PRIMATES

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PRIMATES
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PRIMATES

• General characteristics
• Hands (and feet) adapted for grasping
• Large brains relative to other mammals
• Short jaws
• Forward-looking eyes
• Binocular vision enhances depth perception
• Flat nails on digits
• Relatively well-developed parental care
• Relatively complex social behavior

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PRIMATES

• Earliest primates were likely arboreal
• Grasping hands and feet are adaptations for
  hanging on to tree branches
• Opposable thumb and big toe
• Homo is the only extant primate lacking an
  opposable big toe

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PRIMATES

• Modern primates divided into two subgroups
• Prosimians
• Premonkeys
• Anthropoids
• Monkeys and apes (including humans)

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PRIMATES

• Prosimians
• Premonkeys
• e.g., Lemurs, lorises, pottos, tarsiers, etc.
• Probably resemble early arboreal primates

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PRIMATES

• Prosimian primates and anthropoid primates
  diverged at least 45 million years ago

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PRIMATES

• Anthropoids
• Monkeys and apes, including humans
• Oldest anthropoid fossils 45 million years old
• New and old world monkeys diverged by 40 million
  years ago

New
Old
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PRIMATES

• All New World monkeys are arboreal
• Some Old World monkeys are arboreal, and some are
  ground-dwelling
• Most of both groups are diurnal and social

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PRIMATES

• Four genera of apes
• Hylobates
• Gibbons
• Pongo
• Orangutans
• Gorilla
• Gorillas
• Pan
• Chimpanzees and bonobos

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PRIMATES

• Modern Apes
• Evolved from Old World monkeys
• 25 30 million years ago
• Confined exclusively to tropical regions of the
  Old World

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PRIMATES

• Modern Apes
• Larger than monkeys
• Gibbons are an exception
• Brains proportionally larger than monkeys

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PRIMATES

• Modern Apes
• Long arms, short legs, and no tails
• All are capable of brachiation
• Only gibbons and orangutans are primarily
  arboreal
• Social organization is variable
• Gorillas and chimpanzees are highly social

Gibbon
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HUMAN ANCESTRY

• Humans and apes have shared ancestry for all but
  the last few million years
• Paleoanthropology focuses on this short period
  of time
• The study of human origins and evolution

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HUMAN ANCESTRY

• When measuring against the history o the Earth,
  humans are very recent additions
• Perhaps we are not quite as important as we might
  like to believe

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HUMAN ANCESTRY

• "Humans are not the end result of predictable
  evolutionary progress, but rather a fortuitous
  cosmic afterthought, a tiny little twig on the
  enormously arborescent bush of life, which if
  replanted from seed, would almost surely not grow
  this twig again."
• - Stephen Jay Gould

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HUMAN ANCESTRY

• Terminology
• Anthropoid
• Monkeys, apes, and humans
• Hominoid
• Great apes and humans
• Hominid
• Humans and their bipedal relatives

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DEAR DR. LAURA

• Did we evolve from chimpanzees?
• No. Humans and chimpanzees evolved from a common
  ancestor, which was neither a chimpanzee nor a
  human.

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DEAR DR. LAURA

• Did we evolve from monkeys or apes?
• We did not evolve from any present day monkey or
  ape. However, the common ancestor we share with
  chimpanzees would certainly be considered an ape,
  and common ancestors of both humans and monkeys
  would certainly be considered monkeys themselves.

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DEAR DR. LAURA

• If we evolved from apes, then why are there still
  apes?
• This misconception is due to the tendency of
  people to think of evolution as a linear
  progression toward some goal, which is certainly
  not the case. Adaptive radiations give rise to
  multiple species stemming from a single species.

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DEAR DR. LAURA

• Was the production of humans the ultimate goal of
  primate evolution?
• This view is simply testament to the arrogance
  and self importance of humans. Lets get over it,
  people were not quite that important. Nuff
  said.

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30 35 M.Y.A.

• Early anthropoids were still tree dwellers

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20 M.Y.A.

• Indian plate collided with Asia
• Thrust up Himalayans
• Climate became drier
• Forests (present Africa Asia) shrunk
• Increased savanna (grassland) with fewer trees
• Some anthropoids increasingly exploited this new
  habitat
• Decreased reliance on arboreal environment

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15 M.Y.A.

• Last common ancestor of gibbons and humans
• And of gibbons and chimps, gibbons and gorillas,
  and gibbons and orangutans, for that matter

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10 M.Y.A.

• Last common ancestor of orangutans and humans
• And of orangutans and chimps, as well as
  orangutans and gorillas, for that matter

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8 M.Y.A.

• Last common ancestor of gorillas and humans
• And of gorillas and chimps, for that matter

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5 - 7 M.Y.A.

• Last common ancestor of chimpanzees and humans

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CLOSEST RELATIVE?

• What is our closest living relative?
• What species is the chimpanzees closest living
  relative?
• the gorillas?
• the orangutans?

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HUMAN EVOLUTION

• Major features of human evolution
• Increased brain size
• Altered jaw shape
• Bipedal posture
• Reduced sexual dimorphism
• Extended parental care

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HUMAN EVOLUTION

• Major features of human evolution
• Increased brain size
• 400 450 cm3 6 million years ago
• Similar to modern chimpanzee
• 1300 cm3 today

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HUMAN EVOLUTION

• Major features of human evolution
• Altered jaw shape
• Hominoid ancestors had longer jaws
• Prognathic jaws
• Feature retained by chimpanzees
• Jaws shortened during human evolution
• ? Flatter face and pronounced chin

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HUMAN EVOLUTION

• Major features of human evolution
• Bipedal posture
• Hominoid ancestors walked on four limbs when on
  the ground
• Trait retained by modern apes
• Bipedal posture evolved gt 4 million years ago
• Hominids
• Cause of this change?
• Various hypotheses, but still unclear
• Some of these hypotheses are beautiful examples
  of cultural bias affecting scientific thought

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HUMAN EVOLUTION

• Major features of human evolution
• Reduced sexual dimorphism
• Difference in secondary sexual characteristics
  reduced between males and females
• e.g., Male female size ratios
• Orangutan 2
• Gorilla 2
• Chimpanzee 1.35
• Human 1.2

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HUMAN EVOLUTION

• Major features of human evolution
• Extended parental care
• Enhanced parental care and an enlarged brain
  enhance learning
• Associated with behavioral complexity of humans

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HUMAN EVOLUTION

• What does the fossil record tell us about human
  evolution?
• Many hominid fossils have been found
• All but most recent are from eastern or southern
  Africa
• These fossils represent many different hominid
  species
• Some hominid species coexisted with others

Laetoli footprints, over 3.5 million years old
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HUMAN EVOLUTION

• Our hominid ancestry is branching, not linear
• Multiple species of hominids often coexisted
• Most died out, but we are still here for now

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HUMAN EVOLUTION

• Bipedalism evolved 4 6 million years ago
• Homo and Australopithecus genera best studied
• Bipedalism predated increased brain size

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AUSTRALOPITHECUS

• The first australopithecine was discovered by
  Raymond Dart in 1924 in a South African quarry
• Identified as an early human
• Australopithecus africanus
• Southern ape from Africa
• Fully erect, with a brain much smaller than ours
• The evolution of bipedalism predates the vastly
  increased brain size of humans

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AUSTRALOPITHECUS

• How can one establish bipedalism from a skull?
• a femur?
• pelvic bones?

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AUSTRALOPITHECUS

• In 1974, David Johanson discovered a 40 complete
  Australopithecus skeleton
• Lucy
• Afar region of Africa (Ethiopia)
• Australopithecus afarensis
• From Afar
• 3.24 million year old
• Age determined by radioactive dating
• Slightly older than A. africanus

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AUSTRALOPITHECUS

• In 1974, David Johanson discovered a 40 complete
  Australopithecus skeleton
• Lucy
• Humanlike posture, small brain
• Bipedalism established by skull and pelvic bones
• Human-like below the neck
• Ape-like above the neck

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AUSTRALOPITHECUS

• Additional A afarensis fossils have been found
• Many in the 1990s
• Longevity of the species at least 1 million years

Laetoli footprints, gt3.5 m.y.a.
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AUSTRALOPITHECUS

• Australopithecus anamensis
• Unambiguously human
• Lived gt4 million years ago

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AUSTRALOPITHECUS

• Other putative hominids
• 6 million years old
• Very close to chimpanzee/hominid branching

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AUSTRALOPITHECUS

• Which australopithecines led to Homo?
• Which were evolutionary dead ends?

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AUSTRALOPITHECUS

• A afarensis underwent an adaptive radiation
• ? Robust australopithecines
• Powerful jaws, large teeth
• Adapted for grinding and chewing hard foods
• Evolutionary dead end
• ? Gracile australopithecines
• Similar to A. afarensis
• Lighter feeding equipment
• Adapted for softer foods
• Ancestral to homo

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HOMO

• Homo habilis
• Handy man
• First discovered in 1964
• Louis Leakey, et al.
• Earliest fossils placed in the genus Homo
• 2.5 1.6 m.y.a.

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HOMO

• Homo habilis
• Clear signs of modern hominid skull
  characteristics
• Less prognathic jaw
• Larger brain
• 600 70 cm3
• First known use of manufactured stone tools

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HOMO

• Homo erectus
• 1.8 0.5 million years ago
• Sometimes split into
• Home ergaster (earlier)
• Homo erectus (later end)

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HOMO

• Homo erectus
• Taller than Homo habilis
• Larger brain
• Averaging 1,100 cm3
• Reduced sexual dimorphism
• Malefemale size 1.2
• Same ratio as today
• May offer insight into social structure

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HOMO

• Turkana boy
• 1.6 million years old
• Larger brain
• Likely over 900 cm3 by adulthood
• Classified as Homo ergaster or Homo erectus

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HOMO

• Homo erectus
• First hominid species to migrate out of Africa
• Colonized Asia by 1.5 m.y.a.
• Spread into Europe (timing less certain)

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HOMO

• Homo sapiens
• Evolved from H erectus or H ergaster
• In Africa alone or multiregionally?

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HOMO

• Homo sapiens
• Mitochondrial DNA (mtDNA) can be used as a
  molecular clock
• Human genetic divergence 100,000 years ago
• Supported my nuclear genetic markers
• esp., Y chromosome
• Out of Africa

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HOMO

• Neanderthals
• First discovered in Germanys Neander Valley
• 1856 (1829 elsewhere)
• Lived 200,000 40,000 years ago
• Brains as large as ours
• Shaped differently
• Prominent brow ridge
• Sloping forehead
• Occipital bun

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HOMO

• Neanderthals
• Species or subspecies?
• Homo sapiens neanderthalensis
• Homo neanderthalensis

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HOMO

• Neanderthals
• Contemporary to more modern Homo sapiens
• Cro-Magnon man
• Ultimately disappeared
• Why?

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HOMO

• Neanderthals
• mtDNA analysis of Neanderthal DNA
• Extracted from bone
• Very different from modern H sapiens
• It is very unlikely that Nenderthals contributed
  significantly to our gene pool

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HOMO

• Sure, maybe we are smart, but ..
• Diverse prokaryotes are ubiquitous
• Arthropods outnumber all known species combined
• There are more species of bony fishes alive today
  than all other vertebrates combined
• Dinosaurs ruled the earth for much, much, much
  longer than we did
• We are not as successful as many other groups