ANT100Y1 Lecture Notes - Lecture 4: Paleocene, Plate Tectonics, Pleistocene

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11 Apr 2012
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Lecture 4: Primate and Early Human Evolution
Lecture Goals
General patterns of morphology and phylogenetics for fossil primates
What a hominin is in terms of taxonomy
Morphological trends in hominin evolution:
o Bipedalism
o Expansion in brain sie
o Changes in dental/cranial features
Earth: Plate Tectonics
Continents formed as earth’s crustal plates moved and collided together
Massive change in size, location of continents
Climate, topography, vegetation, animal species distribution all affected
Time France and Climate
See Fig.5.6
Different eras (epochs)
Much higher global average temperature then, than now (12 ° C)
Paleocene “Primates”
Geography and climate
o Hot, no ice caps, many of today’s locations under the ocean
Paleocene & Primate-like Mammals: Plesiadapiformes
Body size: tiny, shrew-sized to size of small dog
Niche: Likely solitary, nocturnal quadropeds; well-developed sense of
smell
Diet: insects and seeds
o Use fossilized dental structures, compare to similar modern-day
species, can infer their diet
Used to be classified as primate because of primate-like teeth and limbs
that are adapted for arboreal lifestyle
Recent theory: plesiadapids NOT primates
o No port orbital bar
o Claws instead of nails
o Eyes placed on side of head (primitive mammalian condition,
similar to what we see in ancient representations of mammals)
o Enlarged incisors
MORE recent theory: plesiadapids and few others ARE primates
o Share a sister taxon relationship with creatures we know as
primates
o Molecular origins before plesiadapids emerged about 58 mya
o First fossilized artifact found 65 mya
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Eocene (56 MYA 34 MYA)
Geography and Climate
Decreasing global average temperature
Grasslands expands
Two Main Eocene Primate Families
Adapidae
o Small 100 g to 6900 g
o Diurnal and nocturnal forms
o Mainly arboreal quadrupeds, some may have been leapers
o Small ate mostly fruit and insects, larger fruit and leaves
o Led to lemurs??
Omomyidae
o 45 g to 2500 g
o some nocturnal, some diurnal
o omomyids thought to been specialized leapers
o teeth: adapted for eating insects and soft fruits, only few species
were leaf-eaters
o led to Tarsiers?? ***similarity in form does NOT always equate with
close phylogenetic relationships
Oligocene (34 MYA 23 MYA)
Geography and Climate
SA still isolated continent
Africa and Mediterranean still separate
India still separate, Himalayan mountains not developed
Slow decrease/plateau, sharp increase in temperature
Oligocene Primates
Three haplorhine features:
o Fused frontal bone
o Full post-orbital closure
o Fused mandibular symphasis
Three taxonomic groups: Parapithecidae
Propliopithecidae
Platyrrhini (monkeys of Central and South America)
o First appearance of primates in C & SA
South American Primates
Primates appear for first time in fossil record of South America towards
late Oligocene
Origins of South American primate unclear
General consensus….may have “rafted” over from Africa
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