ANTH 101 Chapter 9
Why Did Primates Emerge?
Theories of Primate Evolution
Arboreal hypothesis
Primate traits such as grasping hands and binocular vision were adaptations
to life in the trees.
Moving from the ground to the trees caused selective pressures that resulted
in the ancestral primate.
Visual predation hypothesis
Challenges arboreal notion: many mammals are arboreal without having
evolved primate traits.
Matt Cartmill proposed that primate traits evolved in response to preying on
insects and other small creatures.
The exploitation of small prey resulted in the primate suite of adaptations.
However, this visual predation hypothesis does not explain fruit-eating
primates.
Angiosperm radiation hypothesis
Randall Sussman proposed that primate traits were a response to the
development of fruit-bearing angiosperm plants.
The First True Primate: Visual, Tree-Dwelling, Agile, Smart
Primates in the Paleocene?
Paleocene fossils a possible candidate for the early primate ancestor
Plesiadapiforms
Found in western North America, western Europe, Asia and possibly Africa
Lack postorbital bar and other primate traits
Possibly a separate order, but still potentially related to primates
First True Primate: Visual, Tree-Dwelling, Agile, Smart (cont’d)
Eocene Euprimates: The First True Primates
First true primates (euprimates) in Eocene epoch, as early as 55 mya
Clear primate traits, including post orbital bar, large brain relative to body size
Adapids and omomyids
Widely diverse species, most with small body size
May have evolved from proprimates in Paleocene
Evolution occurred in period of global warming
Basal Anthropoids
The Oligocene was a period of global cooling and widespread plant and
animal extinctions.
Most primate fossils from this period come from the Fayum region of Egypt.
Fossils from this time period include prosimian fossils as well as those of
three groups of higher primates.
Apes Begin in Africa and Dominate the Miocene Primate World
The Miocene deposits in Africa provide evidence for a group of primates called
proconsulids, which date to 22–17 mya.
A diverse number of taxa, with 10 genera and 15 species.
Proconsul is the best known of these genera.
Skulls and teeth are apelike in appearance; rest of skeleton is monkeylike.
Apes Leave Africa: On to New Habitats and New Adaptations
The fossil record suggests apes evolved in Africa and spread to Europe and Asia.
Apes in Europe: The Dryopithecids
Larger than earlier apes
Resembled living apes in many traits
Dead End in Ape Evolution: The Oreopithecids
Climate Shifts and Habitat Changes
Climate changes occurred during this time in Europe and Asia, resulting in the
disappearance of fruit resources commonly exploited by the apes.
Miocene Ape Survivors Give Rise to Modern Apes
A few survivors of this event evolved into modern apes.
Apes Return to Africa?
The fossil record for the late Miocene is too fragmentary to shed light on the question
of whether early hominids descended from Miocene ancestry in Europe or Africa.
Monkeys on the Move
As the apes evolved, so too the monkeys in the Old World and the New World
expanded and radiated.
Fossils with cercopithecoid traits first appear in early Miocene.
The radiation of monkeys continued into the Pliocene and Pleistocene, then declined
as habitats and climates changed, or perhaps even due to human hunting.