What is the Evolutionary History of
the Primates?
Cenozoic Timescale
What is the Evolutionary History
of the Primates?
1. EOCENE
54-38 mya
Prosimian Radiations
2 exs: Smilodectes, Necrolemur
2. OLIGOCENE
38-23 mya
Monkey Radiations
2 exs: Apidium, Aegyptopithecus
3. MIOCENE
23-5 mya
Ape Radiations
2 exs: Sivapithecus, Gigantopithecus,
Sahelanthropus
Late Cretaceous Primate-like
Mammal Purgatorius
Last Common Ancestor: lived
sometime in the late Cretaceous
when dinosaurs still dominant
land-dwelling life form [genetic
evidence & diversity of primates
from the Eocene and later]
•
However, fossils of true primates are
not known until approximately 50
mya during the Eocene
•
During the late Cretaceous (>65
mya), ancestral shrew-like mammals
show certain dental and limb bone
features reminiscent of true primates
Primate Origins
If the last
common ancestor
of living primates
did indeed live
between 80 and
90 mya, the
primate lineage
that we are
descended from
would be pushed
back more than
30 million years!
New Discoveries of Early Primates
New discoveries from Eocene of China
reveal an unexpected diversity of early
primates
•
Some ancestors of monkeys, apes and
humans were so tiny that they could
have stood atop a person’s thumb
•
Fossilized foot bones from 2 species
smaller than any other known
creature on the primate family tree
were found at a limestone mine in
Eastern China, bones each about the
size of a grain of rice!
Eocene Primates (Prosimian radiations)
1. Smilodectes (North America)
Like modern lemurs it:
•
was hind-limbed dominated,
indicating ability to leap
long distances
•
had hands & feet w/nails
•
had supple, flexible spine
Unlike modern lemurs it:
•
had generalized dentition
lacking toothcomb, but
retained large canines
•
had fused lower jaw
•
shortened muzzle
Eocene Primates
2. Necrolemur (Europe)
Very similar to the modern tarsier. Its features included:
•
Elongated ankle bones similar to
those seen in Tarsius, indicative
of clinging & leaping
•
Reduced snout and enlarged
orbits, indicative of nocturnal
adaptation
•
More generalized dentition
showing adaptations for insect
eating
•
Ears and eyes like modern
tarsiers, but may have retained a
wet nose
Necrolemur
Tarsius
Oligocene Primates: Anthropoids
(Monkey radiations)

Anthropoids most likely branched off from
the prosimians much earlier than
previously thought. Their distinguishing
features are:
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Eyes rotated more forward compared to
prosimians
Fully enclosed bony eye socket
Dry nose separate from the upper lip
Relatively low crowned, squared off chewing
teeth
Oligocene Primates: El Fayum, Egypt
•
•
•
Over the last 40 years,
Anthropologists have
excavated a fossil rich oasis
in Egyptian Saharan desert
called the Fayum depression
Late Eocene & Oligocene =
the Fayum was a lush
tropical environment
crisscrossed by myriad
streams and rivers
Diverse & abundant
mammals
Oligocene Primates
1. Apidium
•
Dental formula of
2:1:3:3 on both
upper and lower jaws
as in New World
monkeys
•
Short snout & small
eyes suggest that
this was a diurnal
species
•
Postorbital closure
•
Platyrrhine-like
skeleton
Oligocene Primates
2. Aegyptopithecus
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Face Aegyptopithecus, just
after discovery in the river
channel sands of the
Fayum, about 32 mya
lies somewhere near the
base of the family tree of
Old World monkeys, apes
and humans
generalized arboreal
quadruped, with different
sized sexes, traveled
through ancient Egyptian
jungles in small multimale, multi-female troops,
diet thought to have been
mainly fruits and leaves
Aegyptopithecus
Oblique View
Aegyptopithecus
Lateral View
Miocene Primates (Ape radiations)
1. Sivapithecus
•Discovered in Pakistan
•Most anthropologists
convinced of its
relationship to the
Orangutan (left)
•Points of resemblance
to modern Orangs:
1.
Deep, concave face with large front teeth
2.
Narrow distance between the eye orbits
3.
Oval shape eye orbits
4.
Pear-shaped nasal opening
5.
Rim of bone around the upper margin of the orbits
Miocene Primates
2. Gigantopithecus
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Largest primate that ever lived,
thought by some to stand over 10’
tall and weigh close to 1200 lbs.
Died out around 400,000 ya, may
have coexisted with Homo erectus
Some people believe it is still alive
today as the yeti and bigfoot
•These three lower jaws are twice the size
of a Gorilla’s
•most complete specimens known,
discovered in a limestone cavern in China
in 1956
Miocene Primates
3. Sahelanthropus
•
Discovered in Chad (6-7 mya)
•
Most complete cranium from this
period of time & GREAT value in
understanding last common ancestor
of African apes & humans
•
Mosaic of ape & human-like features,
but is at the “ape grade” of evolution
•
Features include:
•
Ape-like cranial capacity (320-380 cc)
•
Ape-like narrow U-shaped upper jaw
•
Very wide distance between the orbits
•
Large, thick continuous brow ridge
•
Human-like flat face
•
Human-like dentition
Ecological Reconstruction
•
Mammals found in association with Sahelanthropus are Eurasian and
African forms that indicate migration into Africa
•
Migration probably due to colder & drier climate in Eurasia
•
Late Miocene apes occur for the most part in Europe and Asia: several of
these species may be hominid ancestors
•
The species could have arisen in Africa, but also possible that its lineage
originated in Europe or Asia