Transcript Chapter 4 - Glenelg High School

Chapter 4
Becoming Human:
The Origin and Diversity
of Our Species
Chapter Preview
To What Group of Animals Do Humans
Belong?
• When and How Did Humans Evolve?
• Why Do Anthropologists Study the Social
Behavior of Monkeys and Apes?
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Monday October 21, 2013
To What Group of Animals Do
Humans Belong?
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Biologists classify humans as Homo sapiens,
members of the primates— a subgroup of mammals.
Biological species are defined by reproductive
isolation and designated by a two part name
including genus (Homo) and species (sapiens).
Other primates include lemurs, lorises, tarsiers,
monkeys, and apes.
Studying the anatomy and behavior of other primates
helps us understand how and why early humans
developed as they did.
When and How Did Humans
Evolve?
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Present evidence suggests that humans evolved
from small African apes between 5 and 8 million
years ago.
Bipedalism, or walking on two feet, was the first
change to distinguish the human evolutionary line.
Several million years after the evolution of
bipedalism, brain size began to expand, along with
development of cultural activities such as making
stone tools.
The earliest stone tools date to between 2.5 and 2.6
million years ago, coinciding with the appearance of
the first members of the genus Homo in the fossil
record.
Is the Biological Concept of Race
Useful for Studying Physical Variation
in Humans?
Biologically defined, race refers to
subspecies, and no subspecies exist within
modern Homo sapiens.
• The vast majority of biological variation within
our species occurs within populations rather
than among them.
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Paleoanthropologists and
Primatologists
Paleoanthropologists are anthropologists
specializing in the study of human
evolutionary history.
• Primatologists are specialists in the behavior
and biology of living primates and their
evolutionary history.
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Evolution Through Adaptation
Evolution refers to changes in the genetic
makeup of a population over generations.
• Genes are basic physical units of heredity
that specify the biological traits and
characteristics of each organism.
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Evolution Through Adaptation
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Evolution takes place through adaptation, a series of
beneficial adjustments of organisms to their
environment.
Adaptation is the cornerstone of the theory of
evolution by natural selection, originally formulated by
English naturalist Charles Darwin in 1859.
In this theory, individuals with characteristics best
suited to a particular environment survive and
reproduce with greater frequency than individuals
without those characteristics.
Tuesday October 23, 2012
Obj: SWBAT understand he importance of
Lucy to Physical Anthropology.
• Drill: What is a Hominid?
• Homework: Finish Synopsis.
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Human Adaptations and
Culture
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Humans relied increasingly on culture as an
effective way of adapting to the environment.
– They figured out how to manufacture and
utilize tools.
– They organized into social units that made
food-foraging more successful;.
– They learned to preserve and share their
traditions and knowledge through the use
of symbols that ultimately language.
Humans and Other Primates
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Humans are one of 10 million species on earth, 4,000
of which are fellow mammals.
Species are populations or groups of populations
having common attributes and the ability to
interbreed and produce live, fertile off spring.
The human species is a kind of primate, a subgroup
of mammals that also includes lemurs, lorises,
tarsiers, monkeys, and apes.
Among fellow primates, humans are most closely
related to apes—chimpanzees, bonobos, gorillas,
orangutans, and gibbons.
Classifying Primates
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Early scientific struggles to
classify great apes, and
identify and weigh the
similarities and differences
between them and humans,
is reflected in early
European renderings of
apes, including this 18thcentury image of a
chimpanzee portrayed as a
biped equipped with a
walking stick.
Wednesday October 31, 2012
SWBAT: understand the physical and social
adaptations that make us human.
• Drill: What physical adaptations have humans
made to differentiate us from primates?
• Homework: none
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Anatomical Adaptations
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Ancient and modern primate groups possess
a number of anatomical characteristics:
– Generalized set of teeth, suited to insect
eating but also fruits and leaves.
– Depth perception
– Intensified sense of touch
– Binocular stereoscopic vision
Anatomical Adaptations
– Brain is large, heavy in proportion to body
weight, and very complex
– Skeleton has adaptations for upright
posture and flexibility of limb movement.
– Fewer offspring born to each female and a
longer period of infant dependency.
Jaws: Reptiles and Mammals
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The jaw of reptiles contains a series of identical teeth.
If a tooth breaks or falls out, a new tooth will emerge.
Mammals possess precise numbers of specialized
teeth, each with a particular shape characteristic of
the group, as indicated on the chimpanzee jaw.
Primate Vision
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Anthropoid primates possess
binocular stereoscopic vision.
Binocular vision refers to
overlapping visual fields
associated with forward facing
eyes.
Three-dimensional vision comes
from binocular vision and the
transmission of information from
each eye to both sides of the
brain.
Behavioral Adaptations
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Primates adapt to their environments not only
anatomically but also through a wide variety of
behaviors.
– Young apes spend more time reaching adulthood
than most other mammals.
– During their growth and development, they learn
the behaviors of their social group.
Two closely related African species of chimpanzee:
common chimpanzees and bonobos, provide models
to reconstruct the behavior of evolving humans
Chimpanzee and Bonobo
Behavior
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Among chimps, the largest social unit is the
community, fifty or more individuals who inhabit a
large geographic area.
Chimps are usually found ranging singly or in small
subgroups consisting of adult males, or females with
their young, or males and females together with
young.
While strength and size contribute to an animal’s
rank in the community, the rank of its mother,
largely determined through her cooperative social
behavior also plays a role.
Nutrition and Hunting:
Chimpanzees
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Jane Goodall’s fieldwork among chimpanzees
revealed they sometimes kill small invertebrate
animals for food, and also hunt and eat monkeys.
Hunting is not done purely for dietary purposes, but
for social and sexual reasons as well.
Fertile females are more successful than others at
begging for meat, and males often share the meat
after copulation.
Males use their catch to reward friends and allies,
gaining status in the process.
Nutrition and Hunting:
Bonobos
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Recent research shows that bonobos in Congo’s
rainforest supplement their diet by hunting.
Among bonobos hunting is primarily a female activity.
Female hunters regularly share carcasses with other
females, but less often with males.
Even when the most dominant male throws a tantrum
nearby, he may still be denied a share of meat.
Discriminatory sharing among female bonobos is also
evident when it comes to other foods such as fruits.
Sexual Practices:
Chimpanzees
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For chimps, sexual activity occurs only when females
signal their fertility through genital swelling.
Dominant males try to monopolize females, although
cooperation from the female is usually required for
this to succeed.
An individual female and a lower-ranking male
sometimes form a temporary bond, leaving the group
together for a few private days during the female’s
fertile period.
Dominant males do not necessarily father all of the
off spring in a social group.
Female Chimpanzee Genital
Swelling
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Female chimpanzees
display their fertility
through swelling of the
genitalia at the time of
ovulation.
In contrast to humans
and bonobos, animals
with time limited
displays are sexually
receptive only during
these times of fertility.
Sexual Practices: Bonobos
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Bonobos do not limit their sexual behavior to times of
female fertility, bonobo female genitals are
perpetually swollen.
Concealed ovulation in bonobos may play a role in
the separation of sexual activity for social reasons
and pleasure from the biological task of reproduction.
Primatologists have observed every possible
combination of ages and sexes engaging in an array
of sexual activities, including oral sex, tongue-kissing,
and massaging each other’s genitals.
The primary function of most of this sex is to reduce
tensions and resolve social conflicts.
Chimpanzee and Bonobo
Childhood Development
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The young chimp or bonobo learns by observation,
imitation, and practice how to interact with others
and manipulate them for his or her own benefit.
Young primates learn to match their interactive
behaviors according to each individual’s social
position and temperament.
Anatomical features such as a free upper lip allow
varied facial expression, contributing to greater
communication among individuals.
Young chimpanzees also learn to how to make and
use tools.
Human Ancestors
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Humans are classified as hominoids, the broadshouldered tailless group of primates that includes all
living and extinct apes and humans.
Humans and their ancestors are distinct among the
hominoids for bipedalism, walking upright on two feet.
Genetic and biochemical studies have confirmed that
the African apes—chimpanzees, bonobos, and
gorillas—are our closest living relatives.
Common Primate Ancestors
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Based on molecular
similarities and
differences, a
relationship can be
established among
various primate groups.
Human Ancestors
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Between 5 and 8 million years ago, humans,
chimpanzees, and gorillas began to follow
separate evolutionary courses.
– Chimpanzees diverged into two separate
species: the common chimpanzee and the
bonobo.
– Early human evolutionary development
followed a path that produced only one
surviving bipedal species: Homo sapiens.
The First Bipeds
During the early Pliocene, 5 million years
ago, the genus Australopithecus appeared in
Africa.
• Australopithecines include a diverse group of
bipedal species with small brains in
proportion to body size.
• One of the other australopithecine species
appears to be a direct ancestor of the genus
Homo.
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Australopithecine Fossil
Locations
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Australopithecine fossils
have been found in South
Africa, Malawi, Tanzania,
Kenya, Ethiopia, and Chad.
Skeletons and Locomotion:
Humans and Chimps
Advantage of Bipedalism
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A way to cope with heat stress.
Allowed them to gather food and transport it
to a place of safety for consumption.
Mothers were able to carry their infants
safely.
They could reach food on trees too flimsy to
climb.
Allowed them to travel far without tiring.
Advantages of Bipedalism
Food and water were easier to spot.
• More likely to spot predators before they got
too close for safety.
• Hands freed from locomotion provided
protection by allowing them to brandish and
throw objects at attackers.
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Early Homo
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Increased meat consumption was important for
human evolution.
Failure to satisfy protein requirements can lead to
stunted growth, malnutrition, starvation, and death.
Without sharp teeth, our ancestors needed sharp
tools for butchering carcasses.
The earliest identify able stone tools have been found
in Africa often in the same geological strata as the
earliest Homo fossils.
Early Homo and Tools
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Stone flakes and choppers mark the beginning of the
Lower Paleolithic, the first part of the Old Stone Age,
from about 200,000 to 2.6 million years ago.
– Flakes were obtained from a “core” stone by
striking it with stone or against a large rock.
– The flakes that broke off had sharp edges,
effective for cutting meat and scraping hides.
– Leftover cores were made into choppers, used to
break open bones.
Early Stone Tools
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The earliest stone tools dated to the beginning of the Lower
Paleolithic between 2.5 and 2.6 million years ago were
discovered by Ethiopian paleoanthropologist Sileshi Semaw at
Gona, in the west-central Afar region of Ethiopia. The 2.6
million-year-old Gona flake is a cutting tool with sharp edges.
Homo habilis
“Handy man.”
• The first fossil members of the genus Homo
appearing 2.5 million years ago, with larger
brains and smaller faces than
australopithecines.
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Tools, Food and Brain
Expansion
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Scenarios about behavioral adaptation in early
Homo, such as the relationship among tools, food,
and brain expansion, propose a feedback loop
between brain size and behavior.
Over time, large-brained individuals contribute to
successive generations, so the population evolves to
a larger-brained form.
Tools, Food and Brain
Expansion
Natural selection for increases in learning
ability has led to the evolution of larger and
more complex brains over about 2 million
years.
• Bipedalism set the stage for the evolution of
large brains and human culture by freeing the
hands for tool making and carrying of
resources or infants.
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Homo erectus and the Spread
of the Genus Homo
Shortly after 2 million years ago, at a time that Homo
habilis and Oldowan tools had become widespread in
Africa, a new species, Homo erectus, appeared on
that continent.
• Evidence of H. erectus fossils almost as old as those
discovered in Africa have been found in the
Caucasus Mountains of Georgia, South Asia, China,
the island of Java, and western Europe.
• Fossil evidence suggests some differences within
and among populations of H. erectus inhabiting
regions of Africa, Asia, and Europe.
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Homo erectus Sites
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Sites, with dates, at which Homo erectus remains
have been found. Arrows indicate the proposed
routes by which Homo spread from Africa to Eurasia.
H. erectus and the Ice Age
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Emergence of H. erectus coincided with the
beginning of the Pleistocene epoch (Ice Age), which
spanned from 10,000 to almost 2 million years ago.
During this period, Arctic cold conditions and snowfall
in the earth’s northern hemisphere created ice sheets
that covered much of Eurasia and North America.
These periods often lasted tens of thousands of
years, separated by intervening warm periods.
During much of this time sea levels were much lower
than today, exposing large surfaces now under water.
H. erectus and the Ice Age
Of all the epochs in the earth’s 4.6 billion-year
history, the Pleistocene is the period in which
humans—from H. erectus to H. sapiens— evolved
and spread all across the globe.
• Our early human ancestors were challenged to make
biological and cultural adaptations in order to survive
and reproduce.
• The principle of natural selection was at work on
humans favoring the perpetuation of certain
characteristics within particular environmental
conditions.
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H. Erectus
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H. erectus had a body size and proportions similar to
modern humans, though with heavier musculature.
Differences in body size between the sexes
diminished compared to earlier bipeds, perhaps to
facilitate successful childbirth.
H. erectus’ average brain size fell within the higher
range of H. habilis and within the lower range of
modern human brain size.
The dentition was fully human, though relatively large
by modern standards.
Homo Erectus Fossil
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One of the oldest—at
1.6 million years—and
most complete fossils of
Homo erectus is the
“strapping youth” from
Lake Turkana, Kenya: a
tall and muscular boy
who was already 5 feet
3 inches tall when he
died at about age 13.
H. erectus Tools
The Oldowan chopper was replaced by the
more sophisticated hand axe.
• The hand axes, shaped by regular blows
giving them a larger and finer cutting edge
than chopper tools, were probably all purpose
implements for food procurement and
processing, and defense.
• H. erectus also developed cleavers and
scrapers to process animal hides for bedding
and clothing.
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Use of Fire
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Fire allowed our human ancestors to continue
activities after dark and provided a means to frighten
away predators.
It supplied them with the warmth and light needed for
cave dwelling, and it enabled them to cook food.
Cooking detoxifies poisonous plants and allows
important vitamins, minerals, and proteins to be
absorbed from the gut rather than passing unused
through the intestines.
When our human ancestors learned to use fire they
dramatically increased their geographic range and
nutritional options.
The Beginnings of Homo
sapiens
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At various sites in Africa, Asia, and Europe, a number
of fossils have been found that date between roughly
200,000 and 400,000 years ago.
The best population sample, bones of about thirty
individuals of both sexes and all ages comes from
Atapuerca, a 400,000-year-old site in Spain.
These bones show a mixture of characteristics of
Homo erectus with those of early Homo sapiens.
“Pit of the Bones”
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In a cave beneath a hillside in Atapuerca, Spain, lies
the Sima de los Huesos (“Pit of the Bones”).
The bottom of the pit is crammed with animal bones,
including cave bears, lions, foxes, and wolves.
Thousands of early human fossils dating back
400,000 years have been found here.
The well-preserved remains come from at least 28
individuals and comprise the greatest single cache of
ancient Homo erectus fossils in the world.
“Pit of the Bones”
Neandertals
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An extremely muscular people living from approximately 30,000
to 125,000 years ago in Europe and southwestern Asia.
With brains of modern size, Neandertals possessed faces
distinctively different from modern humans.
– Their large noses and teeth projected forward.
– They had bony brow ridges over their eyes.
– On the back of their skull, there was a bunlike bony mass for
attachment of powerful neck muscles.
Mousterian Tradition
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Tool-making tradition of the Neandertals and their
contemporaries of Europe, western Asia, and
northern Africa.
Named after the Neandertal site of Le Moustier,
France.
Tools included hand axes, flakes, scrapers, borers,
wood shavers, and spears.
Mousterian peoples buried their dead, cared for the
disabled, and made objects for symbolic purposes.
Neandertals
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As this face-off between paleoanthropologist Milford
Wolpoff and his reconstruction of a Neandertal
shows, the latter did not differ all that much from
modern humans of European descent.
Anatomically Modern Peoples
and the Upper Paleolithic
The Upper Paleolithic was the last part
(10,000–40,000 years ago) of the Old Stone
Age, featuring tool industries characterized by
long slim blades and an explosion of creative
symbolic forms.
• Upper Paleolithic tool kits include “blade”
tools: long, thin, precisely shaped pieces of
stone demonstrating the considerable skill of
their creators.
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Blade Technique
During the Upper
Paleolithic, a new
technique was used to
manufacture blades.
• The stone is worked to
create a striking
platform; long almost
parallel-sided flakes
then are struck around
the sides, providing
sharp-edged blades.
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Pressure Flaking
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Pressure flaking—in
which a bone, antler, or
wooden tool is used to
press rather than strike
off small flakes—is a
technique of tool
manufacture that
became widespread
during the Upper
Paleolithic.
Solutrean Bifaces
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The techniques of the
Upper Paleolithic
allowed for the
manufacture of a variety
of tool types.
The finely wrought
Solutrean bifaces of
Europe, made using a
pressure flaking method
are shaped like plant
leaves.
Hypotheses on the Origins of
Modern Humans
Multiregional Hypothesis - all populations
of archaic H. sapiens are easily derivable
from earlier populations of H. erectus from
the same regions.
• “Eve” Hypothesis - transition from archaic to
anatomically modern H. sapiens took place in
one population, probably in Africa.
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Question
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The _____________ holds that populations
of modern Homo sapiens evolved locally
from populations of Homo erectus, with links
among these populations from gene flow.
A. African origins theory
B. lumping hypothesis
C. bilinear evolution theory
D. multiregional hypothesis
E. punctuated equilibria corollary
Answer: D
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The multiregional hypothesis holds that
populations of modern Homo sapiens evolved
locally from populations of Homo erectus,
with links among these populations from gene
flow.
Spear Throwers
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Spear-throwers (atlatls) allowed Upper Paleolithic people to throw
spears from a safe distance while maintaining accuracy.
Upper Paleolithic artists combined artistic expression with function,
ornamenting spear-throwers with animal figures.
Human Biological Variation
And The Problem Of Race
“Race” refers to subspecies, and no
subspecies exist within modern Homo
sapiens.
• The majority of biological variation within our
species occurs within rather than among
populations.
• Anthropologists have worked to expose the
fallacy of race as a biological concept while
recognizing the existence of race as a social
construct.
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Defining Anatomical Modernity
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This indigenous Australian
does not meet the definition
of anatomical modernity
according to skull shape
proposed in the African
origins model.
Some paleoanthropologists
suggest this narrow
definition is ethnocentric,
because all living people are
clearly members of the
species Homo sapiens.
Factors in the Biological
Definition of Race
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It is arbitrary; there is no agreement on how many
differences it takes to make a race.
Any one race does not have exclusive possession of
any particular variant of any gene or genes.
– Populations are genetically “open,” meaning that
genes flow between them and no fixed racial
groups exist.
The differences among individuals and within a
population are generally greater than the differences
among populations.
The Concept of Human Races
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Many people have become accustomed to viewing
racial groups as natural divisions based on physical
differences.
However, these groups differ from one another in
only 6% of their genes.
For thousands of years, individuals belonging to
different human social groups have been in sexual
contact.
They maintained the human species and prevented
the development of distinctive subspecies.
Genetic Mixing
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Genetic mixing is illustrated by the photo of distant relatives, all
descendents of Sally Hemings, an African American slave, and
Thomas Jefferson, Euramerican, who had 150 slaves at his
plantation and was third president of the U.S. (1801–1809).
Skin Color: A Case Study in
Adaptation
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Skin color is subject to great variation and is
attributed to several key factors:
– the transparency or thickness of the skin
– a copper-colored pigment called carotene
– reflected color from the blood vessels
– the amount of melanin , a dark pigment, in
the skin’s outer layer
Factors in Variation of Skin
Color
Exposure to sunlight increases the amount of
melanin, darkening the skin.
• Selective mating, as well as geographic
location, plays a part in skin color distribution.
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