Hominid Evolution

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Chapter 19
Hominid Evolution
2
Classification Hierarchy (Linnaeus)

• Kingdom Animal
• Phylum Chordate
• Class Mammal
• Order Primates

• Family Hominids
• Genus Homo
• Species Sapiens

Humans and apes diverged 8 Mya
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Humans and Apes

• Diverged 8 million years ago
• gt12 different forms of hominids since then

4
Oldest Hominid

• Sahelanthropus tchadensis,
• the oldest known hominid
• 7 million years old
• discovered in 2002 in Chad

5
Sahelanthropus tchadensis

• Skull found in the African nation of Chad in 2002
• pushed back the origins of humans to nearly 7
  million years ago
• its discovery has raised more questions than it
  answered

6
Bushy Model of Human Evolution

• Paleoanthropologists now think
• human evolution branched many times
• rather than evolving in a somewhat straight line
• Key traits such as
• upright walking
• manual dexterity
• large brain
• evolved more than once, and produced many
  evolutionary dead-ends

7
Fossil hominids
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g_tab/418133a_F2.html
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Oldest Hominid

• Sahelanthropus tchadensis shows a mosaic of
  primitive and advanced features
• The small brain case and most of the teeth are
  chimplike
• Fairly flat nose and the prominent brow ridges
• are features only seen, until now, in the human
  genus Homo
• Looks more human than hominids that came millions
  of years later!

9
Early History of Ancestral Hominids

• Much of our knowledge
• comes from fossils found in a small desert area
  southwest of Cairo, Egypt
• During the Late Eocene and Oligocene
• this region was a lush, tropical rain forest
• supported a diverse and abundant fauna and flora

10
Thousands of Fossil Specimens

• Several thousand fossil specimens
• representing more than 20 species of primates
• recovered from rocks of this region
• One of the earliest ancestral hominids
• was Aegyptopithecus,
• small, fruit-eating, arboreal primate
• weighed about 5 kg

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One of the Earliest Ancestral Hominids

• Skull of Aegyptopithecus zeuxis,

• one of the earliest known anthropoids
• 30 Ma

12
Hominids

• The hominids (family Hominidae)
• primate family that includes present-day humans
• fossil record extending back 7 million years
• Hominids are bipedal
• that is, they have an upright posture
• Skeletal structure shows bipedal traits
• Hominid brain organization larger compared to
  other primates

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Comparison of Locomotion

• Comparison between quadrupedal and bipedal
  locomotion
• in gorillas and humans

• In gorillas the ischium bone is long
• and the entire pelvis is tilted toward the
  horizontal

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Comparison of Locomotion

• Comparison between quadrupedal and bipedal
  locomotion
• in gorillas and humans

• In humans the ischium bone is much shorter
• and the pelvis is vertical

15
Hominids Larger Reorganized Brain

• In addition, hominids show a trend
• toward a large and internally reorganized brain
• A large brain size and organization
• is apparent in the brain of a present-day human

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Response to Climatic Changes

• Many anthropologists think
• hominid features evolved in response to major
  climatic changes
• During this time
• vast savannas replaced the African tropical rain
  forests
• where the lower primates had been so abundant

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Mixed Forests and Grasslands

• As the savannas and grasslands continued to
  expand
• hominids made the transition from true forest
  dwelling
• to life in an environment of mixed forests and
  grasslands

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Geologic Age Ranges
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Oldest Known Hominid

• Discovered in Chad in 2002
• nearly 7-million-year-old skull and dental
  remains of Sahelanthropus tchadensis
• make it the oldest known hominid yet unearthed

20
Australopithecus

• Australopithecines are early hominids
• genus Australopithecus
• Currently, five species are recognized
• A. anamensis
• A. afarensis
• A. africanus
• A. robustus
• A. boisei

21
Evolutionary Scheme

• Many paleontologists accept that
• A. anamensis
• the oldest known australopithecine,
• is ancestral to A. afarensis,
• who in turn is ancestral to A. africanus
• and the genus Homo,
• as well as the side branch of australopithecines
• represented by A. robustus and A. boisei

22
Lucy

• A reconstruction of Lucys skeleton
• Lucy is a 3.5-million-year-old
• Australopithecus afarensis

• Knees worked like modern human knees
• Makes 40 bigger than females
• Males had large crests on the tops of their skulls

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Hominid Footprints

• Preserved in volcanic ash in Tanzania
• Discovered in 1978
• Proved hominids were bipedal walkers at least 3.5
  million years ago

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Hominid Footprints

• Most scientists think the footprints
• were made by Australopithecus afarensis
• whose fossils are found nearby

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Brain Size of A. afarensis

• A. afarensis had a brain size of 380450 cubic
  centimeters (cc),
• larger than the 300400 cc of a chimpanzee
• much smaller than that of present-day humans
  (1350 cc average)

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Apelike Features

• The skull of A. afarensis retained many apelike
  features
• massive brow ridges
• forward-jutting jaw
• teeth were intermediate between those of apes and
  humans
• The heavily enameled molars
• adaptation to chewing fruits, seeds, and roots

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Landscape with A. afarensis

• Re-creation of a Pliocene landscape
• showing members of
• Australo-pithecus afarensis
• gathering and eating
• various fruits and seeds

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Skull of A. africanus

• A reconstruction of the skull
• of Australopithecus africanus
• This skull,
• known as that of the Taung Child,
• was discovered by Raymond Dart in South Africa in
  1924
• and marks the beginning of modern
  paleoanthropology

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Not As Well Adapted for Bipedalism

• It appears the limbs
• of A. africanus may not have been as well adapted
  for bipedalism as those of A. afarensis

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The Human Lineage handy man

• Homo habilis
• The earliest member of our own genus Homo
• lived 2.5-1.6 million years ago
• H. habilis evolved from the A. afarensis and A.
  africanus lineage
• coexisted with A. africanus for about 200,000
  years

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Geologic Age Ranges

• The geologic age ranges
• for the commonly accepted species of hominids

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Characteristics of Homo habilis

• H. habilis had a larger brain (700 cc average)
• than its australopithecine ancestors but smaller
  teeth
• It was about 1.2-1.3 m tall and weighed 32-37 kg

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Homo Erectus

• In contrast to the australopithecines and H.
  habilis,
• which are unknown outside Africa,
• Homo erectus was a widely distributed species
• migrated from Africa during the Pleistocene
• Specimens have been found
• not only in Africa
• also in Europe, India, China ("Peking Man"), and
  Indonesia ("Java Man")

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Survived in Asia Until About 100,000 Years Ago

• H. erectus evolved in Africa 1.8 million years
  ago
• and by 1 million years ago
• was present in southeastern and eastern Asia,
• where it survived until about 100,000 years ago

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H. erectus Differed From Modern Humans

• Although H. erectus developed regional variations
  in form,
• the species differed from modern humans in
  several ways
• Its brain size of 800-1300 cc,
• though much larger than that of H. habilis,
• was still less than the average for Homo sapiens
  (1350 cc)

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Size Similar to Humans

• H. erectus's skull was thick-walled
• face was massive
• prominent brow ridges
• teeth were slightly larger than those of
  present-day humans
• H. erectus was comparable to size to modern
  humans
• between 1.6 and 1.8 m tall
• weighing between 53 and 63 kg

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Skull of Homo erectus

• A reconstruction of the skull of Homo erectus
• a widely distributed species
• whose remains have been found in Africa, Europe,
  India, China, and Indonesia

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H. erectus Was a Tool Maker

• The archaeological record indicates
• that H. erectus was a tool maker
• Furthermore, some sites show evidence
• that its members used fire and lived in caves
• an advantage for those living in more northerly
  climates

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Homo erectus Using Tools

• Re-creation of a Pleistocene setting in Europe
• in which members of Homo erectus are
• using fire and stone tools

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The "Out of Africa" View

• Currently, a heated debate surrounds the
  transition
• from H. erectus to our own species Homo sapiens
• Out of Africa" view
• early modern humans evolved from a small African
  colony
• offspring then migrated from Africa and populated
  Europe and Asia, driving the earlier hominid
  populations to extinction

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The "Multiregional" View

• Multiregional" view
• early modern humans did not have an isolated
  origin in Africa
• established separate populations throughout
  Eurasia
• Occasional contact and interbreeding
• enabled our species to maintain its overall
  cohesiveness
• still preserving the regional differences in
  people we see today

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Homo sapiens Evolved From H. erectus

• Regardless of which theory turns out to be
  correct,
• our species, H. sapiens, most certainly evolved
  from H. erectus

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Neanderthals

• Neanderthals
• inhabited Europe and the Near East
• 200,000 to 30,000 years ago
• Some paleoanthropologists
• as a Neanderthals are a subspecies of our own
  species (Homo sapiens neanderthalensis)
• Others separate species (Homo neanderthalensis)

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Neanderthals Difference

• Main difference between Neanderthals and
  present-day humans is in the skull
• Neanderthal skulls were long and low
• heavy brow ridges, a projecting mouth, and a
  weak, receding chin
• Their brain was slightly larger on average
• than our own, and somewhat differently shaped

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Neanderthal Skull

• Reconstructed Neanderthal skull
• The Neanderthals were characterized
• by prominent heavy brow ridges and weak chin

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First Humans in Cold Climates

• Given the specimens from more than 100 sites
• we now know Neanderthals were not much different
  from us, only more robust
• Europe's Neanderthals were the first humans
• to move into truly cold climates
• enduring miserably long winters and short summers
  
• as they pushed north into tundra ecosystems

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Burial Ceremony in a Cave

• Archaeological evidence indicates
• Neanderthals lived in caves
• and participated in ritual burials
• as depicted in this painting of a burial ceremony
  
• such as occurred approximately 60,000 years ago
• at Shanidar Cave, Iraq

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Cro-Magnons

• About 30,000 years ago
• humans closely resembling modern Europeans
• moved into the region inhabited by the
  Neanderthals and completely replaced them
• Cro-Magnons
• successors of the Neanderthals in France
• 35,000 to 10,000 years ago
• huge advances in development of art and
  technology

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Cave Painters

• Cro-Magnons were cave painters
• Using paints made from manganese and iron oxides
• painted hundreds of scenes on the ceilings and
  walls of caves in France and Spain
• many of them are still preserved today

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Painting From a Cave in France

• Cro-Magnons were very skilled cave painters
• Painting of a horse
• from the cave of Niaux, France

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Cultural Evolution

• With the appearance of Cro-Magnons,
• human evolution has become almost entirely
  cultural rather than biological
• Humans have spread throughout the world
• by devising means to deal with a broad range of
  environmental conditions

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Summary

• Aegyptopithecus 32 Ma (ancestral hominid
  primate)
• Somewhat developed forehead
• Australopithecus 5 Ma (early hominids)
• Afarensis (Lucy) 4 Ma, bipedalism, still tree
  climbers, small skull
• Africanus 2-3 Ma slightly larger brain
• Homo habilis 2 Ma
• Larger brain, less pronounced brow, rounder head,
  smaller face
• Use of stone tools
• Homo erectus 500 K-2Ma
• Larger brain and body
• Longer skull, large brow ridges
• Homo sapiens neanderthalensis 200 K
• Large brains and bodies, lack of frontal lobes?
• Homo sapiens sapiens (cro-magnon) 90 K
• Anatomically similar to humans

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Climate in Human History

• Peak of glaciation 18 Ka
• Present interglacial began 10 Ka
• Climatic Optimum
• 6-7 Ka
• First great civilizations in Middle East
• Some collapsed 3 Ka when climate changed
• Subatlantic Deterioration
• 2.5 Ka
• Reflected in art and invasions

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Climate in Human History

• Drought and famine
• Location of settlements
• Exploration
• Medieval Warm Period began 950 A.D.
• Little Ice Age 1550-1850 A.D.

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Vikings

• Settled Greenland and Iceland during Medieval
  Warm Period
• During Little Ice Age, Greenland was abandoned
  and Iceland struggling
• Ice blocked trade routes, cold weather caused
  poor harvests
• Fish moved southward

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Climate reflected in art

• Little Ice Age at its peak during 2nd epoch

www2.sunysuffolk.edu/mandias/lia/little_ice_age.ht
ml
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Recent History

• Two centuries of warm, mild climate
• Continual drying of northern Africa
• Interglacial should be coming to an end will
  humans prolong it?