Geology Reference
In-Depth Information
Among the hoofed mammals (artiodactyls and perisso-
dactyls), adaptations include modifi cations of the teeth
for grinding vegetation and changes in their limbs for
speed.
The evolutionary history of horses is particularly well
documented by fossils, but scientists also know much
about the evolution of other hoofed mammals, as well as
elephants, whales, and some carnivores.
The primates evolved during the Paleocene. Several
trends help characterize primates and differentiate them
from other mammalian orders, including a change in
overall skeletal structure and mode of locomotion, an
increase in brain size, stereoscopic vision, and evolution
of a grasping hand with opposable thumb.
The primates are divided into two suborders: prosimians
and anthropoids. The prosimians are the oldest primate
lineage and include lemurs, lorises, tarsiers, and tree
shrews. The anthropoids include the New and Old World
monkeys, apes, and hominids (humans and their extinct
ancestors).
The oldest known hominid is
Sahelanthropus tchadensis,
dated at nearly 7 million years old. It was followed by
Orrorin tugenensis
at 6 million years, and then two sub-
species of
Ardipithecus
, at 5.8 and 4.4 million years old,
respectively. These early hominids were succeeded by
the australopithecines, a fully bipedal group that evolved
in Africa 4.2 million years ago. Currently, fi ve australo-
pithecine species are known:
Australopithecus anamensis,
A. afarensis, A. africanus, A. robustus,
and
A. boisei.
The human lineage began about 2.5 million years ago in
Africa with the evolution of
Homo habilis,
which survived
as a species until about 1.6 million years ago.
■
■
■
Homo erectus
evolved from
H. habilis
about 1.8 million
years ago and was the fi rst hominid to migrate out of
Africa. The transition from
H. erectus
to
H. sapiens
is
still unresolved because there is currently insuffi cient
evidence to determine which hypotheses—the “out of
Africa” or the “multi-regional” hypothesis—is correct.
Neanderthals inhabited Europe and the Near East
between 200,000 and 30,000 years ago and were not
much different from us, only more robust and with
differently shaped skulls. They made specialized tools
and weapons, apparently took care of their injured, and
buried their dead.
The Cro-Magnons were the successors of the Neander-
thals and lived from about 35,000 to 10,000 years ago.
They were highly skilled nomadic hunters, formed living
groups of various sizes, and were also skilled cave painters.
Modern humans succeeded the Cro-Magnons about
10,000 years ago and have since spread throughout the
world, as well as having set foot on the Moon.
■
■
■
■
■
■
■
Important Terms
Alpine-Himalayan orogenic belt
(p. 637)
artiodactyl (p. 660)
Atlantic Coastal Plain (p. 648)
australopithecine (p. 665)
Basin and Range Province (p. 643)
browser (p. 660)
Cascade Range (p. 642)
circum-Pacifi c orogenic belt (p. 639)
Colorado Plateau (p. 643)
Cro-Magnon (p. 671)
Farallon plate (p. 644)
grazer (p. 660)
Gulf Coastal Plain (p. 647)
hominid (p. 664)
Homo
(p. 668)
Interior Lowlands (p. 645)
Laramide orogeny (p. 639)
marsupial mammal (p. 658)
monotreme (p. 658)
Neanderthal (p. 670)
North American Cordillera (p. 639)
orogen (p. 637)
Paleocene-Eocene thermal maximum
(p. 656)
perissodactyl (p. 660)
placental mammal (p. 658)
primate (p. 663)
San Andreas transform fault (p. 645)
Tejas epeiric sea (p. 647)
ungulate (p. 660)
Zuni epeiric sea (p. 645)
Review Questions
1. The Himalyas formed when the __________ plate
collided with the __________ plate.
a. _____ North American/Pacifi c;
b. _____ Nazca/Cocos;
c. _____ Indian/Asian;
d. _____ Farallon/African;
e. _____ Atlantic/Middle Eastern.
2. Shallow-angle subduction of the Farallon plate beneath
North America is considered responsible for which of
the following orogenies?
a. _____ Hercynian;
b. _____ Antler;
c. _____ Caledonian;
d. _____ Atlas;
e. _____ Laramide.
Search WWH ::
Custom Search