The Evolution of the Homoinids

1
Chapter 50

• The Evolution of the Homoinids
• Peter Stemler
• Period 2

2
Introduction

• Mammals first appeared 200 million years ago in
  the Mesozoic era
• Three principal mammal lineages the monotremes,
  the marsupials, and the placentals
• Humans are placentral mammals, as are tarsiers,
  lemurs, monkeys, and apes

3
Trends in Primate Evolution

• Most trends in primate evolution seem to be
  related to various adaptations to tree life

4
The Primate Hand and Arm

• First four-legged mammals all had five separate
  fingers and toes on each hand and foot
• Other mammals through selective pressures
  (running, digging, swimming) developed hooves,
  paws, and flippers instead of five fingered hands
• Most primates have nails as oppose to claws.
  Nails allow for manipulation and exploration by
  fingers and toes

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The Primate Hand and Arm

• Primates developed opposable thumb and
  flexibility in the arms
• Radius and ulna could rotate allowing hand to
  move in a semicircle
• Example South American monkeys can rotate the
  arm extensively in the socket for movement in the
  trees

6
Visual Acuity

• Primates home in the trees selectively pressured
  them to develop eyes frontally as oppose to
  laterally
• Almost all primates retinas have cones as well as
  rods
• Cones color vision with fine visual
  discrimination
• Foveas area of closely packed cones that produce
  sharp visual images in retina

7
Care of the Young

• As a result of mammals nursing their young,
  primates tend to have longer, stronger
  mother-child relationships than other vertebrates
• Larger primates the young matures slowly so the
  relationships more prevalent

8
Uprightness

• Orientation of the head, which allows the primate
  to look straight ahead while vertical, another
  adaptation of primates

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Prosimians

• Two Major groups of Primates
• Prosimians lorises, bush babies, tarsiers, and
  lemurs
• Anthropoids Monkeys, apes, and humans
• They are the ancestrial primates that Anthropoids
  branch off from.

http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
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Monkeys

• Larger than modern prosimians, skulls more
  rounded, more intelligent, and full frontal
  vision and color discrimination
• Monkeys arose from prosimian during Eocene epoch,
  38 million years ago

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Monkeys

• Two types of monkeys
• New World monkeys, platyrrhines (flat-nosed)
• Live in South and Central America, strictly live
  in trees
• Old World monkeys, catarrhines (downward-nosed)
• Live in Africa, mostly terrestrial but some
  tree-dwelers

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Apes

• Hominids is the group of apes and humans, grouped
  with Old World monkeys
• 10 different species of apes
• Larger than monkeys, so brain larger
• Have a partially erect stance at all times
  because their arms are longer than their legs
• Four genres Gibbons, Orangutans, Chimpanzees,
  and Gorillas

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Social Behavior of Apes

• Gibbons only monogamous hominids
• Form pairs, each couple lives by themselves with
  its young offspring

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Social Behavior of Apes

• Orangutan males usually mate with more that one
  female

http//www.webshots.com/g/25/36896-sh/41694.html
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Social Behavior of Apes

• Gorillas live in troops of 8 to 24, twice as many
  females as males and many infants and juvenilles
• Large, male leader
• Females only reproduce with the highest ranking
  yet unrelated male gorilla

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Social Behavior of Apes

• Chimpanzees thought to be closest to humans
• As a result that are used for testing by
  scientest
• Have similar patterns to humans

http//www.webshots.com/g/25/36896-sh/41694.html
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The Emergence of the Hominids

• Reymond Dart first discovered skull of a closely
  related human child in 1924 in Taung, South
  Africa
• Raymond Dart named the species fossil
  Australopithecus (southern ape) under the hominid
  group

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Current Status of the Australopithecines

• Australopithecines Lived 3.6 million years ago,
  predecessor to homo habilis
• Four species A. afarensis, A. africanus, A.
  robustus, A. boisei
• Greatest find of the early hominids was Lucy
• Adult female that was pieced together by fossils
  found in Ethiopia

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Homo habilis

• Derived from Australopithecus
• Louis Leakey in 1962 at Olduvai, Africa
  discovered hominid fossils, named new species H.
  Habilis
• Many different theories about where H. Habilis is
  on the evolution table, but for most part it
  comes after A. africanus

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http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
BioBookHumEvol.html
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New Concepts in Hominid Evolution

• Previously thought human evolution occurred in
  constant lineage, however replaced with evolution
  over various species whereas some led to
  extinction

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New Concepts in Hominid Evolution

• Also thought that bipedalism (ability to walk on
  two feet) set humans apart as oppose to superior
  intelligence
• Gives rise to question What selective pressures
  gave rise to bipedalism?
• One Theory, human can kill something easier with
  his hands
• Owen Lovejoy Second Theory, human can bring
  more food greater distances to his family

23
Homo erectus

• Kamoa Kimeu in Kenya found first fossils of Homo
  erectus, 1.6 million years old
• Very similar to modern humans, except in the
  skull
• These were the humans who inhibited caves, used
  hand axes, and discovered fire

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Homo sapiens

• This group of humans has a similar body skeleton,
  but most importantly is similar brain size
• Three subspecies of H. sapiens
• archaic Homo sapiens 400,000 to 200,000 years
  ago. Found in Europe, some in Asia and Africa too
• Homo sapiens neanderthalensis 150,000 to 35,000
  years ago. Found in Europe and parts of Asia.
  Used sophisticated stone tools, buried their dead
• Homo sapiens sapiens 30,000 years ago to
  present. Early Europeans called Cro-Magnon,
  created cave art.

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Origin of Modern Humans

• Evolved in Africa over a period of at least 3
  million years
• Two theories
• Candelabra hypothesis, humans had common ancestor
  until 1 million years ago, then split off and
  each coexisted
• Noahs Ark model, humans evolved from an ancestor
  less that 500,000 years ago and that certain
  species became extinct
• Molecular science supports Noahs Ark Model,
  organelle scrutinized is the Mitochondria