week 1 Flashcards
Background to evolution
Lamarck: 1st to propose idea of ‘higher’ forms & inheritance of traits
Mendel (1865): proposed inheritance to be particulate (i.e. through genes)
Malthus (1798): argued would over-populate if all survived & reproduced
Darwin (& independently Wallace): proposed a means by which change could occur over time: theory of natural selection
Natural selection
Darwin 1859: inspired by finches of the Galapagos which where distinct led to the idea that they had same ancestor
Natural selection
Variation, in heritance, differential reproduction and adaptation
Not thinking forward. Tends to be gradual
Nervous system
All brain are related to similar species
Complex brains and behaviour from simpler brains and behaviour
Complex behaviour involves learning
Evolution of brains
First animal with brain cells appeared 700 million years ago
First brain appeared 250 million years ago
Complexity increases with more recently evolved groups
First humanlike brain appeared 3-4 million years ago
Modern human brains appeared around 200,000 years ago
Evolution of more complex behaviour is linked to the development of the cerebral hemispheres and cerebellum
Increased prominence/folding in more recently evolved groups
Human evolution
Distant ancestor: Australopithecus
Brain size 1/3 of ours; walked upright
H. habilis – used tools (2.8 million years ago)
H. erectus – 1st in Europe & Asia (until 100-30,000 years ago)
H. neanderthalensis – larger brains, communicated with language
H. sapiens – coexisted/bred with above
Encephalization quotient
Past 4 million years: increased body size; disproportionate increase in brain size
EQ: index of brain to body size
Calculated by comparing actual brain size to what one would expect given the animal’s body size
H. sapiens has the largest EQ
Large EQ = more complex behaviours
The overall number and density of neurons also important
EQs are more informative within a closely related group (e.g. primates) because density is constant
Human brain enlargement theories
Climate Change
New environments
Rapid selection for adaptive traits
Lifestyle
Complex foraging
Complexity of social life
Physiology Changes
Enhanced brain cooling
Reduced size of facial muscles
Slowed maturation (neoteny)
Adults retain some infant characteristics – large head
Longer pre-/neonatal period for brain cell production
Maturational changes
Do human brains just grow more?
Evidence from brain development suggest changes in the developmental processes
Frugivorous Primates
Fruit eating in primates is associated with larger brain size
Studies comparing hippocampus size in birds that cache food with controls (
Technical brains
Larger brain size is associated with innovation and technical ability
Overington et al. (2009) find a relationship between innovation diversity (novel foraging techniques) and brain size in birds
Social brain hypothesis
Larger brains evolved with increasing social complexity
Brain size is about group size (Jolly, 1966; Humphrey, 1976)
Dunbar (1998) characterised is at the number (and later quality) of relationships
Animal models
NHA research isn’t representative
Humans are too complex
The results are meaningless
NHA are anatomically and behaviourally very similar to humans
‘Animal models’ can provide information at the modular level
Experimentation on NHA opens many doors in terms of what can be learned
Species comparisons can test evolutionary relationships
Tinbergen’s 1963 4 questions
Function – adaptive value/contribution to fitness
Evolution – phylogenetic context of behaviour
Development – ontogeny of behaviours (e.g. imprinting, learning)
Causation – hormones, genes, nerve impulses, cognition controlling behaviour
