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44 Cards in this Set

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physical anthropology

the study of human biological evolution and human biocultural variation: studying living humans, modern and extinct primates, fossil hominins.

scientific method

analogy and middle range theory

links human behavior & natural processes to physical remains in the archeological record.


4 components:


1) documentation of causal relations between relevant dynamics and observable statics


2) recognition of signature patterns in static remains


3) inference of past dynamics from observation of signature patterns in archaeological record; and


4) evaluation of these inferences.

natural selection

adaptation >> evolution.


Darwin's theory: evolution by natural selection


1. all individuals vary


2. variation is inheritable


3. more individuals can be born into a pop. than can survive & reproduce


4. there is a natural selection that determines which individuals survive

selective pressures

drive evolution. a reason for individuals with certain phenotypes to have either a survival benefit or disadvantage. environmental factors

sexual selection

darwin's ideas: practicality for survival sacrificed for mating. example: bright colors in birds, fish, etc. darwin thought this was a separate evolutionary process but ppl now think this is just a subcategory of natural selection.


an "honest indicator" of genetics; males that can maintain certain "attractive" flashy traits are seen as healthy--usually shows strong immune system.

convergent evolution

similar adaptations due to similar environmental pressures, despite having no shared evolutionary history. = analogous traits

homologous trait

related evolutionarily, sharing the same trait

analogous trait

similar adaptations in unrelated species

ancestral vs. derived traits

ancestral = shared w/ predecessors


derived = newly evolved, diff from predecessors

adaptation

changes in physical structure, function, or behavior that allow an organism to survive and reproduce in a given environment.




changes not always positive: extinction happens all the time




adaptations happen both slowly and quickly: depend on the changes of the environment (selective pressures) new "environmental niches" yield new species.




human adaptations:


-power grip (shared with apes and chimps) + precision grip (unique to humans, good for using tools)


-skin color, hair color, hair texture

gradualism vs. punctuated equilibrium

gradualism: proposed by Darwin. evolutionary change happens over time, slowly




punctuated equilibrium: quick changes in an environment = punctuated event over a short amount of time >> evolution. species must either adapt or go extinct.




stabilized environ > another rapid change > cycle continues.




both paces are happening all the time.


depends on the scale and the time

nuclear DNA

nuclear DNA: (double helix shape discovered by watson & crick in 1953)


codes for amino acids (structural and regulatory proteins)


huge!! (~3 billion base pairs)


1/2 of DNA ladder = rna (w/ corresponding pieces) that gets replicated



mitochondrial DNA

aka mtDNA


relatively small (~20,000 base pairs)


quickly mutates


matrilineal descent


similarly structured to DNA of bacteria (possibly origin of mtDNA?)

genetics: importance to anthro

-tracing evolutionary relationships


-predicting evolutionary trends: esp. for studying disease


-investigating population variation + genetic forensic info


-tracking human relationships, dispersal, and evolutionary patterns




causes of evolution:


1. natural selection via mendelian inheritance


2. mutation


good mutation = adaptively advantageous


bad mutation = adaptively deleterious


3. gene flow - exchange of alleles between populations... aka the gene pool


4. genetic drift

mitosis

somatic (all cells except sperm and egg) cell division


-parent cell has 46 chromosomes, creates 2 daughter cells, ea. w/ 46 identical chromosomes

meiosis

sex cell division


-parent has 46 chromosomes, creates 4 daughter cells, ea. with 23 chromosomes = gametes (egg/sperm)




meiotic division & recombination


-crossing over btwn chromatids (parts of chromosomes) during gathering of parents' DNA


-recombination - the exchange of genetic material btwn homologous chromosomes = the main driver of variation!!

polygenic traits

controlled by two or more genes on different chromosomes. examples in humans: height, skin color, and weight. not inherited thru mendelian inheritance exactly.

pleiotropy

one gene that affects ore than one phenotypic trait

phenotype vs. genotype
phenotype: the physical manifestation of the genotype. natural selection operates on this b/c it is what directly interacts with the environment



genotype: 2 alleles that make up a gene


homozygous dominant/recessive (TT/tt) or heterozygous (Tt)



Gregor Mendel

monk who studied pea plants to understand genetic inheritance of particular traits.


developed mendelian inheritance (genetics)


one allele inherited from the mother, one from the father. predicted using a punnett square

macroevolution vs. microevolution

macroevolution: the evolution of new species (long term)


microevolution: changing allele frequencies within a species that leads to bigger evolutionary change (short term)

speciation

the rise of a new species.


hard to witness because it takes a long time and new species are hard to pinpoint.


how speciation occurs: population division (4 types) and... genetic drift - the change in the frequency of a gene variant in a population due to a random sampling

allopatric speciation

population separation

peripatric speciation

special case of allopatric: population separation but 1 group is much smaller than the other

sympatric speciation

overlap of species, niche or behavioral separation

parapatric speciation

overlap of species, but w/ some other isolation factor

species

biological species concept: if 2 animals can produce a non-sterile offspring, they are members of the same species. **however: asexual reproduction, and mules/ligers




ecological species concept: whether or not 2 species would ever reproduce together naturally (shared enviro/gene pool)

adaptive radiation

after environ. change, species quickly exploit new environ.

what is a primate?

Order = Primates


morphological features:


-generalists (no specialization really)


-collar bone, mobile shoulder joints, knuckle walking/bipedalism


-opposable thumbs + big toes, sensitive, tactile hands @ the ends of digits


-orbits encircled in bone (eye sockets)


-forward-facing eyes, increased reliance on vision and decreased reliance on sense of smell


-large brain size (vs body size)


-reduced # of teeth, compared w/ other mammals


-2 pectoral mammary glands


-one offspring per pregnancy (usually) w/ long parental investment


-general trend toward upright torso posture

Primate evolution and geologic timing

65 mya = meteor killed dinosaurs


gradual cooling >> first major mammalian radiation


K/T boundary @ 62 mya


earliest primate evidence: Archicebus achilles, earliest Haplorhine




Miocene epoch: ~23mya - 5mya


Hominoidea (all apes) began evolving




Pleistocene 2.5 mya - 10kya


us and our bipedal ancestors




HOMINID DIVERGENCIES (LCA split):


Orangutans: 12 mya


Gorillas: 8 mya


Chimps: 6 mya

Miocene apes (hominoids)

miocene = epoch from ~23mya to 5mya


-primates widely distributed: Europe, Africa, Asia, Mid. East


-African: Proconsul = most widely known African variety. modern descendants = lesser apes?


-Eurasian: Dryopithecus - Europe, mid. East. later in Af. prob evolves eventually into humans, chimps, and gorillas (modern great apes)


-mid east: Sivapithacus - looks v. similar to modern orangutans

General primate behaviors

-various environments: deep forest, savanna, high-altitude, cold environ., open environ w/o trees


-social behavior: generally gregarious = complex social relationships


-mating: dominance hierarchies


infanticide -dominant male fathers most offspring > new male takes power. all females w/ babies cannot reproduce > infanticide to allow for reproduction.


matrilocal females stay close to home (jsyk: patrilocal = males stay close to home)

Haplorhines vs. Strepsirrhines

Haplorhines: Tarsiers - dry nose, post-orbital bar behind eye socket


Strepsirrhines:


-most primitive of the primates. prosimians


-more reliance on sense of smell


-lemurs and lorises, galagos


-dental comb and grooming claw


-wet nose

Anthropoids

all apes & monkeys (simians)


-larger body + brain


-increased reliance on vision, greater degree of color distinction


-post-orbital plate


-more generalized dentition (teeth can eat a wide variety of foods)


-longer gestation, maturation, and increased parental care



catarrhines vs. platyrrhines

catarrhines: Old World monkeys & apes. downward-facing nostrils. dental formula: 2 incisors, 1 canine, 2 premolars, 3 molars (2 1 2 3), no prehensile tail = no grabbing




platyrrhines: New World monkeys. sideways-facing nostrils, 2133 dental formula, prehensile tail

Hominoids

all apes.


-Gibbons = lesser apes (smaller bodies)


-Great Apes = us, gorillas, orangutans, chimps


**monkeys have tails, apes do not!

Relative dates vs. Absolute dates

relative dates: older than/younger than


absolute dates: calendric dates

direct vs. indirect dates

direct dates: the object of interest itself is dated


indirect dates: the object of interest's age is inferred by dating something associated w/ it

carbon dating

form of radiogenic dating (use of unstable isotopes - atoms of same element w/ diff # of neutrons)


uses 14C (higher # = more neutrons)


unstable isotopes experience radioactive decay to arrive at a "stable" state


half-life: the time it takes for 1/2 of the original # of radioactive isotopes in a given sample to decay


-exponentially fewer atoms to measure over time = exponential decay


14C >> 14N (Nitrogen)


1,000,000,000,000 12/13C : 1 14C


**Half-life of 14C = 5730 years


start time = death


1. 12/13C in sample is measured


2. expected 14C is calculated using ratio


3. actual 14C measured


4. date is calculated




limitations of carbon dating:


-age = 40-50 kya


-carbon must be present

Potassium-Argon dating

40K - 40Ar Dating


Half-life for 40K = 1.25 billion years


only works for sites 120 kya and older. usually volcanic sites.


"death" = magma turns solid... argon gas trapped in solid

Ape vs. Human characteristics

Apes


-bipedal movement /dist. of body mass: bent knee/bent hip


-pelvlic morphology: thin & long


-smaller brain size


-no angle at the femur


-foot morphology: opposable big toe (divergent) long, curved phalanges. uneven weight dist. b/c of little surface area. small heel


-foramen magnum positioned in the back of the skull


-large, conical canines. sexually dimorphic




Humans


-pelvis: flared + wide


-bigger brain, bipedal (angle @ femur)


-parallel big toe = short, straight phalanges, big surface area, large heel


-foramen magnum centrally located


-small, spatulate canines, sexually monomorphic

Theories for why bipedalism evolved

Rift Valley Geology

~20mya: Somalian tectonic plate trying to separate from N. Af. plate >> E. Af rose in elevation


west of the rift = low elevation, rain forests


east = high elevation, savannas




Savanna hypothesis - change from jungle > savanna. lots of trees = arboreal traits not helpful for open environ. **however, evidence (fossils) show ancestors still lived in wooded areas...




Thermoregulatory hypothesis - upright posture - less direct exposure to the hot sun w/ more exposure to the wind




Predation hypothesis - foraging in open environs = need for awareness of predators. but, predators can also see you more easily...




Load-carrying hypothesis - hands-free moving collected food, tools, offspring to a safer location.




Endurance running - for hunting




Woodland-mosaic hypothesis - patchy environment w/ variation. wooded areas w/ grasslands nearby. resources patchily distributed >> movement to forage >> bipedalism can be seen as a generalized trait

Last common ancestors

Sahelanthropus tchadensis 6-7mya


found in Chad (N. Af-NOT E. Af (us))


-foramen magnum in intermediate position compared to modern humans + chimps (early bipedalism development).


-small cranial capacity (350-375 sq cm), similar to chimps (humans = 1400 sq cm) *bipedalism came before increased brain size?


-increased brain size (encephalization)


-relatively small male canines, but larger molars w/ thin enamel > reduced sexual dimorphism


could mean: separate species or developed later




Orrorin tugenensis ~6mya


-incomplete skeleton. part of mandible, femur found in W. Kenya


-angled femoral neck + groove shift in tendon = bipedal


-smaller hominin-like teeth (vs. tchadensis), thicker enamel




Ardipithecus ramidus 5.8 - 4.4mya


found in Ethiopia. most complete skeleton


-small cranial capactity ~350 sq cm


-reduced canine size


-centrally located foramen magnum


-flared pelvic girdle


-angled femur from hip joint to knee


-long arms (vs leg length)


-long, curved fingers + divergent big toe


*reconstructed enviro = mosaic environ. river nearby w/ some cover & grasslands