Chapter 4
Becoming Human: The Origin and
Diversity of Our Species
1
What Will You Learn?
• Describe the origins and molecular basis of
evolutionary theory.
• Identify the relationship between humans and
other primates.
• Compare the earliest bipeds to one another and
also to chimps and humans.
• Summarize the major biological and cultural
features of human evolution.
• Understand the controversy between humans
and Neandertals.
• Human variation and skin color.
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Evolution through Adaptation
• Evolution refers to change through time.
Biologically it refers to changes in the genetic
make-up of a population over generations.
– Genes are the basic physical units of heredity that
specify the biological traits and characteristics of
each organism.
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Evolution through Adaptation
• Organisms evolve through a series of adaptations
which might be selected for or against by nature.
• Adaptations are the series of beneficial
adjustments of organisms to their environment.
• Natural Selection is the mechanism by which
individuals having biological characteristics best
suited to a particular environment survive and
reproduce with greater frequency than
individuals without those characteristics.
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History of Research on Evolution and
Genetics
• Charles Darwin is most noted for coming up
with the idea of Natural Selection, a theory he
refined through his travels around the globe.
• While he recognized that species had an
ability to adapt to their environment he did
not know how it occurred.
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History of Research on Evolution and
Genetics
• Gregor Mendel is often referred to as the
father of genetics. He provided the “how” of
adaptation through his genetic work involving
pea plants.
• Today, having mapped the human genomethe genetic design of a species - with its
complete set of DNA, we can learn that our
species shares most of its DNA with one other
living primate, the chimpanzee.
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Humans and Other Primates
• Humans are but 1 of the 10 million species on
earth today. A species is a population having
common attributes and the ability to
interbreed and produce viable, fertile
offspring.
• The human species is one kind of primate or
subgroup of mammals that also include,
lemurs, lorises, tarsiers, monkeys, and apes.
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Anatomical Adaptation
• Both ancient and modern humans belong to
the primate order.
• Compared to other mammals, primates have
only a few anatomical specializations while
their behavior patterns are very diverse and
flexible.
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Primate Dentition
• Primates have
generalized teeth,
which allow them to eat
a variety of foods.
• We each have incisors,
canines, pre-molars and
molars although the
number and size may
vary.
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Primate Vision
• Stereoscopic vision and
binocular vision allow
primates to see in 3-D
and perceive depth.
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Primate Brain and Skeleton
• Increased brain size in the cerebral
hemispheres are the areas supporting
conscious thought.
• Flexible limb structure allows primates to be
agile.
• There is greater reliance on vision over smell
as we move up the primate taxonomy closer
to humans.
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Behavioral Adaptation
• The study of primates, particularly apes,
provides anthropologists with clues about the
earliest development of the human cultural
behavior.
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Chimpanzees & Bonobos
• Highly social primates - dwell in groups
• Socially stratified by dominance (male and
female dominance in groups)
• Female bonobos form stronger bonds than
common chimps
• Both sexes may hunt other primates, may
hunt in groups
• Share meat to attract sexual partners
• Sexual practice for pleasure
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Chimpanzee and Bonobo Development
• All social behaviors are learned
• This may include:
– Tool making, food provisioning, shelter
construction, place in social hierarchy, language,
communication, etc.
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Human Ancestors
• Humans are classified as hominoids - a broadshouldered group of primates that includes all
living and extinct apes and humans.
• Humans and their ancestors are known for
their distinct locomotion of bipedalism or
walking on two legs.
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The First Bipeds
•
•
•
•
6 mya, Chad = Orrorin tugensis
4.4 mya, Ethiopia = Ardipithecus ramidus
3 mya, Ethiopia = Australopithecine afarensis
Australopithecines; genus including several
species of early bipeds from southern,
eastern, and central Africa (Chad) living
between 1.1 and 4.3 mya, one of whom was
directly ancestral to humans.
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Early Homo
• Meat consumption is necessary for survival on
the savannah. Much like living apes, ancient
hominids would have solved their need for
meat in a similar way.
• Tool production would have allowed for early
hominids to be more effective scavengers of
meat.
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Lower Paleolithic
• The appearance of stone tools and choppers
marks the beginning of the lower paleolithic
or the first part of the Old Stone Age,
spanning from 200,000-250,000 years ago.
• Oldowan tool tradition is the name given to
the first and oldest stone tools between 2.52.6 mya.
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Early Homo
• Homo habilis - “Handy Man” first fossil
member of the genus Homo appears 2.5 mya,
with larger brains and smaller faces than
australopithecines.
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Homo erectus Fossil Sites
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Homo erectus
• Shortly after 2 mya, at a time when Homo
habilis and Oldowan tools had become
widespread in Africa, Homo erectus emerged.
• Homo erectus - “Upright man.” A species
within the genus Homo first appearing after
Homo habilis, ultimately spreading
throughout the Old World.
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Homo erectus
•
•
•
•
•
•
Narikotome Boy
1.6 mya
Lake Turkana, Kenya
5 feet 3 inches tall
13 years old
60% complete fossil
skeleton
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Critical Thought
• Often paleoanthropologists do not uncover
whole fossil skeletons. They may only find:
– Jaw, teeth, femur or tibia (leg bones), partial skull,
etc.
• Given the above skeletal elements, what
unique things can we still learn about the
lifestyle, diet, environment, or capabilities of
these hominids?
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Fire Making in Early Human
Development
• Remains found in southern Africa suggest H.
erectus may have learned to use fire by 1 mya.
• Without controlled fire it is unlikely early
humans could have survived dropping
temperatures or moved into colder regions
with no protection.
• Fire also allows for cooked foods and wider
diet.
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Beginnings of Homo Sapiens
• Within paleolithic sites in Africa, Asia, and
Europe, a large number of human fossils have
been found that date between roughly
200,000 and 1 mya.
• In Atapuerca, Spain, 6 individuals were
excavated, dating to 800,000 years ago.
– Homo antecessor? Homo heidelbergensis?
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The Neandertal Debate
• Neandertals are a distinct group within the
genus Homo inhabiting Europe and Southwest
Asia from 30,000 -125,000 years ago.
• Largest area of debate is the genetic
relationship among humans and Neandertals.
– Were they a separate species going extinct 30,000
years ago? Or were they an archaic subspecies of
Homo sapiens? If so did they contribute to our
modern day genome?
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Neandertal Tools
• Mousterian tool tradition is the tool industry
associated with Neandertals in Europe and
Southwest Asia, and their human
contemporaries in northern Africa, during the
Middle Paleolithic, generally dating from
about 40,000 to 125,000 years ago.
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Human Evolutionary History
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Anatomically Modern Peoples and the
Upper Paleolithic
• A veritable explosion of tool types and other
forms of cultural expression beginning at
about 40,000 years ago constitutes the Upper
Paleolithic.
• Last part of the Old Stone Age (10,000-40,000
years ago), featuring tool industries
characterized by long slim blades and an
explosion of creative symbolic forms.
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Tools of the Upper Paleolithic
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Tools of the Upper Paleolithic
• Tools of the Upper Paleolithic became smaller
and projectile. Also during this time, art,
carvings, and ornaments appear.
• The spear thrower or atlatl was invented
about 15,000 years ago as a way to increase
distance and maintain accuracy.
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Tools of the Upper Paleolithic
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Chauvet Cave Paintings
• 31,000 years old
• Paintings consist of
many animals such as
bear, horses, wild ox,
rhino, and bison.
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Hypotheses on the Origins of Modern
Humans
• Multiregional hypothesis - states that the
fossil evidence suggests a simultaneous local
transition from H. erectus to modern H.
sapiens throughout the parts of the world
inhabited by early members of the genus
Homo.
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Hypotheses on the Origins of Modern
Humans
• Africa origins hypothesis (Eve,or out of Africa
hypothesis)- uses genetic and other evidence
to argue that all anatomically modern humans
living today descend directly from one single
population of archaic H. sapiens in Africa.
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Human Biological Variation and the
Problem of Race
• In biology, race is a subgroup within a species,
not scientifically applicable to humans
because there exist no subspecies within
modern Homo sapiens.
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Race as a Social Construct
• Throughout time various naturalists and
scholars have attempted to classify and
identify “races.”
• Race has been classified by skin color,
geographical location, ethnicity, intellectual
abilities, etc.
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A Pygmy Man in the Bronx Zoo
• Captured during a raid at
23 years old and 4’11’’
Ota Benga, a Mbuti
Pygmy, was placed into a
primate exhibit as though
he were an animal.
• Once released later in his
life he committed suicide
upon learning he would
never be returned home.
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Race as a Biological Construct
• Often social constructions of race are falsely tied
to the idea that there is a biological foundation to
the concept of human race.
1. Race is arbitrary, there is no agreement on how
many differences it takes to make a race.
2. The biological definition of race is that it does not
mean that any one so-called race has exclusive
possession of any particular variant or any gene(s).
3. There are greater differences among individuals
within a particular population than the differences
among populations.
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Skin Color: A Case Study in Adaptation
• Skin color is genetically coded for by our
melanin - the amount of skin pigmentation
found in the outer layer of skin.
• Melanin is a natural block against the suns
harmful UV rays.
• More melanin can help protect equatorial
populations from over exposure of sun. These
populations also tend to have darker skin.
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Skin Color: A Case Study in Adaptation
• Alternatively individuals living closer to the
poles tend to have lighter skin (less melanin).
• This allows for more absorption of UV rays
which can stimulate Vitamin D production, a
necessary building block for a healthy
skeleton.
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