (e.g. the example on anxiety)
Developmental Psychology
Why sapiens out compete neanderthals?
Group size as had similar language abilities etc
Why out compete on group size?
be kind?
What are some arguments for why being kind is altruistic
Altruism and kin selection - natural selection works at level of genes. Benefits have to outweigh costs but benefits relate to how related you are - more keen to help someone you are related to. I ought to be more altruistic to people who share that gene and this is the case in data.
Reciprocal Altruism
Conditions
- Opportunity for frequent interactions
-Ability to keep track of support given and recieved (memory and gossip)
-Preferentially provide support to individuals who support
– these effects can be shown in computational models of
evolution
… in turn this trait then becomes something advantageous to
look for in a partner as it would help your children to inherit
(and/or learn) the trait.
Talk about gene-culture coevolution
Cultural features (i.e. social learning, responses to disease) that
benefitted survival and expansion of tribes became more widespread.
In turn, they influenced genetic selection; because the environment
has changed. E.g. cooking led to gut reduction; Projectile weapons led to changes in human
hands and shoulders (humans are much better at throwing objects than chimpanzees); Language
led to larynx and brain changes;
Chimpanzee groups also have cultural differences (e.g. in the types of
tools they use and teach their offspring to use).
KEY CONCEPT:
Is the question of biology/instinct vs culture really ‘either/or’?
At the same time, selection pressures on human brains have worked
not just on specific abilities, but on the general ability and instinct to be social and learn from others – to ‘belong’ to your tribe.
We seem to be selected to have adaptable brains from evolving in a fluctulating environment so made to change or adapt
Talk about group selection
This means two things:
Natural selection can sometimes operate at the level of groups /
colonies / tribes (‘group selection’ or ‘multilevel selection’).
Genes that support an instinct to help your tribe can proliferate
(both because tribe members are often related to you, and also the tribe is
your protection and support).
note that this is not the same as simply saying animals will act for the benefit
of their species or groups; such behaviour would be selected against if it
means individuals without the allele supporting this behaviour benefit more
than the individuals showing the behaviour.
Summary of the lecture
Summary:
Natural selection simply means that those individuals most successful at
having successful offspring have a stronger genetic influence on the next
generations than those who have fewer or less successful offspring….
How we behave in groups/tribes (see social lectures) is one of the major
things that determines:
- who has sex with whom (social expectations and opportunities,
marriage customs etc)
- what helps offspring survive and thrive (cooperation, status, response
to disease, etc etc).
Being social animals and having cultures is arguably the most critical
factor of our evolutionary heritage… during human evolution the
environment has been made up of other humans
Approximations
To a first approximation:
- most behaviour is learnt;
- natural selection gave us the machinery to learn it efficiently, the drive to do things that help
learning, and the drive to learn the types of things that are helpful to survival in groups,
including a drive to do what others do (the route to culture?)
Concepts in this module that might be counter-intuitive in natural selection
Don’t fall into ‘the Naturalistic Fallacy’
George Edward Moore
Principia Ethica (1903)
We have to face up to the fact that aggression, war, murder,
theft, deceit, unfaithfulness, racism, sexism, other discrimination
and a host of other unpleasant behaviours have likely been part
of the ‘natural’ behaviour and evolutionary environment of our
tribal ancestry.
That does not justify them or make them inevitable – moreover,
understanding the heritage might help us minimise them
Natural selection: more concepts
It is a fallacy to assume that what is natural
is also good or inevitable
It is therefore illogical to justify (rather than seek to understand)
certain behaviours or inequalities based on evolutionary theories
ie dying of certain disease as ‘natural’ does not mean it is right
Level of explanation evaluation
Mental health and genetics
Many human behaviours or traits may not have
an immediately obvious benefit, appear detrimental, or
even demonstrably reduce survival and/or offspring
(either directly or by diverting time and resources)
e.g. altruism, adventure/risk-seeking, colour blindness,
music, mental illness (e.g. schizophrenia, depression,
anxiety),
And many of these traits have known genetic heritability (especially
mental health)…
Explanations around mental health
Natural selection: counterintuitive cases
What types of explanation are possible?
Possibility 1: too recent. i.e. the genetic risk didn’t lead to
detrimental effects in previous environments.
Possibility 2: the risk may be an unavoidable side effect of
something positive (the genes normally benefit something, but
carry the risk of coming together with other genes to raise the
probability of something detrimental (we met this with the black
death and auto-immune diseases).
Possibility 3: Being a Carrier may have no (or
positive) effect on offspring numbers or survival
(e.g. colour blindness).
Possibility 4: having a spectrum may be beneficial to most
individuals and/or to group success
Possibility 1: too recent. i.e. the genetic risk didn’t lead to
detrimental effects in previous environments.
Questions on the topic
- According to kin selection theory, genes that promote altruistic behaviour will propagate in the
population…
a) Only if the altruism favours immediate family
b) When the costs of that behaviour are outweighed by the benefit to others multiplied by the
probability they share that gene.
c) When the benefits are outweighed by the costs multiplied by the degree of genetic overlap
d) When the recipients are direct descendants rather than siblings or cousins. - The phrase ‘altruism is sexy’ is supported by modelling evidence for THREE of the
following statements. Which statement is the odd one out?
a) Altruism is better rewarded when there is opportunity for frequent interactions
b) There must be memory for support given and received
c) Altruism is only beneficial when individuals are related
d) In circumstances where altruistic individuals benefit on average, it becomes
advantageous to seek a mate who shows altruism. - Which of the following statements is true:
a) Animals will always act for the benefit of their species’ survival
b) Kin selection requires an animal to be able to recognise who is their kin
c) Kin selection can favour simple behavioural rules, such as help people you know well
d) Kin selection depends on the overall proportion of genes you share with others
Answers
1 is B
Questions more
- Which of the following statements is FALSE
a) Genes that support an instinct to help your tribe can proliferate if this helps your children and other kin prosper
b) Genes that support an instinct to help your tribe can proliferate only if all your tribe are your relations
c) Behaviour that favours other members of your tribe would be selected against if it means individuals without the
allele supporting this behaviour benefit more than the individuals showing the behaviour
d) Although natural selection works at the level of genes, group and inter-group behaviours can exert large influences - Our genetic heritage is often contrasted with social learning or culture in popular
thinking. This line of thinking is…
a) Appropriate because if something is socially learnt then genetics and evolution are
irrelevant
b) Inappropriate because culture is too recent to be compared or related to evolution
c) Appropriate because most behaviours are learnt during childhood
d) Inappropriate because cultures influence the propagation of genes through populations - The naturalistic fallacy is a label for:
a) Mistakenly thinking that ancestral humans were more peaceful than modern humans
b) Mistakenly thinking that what occurs ‘naturally’ is therefore good and justifiable
c) Mistakenly thinking that love and friendship are not valued if they are merely vehicles for
propagating your genes
d) Mistakenly forgetting that humans are one of the most dangerous animals (to other humans)
