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Lecture

Biology-Lecture 4 Chapter 7-Primate Evolution From Early Primates to Hominoids Oct 3 2008

by

Department
Anthropology
Course Code
ANT100Y1
Professor
Marcel Danesi

Page:
of 4
Reading Notes
10-03-08
Chapter 7: Primate Evolution: From Early Primates To Hominoids
Interpreting The Fossil Record
y Dentition: the type, number, and arrangement of teeth
y Arboreal Quadrupeds: front and back limbs of the same length, grasping toes and fingers
y Terrestrial Quadrupeds: more adopted to speed, longer limbs, shorter fingers and toes
y Vertical Clingers and Leapers: longer more powerful hind limbs
y Brachiators: longer forelimbs
The Emergence of Primates
y Paleocene Epoch: the geological epoch 65 million to 55 million years ago
y Plesiadapis: the most well known of the Plesiadipiforms, possibly an archaic primate; squirrel
like animal, large snout, incisors, nasal cavity, eye orbits (side of head), claws, no grasping
hands/feet, Not a primate!
y Eocene: a geological epoch 55 million to 34 million years ago during which the first definite
primates appeared
y Adapids: led to modern lemurs and lorises and the mommies led to tarsiers and anthropoids
y Omomyids: larger brain, poster orbital closure around eyes, short face
y Carpolestes: A mouse-sized arboreal creature living about 56 million years ago; a strong
candidate for the common primate ancestor; lacks stereoscopic vision, nails instead of claws,
big toes, grasping hands, feet, common ancestor of all primates
The Environment
y Cretaceous: geological epoch 135 million to 65 million years ago, during which dinosaurs and
other reptiles ceased to be dominant land vertebrates and mammals and birds began to
become important
y Damp, mild, temps began to fall by end of era
y Seasonal and geographic fluctuations in temp began to develop
y Climate became much drier in many areas, vast swamp lands disappeared
y Continental Drift: the movement of continents over the past 135 million years. In the early
Cretaceous (about 135 million years ago) there was two ³super continents´:
Laurisa
, which
included NA and Eurasia, and
Gondwanaland
, which included Africa, SA, India, Australia, and
Antarctica. By the beginning of the Paleocene (about 65 million years ago) Gondwanaland
had broken apart, with some SA drifting west away from Africa, India Drifting east, and
Australia and Antarctica drifting south
y As continents changed position, they moved into locations with different climate conditions
y Large land masses affect wind and weather patterns differently than smaller land masses
y When continents collide mountain ranges are formed (dry conditions on one side/wet on the
other)
y When the locations of continents prevents the movement of ocean currents from the tropics
to the poles, the earths climate becomes colder
y When climate changes so does vegetation
y Paleocene era- large trees w/ large fruits and seeds
y New species of animals evolved as the climate and environment changed
y Deciduous trees, flowering plants
y Insectivore: the order or major grouping of mammals including modern shrews and moles,
that is adapted to feeding on insects
What in Particular May Have Favored the Emergence of Primates
y Arboreal Theory: primates evolved from insectivores that took to the trees
y Taking of trees favored vision over smell
www.notesolution.com
y Searching for food by sniffing and feeling with the snout might suit terrestrial insectivores but
vision would be more useful for searching for food in trees
y Tree climbing favors grasping hands and feet, hind limbs more suited for support and
propulsion
y Eyes became facing forward because of smaller snout
y Weaknesses of Arboreal Theory- Cartmill- tree living is not a good explanation for many of
the primate features because there are living mammals that dwell in trees but seem to do
very well without primate-like characteristics
y Early primates may have been insect-eaters, and that three-dimensional vision, grasping
hands, feet, and reduced claws may have been advantages for hunting insects on slender
vines and branches that filled the under growth of tropical forests
y Sussman- early primates were likely to eat and move about mostly on small branches , not
on large trunks and branches
y If they did, grasping hands and feet, and nails rather than claws would have been
advantageous
y Increased exploitation of flowering plants promoted modern primate characteristics like sharp
vision and the ability to distinguish colours (ex; for nocturnal primates)
y Cartmill- earliest primates were probably nocturnal and they also probably ate fruit as well as
insects
The Early Primates: What They Looked Like
y Eocene- warmer, less seasonal; vast tropical forests
y Primates features at time: nails rather than claws, a grasping, opposable first toe, bony bar
around eye socket, vertical clinging and leaping (locomotion)
Early Eocene Primates: Omomyids and Adapids
y Omomyids: a type of Prosimians with many tarsier like qualities that appeared in early
Eocene epoch
y Large eyes (active at night), long tarsal bones, and very small size
y Two incisors, three premolars each size of lower jaw
y Tetonius- brain had large occipital and temporal lobes (perception/visual memory)
y Adapids: a type of Prosimians with many lemur-like features; appeared in early Eocene epoch
y More active during the day and relied more on leaf and fruit vegetation
y Notharctus- Small broad face, with stereoscopic vision, reduced muzzle
The Emergence of Anthropoids
y First new world primates appear late in oligence when SA was no closer to either Africa or NA
than it is today
y So where did new world monkey come from?- fossil evidence: Bolivia; dates 35 million years
ago including: Branisella, Tremacebus, Dolichocebus, Homonoculus, Soriacebus
y No clear fossil record of the old world forms (the Catarrhines) where they are abundant
today
The Fayum Oligocene Anthropoids
y Uninviting area of desert badlands
y Oligocene: the geological epoch 34 million years ago to 24 million years ago during which
definite anthropoids emerged
y The Fayum yielded to main types of anthropoids the monkey-like parapithecids and the
ape-like propliopithecids
y Parapithecids: small monkey like Oligocene primates found in the Fayum area of Egypt
y 3 premolars, bony partition behind eye socket, broad incisors, projecting canines,
low/rounded cusps on molars, small brain size
y Under 1.3 kg (resembled squirrel like monkeys)
www.notesolution.com
y Small eye sockets, not nocturnal, eat mostly fruit, seeds
y How did Anthropoidal primates get from Africa-> SA?
y Distance back then was only about 3000km (possible ³island hop´- 200km ocean stretch)
y Propliopithecids: dental formula of modern canines
y Two pre-molars, broad lower incisors, projecting canines, lower molars w/rounded cusps
y Aegyptopithecus: best-known propliopithecids; moved around quadruped ally in the trees, 6
kg, ate mostly fruit, long muzzle, small brain, sexual dimorphism
y Palaeoanthropologists think-> specialized characteristics of living old world monkeys, apes,
share similar Catarrhines dental formula= ancestor of both old world monkeys and hominoids
(apes/humans)
Miocene Anthropoids: Monkeys, Apes, and Hominins
y Miocene: epoch from 24- 5.2 million years ago
y Monkeys/apes clearly diverged in appearance in Europe, Asia, Africa
y Temperatures= warmer than Oligocene, conditions-> drier (continental drift)
y Late Miocene- 8-5 MYA- first Hominin emerged in Africa
y Monkey fossils in early Miocene are rare
Early Miocene Hominoids
y Proconsul: the best known genus of proto-apes from the early Miocene epoch; found
mostly in Africa
y Fossil found: Kenya, Uganda (20 million years old)
y Proconsul; lacked tail, arboreal quadruped, moved on ground, fruit eaters, leaves,
y Common ancestor of apes and humans
Middle Miocene Apes
y 17 MYA- distinct hominoid species emerged during warmer part of epoch
y Pierolapithecus: a middle Miocene ape that has wrists and vertebrae that would have made it
capable of brachiation, but also has relatively short fingers like modern monkeys
y Kenyapithecus: an ape-like primate from the middle Miocene found in E Asia. It had very
thickly enameled teeth and robust jaw- diet of hard, tough foods. Possible somewhat
terrestrial
Late Miocene Apes
y Apes diversified and moved into many areas- Euro, Asia, Africa
y Climate turning cooler, drier
y Oreopithecus: extremely long arms, hands, mobile joints, agile brachiator, diet of mostly
leaves , ape-like body, monkey like-head
y Sivapithecus: a genus of ape from the later Miocene known for its thickly enameled teeth,
suggesting hard diet. Found primarily in western and southern Asia and now thought to be
ancestral to organisms
y Dryopithecus: genus of ape from the later Miocene found primarily in Europe. It had thin
tooth enamel, pointed molar cusps quite similar to those of fruit eating chimpanzees of today
y Climate became drier in late Miocene, majority of hominoid forms became extinct, leaving
behind few modern day forms
The Divergence of Hominins from the Other Hominoids
y Molecular biology of the most recent common ancestor of humans and out closest primate
relatives, the chimpanzees, probably lived
The Molecular Clock
y Gibbons- 12 MYA, hominoids- 10 MYA, other apes- from hominoids- 4.5 MYA (the more
similar the chemistry of the primates blood proteins, the closer the primates are in
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