Final Flashcards
Sahelanthropus tchadensis
possible hominin or ape ancestor or both mixture of traits: -small brain -small teeth, canines -heavy brow ridge -elongated skull -large orbital torus
Orrorin tugenesis
small teeth with thick enamel
femora show evidence of bipedal locomotion but not conclusive
upper limb evidence of climbing adaptation
could be prior to pan/hominin split
Ardipithecus ramidus
4.4 to 5.8 MYBP
woodland habitat
anterior position of foramen magnum = upright posture and likely bipedalism
molars intermediate between chimp and australopithecine
larger canines than australopithecines, broader than in chimps
Suspensory locomotion - common ancestral condition?
evidence:
- more horizontal ilia, cup-like pelvis
- open mobile lumbar spine
- more vertical posture, but
- short legs, short arms
Australopithecines
bipedal apes with large thick enamel teeth, reduced canines, ape-size brains, high sexual dimorphism, savannah or open woodlands, mostly vegetarian diet
Australopithecine Body
compromise of locomotor adaptations 1. broad horizontal pelvis 2. extended "free" lumbar vertebrae but! 3. rib cage of a climber-brachiator 4. long curved fingers and slightly diverged big toe of a brachiator
Australopithecine: Small Stature
australopithecines were much smaller than modern humans
would make upright locomotion preferential for a suspensory adapted body frame (like gibbons)
ratio of weight to stature increases with size
Australopithecus africanus
3.6 MYA
6 lumbar vertebrae (one more than humans, 3 more than chimps)
further evidence against knuckle-walking ancestry
also bipedally adapted pelvis and femur
Australopithecine Teeth
reduction of canines and diastema
regressive in all australopithecines
greatest in early species, most reduced in later robust species
Australopithecus anamensis
3.9 to 4.2 MYA
obligate biped
20% larger than A. africanus, sexually dimorphic
larger molars than Ardipithecus, thicker enamel
large elongated canines
Australopithecus afarensis
2.9 to 3.6 MYA
clear bipedal adaptations: knee angle, wide bowl-shaped pelvis
massive face, jaw, molars
canines still protrude beyond tooth row and slight diastema
significant sexual dimorphism
Australopithecus robustus
1 to 2 MYA
large zygomatic arch and sagittal crest
maybe from africanus?
Australopithecus aethiopicus
2.5 MYA
small brain, posterior foramen magnum, massive sagittal keel, and wide zygomatic arch
Australopithecus boisei
1.2 to 2.3 MYA massive molars with extensive wear reduced canines and incisors sagittal crest broad zygomatic arch gorilla size brain likely lived at the same time (1.2 MYA) as some Homo species
Australopithecus sediba
many intermediate features
long thumb, shorter stubby fingers
shape of the pelvis is not as wide as other australopithecines (center) and more like later Homo
Australopithecus garhi
2.5 MYA
large molars and incisors, sagittal crest
femur elongation
evidence of stone tool use:
-broken and scratched bovid and horse bones
-show regular parallel linear scratches
-Oldowan type stone chips found at site
Oldowan Tools
Gona, Ethiopia 2.4 MYA
used by A. garhi, H. habilis, H. rudolfensis, early H. erectus/ergaster
appear to have been made “as needed” at butchery sites
more evidence of scavenging than hunting
Australopithecine vs. Homo adaptations
Australopithecine - bipedal with some suspensory adaptations, grassland habitat, large molars, reduced canines, ape-size brain, high sexual dimorphism
Hominine - fully bipedal, no suspensory adaptation, diverse habitats, small jaw and molars, canines, stay small, enlarged brain, low sexual dimorphism
Homo habilis
1.8 MYA
small molars, thin enamel, reduced incisor
reduced face, rounded cranium, 550 cc brain
reduced sexual dimorphism
Oldowan tools
Homo ergaster
1.75 MYA
small molars, thin enamel, reduced incisors
reduced face, rounded cranium, and 850 cc brain
reduced sexual dimorphism
extensive Oldowan tools
Homo rudolfensis
1.8 MYA
large brain (775 cc)
rounded vaulted cranium
heavy flat face
large incisors and canines compared to molars
first species with a brain size larger than other apes
Australopithecus face; Homo brain
Homo naledi
currently classified as a transitional species because that is the most parsimonious
strange (cave) location in which it was found
some evidence to suggest a much longer persistence of australopithecines
Homo ergaster
1.75 MYA
larger brain (850 cc), rounded cranium
reduced face and zygomatic arch
reduced molars, thin enamel, small canines compared to incisors
extensive Oldowan usage
robust but otherwise modern post-cranial skeleton, but smaller brain/long robust skull
coexisted with A. boisei for a while (did they hunt boisei?)
Transition to Homo ergaster
marked by an increase in both body size and brain size over any australopithecines
all correlates of arboreal adaptations vanish
loss of sexual dimorphism
Acheulean tool technology
first appear in Africa between 1.5 and 1.2 MYA
sharp bifaced tools with complex shaped edges, made from carefully selected stone materials
some of the sharpest are made from volcanic glass
rare in Asia
The Mind of Homo Erectus
brain size (900-1200cc) is in the low modern range (1000-2000cc)
sexual dimorphism similar to modern humans
highly mobile societies
stable foraging adaptation
adaptation to diverse ecosystems
no external symbols (artwork)
Homo heidelbergensis
700,000 years ago modern brain size (1500-2000 cc) elongated cranium robust face, with large orbital torus prognathic, high forehead
Homo neanderthalensis
confined to Europe and Middle East, including Iraq and Israel
from 120,000 to 30,000 years ago
brain size above the modern average size
less prognathous robust face, orbital torus, large nose, extensive turbinates
exhibit many distinctive skeletal features shared with earlier homo species but not modern ones
extinction likely caused by low temperatures
Mousterian technology
multiple stage tool manufacture with preparation of cores to better produce shaped flakes with broad continuous edges
=complex planning and visualization of an indirect consequence
specialized points; possible hafting
Neanderthal DNA
possible to do genetic testing because not always fully fossilized (this is not true of any other ancestor)
likely interbred with eurasians
some likely had fair skin and red hair, some had brown eyes and brown hair
deliberate Neanderthal burial sites have been found; evidence shows they cared for the infirm and elderly
may have had complex cultural traditions and beliefs
Tracing Y chromosome “Adam”
long arm of the Y chromosome does not recombine in sexual reproduction
inherited intact from father to son
therefore transmitted in an all or none fashion and so can be precisely traced from individual to individual without loss
“rooted” in Africa because the greatest genetic differences between individuals are found in Africa
Low Genetic Variation
suggests a recent common origin from a small population
all modern humans show less gene diversity than small populations of nonspecific apes
even Neanderthals are closer to humans than different chimp populations are to one another
genetic evidence: all modern human populations and “races” diverged from a common African population as recently as 70,000 years ago
Body Lice
diversification suggests that migration out of Africa may have involved the first continuous use of clothing
body lice live and reproduce in clothing and only contact skin to feed, large recent clade suggests that humans began to wear clothing 72,000 years ago
Flynn Effect
mean IQ has been steadily increasing in industrialized countries (even when corrected for culture- and generation-specific content)
IQ has high heritability
Correlations with Absolute Brain Size
as body, brain, and life-span increase:
slowing of metabolism, maturation, reproduction, and even reaction time
greater opportunity for trial and error and learning from others
instinct may be less critical for survival
Encephalization
measure of brain proportion that tries to “correct” for allometric effects
not just brain/body ratio (which changes with size)
measure of positive deviation with respect to the average brain/body size trend of other mammals
primates deviate above the average trend for all mammals
Encephalization: The Chihuahua Effect
small dog breeds can be as encephalized as primates (like chihuahuas)
some are nearly as encephalized as humans
but this does not necessarily make them more intelligent - they have been artificially bred for dwarfism or gigantism
3 Mechanisms for Encephalization
- post-cranial reduction = primate shift (two phases)
-embryonic reduction of tissues comprising post-cranial body structures but not the brain in early embryogenesis - forebrain stem cell over-production = human shift
-prolongation of brain growth phase - reduced postnatal body growth = dwarfism
-regulated by growth hormone influences on the post-cranial body after major fetal brain growth phase
Humans combine mechanisms 1 and 2
neurons
information processing cells of the brain
unique in many ways:
1. once produced they do not divide again
2. ionically polarized, highly reactive surfaces (maintained by ion pumps)
3. elaborate specialized input (dendrite) and output (axon)
4. axons contact other distant neurons or synapses, where release of neurotransmitters stimulates or inhibits that neuron’s activity
5. require support cells (glia) to provide oxygen and glucose
Gray and White Matter
gray matter - densely packed neuronal soma
white matter - densely packed myelinated connections
gray matter sheets are called cortex
gray matter clumps are called nuclei or ganglia
white matter forms into tracts of parallel axons
Frequency “map”
spiral shaped cochlea is organized as tono-topic map
hair cells in the cochlea create nerve impulses when they are “bent” by pressure waves
spiral shape distributes different sound frequencies to different positions within it
preserved in the auditory cortex of the temporal lobe
Visual “maps”
projections from the retinas partially cross at the optic chiasm, sending information from the contralateral (opposite side) visual fields to opposite sides of the visual cortex
retinotopic map organization is preserved, but so is the binocular visuotopic map
Brain Development and Cell Death
more nerve cells die in the first two years than during the rest of life span
over-production and selective elimination due to competition is analogous to natural selection
prenatal loss of spinal motor neurons is extensive, but allows the brain to “adapt” to the body
Sensitive/critical periods
transient period during which neural development is responsive to environmental input
biased learning with a narrow maturational window - eg bird song or human language
cued by species-typical “expected” developmental environments (eg imprinting)
Imprinting
super-learning
salmon hatch in streams, then migrate, only to return years later based on subtle odor cues they imprinted on
ground-dwelling birds must learn to recognize their parent within hours of hatching and develop a strong attachment; follow their parent to find food and avoid predation
Behaviorism
BF Skinner: the blank slate
argued that behavior can be divided neatly into instinct and learning, and that all learning depended only on laws of association and reinforcement
eg stimulus response learning paired with rewarding or aversive consequences = reinforcement
assumed that environmental contingencies can explain all complex non-instinctual behaviors
Sauce Bernaise phenomenon and John Garcia
taste aversions can be learned within a single trial if nausea is produced within a short time (super learning)
–> even if the food did not cause the nausea
John Garcia: easy associations between smell/taste and nausea, sight/sound with electric shock
exemplifies predisposed learning biases
John Garcia: evolved biases for learning
learning is not just dependent on density and structure of reinforcement
learning biases are innate and affect how experiences influence the development of behavior
effects of “nurture” are biased by “nature”
supernormal stimuli
herring gull chicks get their parents to regurgitate food by pecking a red spot on their beaks
unlearned behavior can be elicited by a red pencil
herring gulls can be tricked if their eggs are replaced by quite divergent alternatives (giant egg)
Rule: A mental capacity evolves only if…
…there is an evolutionary consequence
parasitized birds are capable of distinguishing their own eggs from a cuckoo’s eggs, but not that they are feeding cuckoo chicks
this is b/c by that time it is too late to start a new nest and raise chicks to maturity
possibility of a mistake, risk of abandoning slightly variant chick
facilitated learning
eg oyster-catchers, which spend many months in the company of their parents to learn to feed safely and effectively on oysters (so as not to break their beaks)
no specific oyster-opening instinct, but many attentional/behavioral/social biases that facilitate learning
facilitated learning + language
similar to bird song
early learning of language, well before ability to read or write
“wild children” isolated in early childhood offer evidence of a critical period for language acquisition
“motherese”
non-human “communicative” behaviors
innate, automatic, unanalyzed, non-combinatorial
linked directly to arousal state
interpreted innately or spontaneously
iconic (looks/sounds like) or indexical (predictably correlated with) what it signals
Language vs. innate emotional vocalizations
innate emotional vocalizations = laughter, sobbing, grains
language is cortically controlled
innate vocalizations are controlled by the limbic system
Aphasia
Broca’s: disturbance of the ability to produce speech
difficult word production, loss of fluency, telegraphic speech, difficulties with production and comprehension of syntax
Wernicke’s: disturbance of language comprehension
errors of word comprehension and production without loss of fluency, some semantic confusion
What makes language unique?
- requires the capacity to learn to articulate a wide range of oral sounds by mimicking others’ speech sounds
- uses a repertoire many orders of magnitude larger than than any other species (vocabulary)
- uses combinatorial means to generate new meanings and references (grammar/syntax)
- uses variant sound combinations to create meaningful words (duality of patterning)
- differs in its way of referring to things (symbolic): allows reference to past, future, abstract objects
laryngeal operation
attached to the hyoid bone and suspended from the base of the skull and the tip of the jaw
vocal fold tension is controlled by the muscles that move 4 cartilages with respect to one another
steps:
1. inter-arytenoid muscles rotate the paired arytenoid cartilages inward to bring the vocal folds together
2. muscles rock the thyroid cartilage forward on the cricoid cartilage to create vocal fold tension
3 basic semiotic relationships
iKON: reference by likeness
drawing, pantomime, camouflage, sculpture
index: reference by physical-temporal correlation
pointer, symptom, correlated feature, sample
symbol: reference by conventional symptom only
word, insignia, religious icon
human larynx
positioned lower compared to other primates
allows a wider range of vocal sounds with less nasality
Obstetric dilemma
human babies are born immature (altricial) compared to most other mammals
birth is far more traumatic for both mothers and newborns than most other species
human brains have enlarged in hominid evolution
the pelvis has narrowed/shortened to provide efficient bipedalism
uniparous vs multiparous characteristics
uniparous: mostly have precocial babies and relatively easy births; humans are the rare exception
multiparous: litter size correlates with shorter gestation and immature neonates
effects of hominid evolution on birth
human birth is difficult, human babies are altricial
advantages of maintaining human gestation length were sufficient to prevent earlier birth (despite maternal pelvic constraints)
human brain growth continues at fetal rates after birth, meaning that human infants are born more altricial and demand more prolonged and extensive care than other primates
summary of childbirth stuff
- human fetal brain growth is typical for a mammal
- human gestation length is typical for an ape
- increase in brain size –> increase in altriciality
menopause
few remaining mature follicles cannot produce enough estrogen and progesterone to maintain hormonal feedback to the hypothalamus and pituitary
leads to hormonal dysregulation and loss of remaining immature oocytes
why menopause?
we age slower than our body size predicts –> suggests that menopause arose as a side-effect of extended lifespan for our body size
not an adaptation
possible aging mechanisms
evidence for damage theories: -basal metabolism (rate of living) -body size correlation -oxidative damage -telomere deletion/repair evidence for evolved obsolescence: -comparative reproductive trade-offs -iteroparity/semelparity differences -predation rate and arboreality effects -disposable soma theory -pleiotropic partitioning
steroid hormones
regulate gene expression
both water and fat soluble, pass easily through cell membranes, bind to receptor molecules in target cells, which modifies gene expression and protein synthesis
hormones are synthesized from cholesterol and each other
one control system: two sexes
male and female gonadal axes are regulated by the same hypothalamic and pituitary hormones
LH and FSH perform homologous functions with respect to hormone production and gamete maturation in the two sexes
sexual differentation of the external genitals
male and female external genitalia are also formed from a common substrate
testosterone and its metabolites differentiate the male, by closing the ano-genital opening to make penis and scrotum
female form is the “default” pattern and does not require hormonal intervention to develop
sex chromosome disjunction errors
Kleinfeldter’s Syndrome: XXY karyotype, male hormones until puberty when breasts enlarge (gender identity is male)
Turner’s Syndrome: X0 karyotype, female genitalia but some physical abnormalities (gender identity is female)
Androgen insensitivity syndrome: XY chromosomal male with faulty testosterone receptor, feminized external genitalia (gender identity mostly female)
4 idependently modifiable dimensions of gender-specific behavior
- attachment
- affiliative-nurturant vs aggressive-detached - sexual partnering/male choice
- long-term reluctant vs variety-promiscuous
- status attributes vs physical attributes - erotic target
- male vs female physique - self image
- male vs female physique
atypical “life history” in humans
life history = typical sequence and schedule of maturational/senescence events human heterochrony: immature birth prolonged brain maturation prolonged childhood adolescence post reproductive life extension
adolescence as a bio-social creation
with industrialization, there has been a significant decline in the age of sexual maturity in both sexes
and a significant postponement of marriage and first conception
in pre-industrialized societies, marriage is generally close to the age of sexual maturity
–> social consequence of spending nearly a decade of life sexually mature but societally prevented from reproducing?
self-domestication of humans
domestication = relaxation of selection on a number of critical physiological, emotional, and cognitive adaptations
- possibility of language depends on a loss of innate biases rather than introduction of an innate language faculty
- novel artificial niche - resulting in unprecedented natural selection on mental functions
- produces changes in brain size, regional proportions, and connection patterns to adapt to these special demands
finch analogues in language
- both have lost the link with specific emotional states
- equalization of transition biases from sound to sound
- increased influence of auditory learning for vocalization
- many more widely distributed forebrain structures were recruited and function synergistically
- vocal repertoire largely determined by social transmission
- innate call features are still used to express emotion as speech prosody
mutually exclusive mnemonic mechanisms
procedural memory - frontal-striatal-cerebellar circuit creates memory traces for skilled action by constant repetition and fine tuning
episodic memory - sensory-hippocampal circuit creates memory traces for singular experiences by correlations between features
language: source of a new synergistic form of memory (narrative memory)h
humans’ symbolic “savant” syndrome
we compulsively expect to interpret things symbolically
symbolic reframing of iconism
uniquely human emotions, result of dissonant icons
niche construction
short-circuit of natural selection
beavers modified their ecosystem so that beaver bodies have had to adapt to the aquatic niche created by beaver activity
symbolic niche evolution
dual inheritance theories
refers to the parallel transmission of information and influence both by genetic and by communication-learning mechanisms
two forms of inheritance aren’t symmetric b/c the ability to transmit and acquire non-genetic information is a consequence of evolved capacities
form and content of the communication and biases of the learning processes that support socio-cultural-technological transmission will tend to be influenced by evolved psychological biases
maladaptation
modern environments diverging from the human EEA
EEA = environment of evolutionary adaptation
causes of maladaptation
- selection conditions change
eg agriculture, industry, migration - causality is not understood, or hard to discover
eg Kuru, colostrum denial, birth control - elites (empowered individuals) manipulate others
eg war, religious sacrifice, status polygyny - costs of exploitation accumulate over time
eg ecological over-exploitation, global warming
Kuru
a prion disease
prions = proteins related to naturally occurring brain proteins
bind to these normal proteins and change their shape (conformation)
these then become prions, which are not broken down, accumulate in the brain, cause neuron death
cultural enhancement of prion propagation = cannibalism
colostrum “pre-milk”
thick yellowish liquid that has little protein, fat, or milk sugar
primary breast “milk” for the first days afterbirth
fills breast alveoli prior to birth
rich in igG antibodies - may have evolved to protect the alveoli from infection
ingestion by neonate protects the infant from intestinal bacteria, etc.
withheld from some newborns in some cultures as bad milk –> hard to link to infant mortality
demographic transition
how technology fools biology
increased female education and autonomy, increased education generally –> reduced birth rates, later marriage, upward shift in age pyramid
increased localized population densities = increased interdependence among strangers
increased communication and information sharing –> decreased personal violence and decreased tolerance for accepting inequality and suffering –> predictive science and increased potential for innovation
Final Summary
- humans have inherited evolved learning biases, social emotions, and behavior tendencies relevant to a past EEA
- these “expect” and depend on certain environmental inputs for normal development
- we have been evolving for over 2 million years in an artifically constructed niche of symbols and tools
- this forms a parallel inheritance process that has its own evolutionary logic that is still poorly understood
- human psychological adaptations have co-evolved with this artificial niche and our brains “expect” this culturally transmitted information to inform normal brain development
- this dependency has produced a kind of self-domestication that has produced considerable flexibility of behavior
- industrialization has produced an environment very different from our EEA (more maladaptation)
- knowledge and communication can “fool” our evolved tendencies into producing maladaptation (not all of which is bad)
