module 3: from tree shrew to ape

cenozoic era

• 65 million years ago— after dinosaurs became extinct

• overall cooling trend with fluctuations (at beginnings and ends of epochs)

• changing temperatures caused by plate tectonics and ocean currents— affects the amount of heat

order of cenozoic epochs from oldest to most recent

• tertiary

  • paleocene

  • eocene

  • oligocene

  • miocene

  • pliocene

• quaternary

  • pleistocene

  • holocene

paleocene epoch

• angiosperms had just had an adaptive radiation

  • their nectar attracted animals that inadvertently carried pollen to other plants

• evolved new, large fruit types

  • animals ate fruit and inadvertently spread seeds

• angiosperms became dominant tree species— replaced gymnosperms

• end: primate-like creatures called plesdiadapiforms

pre-angiosperm forests

• world dominated by non-flowering trees (gymnosperms)

  • pollen spread by wind

• hot

• open

• not particularly complex

• dominant animals: reptiles

angiosperm forests

• lush

• many layers

• closed canopy

  • area at the top where light doesn’t pass through very well— many niches

• dominant animals: mammals and birds

gymnosperms

non-flowering trees that rely on wind pollination

consequences for early primates of adaptive radiation of angiosperms

• angiosperm hypothesis— earliest primate ancestors were able to eat AND insects due to abundant availability of fruit and flowers in the terminal branches of tropical forest trees

• led to adaptations

  • forward facing eyes

  • short-range of olfactory capabilities

  • grasping hands and feet

  • eat pollinators

plesiadapiforms

• diverse, successful group found in north america and europe during paleocene epoch

• insectivorous and frugivorous (insect & fruit eaters)

• NOT classified as primates

  • similar traits:

    • grasping hands

    • molar shape

  • different traits:

    • eyes on side of head— no binocular vision

    • long snout

    • claws instead of nails

    • no post-orbital bar

• probably a sister taxon to euprimates (true primates), not the earliest primates

eocene epoch

• adaptive radiation of primates— many groups pop up

• beginning: global temperatures rose dramatically

  • change in global rainfall patterns

  • up to 50% of marine life killed

  • many terrestrial mammals went extinct, but numerous modern mammalian orders emerged

• northern latitudes had tropic climates— rainforests

• primates like tropics: allowed for them to migrate

• radiation of primate species

• end: lots of primate diversity due to expansion of tropical climates

  • last common ancestor/origins of strepsirrhinis and haplorrhinis

ecocene primate characteristics

• post-orbital bar

• shorter snouts than other mammals

• forward-facing eyes

• nails instead of claws

• opposable thumbs and big toes (first digits)

two major groups of primates during ecocene epoch

• omomyiformes

• adapiformes

omomyiformes

• major ecocene primate group

• resembled tarsiers, but NOT ancestors

  • small size

  • insectivorous

  • nocturnal

  • leapers

  • likely NO tapetum lucidum

adapiformes

• major ecocene primate group

• resembled lemurs but NOT ancestral

  • generalized arboreal quadrupeds with some leaping

  • folivorous (leaf eaters)

  • diurnal (active during the day)

eosimiidae

• tiny primates

• likely ancestors of haplorrhines evolving in asia

• last common ancestor of all monkeys and apes

oligocene epoch

• beginning: massive cooling event

  • surface sea water much cooler

  • antarctic ice cap developed

  • northern-most tropical forests disappeared

    • much more restricted area where primates could live

• big drop in primate diversity

• haplorrhine primates in the fayum, egypt

• end: warming climate

  • northern tropical forests return

the fayum, egypt

• earliest unambiguous haplorrhines found here

  • reduction of snout compared to strepsirrhines

  • post-orbital closure

  • mandibular fusion

aegyptopithecus

• one of the earliest catarrhines (group containing OWMs and apes)

  • came before split of OWMs and apes

• generalized molars

• raccoon-sized

• climbers

rafting hypothesis

• primates and rodents drifted across oceans through currents from Africa to South America on natural rafts of vegetation and debris launched during storms

• most likely scenario for primate evolution in South America

• rafted from Africa to South America

  • supported by flow of ocean currents at the time

  • caviomorph rodents with African roots appear in South America at the same time

  • all new world monkeys are descendants of this event

miocene epoch

• beginning: warming climate

  • re-emergence of tropical climates suggests another primate radiation

  • ape radiation, very few monkeys

  • preconsul, dryopithecus, oreopithecus, and sivapithecus species

• mid/late: ape diversity decreasing everywhere

  • huge gap in fossil record in africa— few suitable fossil sites, very few/poorly preserved african ape fossils

most recent living relatives of humans

chimps and bonobos

darwin’s argument of origin of humans

african origins due to morphological similarities and molecular phylogenies

preconsul species

• genus found in about 6 localities

• mainly found in africa

• share traits with apes

  • y5 molar pattern

  • drastically reduced snouts

  • larger than normal brain

  • flexible shoulder

oreopithecus

• late miocene

• found in tuscany, italy

• long arms, short legs

• short trunk

• mobile joints

• possibly bipedal

  • foot shows unique adaptation for stability on two feet

    • widely displaced big toe

    • inner ear bony labyrinth

ape fossils in africa during mid/late miocene epoch (15-8 mya)

• huge gap in the fossil

• few suitable fossil sites

• very few fossils

• poorly preserved

pliocene epoch

pleistocene epoch

holocene epoch

when did the earliest south american primates live?

during eocene-oligocene epochs