Ultimate Flashcard Extravaganza
Evolution Before Charles Darwin
Enlightenment - no divine right to rule, natural phenomena are mechanically caused by external forces
Erasmus Darwin - Charles’ grandfather, organisms’ sensitivity to the environment shapes their minds and bodies, better forms have increased over time
Jean-Baptiste Lamarck
Jean-Baptiste Lamarck
- animals have an internal drive to physically accommodate to environmental conditions and become more complex
- persistently successful accommodations can become so habitual that they become physiologically based and get passed on to offspring
3 Influences of Darwin’s Theory
Charles Lyell (geologist) Thomas Malthus (economist/demographer) Alfred Russell Wallace (naturalist)
Charles Lyell
geologist, friend of Darwin
argued for a very slow and incremental pace of geological change
Thomas Malthus
economist and demographer
emphasized danger of uncontrolled human reproduction with limited resources
helped Darwin see the role of resource competition
Alfred Russell Wallace
independently discovered the theory of natural selection; letter prompted Darwin to submit their theories together in 1859
“Survival of the Fittest”
“fitness” is really “fittedness” - term was coined by Herbert Spencer, not Darwin
fitness is not determined by health or strength, but by reproductive success and ability to adapt to environment
3 dimensions of biological analysis
length - longitudinal analysis (homology)
breadth - comparative analysis (analogy)
depth - functional analysis (physiology)
How nature “backs up” her data
- Things naturally tend to fall apart and complicated mechanisms tend to wear out and fail
- One defense is to make copies
- Copying is never perfect - variation is inevitable
- Copying takes time and energy
- Some copying processes will be more profligate or successful than others
- Favored copying processes will be ones that best “fit” the conditions
Herbert Spencer
coined the phrase “survival of the fittest”
argued that evolution argued by Lamarckian use-inheritance
believed that learned habits could be passed on by reproduction –> social progress could lead to biological progress
argued that “primitive” societies were less evolved “races”
Haeckel and Progress
argued that evolution tends toward greater complexity
humans were presumed to occupy the highest rung on the biological ladder and were “the most evolved”`
Why Evolutionary Misconceptions are Wrong
Evolution is not linear and not necessarily progressive.
Its tendency is to diversify and expand into novel niches.
Evolution spontaneously tends toward increasing complexity because there is nowhere else to go.
“Planet of the Apes” Fallacy
nothing about natural selection produces inevitable trends, even improvement
humans didn’t replace or improve upon apes
Types of Selection
stabilizing selection - selection against extreme phenotypes that deviate from the mean
directional selection - selection favors extremes
disruptive selection - either extreme is favored
eg Japanese pheasants
The Red Queen analogy
the environment is always a moving target
it can look like there is an “arms race” between organisms adapting to the same environment, but they are just trying to keep up with the same changing environment
sometimes you have to run fast just to stay where you are
Mendel’s Basic Discovery
simple traits are controlled by an interaction between the two “doses” of each gene type (allele) that are present in each plant
because of this, they can interact or mask each other’s effects (dominant/recessive)
independently assort in subsequent generation according to simple binomial rule
Protein Functions
catalysts - aid chemical reactions, eg digestive enzymes
structural elements - or link other molecules, eg skin and hair
recognition or signaling - for cell cell communication
molecular “chaperones” - for other molecules that bind or transport eg hormone receptors and hemoglobin oxygen transport
SNPs
single nucleotide polymorphisms; different people can have different bases in a specific location
can be used for identification, diagnosis, and tracing ancestry
Genetic “drift”
statistical sampling effects producing random selection
there is always a 50% loss in genes from each parent
sex leads to inevitable gene elimination by chance
Founder Effect
a small group initially founds a population and diversifies from there
reduces genetic diversity
Why shift to a genetic perspective?
all bodies eventually perish! what persists are the genes that contribute to those traits
but: the particular combination of genes and traits that constitute an individual will likely never recur, except for in identical twins and asexual species
eg. Secretariat effect
Sickle Cell Anemia
sickle cell is only produced by the genetic mutation if both hemoglobin A molecules are sick type
hetereozygotes have 50% hemoglobin beta exhibiting mutation, which does not cause anemia but a low level of cell damage
this is sufficient to expose the malaria parasite to the immune system and help eliminate it
so: sickle cell heterozygotes are positively selected for
balanced polymorphism
Mitochondrial DNA
not contained within the cell nucleus but within the organelle
mitochondria are passed on in the cytoplasm of the ovum and therefore come only from the mother
mtDNA has bacterial origin!
(Y chromosome DNA is similar - only passed through male lineage)
Y chromosome inheritance
long arm of the Y chromosome does not recombine in sexual reproduction
inherited intact from father to son
therefore transmitted in all or none fashion and can be traced from individual to individual
gene duplication –> functional divergence
eg hemoglobin:
spontaneous degradation of duplicate genes produced beta-hemoglobin variants with different oxygen affinities
problem of transferring oxygen from maternal to fetal hemoglobin provides “functional niches” that variant hemoglobins can fit
Regulatory Genes
produce proteins that control patterns of gene expression in the different cells of a body
Extended Phenotype
selectively favored effects are expressed outside the body that produces them
genes can produce molecules whose primary focus is to control another species’ development or behavior
Death as a Reproductive Strategy
trade-off point between maintaining a body and instead putting that energy into reproduction is different for different species/life stages
salmon kill themselves in an effort to arrive upstream ahead of competitors and produce hundreds of offspring
mantis males easier to be caught and eaten late in the breeding season when chances of reproducing are slim and nutrition from eating their bodies could aid female reproduction
Sex has evolutionary costs
- only a random half of one’s genome gets passed to each offspring, and some genes don’t get passed on
- good gene combinations tend to get broken-up in each generation (Secretariat effect)
- time and resources are required to locate a mate, and often in fighting for mates
- probability of encountering a potential mate is reduced by 50%
- males use up resources and don’t contribute to offspring nourishment and health
Sex requires social interaction
- over the course of evolution, sexual reproduction has played the dominant role in promoting social behavior and cooperative organization within a species
- by distributing mutually exclusive reproductive adaptations among different individuals the advantages and disadvantages of each are separated
- traded off against the costs of making autonomous reproduction impossible, resulting in different combinations of sexual traits
sexual reproduction involves a mix of:
- Recombination (genes)
- Anisogamy (sperm and ova)
- Gender (male and female)
Why recombination?
genes must work in combination with one another
necessary to have them linked to keep working combinations together during reproduction
but this risks having a damaged gene ruin the reproductive chances of any linked gene
periodic recombination (shuffling) allows genes to escape linkage with “bad” genes
Anisogamy
“not the same gametes”
different gamete phenotypes: usually haploid, as in ova and sperm
sperm selected for: high numbers, low production costs, easy dispersal, high genetic diversity –> small, mobile, expendable
ova selected for: robustness, ample metabolic resources –> large, immobile, easily protected
Hermaphroditism
(both kinds of gametes) requires a compromise with respect to gender-distinct bodies where both dispersal-variation and investment-protection can be independently maximized
usually in conditions where access to mates is reduced
Sex vs. Body Gender
sex - typically understood in terms of male and female, used to refer to either whole animal bodies or to the organs of reproductions in plants that carry sperm (pollen) or ova (egg cells)
gender - linguistic designation of nouns and pronouns typically into masculine, feminine, and neuter grammatical types; has come to be used by analogical extension to refer to masculine vs feminine “roles” aka GENDER IS A SOCIAL CONSTRUCT
Conditions that Favor Asexual Reproduction
minimal competition for resource
predictable conditions
higher reproductive rate, lower variation
Conditions that Favor Sexual Reproduction
significant competition for resources
unpredictable conditions
lower reproductive rate, higher variation
Blue-Headed Wrasse
sex change
all begin life as females
live in a school defended by a single male, who is much larger on average, has a distinct blue head, and inseminates all eggs of the school
if this male dies, the larger females will compete and one will transform into a male developing a blue head
Anemonefish
“clownfish”
have an ability to prevent anemones from stinging them
pairs “nest” in an anemone where they raise young who can feed off prey paralyzed by anemone
begin life as males capable of producing sperm
young males pair up with older females who have successfully defended an anemone “nest site” in which to raise the young
older female dies, younger male undergoes a sex change to become a female and gonads begin to produce ova
young males will be attracted to mate with female
Darwin’s Theory of Sexual Selection
explains the evolution of apparently nonfunctional, superfluous, or harmful traits including human intelligence
emphasizes Darwin’s focus on reproduction
basic logic - reproductive competition not only dissociates members of a species into distinct sexes, but can lead to competition within the same sex for access to reproduction
Darwinian Logic of Sexual Selection
- better reproduction is more important than optimizing survival or access to resources
- there are often major differences in an individual’s reproductive output
- possibility of increasing reproduction could lead to competition for mates
- traits that trade health and survival for reproductive advantages will evolve where not blocked by natural selection
Modern Logic of Sexual Selection
- sex that contributes more time, energy, and risk in support of offspring is “limiting resource” for other sex
- sex that invests more evolves greater discernment of mates; sex that invests less evolves a means to bias the selection in its favor by increasing the total number of mates
- manipulation of mating changes may occur via aggressive exclusion of competitors, competition over valued resources, promiscuity, risky displays that signal health or vitality
Displays as Handicaps
eg widowbirds
widow bird males have long tails that attract both females and predators
experimental manipulation shows that females prefer longer than normal tails
Tournament Reproductive Strategy
about 98% of mammals, sexual dimorphism, male energy largely devoted to competition and no male parental investment, high variance in male reproductive success
male display; female choice
high polygyny - rival males are excluded
Pair Bonding Reproductive Strategy
95% of bird species
sexual monomorphism, male energy divided between competition and parental investment, low variance in male reproductive success
mutual courtship
low degree of polygyny, some polyandry, mostly mated pairs
Male Defense: either resources or females
resource defense - males compete for territories that attract females, who spend more time there and are available for mating
female defense - food is widely distributed and females feed in groups, so males compete to prevent other males from mating with them
Bowerbirds
competing for mates using artifacts:
male bowerbirds attract mates with elaborately constructed and decorated displays (bowers) that only superficially resemble nests
females will mate in the bowers and then raise young on their own
males compete for attractive objects to decorate their bowers, often stealing from other bowers
Factors contributing to pair bonding
- offspring that require extensive or prolonged care to reach a stage where they can forage for themselves
- non-abundant, non-clumped food resources
- limited nest or burrow sites, or sites requiring defense or significant effort to produce
- low population densities
Bird and Mammal Cooperative Care
- cooperative rearing strategies are generally rare, but can be found in environments where resources (like nesting sites) are rare
- because defending a nest site poses additional demand, sometimes this can require more than one male and one female
- in these conditions it may be advantageous for fledglings to remain with parents, feed and defend the new brood until they gain skills to successfully establish a new nest
Helper-at-the-nest
larger the “clan” the better the nest site they can cooperatively defend
helpers’ short term postponement of their own reproduction is not a cost because it is unlikely that on their own the young offspring would survive
by assisting their parents during this time they are passing on their genes “by proxy”
Lions
female lions - social carnivory, they cooperatively hunt and cooperatively care for offspring so while many females can hunt many others can remain behind to care for cubs
male lions - compete to defend a pride of females, commit infanticide when females are not in estrus with the previous pride lion’s cubs still nursing
Reciprocal Altruism in Vampire Bats
vampire bats roost in large social groups
feeding is highly unreliable and high metabolisms make them susceptible to starvation and dehydration
at some point most individuals will require supplemental feeding from roost-mates
Conditions Favoring Reciprocal Altruism
low cost to giving aid, high benefit of giving aid
long-term association allows ample time to reciprocate and assess reciprocation
means of identifying individuals
means of punishing/exclusive non-reciprocators
Obligate Social Living
not just male and female - eg ants and bees
can lead to segregation of gender functions into more than 2 body types
1. drone (haploid male, fertile)
2. queen (diploid female, fertile due to added hormones)
3. worker (diploid female, sterile due to lack of hormones)
Honeypot Ant Eusociality
- workers act as storage vessels called “repletes” for honey used to feed brood and others
- specialized workers store honey in their abdomen for the colony to use when resources become scarce
- specialized body types are a form of “kin” altruism
Termite Eusociality
exception that proves the rule about kin selection
colony inbreeds generation after generation, resulting in very high levels of relatedness
have many non-reproductive “castes” with distinct body types and behavioral predispositions
gender roles are determined by hormones and pheromones as well as season, size, age of colony
fertilized females (queen gives birth to both males and females) will attempt to establish their own colony
Naked Mole Rat
a eusocial mammal
live in underground colonies, produced by a single breeding female who suppressed fertility of male and female workers with pheromones
a few breeding males also act as guards if colony is threatened
highly inbred, like termite colonies
workers dig elaborate tunnel systems and bring food back to the breeding chamber
Colugo “Flying Lemur”
closest "outgroup" to primates location: Southeast Asia not a primate or a bat, arboreal glider frugivory-insectivory uniparous, carries young
Tupaia “Tree Shrew”
next closest outgroup to primates arboreal locomotion insectivorous grasping hands, primate-like ears, binocular vision large snout/nose
Initial Primate Specialization 65 MYA
arboreal, noctural, insectivore/carnivore
large, forward-facing eyes
clinging-leaping-grasping
single birth, carries young
arboreal nocturnal hunting requires the ability to see in the dark and judge depth
Prosimians: Tarsiers
SE Asia, nocturnal hunter of insects, frogs, reptiles
clinging-leaping
solitary hunters, pair bonds and small groups
glaborous fingertips
Prosimians: Galagos (“Bush Babies”)
nocturnal, clingers and leapers
gumivory and insectivory
pair bonding with joint territory defense
multiparous litters
nest in hollow trees where young are left
Prosimians: Lemur Catta (“Ring Tailed Lemur”)
highly social, live in large multi-male multi-female groups, dominance hierarchies and male-male competition
tails are used for social communication
Lemur Diversity
typically diurnal, reduced eyes and enlarged snout with wet nose
include frugivores, folivores, and insectivores
include solitary and group living species
ancestors of lemurs were isolated on Madagascar with few predators or competitors and differentiated into diverse species with diverse adaptations
Prosimians
smaller bodies, smaller social groups, un-fused mandible, more insect and gum eating, nocturnal, some reliance on olfaction, limited color vision
Anthropoids
larger bodies, larger social groups, fused mandible, more fruit and leaf eating, diurnal, even less reliance on olfaction, extensive color vision
Locomotion
prosimians: clinging and leaping
monkeys and apes: arboreal quadrupeds, terrestrial quadrupeds, suspensory motion
Origin of the Anthropoid Primates
shift to diurnal feeding on fruit fruit co-evolved with birds as seed dispersers changes: 1. reduced eyes 2. change in tooth structure 3. reduced muzzle and nose 4. closure of the orbit
Loss of Vitamin C Synthesis
result of the shift to frugivory
- ascorbic acid not in diet = selection for endogenous synthesis
- dietary substitution
- dependence and re-adaptation
Color Vision
fruit initially evolved for seed dispersal by birds, which have good color vision
ripeness indicated by color
dependence on dietary ascorbic acid associated with selection for 3-color vision, changes in taste receptors, tolerance for alcohol (from over-ripe fruit), etc
New vs Old World Monkeys
NWM - platyrrhine (outward facing nostrils), 3 premolars, can have prehensile tails
OWM - catarrhine (downward facing nostrils), 2 premolars, never have prehensile tails
New World Monkeys: Assortment
marmosets - gumivores, defend territory
owl monkeys - convergent adaptations with prosimians, only monkey adapted to nocturnal foraging
spider monkeys - locomotion using prehensile tail
howler monkeys - defend territory using loud vocalization aided by an enlarged lower jaw and hyoid bone
uakari - Ally Boville
Old World Monkey Specialization
bilophodont molars, ischial callosities
diverged from apes with respect to locomotor adaptations (quadrupedal monkeys vs suspensory apes)
OWM further diverged into two groups with respect to dietary adaptations and specialized digestion (folivorous colobines vs omnivorous cercopithecines)
Colobines
specialized group of Old World Monkeys with adapted digestive system for folivorous diet
arboreal quadrupeds
OMW Arboreal Quadrupeds
equal length arms and legs, rigid lumbar spine, four grasping hands, horizontal body
Cercopithecines
omnivorous
includes baboons, macaques, guenons
terrestrial quadrupeds
OWM Cercopithecines: Macaques
cheek pouches allow them to carry extra food without eating it
live in multi-male, multi-female troops
males usually emigrate from their troop to a new one while females stay with kin
males often form small coalitions
female dominance inherited from mother’s rank
Advantages of Monkey Sociality
defense of patchy resources predator defense grazing tracking social transmission of foraging kinship continuity (of one sex)
Disadvantages of Monkey Sociality
sexual competition
feeding competition
male paternity uncertainty
Infanticide in Langur Monkeys
Hanuman <3 langurs live in large single dominant male polygynous troops
when the dominant male is deposed, the new male systematically attacks and kills infants
this brings females back into estrus
females may feign sexual receptivity in order to protect their infants
OMW Cercopithecines: Baboons
widespread in sub-Saharan Africa and live in large multi-male, multi-female groups that tend to forage on the ground
mandrills: baboon species that live in forests, form single-male polygynous groups and have been known to kidnap females from other groups; most sexually dimorphic baboons
gelada baboons: forage on grasses in very large troops of smaller harems controlled by highly aggressive dominant males
Southeast Asian and African Apes
apes are far less numerous than monkeys, range is restricted to tropical forests of Africa and SE Asia
reflects primary adaptations for aboreal locomotion and foraging
range of apes used to be significantly greater 10-20 MYA
Ape Locomotor Adaptations
lack of tail, long curved fingers, highly mobile shoulder girdle and hip joint, shortened thumbs, four grasping limbs, vertical posture, mobile lumbar vertebrae, conical rib cage, wrist rotation, scapulae (shoulder blades) located on back
Asian Apes: Gibbons
small frugivorous brachiators
specializations for brachiation, coupled with small body size, predispose gibbons to walk bipedally when on the ground
gibbon pairs cooperatively defend a territory by singing duets twice a day
each sex drives off rivals of the same sex
Asian Apes: Siamangs
like gibbons, sing to defend territory (but only males sing) and also pair bond
specialized throat pouches for long distance vocalization
Asian Apes: Orangutans
Borneo and Sumatra
sexually dimorphic, males distinguished by fat pads
locomotion - quadra-manual, suspensory, mixed terrestrial forms of locomotion
also: infant ventral clinging and dorsal riding
isolated foraging
Orangutan Terrestrial Locomotion
variety of knuckle-, fist-, and wrist- walking strategies
African Great Ape Habitats
African apes except humans are confined to the equatorial forests (this environment is not good for fossilization)
Gorillas and chimpanzee habitats overlap, but bonobos are separated by the Congo River
African Apes: Gorillas
- folivorous, enabled by large digestive systems
- most of the day is taken up with eating and moving
- single large dominant “silverback” male with 3-8 females, infants, and some adolescent males
- no distinct territories and forage over large areas
- mature males develop silver hair on their backs and defend troop females, while young males attempt to abduct females and form new troops
Gorilla Group Structure
single dominant, sexually dimorphic "silverback" male mobile female-group foraging female-defense polygyny female transfer (abduction) male emigration to form a new group
Gorilla Locomotion
Terrestrial: mostly knuckle-walking but some bipedal walking is possible
Arboreal: possible but limited by size, more common in females
African Apes: Chimpanzee
Pan troglodytes - Central and West Africa
omnivorous, arboreal and terrestrial foraging
knuckle-walking
large multi-male, multi-female social groups
male cooperative territory defense
male hunting of monkeys
Chimpanzee Foraging Patterns and Emigration
individual females and young forage together in male-defended territories
female foraging territories overlap with each other
females leave their natal troops at puberty to join nearby male territories, while males remain with their natal troops
Chimpanzee Male-Kin Coalitions
reduced male-male aggressive competition, male hierarchy weakly limits sexual access
female fertility is advertised by perineal swelling and active solicitation during estrus
male kin-cooperation: extensive repertoire of social communication, involving vocalization/grooming/tactile contact
Chimpanzee Group Structure
multi-male, multi-female groups
modest sexual dimorphism
territory defense by male coalition
female transfer/ male continuity
Chimpanzee Tool Use
transmission of tool use by observation and crude imitation; no clear evidence of “training”
mastering a complex skill may take many years
also seen in capuchin monkeys
made possible by combination of continued social living, need to extract difficult foods, hands, large brains
Chimpanzee Hunting and Violence
males engage in regular cooperative hunting of colobus monkeys
kills are shared with females and young
male groups may attack and kill isolated males from neighboring troops
infanticide of infants brought into territory may also occur
Chimpanzee Infanticide
female “troop transfer” occurs when she reaches young adulthood, may be pregnant at this time
males and females will often harass new females in the troop and can kill an infant she is carrying
females have also been known to kill infants of other females within the same troop
African Apes: Bonobos
Pan paniscus - Central African forests
omnivorous, forage in large multi-sex multi-age social groups
minimal dominance hierarchy, weakly territorial, highly sexual
bonobos do not overlap with chimpanzees and therefore are not in competition for the same foods
Bonobo Locomotion
versatile locomotion:
agile arborealists, and on the ground both knuckle-walking and bipedalism are common
foraging on the ground may require use of arms for carrying food and offspring while erect; infants usually ride dorsally
Bonobo Social Structure
mobile multi-male, multi-female foraging groups
territorial but with minimal territory conflict and common troop exchange, mostly females
minimal dominance hierarchy not predictive of mating priority, females often dominant over males, males inherit rank from mothers
Bonobo Sexual Behavior
sexual swelling in females is extensive and long-lasting and accompanied by intense interest; as a result, same-sex stimulation among friends is common
interactions may involve many individuals of any sex or age
why so frequent? food is widely available, not season, no hunting
no competition with gorillas, etc., for ground-based foods
minimal male-male competition, social groups are large and all individuals forage together
Chimpanzee vs Bonobo Sex and Social Function
chimpanzees: highly competitive male access, minimal male-female bonding, minimal same-sex copulation
bonobos: no sexual competition, strong male-female friendships, considerable same-sex copulation with friends
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 amanensis
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
Grey 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
whenever Ally makes noise
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 differentiation 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)
