Primates

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Primates Humans

• By Tia L. See

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Primates are an order of the class Mammalia

• Primates, an order that includes lemurs, monkeys,
  and humans, falls under the class Mammalia.
• Mammalian characteristics are
• - Females with mammary glands which produce
  milk to feed offspring
• - Hair, fat layer under skin to retain heat
• - Endothermic and usually a high metabolic
  rate
• - Respiratory system and circulatory system
  (with four- chambered heart) support metabolism
• - Diaphragm helps ventilate lungs
• - A larger brain than other vertebrates of
  equal size, capable learners
• - Differentiated teeth for chewing many kinds
  of foods

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Early Evolution of Mammals

• Mammalians are amniotes called synapsids.
• Synapsids have a a single temporal fenestra, a
  hole behind the socket on each side of the skull.
• In mammals, 2 of the bones that once made up the
  jaw joint are now part of their middle ear.
• The first true mammals arose during the Jurassic
  period.
• The three major types of mammals emerged by the
  early Cretaceous period.

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The 3 Forms of Mammalia

• Orders of Mammalia fall under one of three
  categories
• Monotremes, or egg-laying mammals (i.e.,
  platypus)
• Marsupials, or mammals with a pouch (i.e.,
  wallaby)
• Eutherians, or placental mammals (i.e.,
  PRIMATES).

Eutherian, baboon
Monotreme, platypus
Marsupial, wallaby
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General Primate Characteristics

• Primate characteristics are
• - Hands, feet adapted for grasping, flat
  nails instead of narrow claws
• - Skin ridges on fingers
• - Larger brain, shorter jaw than other
  mammals
• - Forward-looking eyes close together on front
  of face
• - Well-developed parental care
• - Complex social behavior

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More on Primates

• Early primates were tree-dwellers and many of the
  primate characteristics are adaptations for this
  lifestyle
• All living primates, except humans, have a big
  toe set far apart from the other toes, making it
  easier to grasp branches with feet
• Monkeys and apes have opposable thumbs, meaning
  they can touch the ventral surface of all four
  fingertips with the ventral surface of the thumb
  on the same hand
• A unique bone structure at the base of the human
  thumb allows for more precise manipulation than
  other primates and improved dexterity, an example
  of descent with modification
• The overlapping visual fields of the
  forward-looking eyes improve depth perception,
  another important adaptation for tree-dwellers

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Living Primates

• There are 3 main groups of living primates
• 1) Lemurs, lorises, and pottos Lemurs are found
  in Madagascar and lorises and pottos live in
  tropical Africa and southern Asia. These primates
  probably resemble early arboreal primates.
• 2) Tarsiers Tarsiers live in Southeast Asia.
  This group is more closely related to the third
  group of primates
• 3) Anthropoids Anthropoids include monkeys and
  apes and can be found all over the world.

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The Anthropoids MONKEYS

• Monkeys do not make up one monophyletic group.
  Instead they are defined as either New World
  monkeys or Old World monkeys.
• Both types of monkeys supposedly originated in
  Africa or Asia. Fossil evidence suggests that New
  World monkeys first colonized South America about
  25 million years ago, when South America and
  Africa had already drifted apart. The theory is
  that New World monkeys rafted on logs and other
  debris to get from Africa to South America.
• After millions of years of adaptive radiation,
  New World monkeys have become completely arboreal
  while Old World monkeys include both arboreal and
  ground-dwelling species.
• Most monkeys in both groups are diurnal (active
  during the day) and social creatures.

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Old World v. New World
New World monkeys like the spider monkey have a
prehensile tail and nostrils that open to the
sides.
Old World monkeys like the mandril lack a
prehensile tail and have nostrils that open
downward.
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More Anthropoids APES

• Apes is an informal title for a group of genera
  which include Hylobates (gibbons), Pongo
  (orangutans), Gorilla (gorillas), Pan
  (chimpanzees and bonobos), and Homo (humans).
• Apes separated from Old World monkeys around
  20-25 million years ago. Nonhuman apes are now
  found solely in the tropical regions of the Old
  World.
• CHARACTERISTICS
• All apes, with the exception of gibbons, are
  larger than New or Old World monkeys.
• They all have relatively long arms, short legs,
  and no tail.
• Orangutans and gibbons are the only primarily
  arboreal species of ape.
• Apes social organization varies. Gorillas and
  chimpanzees are highly social apes.
• Apes also have a larger brain in proportion to
  their bodies and exhibit more flexible behavior.

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Nonhuman Apes
Gibbons (above) live only in Southeast Asia.
Their long arms and fingers facilitate
brachiating.
Chimps (above) live in tropical Africa and feed
and sleep in the trees. Chimps are intelligent,
social primates.
Gorillas (above) are the largest apes. These
herbivores are found in Africa and live in groups
of up to 20 gorillas.
Orangutans (left) are unusually shy for apes.
They live in the rain forests of Sumatra and
Borneo and spend most of their time in the trees.
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HUMANS
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Humans General Info

• Humans, or Homo sapiens, are roughly 200,000
  years old.
• The genomes of humans and chimpanzees are 99
  identical, but humans and chimps differ in the
  expression of 19 regulatory genes.
• Uniquely human characteristics include
• Bipedalism
• Larger brain than other apes, capable of symbolic
  thought, language, and manufacturing, using
  complex tools
• Reduced jawbones and jaw muscles
• Shorter digestive tract

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Paleoanthropology the study of human origin

• Paleoanthropologists study hominins, or extinct
  species that are more closely related to man than
  chimpanzees.
• The oldest hominin found is Sahelanthropus
  tchedadensis, which lived 6-7 million years ago.
  This and other hominins show anatomical
  similarities to humans such as reduced canines
  and fairly flat faces. They also have the foramen
  magnum underneath the skull (the foramen magnum
  is a hole at the base of the skull where there
  spinal cord exists). This and the leg bones of
  Australopithecus anamensis suggest bipedalism in
  hominins.
• Human characteristics did not all evolve at once
  for instance, hominins show evidence of
  bipedalism when their brains were far smaller
  than the human brain
• 2 MISCONCEPTIONS
• - Hominins are NOT chimpanzees.
• - Homo sapiens did not result from a linear
  evolutionary path, but is rather the only
  surviving species on an evolutionary tree.

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Hominin Species Timeline
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Australopiths

• Got their name from discovery in South Africa of
  Australopithecus africanus (literally southern
  ape of Africa), a find that proved bipedal with
  human-like hands and teeth, but a brain only 1/3
  the size of a modern-day human brain.
• Another Australopith is Australopithecus
  afarensis. A 3.2-million-year-old skeleton of A.
  afarensis was found 40 complete. It was named
  Lucy, and stood only 1 m in height. Lucys brain
  size was the same as a chimpanzees and long arms
  capable of arboreal locomotion. Still, she had a
  pelvis and skull that indicated bipedalism.
• More robust Australopiths were the Paranthropus
  boisei, which had sturdier skulls and more
  powerful jaws and teeth than the other
  Australopiths.

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Bipedalism

• One theory suggests that bipedalism began because
  of a collision between the Indian and Asian
  tectonic plates about 10 million years ago. This
  made the climate drier, and the forests of Africa
  and Asia contracted leaving more open ground and
  grasslands. Our arboreal ancestors were then
  forced to adapt to lack of canopy and more arid
  climate. Bipedalism would allow locomotion on the
  ground that would save energy in more arid
  environments.
• Scientists question this theory because hominins
  with signs of bipedalism were found in mixed
  habitats that included forests. These hominins
  did not even use bipedalism as a main form of
  getting around. Bipedalism wasnt a primary form
  of locomotion until about 1.9 million years ago.

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Tool Use

• Humans arent the only apes capable of tool use.
  Other apes such as orangutans and chimpanzees are
  also capable of sophisticated tool use.
• The oldest evidence of hominin tool use is 2.5
  million years old by Australopithecus garhi, a
  hominin with a small brain. This proves that
  sophisticated tool use occurred before the
  evolution of large brains in hominins.

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Homo Habilis

• The earliest Homo on record is Homo habilis. The
  fossils were 2.4 to 1.6 million years old and
  showed that H. habilis had a shorter jaw and
  larger brain volume than Australopiths. This
  species is know to be found with sharp stone
  tools.

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Homo ergaster

• H. ergaster fossils date back 1.9 to 1.5 million
  years. Its brain was larger than that of H.
  habilis with hips adapted to long-distance
  walking. Its straight, short fingers suggest it
  was the first species not to climb trees. Smaller
  teeth indicate that they ate either more meat and
  less plant material than australopiths or they
  prepared their food before eating.
• They created more sophisticated tools.
• Sexual dimorphism Males weigh 1.2 times as much
  as females.

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Homo erectus

• H. ergaster was originally thought to be a member
  of H. erectus.
• H. erectus was the first species to leave Africa.
• Fossils and DNA studies show that H. erectus
  became extinct at some point after 200,000 years
  ago.

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Neanderthal

• True name is Homo neanderthalenis
• Lived in Europe and the Near East by 200,000
  years ago, but never beyond the region
• Brain as large as that of modern-day humans
• Buried their dead
• Made hunting tools from stone and wood
• Went extinct about 28,000 years ago
• Once considered an evolutionary stage between H.
  erectus and Homo sapiens, but some argue this is
  not accurate mitochondrial DNA shows that
  Neanderthals hardly contributed to the H. sapiens
  gene pool. However, human and Neanderthal nuclear
  DNA seem to be consistent with limited gene flow,
  suggesting that Neanderthals are an evolutionary
  step for humans.

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Homo sapiens Modern Man

• H. sapiens ancestors originated in Africa
• Lack heavy brows of H. erectus and Neanderthals
  and more slender than other hominins.
• DNA analyses show that living humans are more
  closely related to each other than to
  Neanderthals
• Also, Europeans and Asians share a relatively
  recent common ancestor while Africans tend to
  branch off the human family tree at a much
  earlier point.
• Studies of Y chromosome show humans migrated
  beyond Africa in one or more waves, first into
  Asia, then Europe and Australia.
• There is a lot of controversy about a new find,
  an 18,000-year-old Homo floresiensis skeleton. H.
  floresiensis is mush shorter than H. sapiens with
  a much smaller brain. Despite a few derived
  traits that mightve linked it to H. erectus,
  most scientists believe it was a small H. sapiens
  with a condition called microcephaly. However,
  the wrist bones are more similar to nonhuman apes
  and early hominins, strong evidence that H.
  floresiensis is a new hominin.
• 77,000-year-old art shows sophisticated thought
  appearing in H. sapiens.
• The gene FOXP2 is thought to explain the
  uniqueness of human language and cognitive
  abilities at leas in part.

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Okay, now for review

• What are the three groups of mammals?
• Marsupials, Monotremes, and Eutherians
• What group of primates do humans belong to?
• Anthropoid
• Which hominin was the first to show sexual
  dimorphism?
• Homo ergaster
• Name three ape characteristics.
• Generally social, larger brain, generally larger
  bodies

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F I N