Chapter%2034:%20Humans

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Chapter 34 Humans

• Section 1 Primates and Human Origins

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Primates and Human Origins

• Humans evolved from common ancestors we share
  with other living primates such as chimpanzees
  and apes
• Our species most likely evolved in Africa and
  then spread around the world
• We know that the first Homo sapiens appeared
  around 500,000 years ago
• Humans did not appear until dinosaurs had been
  extinct for more than 60 million years

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What are Primates?

• As a group, primates share several important
  adaptations, many of which are extremely suitable
  to a life spent mainly in trees
• Faces are much flatter than those of other
  mammals
• Eyes point forward
• Allow both eyes to inspect the same area at the
  same time
• Information gathered by the eyes is processed by
  highly developed visual centers in the brain
• Produces binocular vision
• 3-D

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What are Primates?

• Snout is reduced in size
• Flexible fingers
• Curl around objects
• Hold objects in hands or feet
• Swing from branch to branch with ease
• Ball and socket joint at shoulder
• Large and complicated cerebrum
• Display far more complex behaviors than other
  animals

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How Did Primates Evolve?

• Very early in their history, primates split into
  several evolutionary lines
• Prosimians
• Includes lemurs, lorises, and aye-ayes
• Almost entirely nocturnal
• Large eyes adapted for seeing in the dark
• Anthropoids
• Includes monkeys, apes, and humans
• Has given rise to several major primate branches

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How Did Primates Evolve?

• Two anthropoid branches the two major groups of
  monkeys and apes separated around 45 million
  years ago when the continents on which they lived
  moved apart and were no longer connected by land
  bridges
• New World Monkeys
• Evolved into the monkeys found today in Central
  and South America
• Almost all tree dwellers
• Prehensile tails

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How Did Primates Evolve?

• Old World Monkeys
• Extend from Africa all the way across Asia to
  Indonesia and Japan
• No prehensile tail
• Spend most of their time on the ground
• Includes hominoids
• Gorillas, gibbons, orangutans, chimpanzees, and
  Homo sapiens

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Chapter 34 Humans

• Section 2 Hominid Evolution Human Ancestors and
  Relatives

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Hominid Evolution Human Ancestors and Relatives

• Between 4 and 9 million years ago, the hominoid
  line in Africa gave rise to a small group of
  species that we now recognize as our closest
  relatives
• Hominids
• Not yet human but showed several evolutionary
  trends that distinguish them from other hominoids

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What Are Hominids?

• Hominids were omnivores that ate both meat and
  vegetable foods, as modern humans do
• As time progressed, the spinal column, hip bones,
  and leg bones of these animals changed shape in
  ways that made it easier for them to walk upright
  on two legs
• Bipedal locomotion

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What Are Hominids?

• Because our ancestors could walk erect, their
  hands were free to use tools more often
• At the same time, the thumb of the hominid hand
  became more and more independent from the other
  fingers
• The evolution of an opposable thumb enabled
  ancient hominids to grasp objects and use them as
  tools more effectively than other primates

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What Are Hominids?

• Hominids also displayed a remarkable increase in
  brain size
• Chimpanzees, our closest relatives among the
  apes, have a brain size of about 280 450 cubic
  centimeters
• The brain of Homo sapiens, on the other hand,
  ranges in size from 1200 1600 cubic centimeters
• Enormously expanded human cerebrum
• thinking area of the brain

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How Did Hominids Evolve?

• Much of our most recent evidence for hominid
  evolution comes from a small area in eastern
  Africa between Tanzania and Ethiopia
• There, several researchers have found fossils of
  several species of hominids dating from about 4
  million to about 1.5 million years ago

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Australopithecus The First Hominids

• The first hominid fossil to be found, a nearly
  complete skull of a young child, was discovered
  in South Africa in 1924
• Australopithecus
• Southern Ape
• Because the skull belonged to a child, it could
  not be used to determine how adults of the
  species looked
• But 12 years later, investigators in Africa found
  fossils of adult australopithecines
• One of the fossils was part of a hip bone,
  indicating that Australopithecus walked upright
• An essential step in the evolution of our species
  from an apelike ancestor

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Australopithecus The First Hominids

• Since those discoveries, researchers have found
  many more complete hominid fossils
• In 1974, a team led by Donald Johanson and Tim
  White found a nearly complete Australopithecus
  skeleton
• From the shape of the pelvic bone, it was clear
  that this skeleton had been that of a female
• Lucy

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Australopithecus The First Hominids

• In 1977, anthropologist Mary Leakey made another
  discovery a set of fossil hominid footprints
• From the size of the prints, they were probably a
  parent and an offspring
• Clear evidence that the animals that made the
  footprints walked erect on two legs, as humans do
• No stone tools have been found among
  Australopithecus fossils, but they may have used
  twigs and stones as tools in a way similar to
  that of chimpanzees today

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Australopithecus The First Hominids

• Most current studies suggest that there were at
  least four species of Australopithecus
• A. boisei
• A. robustus
• A. afarensis
• A. africanus
• These species all lived between 4 and 1.5 million
  years ago, walked upright, and had much smaller
  brains than present-day humans

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Homo habilis

• For a while, australopithecines were the only
  known links in the chain of human evolution
• Then anthropologist Richard Leakey found another
  hominid fossil with a smaller face and
  significantly larger brain than the
  australopithecines
• Leakey felt this species was similar enough to
  humans to be placed in our own genus, Homo
• Fossils of this hominid were found along with
  tools made of stone and bone
• Homo habilis
• handy-man

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Homo habilis

• Near one of these fossil finds is the oldest
  human settlement yet discovered (Kenya)
• The settlement was found at a level in the rock
  dated at 1.9 million years ago
• The main site is a circular stone structure about
  4 meters in diameter
• Inside, the floor is littered with animal bones
  and stone tools

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Homo erectus

• Within a few hundred thousand years Homo habilis
  disappeared and was replaced by a larger brained
  species called Homo erectus
• By 1 million years ago, this species had spread
  over most of the Old World, from Africa to Europe
  to Asia
• Homo erectus was an excellent tool maker
• Carefully chipped and balanced hand axes have
  been found with Homo erectus fossils throughout
  the world
• In caves in China that are at least half a
  million years old, charred animal bones have been
  found around fire sites
• Must have used fire for cooking

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Homo sapiens

• About 500,000 years ago, the first hominids
  assigned to our own species appeared
• These hominids, often called archaic Homo
  sapiens, would not be easily recognizable as
  modern humans
• Little is known about this species

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Homo sapiens

• Around 150,000 years ago, a new hominid walked on
  Earth
• First discovered in the Neander valley in
  Germany, this species was called Neanderthal man,
  or Homo neanderthalensis
• Now, based on more complete fossil evidence,
  Neanderthals have been placed in our own species
  and are called Homo sapiens neanderthalensis

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Homo sapiens

• Neanderthal man could probably walk down a busy
  street today and not be noticed
• These early members of our species were
  successful for a time and became common
  throughout Europe and the Middle East by 70,000
  years ago

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Homo sapiens

• The first hominids truly identical to modern
  humans appeared in locations scattered throughout
  the Old World roughly 100,000 years ago
• These large-brained people, called Cro-Magnon,
  were more slender than the Neanderthals and had a
  more complex culture
• They made a wide variety of stone and bone tools,
  including spear points, knives, chisels,and
  needles
• Fossils of Cro-magnon are now classified as
  modern humans, Homo sapiens sapiens

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Homo sapiens

• Most paleontologists interpret the dates of
  Cro-Magnon fossils found throughout the world as
  indicating that modern humans originated in
  Africa and from there spread out over the rest of
  the world
• However and wherever Cro-Magnons originated,
  there is ample fossil evidence that they lived
  side by side with Neanderthals in several
  locations for some time
• Then, around 30,000 years ago, the Neanderthals
  disappeared

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Homo sapiens

• Some scientists believe that Cro-Magnons
  interbred with Neanderthals, blending their
  characteristics
• Others believe that the more intelligent
  newcomers killed off their older relatives
• In either case, only Homo sapiens sapiens
  remained to populate the rest of the world