human and primate evolution
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Primate and Human
EvolutionUnit 4
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Half a Billion Years of Backbones
By the end of the Cambrian period, some 540 million years ago An astonishing variety of animals inhabited Earths oceans
One of these types of animals Gave rise to vertebrates, one of the most successful groups of
animals The animals called vertebrates
Get their name from vertebrae, the series of bones that make upthe backbone
There are approximately 52,000 species of vertebrates
Which include the largest organisms ever to live on the Earth
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Mammals, class Mammalia
Mammals are amniotes (members include reptiles, birds and mammals) that have hair and
produce milk.
Amniotes have their origin in the amniotic egg which allows embryos to develop on land in an
aquatic medium.
Are represented by more than 5,000 species
Mammals
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Derived Characters of Mammals
Mammary glands, which produce milk Are a distinctively mammalian character
Hairis another mammalian characteristic Mammals generally have a larger brain
Than other vertebrates of equivalent size
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Early Evolution of Mammals
Mammals evolved from synapsids, a group of amniotes who initially did not have hair but later evolved into large
herbivores and carnivores during the Permian period and later became mammal-like in the late Triassic period.
The early forms of mammals were small, hairy and fed on insects at night and still laid eggs.
During Jurassic period, the first true mammals arose but were still small probably because of the presence of large-
bodied dinosaurs.
Early Cretaceous, the three major lineages of living mammals emerged: monotremes (egg-laying mammals), marsupials
(mammals with a pouch) and eutherians (placental mammals).
After extinction of dinosaurs, pterosaurs and marine reptiles duirng later Cretaceous period, mammals underwent an
adaptive radiation.
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Monotremes
Monotremes Are a small
group ofegg-
laying mammalsconsisting of
echidnas and the
platypus
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Marsupials Marsupials
Include opossums, kangaroos, and koalas
A marsupial is born very early in its development
And completes its embryonic development while nursing within a maternal pouch called a
marsupium
(a) A young brushtail possum. The young of
marsupials are born very early in their
development. They finish their growth
while nursing from a nipple (in their
mothers pouch in most species).
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In Australia, convergent evolution Has resulted in a diversity of marsupials that resemble
eutherians in other parts of the world
Marsupial mammals Eutherian mammals
Plantigale
Marsupial mole
Sugar
glider
Wombat
Tasmanian devil
Kangaroo
Deer mouse
Mole
Woodchuck
Flying squirrel
Wolverine
Patagonian cavy
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Eutherians (Placental Mammals)
Compared to marsupials Eutherians have a longer period of pregnancy
Young eutherians Complete their embryonic development within a
uterus, joined to the mother by the placenta
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Phylogenetic
relationships ofmammals
Ancestral mammal
Monotremes Marsupials Eutherians
Monotremata Marsupial ia Xenarthra
Proboscidea Sirenia
Tubulidentata
Hyracoidea
Afrosoricida (golden
moles and tenrecs)
Macroscelidea
(elephant shrews)
Rodentia
Lagomorpha
Primates
Dermoptera
(flying lemurs)
Scandentia
(tree shrews)
Carnivora
Cetartiodactyla
Perissodactyla
Chiroptera
Eulipotyphla
Pholidota
(pangolins)
Possible phylogenetic tree of mammals.
All 20 extant orders of mammals are listed
at the top of the tree. Boldfaced orders
are explored on the facing page.
This diverse clade includes terrestrial
and marine mammals as well as bats,
the only flying mammals. A growing
body of evidence, including Eocene
fossils of whales with feet,
supports putting whales in
the same order (Cetartiodactyla)
as pigs, cows, and hippos.
This is the largest eutherian
clade. It includes the rodents,
which make up the largest
mammalian order by far, with
about 1,770 species. Humans
belong to the order Primates.
All members of this clade,
which underwent an adaptive
radiation in South America,
belong to the order Xenarthra.
One species, the nine-banded
armadillo, is found in the
southern United States.
This clade of eutherians evolved
in Africa when the continent
was isolated from other
landmasses. It includes
Earths largest living land
animal (the African elephant),
as well as species that weigh
less than 10 g.
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The major
eutherian
orders
ORDERSAND EXAMPLES
MAINCHARACTERISTICS
MonotremataPlatypuses,echidnas
Proboscidea
Elephants
Sirenia
Manatees,dugongs
CetartiodactylaArtiodactyls
Sheep, pigscattle, deer,
giraffes
Lagomorpha
Rabbits,hares, picas
Carnivora
Dogs, wolves,bears, cats,weasels, otters,
seals, walruses
XenarthraSloths,
anteaters,armadillos
CetaceansWhales,dolphins,
porpoises
Echidna
African elephant
Manatee
Tamandua
Jackrabbit
Coyote
Bighorn sheep
Pacific white-sided porpoise
Lay eggs; no
nipples; youngsuck milk fromfur of mother
Long, musculartrunk; thick,loose skin; upper
incisors elongatedas tusks
Aquatic; finlike
forelimbs and
no hind limbs;herbivorous
Reduced teeth orno teeth; herbivorous(sloths) or carnivorous
(anteaters,armadillos)
Chisel-like incisors;
hind legs longer thanforelegs and adapted
for running andjumping
Sharp, pointed canine
teeth and molars forshearing; carnivorous
Hooves with aneven number
of toes on eachfoot; herbivorous
Aquatic; streamlined
body; paddle-likeforelimbs and no
hind limbs; thicklayer of insulatingblubber; carnivorous
Diet consists mainlyof insects and othersmall invertebrates
Adapted for flight; broad
skinfold that extendsfrom elongated fingers
to body and legs;carnivorous orherbivorous
Hooves with an
odd number of toes
on each foot;herbivorous
Opposable thumbs;
forward-facing eyes;well-developed
cerebral cortex;omnivorous
Chisel-like, continuously
growing incisors worndown by gnawing;
herbivorous
Short legs; stumpy tail;herbivorous; complex,multichambered
stomach
Teeth consisting of
many thin tubescemented together;
eats ants and termites
Embryo completesdevelopment inpouch on mother
ORDERSAND EXAMPLES
MAINCHARACTERISTICS
MarsupialiaKangaroos,opossums,
koalas
Tubulidentata
Aardvark
Hyracoidea
Hyraxes
ChiropteraBats
Primates
Lemurs,monkeys,
apes,humans
Perissodactyla
Horses,
zebras, tapirs,rhinoceroses
RodentiaSquirrels,beavers, rats,
porcupines,mice
EulipotyphlaCore insecti-
vores: somemoles, someshrews
Star-nosed
mole
Frog-eating bat
Indian rhinoceros
Golden lion
tamarin
Red squirrel
Rock hyrax
Aardvark
Koala
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Primates
The mammalian order Primates include Lemurs, tarsiers, monkeys, and apes
Humans are members of the ape group
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Derived Characters of Primates
Most primates
Have hands and feet adapted for grasping (prehensile hands
and feet)
Primates also have A large brain and short jaws
Forward-looking eyes close together on the face, providing
depth perception
Well-developed parental care and complex social behavior
A fully opposable thumb
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Living Primates
There are three main groups of living primates:
1. The lemurs of Madagascar and the lorises and pottos of tropical Africa
and southern Asia
2. The tarsiers from South East Asia
3. The anthropoids, which include monkeys and apes found worldwide
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The oldest known anthropoid fossils, about 45 million
years old
Indicate that tarsiers are more closely related to anthropoids
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Ancestral primate
Lemurs,loris
es,andp
ottos
Tarsiers
NewW
orldmonkeys
OldW
orldmonkeys
Gibbons
Orangutans
Gorillas
Chim-
panzees
Humans
Anthropoids
0
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Both New and Old World monkeys are thought
to have originated from Asia or Africa (Old
World). The fossil record indicates thatNew World
monkeys First appeared in theNew World (South America)
during the Oligocene
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New World and Old World monkeys Underwent separate adaptive radiations during their many
millions of years of separation
(a) New World monkeys, such as spider
monkeys (shown here), squirrel monkeys, and
capuchins, have a prehensile tail and nostrils
that open to the sides.
(b) Old World monkeys lack a prehensile tail, and their nostrils
open downward. This group includes macaques (shown here),
mandrills, baboons, and rhesus monkeys.
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The other group of anthropoids, consists of primates informally calledapes.
Apes include gibbons, chimpanzees and bonobos and the genus Homo(humans)
(a) Gibbons, such as this Muller's gibbon, are
found only in southeastern Asia. Their very
long arms and fingers are adaptations for
brachiation.
(b) Orangutans are shy, solitary apes that live in the rain
forests of Sumatra and Borneo. They spend most of
their time in trees; note the foot adapted for grasping
and the opposable thumb.
(c) Gorillas are the largest apes: some
males are almost 2 m tall and weigh
about 200 kg. Found only in Africa, these
herbivores usually live in groups of up to
about 20 individuals.
(d) Chimpanzees live in tropical Africa. They
feed and sleep in trees but also spend a
great deal of time on the ground. Chimpanzees
are intelligent, communicative, and social.
(e) Bonobos are closely
related to chimpanzeesbut are smaller. They
survive today only in the
African nation of Congo.
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Derived Characters of Hominids
A number of characters distinguish humans from other apes
Upright posture and bipedal locomotion
Larger brains
Language capabilities Symbolic thought
The manufacture and use of complex tools
Shortened jaw
S-shaped vertebrae column
Reduced canine teeth
Presence of foramen magnum at the base of the skull through which the
spinal cord exits
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The Earliest Humans
The study of human origins
Is known aspaleoanthropology
Paleoanthropologists have discovered fossils of approximately 20 species of extinct hominoids
That are more closely related to humans than to chimpanzees
The oldest of these hominins, Sahelanthropus tchadensis, lived about 6-7 million years ago.
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These species are known as hominids/homininsHomo
sapiens
Homo
neanderthalensis
Homo
ergaster?
Homo
erectus
Homo
habilisHomo
rudolfensis
Paranthropus
robustus
Paranthropus
boisei
Australopithecus
garhi
Australopithecus
africanus
Australopithecus
afarensis
Kenyanthropus
platyops
Australopithecus
anamensis
Ardipithecus
ramidus
Orrorin tugenensis
Sahelanthropus
tchadensis7.0
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earsago
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Hominids originated in Africa
Approximately 67 million years ago
Early hominids
Had a small brain, butprobably walked upright, exhibiting
mosaic evolution
Two common misconceptions of early hominids include
Thinking of them as chimpanzees
Imagining human evolution as a ladder leading directly to
Homo sapiens
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Australopiths Genus Australopithecus
Australopiths are hominids
That lived between 4 and 2 million years ago
Got their name from the 1924 discovery in South Africa ofAustralopithecus africanus which means southern ape of Africa which
lived between 3 and 2.4 million years ago.
A. africanus is believed to have walked fully erect (bipedal) and had human-like hands and teeth but brain volume about 1/3 of the
brain of present-day human.
In 1974, a fossil of another species was discovered Australopithecus afarensis in the Afar region of Ethiopia. This fossil was
about 3.2 million years old and belonged to a female and was named Lucy.
Lucy was short, about 1m tall, with a brain volume of 400 ml and had a long lower jaw
In 1992, the oldest Australopithecine fossil so far discovered was named A. ramidus and is dated about 4.4 million years old and is
placed at the base of the hominid phylogenetic tree based on its teeth structure.
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Australopiths Genus Australopithecus
(a) Lucy, a 3.24-million-year-old skeleton,
represents the hominid species
Australopithecus afarensis.
(b) The Laetoli footprints, more than
3.5 million years old, confirm that
upright posture evolved quite early
in hominid history.
(c) An artists reconstruction of what
A. afarensis may have looked like.
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Paranthropus robust forms
A group of early hominids more robust in form than Australopithecus has been
placed in a separate genus Paranthropus.
Three species have been described and dated from 2.8 to 1.6 million years old and
they are P. robustus, P. boisei and P. aethiopicus.
These fossils had a marked crest on the top of the skull, enormous cheek teeth withpowerful jaws for grinding and chewing hard, tough foods, cranial capacity of 550
ml and are thought to be vegetarian.
Stone tools and pieces of antelope bones, which appear to have been used for
digging in the ground for tuber and other plants, occur with these fossils.
It is thought that Homo used the stone tools while Paranthropus used the digging
tools.
Paranthropus appears to be an evolutionary line that became extinct.
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Bipedalism and Tool Use
Based on the fossil records, the evidence shows two emerging trends bipedalism and tool use.
Hominids began to walk long distances on two legs
About 1.9 million years ago as these hominins lived in more arid environments where bipedal walking requires less energy than walking on all fours.
The oldest evidence of tool usecut marks on animal bones
Is 2.5 million years old found in Ethiopia.
Interestingly, the hominin fossils found at the same site had a relatively small brain and have been named Australopithecus garhiand could have the
creators of the stone tools used on the bones suggesting that stone tool use originated first before evolution of large brains in hominids.
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EarlyHomo The earliest fossils that paleoanthropologists place in our genus
Homo
Are those of the speciesHomo habilis, ranging in age from
about 2.4 to 1.6 million years
Homo habilis had shorter jaw and a larger brain volume about
600-750 ml
Sharp stone tools have been found withH. habilis
Giving this species its name, which means handy man
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Homo ergaster
Homo ergaster
Was the first fully bipedal, large-
brained hominid (over 900 ml)
Existed between 1.9 and 1.6 million
years
Had long, slender legs with hip joints
adapted for long-distance walking.
Fingers were relatively short and
straight, suggesting thatH. ergasterdid not climb trees like previous
hominids.
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Homo erectus
Homo erectus
Originated in Africa approximately 1.8 million years ago
Was the first hominid to migrate out of Africa
Fossils of H. erectus were found in South East Asia Java Manfrom Indonesia and Peking Man from China
The intelligence conferred by the larger brain size of H. erectus
equipped it to make more sophisticated tools than those of H. habilis
and its wide distribution indicates its success.
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Neanderthals
Neanderthals,Homo neanderthalensis
Fossils about 40,000 years old were found in a cave inNeander Valley in Germany.
Lived in Europe and the Near East from 200,000 to 30,000 years ago
Were large, thick-browed hominids
Became extinct a few thousand years after the arrival ofHomo sapiens in Europe Neanderthals had abrain as large as present-day humans, buried their dead and
made hunting tools from stone and wood.
The fact that they left evidence of rituals and burials suggests that they were capable
ofabstract thought.
Neanderthals overlapped with Homo sapiens for many millennia and may haveinterbred with them before becoming extinct.
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Homo sapiens
Homo sapiens
Appeared in Africa at least 160,000 years
ago
The oldest fossils ofHomo sapiensoutside Africa
Date back about 50,000 years ago
The early humans lacked the heavy brow
ridges of H. erectus and Neanderthals andwere more slender than other hominids.
The rapid expansion of our species
May have been preceded by changes to the
brain that made symbolic thought and other
cognitive innovations possible
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Out-of-Africa or Multiregional origin of Homosapiens?
There are two competing theories for the geographic origin of H. sapiens.
Both theories accept that H. erectus populations migrated out of Africa
more than one million years ago.
Out-of-Africa theory says that a second wave of migration of anatomically
modern humans occurred about 100, 000 years ago. Thus, H. sapiens
evolved in Africa from ancestral stock similar to H. ergaster and then
replaced all other populations of Homo, including Neanderthals.
The multiregional theory rejects the idea of a second wave of migration
and hypothesizes that modern humans, H. sapiens, evolved semi-
independently from H. erectus-like stock in a number of different regions
of the world hence the name multiregional theory resulting in a single
species but made up of many different races.
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