Ch' 19The Neogene World

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Ch. 19The Neogene World
Holocene
12,000 years
Pleistocene
1.8

• Neogene Period includes Miocene, Pliocene and
  Pleistocene epochs
• Beginning of Holocene was approx. 12,000 years
  ago

Pliocene
5.3
Neogene
Miocene
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Cenozoic
Oligocene
Paleogene
Eocene
Paleocene
65
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Todays outline

• Glaciation
• Human evolution

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Continental glaciation

• Early Neogene climate was relatively mild
• In mid-Pliocene time, 3.2 million years ago,
  modern ice age began
• Ice age continues today, although glacial maxima
  and minima are cyclical, and we are now in an
  interglacial episode

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NorthernHemispherecontinentalglaciers
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Continental glaciation

• Bering Land Bridge was ice-free and a corridor
  for faunal interchange between North Americ and
  Asia

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Waxing and waning of glaciers

• High frequency glacial and interglacial cycles
• Periodic changes in the tilt of Earths axis
  relative to plane of orbit
• Periodic changes in the orbit itself, due to
  gravitational pull of other planets
• Cycles can be documented through oxygen isotope
  records
• Waxing and waning has displaced plant ecosystems
  by up to 20 latitude

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Oxygenisotoperecord
(these should be positive numbers)
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Displacement of floral ecosystems
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Origin of the Great Lakes and Lake Bonneville

• Retreat of glaciers after the most recent glacial
  interval left behind large basins that eventually
  filled with water
• Great Lakes formed within the past 10,000 to
  15,000 years
• Lake Bonneville covered much of Utah now the
  Great Salt Lake is a tiny remnant

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Great Lakes and Lake Bonneville
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What was the ultimate cause of Pliocene-Pleistocen
e glaciation?

• Probably related to creation of Isthmus of Panama
• Modification of global ocean currents
• Separation of Atlantic and Pacific oceans
  resulted in dramatic cooling of Arctic Ocean water

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Human Evolution Superfamily Hominoidea includes
gibbons, man, and apes. Homo is the only
genus in Family Hominidae sapiens is the only
species in the genus Homo.
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Early origins

• Earliest hominoid fossils are from Africa, 20
  Ma (early Miocene)
• These early hominoids are probably ancestral to
  both modern hominids and pongiids, but fossil
  record is spotty
• mid- to late-Miocene was a time of hominoid
  radiation throughout Africa and Eurasia (more
  apes then than now!)
• By latest Miocene time, only one genus had
  survived Gigantopithecus

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Australopithecines

• Earliest true hominids appeared at
  Miocene-Pliocene transition, 5.3 Ma, the
  australopithecines
• Australopithecus, Paranthropus
• Australopithecus (4.0-2.3 Ma) was somewhat
  intermediate in appearance between modern apes
  and humans (but not an evolutionary
  intermediate)
• Males larger than females (4.5 ft vs. 3.5 ft)
• Brain size barely larger than modern chimp
• Bi-pedal, but spent much time in trees

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Australopithecus
Lucy, a female of the Species A.
afarensis, found in 3.2 Ma beds In Ethiopia
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Bi-pedalAustralopithecustracks preservedin
volcanic ash,3.0 Ma, fromTanzania
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Early Homo

• Australopithecus branched into at least two
  species (A. afarensis and A. africanus)
• earliest Homo originated from Australopithecus
  approximately 2.4 Ma
• By 2.0 Ma, at least two species of early Homo
  were in existence

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Hominidstratigraphy
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Early Homo

• Characteristics of early Homo
• Large brain (800 cm3 vs only 450 cm3 for
  Australopithecus)
• Smaller teeth
• Ability to make and use stone tools
• Meat in diet
• Spent most of the time on the ground (not in
  trees)

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Skull of Homo habilis
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Brain size vs. mode of life

• Brain of all newborn primiates 10 of body
  weight
• Brain growth stops shortly after birth in monkeys
  and apes
• Brain growth continues for 1 year in Homo
• Homo development is delayed relative to chimps
  and apes
• Delayed maturation of Homo requires significant
  parental care
• Parents must hold babies, thus arms not free to
  hold onto tree branches

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Brain size vs. mode of life

• Development of large brain may be related to
  climatic change in Africa (2.5 Ma)
• Drying out of climate reduced forests
• Life on ground may have paved the way for
  prolonged parental care
• Bipedalism probably preceeded increase in brain
  size

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Homo erectus

• Homo erectus evolved from early Homo
  approximately 1.6 Ma
• First hominid to migrate beyond Africa
• Peking Man, Java Man
• Looked similar to modern humans, but
• Slightly smaller brain (1000 cm3 vs 1400 cm3)
• Narrower pelvis

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Homo erectus
Bones of an 11 or 12 year old boy (1.6 Ma)
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Homo neanderthalensis

• Neanderthal fossils are known in Eurasia in beds
  ranging from 100,000 to 35,000 years old
• Probably originated from a European or Asian
  population of H. erectus or related species
• Fossils commonly found in cave deposits
• Probably practiced some form of religion
• Buried dead family members with food and tools

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Neanderthalburial
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Homo sapiens

• Homo sapiens (modern humans) originated in Africa
  150,000 ybp (presumably from an African
  popolation of H. erectus or related species)
• DNA from H. sapiens and H. neanderthalensis
  indicates that ancestral populations may have
  diverged by 500,000 ybp

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Homo sapiens

• Homo sapiens seemingly stayed in Africa for
  several tens of thousands of years before
  migrating to Europe
• Oldest European fossils of H. sapiens are 33,000
  ybpabout the same time H. neanderthalensis
  vanished
• Did we kill the only other species of hominids?