The Origin and Diversity
of Our Species
To What Group of Animals Do Humans Belong?
When and How Did Humans Evolve?
Is the Biological Concept of Race Useful?
How Are Humans Classified
Biologists classify humans as Homo sapiens
which are members of the animal order
In biology a species is defined by its ability to
reproduce with other members of it’s species
while producing fertile offspring. All species
remain reproductively isolated from one
How Are Humans Classified Biologically?
Each species is given two separate names
(binomial nomenclature) for example the
biological terms for human is Homo sapiens.
This system began by an mid 18th century
scientist named Carolus Linnaeus.
When and How Did Humans Evolve?
There are two main sub orders of Primates
including: Prosimii and Anthropoidea.
Prosimii includes: lemurs, lorises,and tarsiers.
Anthropoidea includes: monkeys, apes, and
Apesinclude such animals as Chimpanzees,
Bonobos, Gorillas, and Orangutans.
Anthropologists who specialize in the study of
all non-human primates are called
Their focus of study is on the anatomy and
behavior of other primates to better help us
understand how and why early humans
developed as they did.
When and How Did Humans Evolve?
Present evidence suggests that humans evolved
from small African apes between 5 and 8
million years ago.
The locomotion pattern of bipedalism (walking
on two legs) as opposed to traditional primate
quadrapedalism (walking on four legs, was the
first step towards becoming human.
Several million years after the emergence of
bipedal hominids, 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.
Evolution Through Adaptation
Adaptation is the cornerstone to understanding
biological changes among our species as well as
others. Evolution refers to changes in the genetic
makeup of a organism over a series of generations.
One way that evolution can work is through
adaptation. This is when an organism can make
beneficial changes to best adapt to its’ environment.
This is done through a process known as natural
Evolution Through Adaptation
The theory of natural selection was first formulated
by a 19th century naturalist, Charles Darwin.
In his theory, individuals with characteristics best
suited to a particular environment survive and
reproduce with greater frequency than individuals
without those characteristics.
Mutations in genes are the cause for variation among
all living organisms. These are random changes in the
genetic coding process. Genes are the basic physical
units of heredity. These make up the physical and
biological aspect of all living organisms.
Ancient and modern primate groups possess a
number of anatomical characteristics, below are just
Generalized set of teeth, suited to omnivorous eating
pattern (plants and animals). Most all primates have a
diet consisting of insects and a variety of leafy greens.
Intensified sense of touch (tactile pads)
Binocular stereoscopic vision
Dentition Comparison of: Reptiles
The mandible (jaw) of reptiles contains a
series of identical teeth. If a tooth breaks
or falls out, a new tooth will emerge.
These teeth are generally similar in shape
and size. They are considered to be
specialized because the diet patterns are
Mammals possess a generalized dentition
consisting of a 2:1:2:3 or 2:1:3:3 dental
2: Incisors, 1: Canine: formula. Notice each tooth is different
2: Pre-Molars, 3: Molars providing a different function for eating.
Brain is large in proportion to body size with
Primate skeleton has adaptations for an upright
posture or towards an up right posture with a more
flexible limb structure.
Each female will produce fewer offspring (1-2) on
average per birth. This allows for a longer
maturation period due to infant complexity and
dependency on the mother.
Anthropoid primates possess
binocular stereoscopic vision.
Binocular vision refers to
overlapping visual fields
associated with forward facing
Three-dimensional vision comes
from binocular vision and the
transmission of information from
each eye to both sides of the
Primate vision become increasingly important
for arboreal (tree dwelling) mammals. Most
primates are also diurnal except for some
prosimians which means they are active during
Vision becomes more crucial to survival and
finding food sources than smell.
Not only will primates adapt to their ecological
environments but they will also adapt to cultural
environment through learned behaviors.
Young primates will learn the social behaviors of the group
while they are developing. This might include understanding
the hierarchy of the group, finding food sources, and
The most closely related and one of the most
understood apes to humans is the chimpanzee:
common chimpanzees and bonobos. They provide
models to reconstruct the behavior of evolving
Chimpanzee and Bonobo Behavior
Among chimps, the largest social unit is the community,
fifty or more individuals who inhabit a large
Chimps are usually found ranging singly or in smaller
groups 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
among the community, the rank of its mother, largely
determined through her cooperative social behavior
also plays a role.
Early primatologists believed that groups were male
dominated because they were generally larger and
more physical strong than females. More modern
research suggests that the hierarchy may play a more
significant role than just size and strength.
In this model a high ranking female may outrank a low
Although male dominance does seem to favor
chimpanzee groups, there can be female dominance in
Nutrition and Hunting: Chimpanzee
Jane Goodall’s fieldwork among chimpanzees revealed they
sometimes kill small invertebrate animals for food, and also
hunt and eat monkeys- not of their own kind.
Primatologists Craig Stanford observed that hunting is not
done purely for dietary purposes, but for social and sexual
reasons as well.
He noted that much hunting takes place during dryer seasons
when females are at their most fertile peak. Since the female
will be signaling that she is ready to mate she is in need of an
increased nutritional requirement. Meat sharing by males
may attract a female partner.
Fertile females are more successful than others
at begging for meat, and males often share
the meat after copulation.
Males may also use their catch to reward
friends and allies, gaining status in the process.
Bonobos are also known to hunt meat for
similar purposes but their methods may differ
slightly than the traditional (common)
Nutrition and Hunting: Bonobos
Recent research shows that bonobos in Congo’s
rainforest supplement their diet by hunting similar to
other common chimps. However hunting is a primarily
Female bonobos will rarely share their meat (or fruit)
with other females let along a male in the group.
More dominant males might attempt to obtain a share
of meat from a female and she will very likely refuse.
Sexual Practices: Chimpanzees
Not only do chimpanzees and bonobos have
differing hunting patterns but sexual ones as
For chimps, sexual activity occurs only when
females signal their fertility through genital
swelling. Here dominant males may try to
Dominant males try to take control over fertile
females, although cooperation from the
female is usually required.
A lower ranking 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 are not the sole fathers of all
offspring in these groups. Since there is a
hierarchy all males can generally mate with a
female in their status.
Sexual Practices: Bonobos
Unlike the common chimpanzee Bonobos do not limit
their sexual behavior to the fertile peak of the
females because female genitals are perpetually
The primary function of most sexual interactions
among bonobos is to reduce tensions and resolve
Concealed ovulation in bonobos may play a role in the
separation of sexual activity for social reasons and
pleasure from reproduction purposes.
Bonobo sexual activity has been widely observed
and documented. Below is a list of activities
Massaging of one another's genitals
Male-Male mounting rubbing scrotum
Female-Female genital rubbing
Each activity can range in rank, gender, and age
Chimpanzee and Bonobo Childhood
Young chimps and bonobos learn their cultural
in a similar transmission that humans learn their
Simulating other elder's behaviors based on
their social ranking and disposition. Their
facial features such as their free upper lip
allow variety of facial expressions that help
them to communicate emotion to other group
They also learn other behaviors such as how to
make and use tools. Some chimps will go so
far as to modify the tools they have fashioned
for termite fishing. They will keep these tools
for specific purposes and use them when
Bonobos do not show the advanced too making
abilities of the common chimp.
Our Human Ancestors
Humans are classified as hominoids, the broad-
shouldered tailless group of primates that includes all
living and extinct apes and humans. The
anthropologists who study the human fossil record are
known as paleoanthropologists.
Humans and their ancestors are distinct from all other
primates due to their bipedal advantage.
Genetic research has confirmed that the African
apes; chimpanzees, bonobos, and gorillas are our
closest living relatives.
Common Primate Ancestors
This phylogentic tree shows
humans and our taxonomic
position from a genetic level.
It starts with Prosimians at the top
which are the farthest away from
humans- genetically and
chimpanzees at the bottom which
are the closest to humans-
Through the comparison of genetic material, scientists
have estimated the divergence of human ancestors from
the ape lineage to be around 5-8million years ago.
Gibbons first diverged followed by orangutans
Next Gorillas would have diverged followed last by
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
Five million years ago during the beginning of the Pliocene
epoch the genus Australopithecus appeared in Africa.
Australopithecines included a diverse group of bipedal species
with small brains in proportion to body size. They spanned a
period of about 4.3-1.1million years ago.
These australopithecines had petite body frames and they
were shorter on average than modern day human. Ranging in
size from 3 feet to 5 feet.
One of the australopithecine species appears to be a direct
ancestor of the genus Homo.
Advantage of Bipedalism
Bipedalism as mentioned previously is one of the
single most distinguishing factors of the human
species. It has been suggested that there are several
critical factors that would have supported an
adaptation towards bipedalism from
A way to cope with heat stress.
He freeing of hands to better gather and find food and
Mothers were able to carry their infants safely.
Skeletons and Locomotion: Humans and
Notice the shape of the
spine and placement of the
foramen magnum on each
Then note the body size
and limb size in comparison
on both the human and the
A need for meat was important for human evolution
to occur. Life on a savanna means less protein
availability from plant resources leading to a
necessary need for animal protein from meat.
Modern chimpanzees that occupy savanna regions
suffer from the same challenges as early hominoids.
Failure to satisfy protein requirements can lead to
stunted growth, malnutrition, starvation, and death.
Early Homo Tools
In order to survive and obtain the correct nutrition
early human ancestors needed sharp tools for
butchering carcasses because they lacked sharp teeth
for killing and eating meat.
The earliest evidence of stone tools have been found
in Africa often in the same geological strata as the
earliest Homo fossils.
Chimpanzees on the other hand spend much of their
time finding insects to satisfy their protein needs.
The First Stone Tools
Stone flakes and choppers are the hallmark of early
hominid culture. The emergence of these mark the
beginning of the Lower Paleolithic, the first part of the
Old Stone Age, from about 2.6 million years ago-
200,000/ (250,000) 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 animal bones to reach nutrient rich marrow cavities.
Tools, Food and Brain Expansion
Larger brains provided advantages for early homo
that contributed to their reproductive success. There
are several ideas about the relationship between
early tool making and food. There seems to be a link
between the two.
Over time, large-brained individuals contribute to
successive generations, so the population evolves to a
Tools, Food and Brain Expansion
There are some Oldowan tool sites that provide
paleoanthropologists with both biological and
cultural information about early Homo.
These sites contain both stone tools and animal
bones suggesting that these sites were occupied
over several seasons.
Ultimately this tells a story of improved social
The first species in the genus Homo that appeared
about 2.5 million years ago in Africa.
They exhibited larger brains and smaller more
human like faces than australopithecines.
This species is considered to be the first stone tool
maker and is often associated with Oldowan tools.
Homo erectus and the Spread of the
At about 1.8 million years ago in Africa
another species in the genus Homo appeared.
This species is known as Homo erectus (upright
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
Fossil evidence suggests some differences within
and among populations of H. erectus inhabiting
regions of Africa, Asia, and Europe.
Some paleoanthropologists will consider Homo
erectus fossils from Africa (H. ergaster) and those
found out side Africa (H. erectus) as reproductively
differing species. Others assume they had the
ability to mate.
There is no doubt that this was the first
widespread species in the ancestral lineage of
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 as all similar in all
hominoids, though relatively large by modern
H. erectus Tools
The Oldowan tools were replaced by the more
advanced hand axe of the Acheulian tradition most
often associated with H. erectus.
The hand axes, which were created by chipping
away flakes and using the main core of the rock. The
end tool will have a point and a rounded bottom.
Although they varied in size by region most fit into a
They were probably all purpose implements for food
procurement and processing, and defense.
The hand axe was not used for spears or
arrows which are not yet developed at this
H. erectus also developed cleavers and
scrapers to turn precious animal hides into
possible clothing and bedding for warmth.
Use of Fire
It is thought that H. erectus was the first hominid to have
the controlled usage of fire. This would have allowed our
human ancestors to continue activities after dark and
provided them protection from predators.
Fire also provides several other basic needs such as;
warmth, light, and it enabled them to cook food.
Cooking can allow animal meat and plants to be better
absorbs through the intestinal tract while allowing
vitamins, minerals, and proteins to be absorbed.
Ultimately, the controlled use of fire allowed early homo
to expand their geographical region, a better chance at
survival in artic temperatures, and better nutritional
H. erectus and the Ice Age
H. erectus emerged with the onset of the last ice age
approximately 2 million years ago. The last ice age
(Pleistocene Epoch) ended about 10,000 years ago long
after H. erectus had become extinct.
Naturally the climatic changes during this time were drastic as
Artic winds created abundant snowfall and the majority of the
earths northern hemisphere (Eurasia & North America) was
intermittingly covered by glaciers and ice sheets.
Glacial periods would last for tens of thousands of years often
becoming interrupted by a warming period known as an
interglacial period which also varied in length. During this time
melting ice sheets would create fresh waterways and rising sea
levels while warming the earth only to be covered several
thousand years later by another ice sheet.
H. erectus and the Ice Age
It was during the Pleistocene epoch that humans evolved
from H. erectus and eventually reached all areas of the
These early human ancestors were constantly striving to
find ways to adapt to their ever changing environment.
They were challenged to make biological and cultural
adaptations in order to survive and reproduce.
Although mutations still account for variation among these
early populations, natural selection was a consistent factor
on all living organism populations to ensure that survival
of the most well adapted species to their changing
The Beginnings of Homo sapiens
Today humans have reached all continents of
the globe, but where did they first begin their
There are various sites in Africa, Asia, and Europe
where many skeletal fossils and cultural materials
have been found that date between roughly
200,000 and 400,000 years ago.
Atapuerca, Spain holds one of the most abundant
archaeological site for early transitional fossils
between H. erectus to H. sapiens.
This site contains fossilized skeletal fragments from
over 30 individuals both male and female all under
the age of 40 years old.
These fragments show consistent overlapping of brain
size- bigger than H. erectus yet smaller than H.
Neanderthals are among the most highly debated
species in the human lineage. Paleoanthropologists
have debated it’s taxonomic placement for several
decades. Current mitochrondrial DNA (mtDNA)
testing suggests that Neanderthals are not in the
direct human lineage.
They were a cold weather adapted species living
from approximately 30,000 to 125,000 years ago in
Europe and southwestern Asia. Their physical
adaptations to the artic temperatures made them
very muscular people.
With brains slightly larger than those of
modern humans, Neanderthals possessed faces
distinctively different from modern humans.
Large noses and forward projecting teeth.
They had large bony brow ridges over their eyes.
On the back of their skull there was a bun like bony
mass for large muscle attachments from the
powerful neck and jaw.
Mousterian tools associated with Neanderthals are
more advanced than other tool traditions yet seen at
this time. These tools are made in a different pattern
than previous. The have been found in Europe,
western Asia, and northern Africa associated with
Neanderthal fossil remains.
Tools from this tradition included hand axes, flakes,
scrapers, borers, wood shavers, and spears.
Neanderthals were known to occasionally bury their
dead, care for the disabled, and make objects for
Anatomically Modern Peoples and the
The Upper Paleolithic was during the last part
(10,000–40,000 years ago) Ice Age. It is defined by
the emergence of anatomically modern humans, tool
industries common to having long slim blades, art, and
other creative implements.
The Upper Paleolithic tool kits includes “blade” tools:
long, thin, precisely shaped pieces of stone
demonstrating the advancement of intelligence and
creativity at this time.
During the Upper
Paleolithic, a new technique
was used to manufacture
The stone is worked to
create a striking platform;
long almost parallel-sided
flakes then are struck
around the sides, providing
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.
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.
Hypotheses on the Origins of Modern
There are two main theories to explain how archaic
humans populated the old world.
Multiregional Hypothesis - This theory states that
early H. sapiens are developing in Africa, Asia, and the
Europe from earlier populations of H. erectus.
Recent African origins hypothesis – This theory states
that the transition from archaic to anatomically modern
H. sapiens took place in one population in Africa.
Modern humans then left Africa displacing all other
living populations apart from H. sapiens.
The Biological Concept of Race
Is the Concept of Race Useful for Studying Physical
Variation among Human populations?
Culturally speaking there is a concept of race. Which will be
outlined further throughout the chapters.
From a biological standpoint race refers to a subspecies, and
no subspecies exist within modern Homo sapiens.
The vast majority of biological variation within our species can
be attributed to environmental, and genetic factors.
Anthropologists as well as other disciplines within the social
sciences have worked hard to illustrate the issue of race as
being biologically invalid. Although they recognize that race
exists as a cultural and social construct.
Race as a Biological Construct
Often the cultural and social view of race is
heavily linked to the idea that there is a
biological basis for races to exist. The
following will illustrate that there are three
main factors to consider about race in a
Race as a Biological Construct
1. Race is an arbitrary concept; there is no agreement on how
many differences it takes to make a race or on how many
races there should be.
2. No one race holds exclusivity to a particular gene(s) or
variant of gene(s).
Populations are genetically “open,” meaning that genes flow
between them and no fixed racial groups exist.
3. The differences among individuals within a population are
generally greater than the differences among outside
“Most of what separates me genetically from a typical African or
Eskimo also separates me from another average American of European
ancestry” (James Shreeve, Science writer)
Many people have become accustomed to viewing
racial groups as natural divisions based on physical
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
They maintained the human species and prevented
the development of distinctive subspecies.
Skin Color: A Case Study in Adaptation
The idea of race most commonly linked with the
variations of skin color is actually the cause of
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
The amount of one’s exposure to sunlight increases
the amount of melanin which will in turn darken the
pigment (melanin) in the skin.
In the northern hemisphere where natural sunlight is
less than in the southern hemisphere native peoples
have lighter skin colors. On the other hand peoples
native to the tropical regions or along the
equatorial line have darker skin colors.
Selective mating, as well as geographic location,
plays a part in skin color distribution.
The amount of natural sunlight one receives is thought to be
linked to the production of vitamin D in the body. The more
sunlight the more vitamin D production. Vitamin D plays a
significant role in the overall physical health of people. It
helps to build and maintain calcium which in turn creates a
strong skeletal structure.
The lighter the skin the more advantage for the absorption of
sunlight to produce vitamin D. The darker the skin the more
protection from an overexposure to Vitamin D which can lead to
Tell the class that they will be acting the part of
paleoanthropologists and assign them to groups of 4-5
students- works best. This can be also done in a larger lecture
but it will work better if you place the pictures over head and
allow all students to look at them simultaneously.
Gather pictures of more well known hominid fossil skulls and
skeletal features. Depending on the amount of time available
use more or less. Make copies of about 10 different features
ranging from monkeys, apes, australopithecines, early, and
late homo species.
Do not put any information on the photos except the date the
fossil has been given as well as the location for which it was
found. For example take a photo of “Lucy” and tell the class
that it has been dated to 3.2 and found in Ethiopia. Make sure
not tell the class the name of the photo as this is the point of
The students will need to identify the genus and species based upon the
physical features of the fossil photo. This will help to retain the lecture
material relating to physical changes and adaptations of the human
Emphasize such features as:
Bipedalism vs. quadrapedalism
Skull shape & size
Location of species
Dates of species
Although only some students will “guess” correctly this is not the point, rather
reinforcing the features that you have covered.
The following are websites that contain a series of
up to date visual photos of the hominid fossil record.