Transcript Document

Evolution, Psychology, Evolutionary
Psychology and Human Uniqueness
Stephen Walker
MSc Psychological Research Methods
PSYC073P
Epistemology and Philosophy of Science
December 12th 2006
Overview
• There will inevitably be some overlap with
nature/nurture issues (Dec 5th)
• There is also a a contrast between
evolutionary or biological psychology and
social constructionist or psychosocial
approaches (Nov 28th)
• At least two kinds of reductionism will be
illustrated: explaining behaviours as
adaptations, and explaining behaviours in
terms of neural circuits that control them.
Outline
• I will start off by looking at animal
behaviour, where evolution has relevance.
• “Evolutionary Psychology” is based on the
claim that human psychology is strongly
determined by human evolution.
• The evidence for these claims is often
extremely weak, but I will look at a few
recent examples.
• I will also look briefly at the evidence
concerning the course of human evolution.
Paper Handout
• *NB* the paper handout includes only a small
fraction of the slides in this presentation: a pdf of
most of the slides will be available on the intranet
• The paper handout includes a list of alternative
books on human evolution which are in BK library
on page 6
• Any pieces of work mentioned in the presentation
should have its citation listed on pages 7 & 8 of
the handout.
Fossils versus Genomics
• There are epistemological difficulties in studying
human evolution.
• The difficulties are in inferring the past course of
human evolution from a limited number of fossil
finds.
• But in the last 10 or 15 years technologies have
become available allowing geneticists to pinpoint
where and when the human genome has
undergone significant changes.
Evolution and DNA
There is a huge amount of
information pertinent to
evolution produced by
recent technologies: these
are citations for the paper by
Altschul et al. (1990) about
a search tool for DNA and
protein sequence databases
Wikipedia says this was the most widely cited of all
scientific papers published in the 1990s
Genomics and Bioinformatics
• DNA sequencing, inc human and chimpanzee
• Gene splicing and genetic engineering
• Gene expression data from ‘Microarrays’
The Darwinian Theory of Evolution −
“Descent with Modification”
 There are inherited differences between
individuals
 These include random variations
 Resources are not unlimited
 Some individuals will flourish more than
others and produce more offspring
 Natural selection occurs if a population
changes over generations because of this
Evolution — II
• The first point about evolution is that it
connects the human species with the rest of
the animal kingdom,
• However, it is also possible and indeed
likely that the course of human evolution
has led to humans being uniquely different
from all other currently living species
Human Uniqueness on behavioural grounds
Almost all animal
behaviour is genetically
pre-programmed (by
evolution) to fit an
ecological niche (Darwin, 1859;
Tinbergen, 1951; Manoli and Baker, 2004)
Almost all human
behaviour involves
cultural learning
(Tomasello and Razoksky, 2003; Tomasello
et al., 2005)
Darwin (1859) The Origin of Species
• Chap VII “Instinct”. Not defined, but three main
examples
• The instinct of the female cuckoo to lay small eggs
in other bird’s nests, and the egg-ejection behavior
of the newly hatched cuckoo chick;
• Slave-making instincts in some
species of ant
• The cell-making instinct of the
honeybee
• The behaviors were seen by
Darwin as not necessarily
dependent on anatomical
characteristics
Darwin on Honey bees
• Darwin thought that the honey comb was “absolutely
perfect in economising labour and wax” on the
grounds of geometry.
• But it also “can be explained by natural selection
having taken advantage of numerous, successive,
slight modifications of simpler instincts”. These were
based on spheres as in bumble bees, with S. American
stingless bees intermediate. NB thousands of solitary
bees which do not store honey
Another of Darwin’s examples:cuckoos
Another of Darwin’s examples:cuckoos
Darwin (1859) page 185 function and form
http://darwin-online.org.uk
• “…. the acutest observer by examining the dead
body of the water-ouzel would never have
suspected its sub-aquatic habits; yet this
anomalous member of the strictly terrestrial thrush
family wholly subsists by diving,—grasping the
stones with its feet and using its wings under
water.”
• Actually has some anatomical adaptations: 3rd
eyelid, nostril flaps and oil gland 10 times larger
than non-aquatic perching birds.
• But Voelker (2002) agrees that the thrush is the
closest relative and suggest that dippers diverged
only 4m years bp
Darwin (1859) page 185
http://darwin-online.org.uk
• And the behavioural adaptation would have come
first −
• Thrushes foraging in streams instead of solid
ground would then find enlarged oil glands useful
Dipper diet includes aquatic insect larvae
• Caddis fly larvae build themselves cases, in
various ways depending on the species.
• The Darwinian position would be that they inherit
the behaviours required for this task.
• But in fact Stuart and Currie (2002) found that
there was little relation between the types of
behaviours and the structural end-product across a
variety of species.
• Do species need a ‘genetic blueprint’ for the endproduct?
Evolution connects the human species with
the rest of the animal kingdom
Era
Cenozoic
Period, begins (Million Years)
Quaternary
Holocene 0,01
Pleistocene 1.6
Tertiary
Pliocene
5
Miocene
23
Oligocene 35
Eocene
56
Paleocene 65
145
210
250
Dinosaurs
Mesozoic
Cretaceous
Jura
Trias
290
360
410
440
505
545
Reptiles, birds, mammals
(Amniotes)
Paleozoic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Proterozoic
Archean
2500
3800
Precambrian
Man
Primitive fish
Oldest fossils of complex animals
Creation of extant phyla
First multicellular organisms
First bacteria
Lappin et al., 2006; standard texts
EVOLUTIONARILY CONSERVED MOLECULAR GENETIC MECHANISMS FOR
PATTERNING THE EMBRYONIC BRAIN .
Reichert, H., & Simeone, A. (2001)
Fly mutant
restored
with human
gene
Fly mutant
restored with
mouse gene
Mouse mutant
restored with
fly gene
Bishop et al., 2002
Ethological analyses of animal behaviour
Vitalists believed in the
instincts as mystical…. and
behaviourists were
preoccupied with
learning…the way out was
focussing on the survival
value of behaviour patterns.
“Behaviour patterns
become explicable when
interpreted as the result of
natural selection, analogous
with anatomical and
physiological
characteristics.”
Tinbergen
1951, title and frontispiece
Genome news network
Zig-zag dance
Experimental stimulus variation
• There is no entry for gene
in the 1951 index
• But instinct and “innate”
are the themes, and refers
to genetics and mutations
in the chapter on “The
Evolution of Behaviour”
• Tinbergen included some
ill-advised evolutionary
psychology
• But there is a case that
explanations for
stickleback and human
behaviour should be
fundamentally different.
A Study of Instinct
1951
Instinct - 2
• Tinbergen (1951) stressed two key concepts
• 1. “sign stimuli” e.g. redness for
sticklebacks.
• 2. The “innate releasing mechanism”, by
which particular sign stimuli release
particular instinctive behaviour patterns
• He believed these concepts applied to
mammals
• But the evidence is much clearer with lower
vertebrates and invertebrates
E.g. Spiders
The orb web
A first attempt
e.g. spiders 2
Darwin’s comment on spiders
“Thus everywhere in nature are battle, craft, and
ingenuity, all following the merciless law of
egoism, in order to maintain their own lives and to
destroy those of others” Charles Darwin writing
in Animal Intelligence by G.J. Romanes (1882),
commenting on wolf and trapdoor spiders, p. 213
Innate behaviours e.g. fruitfly courtship
Kimura, K. I., Ote, M., Tazawa, T., & Yamamoto, D. (2005).
Fruitless specifies sexually dimorphic neural circuitry in the
Drosophila brain. Nature, 438(7065), 229-233.
“…..we identify a subset of fru-expressing interneurons in
the brain that show marked sexual dimorphism in their
number and projection pattern……. Fru expression can
produce a male-specific neural circuit,”
“Throughout the animal kingdom the innate nature of basic
behaviour routines suggests that the underlying neuronal
substrates necessary for their execution are genetically
determined and developmentally programmed” Manoli &
Baker (2004).
e.g. fruitfly aggression
Vrontou et al., (2006) fruitless regulates aggression and
dominance in Drosophila Nature Neuroscience, 9,(01 Dec 2006), 1469 - 1471
When competing for resources, two flies of the same sex
fight each other. Males and females fight with distinctly
different styles, and males but not females establish
dominance relationships. Here we show that sex-specific
splicing of the fruitless gene plays a critical role in
determining who and how a fly fights, and whether a
dominance relationship forms.
“our data indicate that aggressive behaviors are
hardwired into the fly’s nervous system”
also vertebrates e.g. zebrafish
Gahtan, E., Tanger, P., & Baier, H. (2005). Visual prey
capture in larval zebrafish is controlled by identified
(four of them) reticulospinal neurons downstream of the
tectum. Journal of Neuroscience, 25(40), 9294-9303.
“Many vertebrates are efficient hunters and recognize
their prey by innate neural mechanisms. During prey
capture, the internal representation of the prey's
location must be constantly updated and made available
to premotor neurons that convey the information to
spinal motor circuits.”
“Seven-day-old zebrafish oriented toward, chased,
and consumed paramecia with high accuracy.”
Also birds
e.g. Dilger
(1961)
Also for mammals
Choi et al. (2005) Lhx6 delineates a pathway mediating
innate reproductive behaviors from the amygdala to the
hypothalamus, Neuron, 46(4), 647-660 (in embryonic and adult mice)
“Virtually all metazoan organisms exhibit innate
reproductive and defensive behaviors that are triggered
by signals sensed from conspecifics or predators. ….
The stereotypical nature of these behaviors suggests
that their underlying neural circuits are likely to be
genetically ‘hard-wired’.”
“In mammals, innate reproductive and defensive
behaviors are mediated by anatomically segregated
connections between the amygdala and hypothalamus.”
Slide 4 from the 2004 Nobel Lecture: Linda Buck
Contrasts
• there remain very contrasting positions within
contemporary psychology particularly relating to
how much emphasis is given to broadly biological
as opposed to psychosocial evidence and theory.
• The contrasts are less stark if we use “horses for
courses”: explaining how the olfactory system
works in mice is different from theorising about
voting intentions in the Ukraine (2004) or the Tory
leadership election (2005) or political events in
Lebanon (2006)
Evolutionary Psychology
• Attempts to explain human psychology as a
series of specialized adaptations
• Driven in part by Chomskyan linguistics
(see last week’s lectures): Pinker has
written several more general books, most
recently “The Blank Slate” (2002) as well
as “The Language Instinct (1994)
Adaptations
• Williams (1966) defined an adaptation as “a
characteristic that has arisen through and
been shaped by natural and/or sexual
selection.
• It regularly develops in members of the
same species because it helped to solve
problems of survival and reproduction in
the evolutionary ancestry of the organism.
• Consequently it can be expected to have a
genetic basis ensuring that the adaptation is
passed through the generations”.
Spandrels
Gould and Lewontin, 1979; Gould, 1997
“An adaptationist programme has dominated
evolutionary thought in England and the United States
during the past forty years. It is based on faith in the
power of natural selection as an optimizing agent.”
We fault the adaptationist programme for its
unwillingness to consider alternatives to spandrels and
adaptive stories……..”
exaptations are
side effects of
natural selection
Evolutionary Psychology
Bjorklund, D. F., & Smith, P. K. (2003). Evolutionary developmental
psychology: Introduction to the special issue. Journal of Experimental
Child Psychology, 85(3), 195-198
Evolutionary psychology, originally on the fringe of
academic psychology.., has gained respectability
within the last decade. Articles written from an
evolutionary psychological perspective are found in
the field’s most prestigious outlets; it has
professional societies and journals of its own;
college courses and textbooks are devoted to it; and
there are academic positions specifically designated
for evolutionary psychologists.
Tooby and Cosmides
• Cosmides, L. (1989). The logic of social
exchange: has natural selection shaped how
humans reason? Studies with the Wason
selection task. Cognition, 31: 187 - 276.
• Duchaine, B., Cosmides, L., & Tooby, J.
(2001). Evolutionary psychology and the brain.
Current Opinion in Neurobiology, 11(2), 225230.
Swiss Army Knife
Cosmides: The Swiss Army knife is a flexible tool. Its
flexibility is not the result of having just one tool that is
applied to all problems. Instead, it is a bundle of tools,
each well-designed for solving a different problem –.
Similarly, the human mind does not have just one
blunt tool for solving all problems – and if it did, we
would be very limited indeed..
Cosmides (1989)
• Logic: If P then Q is only violated by P & ~Q
• Typically participants do not use this logic in the
Wason 4 card test (if vowel, theneven number on
back)
• A. if you have a bus pass, then you travel by bus
• B. if you travel by bus, then you have a bus pass
• Cosmides used many more elaborate scenarios,
and found a strong bias towards “detecting
cheaters” in that participants get A wrong, but B
right.
• But there is widespread disagreement, both
with the specific claims made about
reasoning and the Wason card-turning test,
• And with the general claims about highly
specialized mental tools for solving specific
problems
Examples
• However, a few examples follow of papers
firmly in the field of evolutionary psychology in
recent issues of reputable journals.
• Catatonia, Anorexia Nervosa and depression are
proposed as adaptations,
• there is a fairly general theory about individual
decision rules interacting with group dynamics,
• a paper proposing an evolutionary account of
human facial expression of pain,
• and a paper arguing that a human “innate
releasing mechanism” for understanding agency
is a key feature of religious concepts of the
supernatural.
Moskowitz, A. K. (2004). “Scared stiff”:
Catatonia as an evolutionary-based fear
response. Psychological Review, 111(4), 9841002.
Guisinger, S. (2003). Adapted to flee famine: Adding an
evolutionary perspective on anorexia nervosa.
Psychological Review, 110(4), 745-761.
Anorexia nervosa (AN) is ..attributed to
psychological conflicts, attempts to be fashionably slender,
neuroendocrine dysfunction, ……. Considerable research
reveals these theories to be incomplete…..
This article presents evidence that AN's distinctive
symptoms of restricting food, denial of starvation, and
hyperactivity are likely to be evolved adaptive
mechanisms that facilitated ancestral nomadic foragers
leaving depleted environments; genetically susceptible
individuals who lose too much weight may trigger these
archaic adaptations. This hypothesis accounts for the
occurrence of AN- like syndromes in both humans and
animals and is consistent with changes observed in the
physiology, cognitions, and behavior of patients with AN.
Guisinger table
Depression
• Allen, N. B., & Badcock, P. B. T. (2006). Darwinian
models of depression: A review of evolutionary accounts of mood and
mood disorders. Progress in Neuro-Psychopharmacology & Biological Psychiatry, 30(5), 815-826.
• According to the social risk hypothesis, depression
represents an adaptive response to the threat of
exclusion from social relationships that, over the
course of evolution, have been critical to maintaining
an individual's fitness prospects
• in the ancestral environment, depression induced: (i)
sensitivity to social risk/threat; (ii) signaling
behaviours that elicit social support; and (iii) a
reduction in risky behaviours
Kenrick, D. T., Li, N. P., & Butner, J. (2003). Dynamical evolutionary
psychology: Individual decision rules and emergent social norms.
Psychological Review, 110(1), 3-28.
• Following evolutionary models, psychological
mechanisms are conceived as conditional decision
rules designed to address fundamental problems
confronted by human ancestors,
• A new theory integrating evolutionary and
dynamical approaches is proposed.
• Three series of simulations examining trade-offs
in cooperation and mating decisions illustrate how
individual decision mechanisms and group
dynamics mutually constrain one another, and
offer insights about gene-culture interactions.
Kenrick and Butner, 2004
“At the most general level, evolutionary
psychology can be defined as the study of
cognitive, affective, and behavioral mechanisms as
the solutions to recurrent adaptive problems.”
“Along with the morphological features designed
by natural selection, organisms also inherit central
nervous systems……The behavioural
inclinations of a bat would not work well in
the body of a dolphin or giraffe and viceversa.”
Kenrick and Buttner wrong
• over a period of 35 years in Sweden (1965-
1999), there was no overall overrepresentation of stepchildren as victims.
• Temrin, Nordlund, & Sterner, H. (2004)
• In families with both stepchildren and
children genetically related to the offender,
genetic children tended to be more likely to
be victims.
Williams, A. C. D. (2002). Facial expression of pain: An evolutionary
account. Behavioral and Brain Sciences, 25(4), 439-+.
• This paper proposes that human expression of pain ..,,
arises from evolved propensities.
• The function of pain is to demand attention and
prioritise escape, recovery, and healing; where others
can help …, a distinct and specific facial expression of
pain from infancy to old age, consistent across stimuli,
and recognizable as pain by observers.
• ……..there has been skepticism about the presence or
extent of pain, judgments of malingering, and
sometimes the withholding of caregiving and help.
• … an evolutionary account can generate improved
assessment of pain and reactions to it.
Darwin’s “The expression of the emotions in
man and animals” (1872)
Peleg et al. (2006). Hereditary family signature of
facial expression. PNAS 103(43), 15921-15926
• Correlated facial expressions in congenitally blind
subjects and their seeing relatives, anticipates
genes.
Further examples
• Rhodes, G. (2006). The evolutionary psychology
of facial beauty. Annual Review of Psychology, 57, 199-226.
• face preferences may be adaptations for mate
choice because attractive traits signal important
aspects of mate quality, such as health
• Averageness, symmetry, and sexual dimorphism
are good candidates for biologically based
standards of beauty
Atran, S., & Norenzayan, A. (2004). Religion's evolutionary landscape:
Counterintuition, commitment, compassion, communion. Behavioral and
Brain Sciences, 27(06), 713-730.
• Religion is not an evolutionary adaptation per se,
• but a recurring cultural by-product of the complex
evolutionary landscape
• A key feature of the supernatural agent concepts
common to all religions is the triggering of an
“Innate Releasing Mechanism,” or “agency
detector,”
• whose proper (naturally selected) domain
encompasses objects relevant to hominid survival
– such as predators, – but which actually extends
to moving dots on computer screens, voices in
wind, and faces on clouds.
Domain General and Domain Specific
• The “Swiss army knife” idea is more formally
expressed in terms of domain specific or
modular capacities.
• The next paper argues that general intelligence
is also domain-specific
• This is dangerous for Evolutionary Psychology,
since it opens the door to the idea that human
evolution ended up by providing us with very
open-ended and general purpose psychological
capacities.
Kanazawa, S. (2004). General intelligence as a domainspecific adaptation. Psychological Review, 111(2), 512-523
• General intelligence (g) poses a problem for
evolutionary psychology's modular view of the
human brain. The author …. argues that general
intelligence evolved as a domain-specific
adaptation for the originally limited sphere of
evolutionary novelty in the ancestral
environment…
• It has accidentally become universally important
merely because we now live in an evolutionarily
novel world
Kanisawa, Psych Review 2004
More Domain General ideas
Atkinson, A. P., & Wheeler, M. (2004). The grain of
domains: The evolutionary-psychological case against domain-general
cognition. Mind & Language, 19(2), 147-176.
..evolutionary psychologists have argued that our
innate psychological endowment consists of
numerous domain- specific cognitive resources,
rather than a few domain-general ones. … We
conclude (a) that the fundamental logic of
Darwinism,….. does not entail that the innate mind
consists exclusively, or even massively, of domainspecific features, and (b) that a mixed innate
cognitive economy of domain-specific and domaingeneral resources remains a genuine conceptual
possibility.
Human Ancestors
• “psychological mechanisms are
conceived as conditional decision rules
designed to address fundamental
problems confronted by human
ancestors” (Kenrick and Butner, 2004)
• This is a typical claim in evolutionary
psychology, but there seems little
detailed interest in what human
ancestors might have done.
Human Evolution
• The epistemology of human evolution is
necessarily difficult, since it relies on
fossils, but fossil evidence has a
reasonable track record in other areas,
and human artefacts, in particular stone
tools, provide another source of
evidence
Human evolution, summarised on p. 6 of handout
Millions
top
Family Tree
A new early fossil (2006)
Alemseged, Z., et al. (2006). A juvenile early hominin
skeleton from Dikika, Ethiopia. Nature, 443(7109), 296-301
Dikika is only 4km from where ‘Lucy’ was
found (Australopithecus afarensis )
The Dikika specimen, from 3.3m yrs ago was
about 3yrs old and probably female.
The legs were human-like for bi-pedal
walking, but the arms and hands ape-like.
The hyoid bone (for the larynx) was also
ape-like
New Neanderthal data: Green et al., (2006)
• Suggests common ancestor ~450,000 yrs ago
Human uniqueness
• The human brain is uniquely large
• It is also functionally lateralized in a
way which differs from chimpanzees
• It may be metabolically enhanced
Cacares et al (2003)
• It may include different physiological
components (Allman et al., 2005)
• It may be organized uniquely, e.g.
large frontal lobes (Deacon, 1997)
Number of neurons in the nervous system
1,000,000,000,000
350,000,000,000
100,000,000,000
500,000,000
300,000,000
50,000,000
850,000
250,000
20,000
381
302
•
•
•
•
•
•
•
•
•
•
•
Homo sapiens (maybe 1014)
Chimpanzee
Rhesus monkey
Mouse
Octopus
Stickleback
Honey bee
Fruitfly
Sea slug
Thread worm male
Thread worm
In Striedter, G. F. (2006). Precis of Principles of brain evolution.
Striedter brain szie
Dorus, S., et al. (2004).
Accelerated evolution
of nervous system
genes in the origin of
Homo sapiens. Cell,
119(7), 1027-1040
Human, chimp,
organg, Rhesus
primary
microcephaly
Ponting and Jackson, 2005
• …….recent advances from the cloning of two human disease
genes promise to make inroads in the area .. of brain size
evolution.
• Microcephalin (MCPH1) and Abnormal spindle-like
microcephaly associated (ASPM) are genes mutated in primary
microcephaly.
• In this, the brain is of a size comparable with that of early
hominids.
• It has been proposed that these genes evolved adaptively with
increasing primate brain size. ….both genes have undergone
positive selection during great ape evolution.
• the evolutionary patterns of all four presently known primary
microcephaly genes are consistent with the hypothesis that
genes regulating brain size during development might also play a
role in brain evolution in primates and especially humans
(Evans, 2006)
More on brain size genes
• Evans et al., (2005) claim the microcephalin
has continued to evolve adaptively in
modern humans
• They say one genetic variant of
microcephalin appeared as recently as
37,000 years ago.
• The same team (Merkel-Bobrov et al, 2005)
say that APSM, another gene regulating
brain size, had a new variant only 5,800
years ago
Huxley’s
comparisons
“So far as cerebral structure goes
therefore, it is clear that man differs less
from the Chimpanzee or the Orang, than
these do even from the monkeys, and that
the difference between the brains of the
Chimpanzee and of Man is almost
insignificant, when compared with that
between the Chimpanzee brain and that of
a Lemur. “(Darwin, 1874/1901, p. 312)
semendeferi1
The Semendeferi et al., (2002) table
Semendeferi table
Brain re-organization: expansion of the frontal
lobes
The sherwood 2005
• Schoenemann et al.(2005) recently suggested that
prefrontal white matter is disproportionately larger
in humans than in other primates
• but Sherwood et al. (2005) countered that a) the
boundary between prefrontal and other cortex is
not well defined; and b) that in any case, although
the data showed humans having more white matter
than the average primate, they did not show a
difference between humans and great apes.
•
•
•
•
Allman et al 2005
Von Economo neurons (VENs) are a
recently evolved cell type which may be
involved in the fast intuitive assessment of
complex situations.
As such, they could be part of the circuitry
supporting human social networks.
We propose that the VENs relay an output
of fronto-insular and anterior cingulate
cortex to the parts of frontal and temporal
cortex associated with theory-of-mind
We propose that in autism spectrum
disorders the VENs fail to develop normally
Allman et
al., 2005
Human Brain Asymmetries
Hutsler, 2003
7 autopsies:
50-97 yrs of
age.
No
chimpanzees
Sun, T., & Walsh, C. A. (2006). Molecular approaches
to brain asymmetry and handedness. Nature
Reviews Neuroscience, 7(8), 655-662
Sun, T., & Walsh, C. A. (2006). Molecular approaches
to brain asymmetry and handedness.
Elevated neuronal activity?
• Caceres et al. (2003) applied a variety of genetic
techniques to the cortical tissue (removed post-mortem) of
humans, chimpanzees and rhesus macaques.
• These suggested that humans and chimpanzees are more
similar to each other than to the macaques, which is as
expected,
• but also that there were dozens of genes that were
expressed very differently in human and chimpanzee
cortex, with 90% of these being expressed more actively in
humans than in chimpanzees, which suggested that
• The human is brain is characterized by “elevated levels of
neuronal activity”.
• As a contrast, comparing gene expressing in the human
and chimpanzee heart and liver revealed very little
difference of this kind.
Sherwood, C. C., et al. (2006). Evolution of increased glia-neuron ratios in the human
frontal cortex. PNAS, 103(37), 13606-13611.
• the human glia-neuron ratio in the prefrontal region did not differ
significantly from predictions based on brain size.
• Further analyses of glia-neuron ratios across frontal areas in a
humans, chimpanzees, and macaque monkeys showed that regions
involved in specialized human cognitive functions, such as "theory
of mind" (area 32) and language (area 44) have not evolved
differentially higher requirements for metabolic support.
• …greater metabolic consumption of human neocortical
neurons relates to the energetic costs of maintaining
expansive dendritic arbors and long-range projecting
axons in the context of an enlarged brain.
• “Sherwood
et al. (1) provide support for the
idea that the human brain is more or less
a large hominoid (ape) brain and can be
understood in that context.”
• Enard et al., (2002) did cross-species comparisons
of the DNA for FoxP2, which when mutated gives
rise to articulatory disorders in humans. Although
it is “highly conserved” their data suggested that
“this gene has been the target of selection during
recent human evolution.
• Watakabe et al., (2006) review gene expression
profiling of postnatal rhesus neocortex. Although
there is overall homogeneity of gene expression
across different cortical areas, a few genes show
marked area-specific patterns, e.g. genes specific
to visual cortex and to association cortex.
More genetic suggestions for human uniqueness
• Prabhakar et al, (2006) found many humanspecific changes in regulatory sequences of DNA
with almost no overlap with chimpanzee
equivalents and suggest that these may have
contributed to uniquely human features of brain
development.
• Pollard et al., (2006) found a particular regulatory
gene expressed especially in certain neurons in
human neocortex from 7 to 9 gestational weeks
and say that this and similar “human accelerated
regions provide new candidates in the search for
uniquely human biology”
Paleontological evidence from human
evolution
• Stone tools provide the main currently
available clues to human evolution
• But partly because they survive only
periods of geological time
• Other artifacts made from wood and
bone may have been important, even if
nothing now survives
Psychologist
cover
Oldowan tools >2m years
Acheulian
tools
1,4 m – 0.5 m
yrs, mainly
Homo erectus
Size of Handaxes
Neanderthal
tools, 400k yrs
ago – 100k
(Mousterian)
Approx 25 k
years ago,
modern homo
sapiens
Delagnes & Roche (2005)
• Even 2.34m years ago there was a highly
controlled technology for producing stone flakes
following constant technical rules and resulting in
high productivity.
• Their data consists of reconstructions of cobble
reduction sequences --- putting the flakes back
together, e.g.
Delagnes & Roche (2005) 2.34m years ago
The hand and tools
The hand and tools
• Some apes from around the time of the last
common ancestor seemed to have hands
like early hominids (Moya-Sola et al, 2005;
Alba et al., 2003)
• Since modern apes show some evidence of
tool use it is likely that the hands became
adaptively useful from the very earliest
stages of bipedalism.
Chimpanzee tools
The hand and tools: Castiello 2005
Findings from patients
with brain damage who
have difficulty in
grasping objects are
difficult to reconcile with
neurophysiological
findings, ……….
……as the patients' lesions are confined to regions that,
in monkeys, do not seem to be involved in graspingrelated visuomotor transformations ---
Napier (1980)
Napier infants
Napier, ape
hands
Napier, power
and precision
grips
Napier – Screwtop
The hand and tools: conclusion
• The consequence of evolution is that
humans have domain-general potential for
manual skill
• The hands can be used for anything
anatomically possible
• There is no evidence for completely
steretotyped movements, even for the
precision grip (Wong and Whishaw, 2004)
Wong, Y. J., & Whishaw, I. Q. (2004). Precision grasps of children and young
and old adults: individual differences in digit contact strategy, purchase pattern,
and digit posture. Behavioural Brain Research, 154(1), 113-123.
The grasping patterns of male and female young
adults, older adults and children were examined as
they reached (with both left and right hand) for five
small beads (3-16 mm diameter).
Frame-by-frame analysis of grasping indicated a high
degree of variability in digit contact strategies,
purchase patterns and digit posture both within and
between subjects.
Other technologies: Neanderthal hut
Mammoth remains
Other technologies: Cave
paintings, Southern France
and Spain, 31,000 to 8,000
year before present
Chauvet (31k) bison with active legs
Detail of horses at Chauvet (31k)
Hand at Chauvet (31k)
Lamp at Lascaux
(13k)
Bull at Lascaux
(13k)
Functional differences: cultural learning
• Tomasello & Rakoczy (2003) have argued that there are
and invention
•
•
•
•
two (initial) stages of uniquely human social cognition.
The first stage is observable in one year olds, who have
an understanding of other persons as intentional agents,
This enables them to take part in pretend play, and is
important as a prerequisite for shared attention and early
social and linguistic learning.
The second stage is the “Theory of Mind” belief-desire
psychology which normally starts around 4 years of age,
but which is dependent on several years of linguistic
communication.
These early stages of uniquely human social cognition
enable the cultural “ratchet” of social and
technological innovation (Tomasello et al., 2005)
“And so if we imagine a human child born onto a
desert island, somehow magically kept alive by
itself until adulthood, it is possible that this
adult’s cognitive skills would not differ very
much – perhaps a little – but not very much, from
T and rakoczy
those of other great apes.” (p. 121)
Understanding and sharing intentions
Tomasello et al., 2005
• a species-unique motivation to share emotions,
experience, and activities with other persons..
Leading to ..
• “species-unique forms of cultural cognition and
evolution”
Understanding and sharing intentions 2
Tomasello et al., 2005
• “But then about 2 million years ago, when the
manufacturing of tools began to be especially
important .., individuals who could analyze
intentional actions even more deeply, … were at a
selective advantage.”
• But prefer not to end with .. evolutionary
scenarios, but with our ontogenetic model, of
which more components are directly testable
Human Uniqueness on behavioural grounds
Almost all animal
behaviour is genetically
pre-programmed (by
evolution) to fit an
ecological niche (Darwin, 1859;
Tinbergen, 1951; Manoli & Baker, 2004; Choi et al.
2005)
Almost all human
behaviour involves
cultural learning
(Tomasello and Razoksky,
2003; Tomasello et al., 2005)
Reading
• As last week for nature/nurture
• Any of the papers quoted.
• Or a debate initiated by Lickliter, R., &
Honeycutt, H. (2003). Developmental
dynamics: Toward a biologically plausible
evolutionary psychology. Psychological
Bulletin, 129(6), 819-835.
• Or take a brief look at one of the books on
human evolution listed in the handout.
Books on Human Evolution (alternatives)
on page 6 of handout
Bradshaw, J. L. (1997). Human Evolution: A
Neuropsychological Perspective. Hove: Psychology Press.
BK lib 599.935BRA.
Johanson, Donald C., and Edgar, Blake (2001) From Lucy
to Language. London: Cassell paperbacks. 2 copies in
Main Birkbeck Library, classmark=599.938 JOH
Jones, S., Martin, R. D., & Pilbeam, D. R. (1992). The
Cambridge encyclopedia of human evolution. Cambridge
[England] ; New York, NY, USA: Cambridge University
Press, BK lib 599.9 CAM, 3 copies
Richards, G. (1987) Human Evolution. Routledge:
London. (Bk Lib GYW, N [Ric])
Conclusions
• Evolutionary theory is essential for many areas
of animal behaviour, and rapid advances in
molecular genetics may impinge on
knowledge of the physiological underpinnings
of human capacities
• But a crucial outcome of human evolution was
a fairly open aptitude for cultural and
technological invention
• The human brain may not be equivalent to a
blank slate, but it has large areas of free space
for cultural and historical changes — the blank
parts may be the most important.