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

    60

    50

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    Millionsofyearsago

    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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    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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