anthro exam 2

major eras

paleozoic (543-252 ma): early life

mesozoic (251-65 ma): dinosaurs and early mammals

cenozoic (65 ma-present): mammals dominate, human evolution

cenozoic periods

paleogene (65-23 ma): warm, early primates

neogene (23-2.6 ma): cooler, apes and early hominins

quaternary (2.6 ma-present): ice age, homo evolution

epochs

paleocene→first primate-like animals

eocene→first true primates

oligocene→early monkeys

miocene→apes diversify

pliocene→early hominins

pleistocene→homo spreads

holocene→modern humans

types of fossils

macrofossils: bones, teeth

microfossils: microscopic remains

trace fossils: footprints, behavior evidence

fossilization conditions

rapid burial, low oxygen, hard body parts

relative dating

stratigraphy: layers of rock accumulate over time; deeper = older

paleomagnetism: uses earth’s magnetic field reversals recorded in rocks to match a fossil layer to a known time period

biochronology: uses fossil species with known time ranges to estimate the age of a site

absolute (chronometric) dating

radiometric (e.g., potassium-argon)

luminescence (OSL; sunlight)

dendrochronology (tree rings)

convergent lines of evidence

multiple dating methods used together

key primate features

forward facing eyes (binocular vision)

reduced snout (less reliance on smell)

grasping hands/feet

postorbital bar/closure

larger brains

major hypotheses for primate evolution

arboreal: adaptations for tree living

visual predation: hunting insects → depth perception

angiosperm: fruit/flower exploitation

plesiadapiforms

primate-like but not true primates

had claws, no full eye convergence

eocene primates

first true primates

warm climate

adapids (lemur-like) and omomyids (tarsier-like)

oligocene primates

cooler climate

first anthropoids (monkeys, apes, humans)

miocene apes

traits: no tail, y-5 molars, larger brains

climate cooling → forests shrink → ape decline

important miocene apes

proconsul: early ape

sivapithecus: ancestor to orangutans

european apes (dryopithecus)

key adaptations for bipedalism

foramen magnum underneath skull, s-shaped spine, short wide pelvis, valgus knee, arched foot

why bipedalism

carrying food/tools, energy efficiency, heat regulation, foraging advantages

earliest hominins

sahelanthropus: possible earliest, small brain

orrorin: femur suggests bipedalism

ardipithecus: bipedal + arboreal

australopithecus

full bipedal but still climbed, small brains, reduced canines

a. afarensis (lucy), a. africanus

paranthropus

robust, huge teeth + chewing muscles

not ancestors of homo

homo erectus

first to leave africa, larger brain (~875cc), modern body proportions

acheulean tools, possible fire use, increased social structure

long childhood, altricial babies (dependent)

homo heidelbergensis

likely ancestors of neanderthals (europe) and homo sapiens (africa)

neanderthals

large brains (~1520cc), cold-adapted bodies, skilled hunters, used tools + fire

care for injured, possible burial practices, interbred with humans (1-2% DNA in non africans)

life history theory

energy → growth, maintenance, reproduction

humans = slow life history

big brain tradeoffs

brain = 2% body weight, 20% energy

tradeoff with gut (expensive tissue hypothesis)

brain evolution hypotheses

social intelligence, behavioral flexibility, cognitive buffer