Australopithecus Homo erectus Homo sapien
Evolution is the progressive change in
organisms over time
Human evolution began about 60 million
years ago with the earliest mammals that had
long snouts, sharp teeth and large eyes.
Gradually they evolved at least 3 notable
◦ More flattened molars
◦ Grasping hands and feet with plausible first digits
that were obvious advantages in their habitat.
◦ Forward direct eyesight.
It is believed that this common ancestor then
branched off into two linages:
◦ Prosimian lineage – giving rise to present day
lemurs, lorises, pottos and tarsiers
◦ Anthropoid lineage – giving rise to the present
day monkeys, apes and humans.
It is then believed that the anthropoid lineage
split a number of times to give rise to the
Old World and New World monkeys and
Present day these are: gibbons, orangutans,
gorillas, two species of chimpanzee and
They have no tails, longer front limbs than
hind limbs and larger brains relative to body
size than monkeys.
Humans vs. Other Hominoids
They share a wide range of physical and
behavioral traits with other hominoids and
exhibit dramatic genetic similarity.
Key distinguishing features:
HUMANS GREAT APES
• Bipedal motion – and • Narrow pelvis
related anatomical features
such as wide pelvis and • Smaller brain
curved vertebral column
• Only use simple tools
• Greatly enlarged brain
• Have no structured
• Complex language language
• Construction and use of
Emergence of Humans
Fossils of early humans were found in Africa
Current fossil record shows that the hominid
evolution is full of many branching lineages
and related species, that have now all become
The hominids include all descendants of the
most recent common ancestor of the human
Hundred of specimens indicate that at least six different
species of australopithecines lived in Africa between 4.2
and 1.0 mya.
Ardipithecus ramidus (5.2-5.8 mya) is the oldest dated
Other fossils have shown that human ancestors evolved
the ability to walk upright long before they had large
Recent evidence from A. afarensis and later species (A.
africanus) suggest that both may have been knuckle
walkers, a trait previously thought to be unique to
chimpanzees and gorillas.
The selective advantage gained by bipedal motion is
uncertain – possibilities include greater speed and
efficiency, enhanced ability to gather and carry food, as
well as to see over tall grass.
It is hypothesized that 3 mya an
australopithecine ancestor gave rise to the
subsequent ancestors of two lineages:
◦ believing that one branch gave rise to a number of
robust species with heavy jaws and relatively
◦ while the other ultimately gave rise to the first
members of the genus Homo.
◦ The most dramatic early fossils found to date!
◦ A skeleton of Australopithecus afarensis, dated to
◦ Bipedal and standing about 1 m tall, this species
had many apelike features:
Large canine teeth
Finger and toe bones well suited to climbing
Relatively small brain (400 cm3)
It is believed that H. habilis or a closely related
species gave rise about 1.6 mya ago to H. erectus,
a species that used a variety of stone tools and
This species shows a strong trend toward
current human features.
Fossil record shows close to 2 mya H. erectus
gradually spread out from Africa into Europe and
Over the last 600, 000 years it may have evolved
into two or three species of early humans.
1. Multiregional hypothesis
◦ proposes that anatomically modern humans
evolved in parallel in a number of places
including Africa, Europe, Asia and possibly
Continuous gene flow between the
populations would account for them not
becoming distinct species.
2. The Monogenesis (African Replacement)
◦ Proposes that H. sapiens evolved only in Africa and
then migrated to other continents, displacing the
Neanderthal and other descendants of the earlier H.
◦ The most current molecular evidence, including
recent findings from the Human Genome Project,
strongly favors the monogenesis hypothesis.
Findings suggest that humans have existed in Africa far longer
than in other parts of the world
Examination of mitochondrial DNA (passed maternally) and
studies of the Y chromosome also reveal greater variability
among African populations.
Primate Order Characteristics
Better sight than
Limbs for climbing
Characteristics of Hominid Family
Homo erectus, Australopithecus,& Human
Why did humans evolve?
Bipedal & larger
Need to hunt &
Did Humans Evolve from Apes?
The have a similar common ancestor
They are both: animalia, chordata, mammalia,
primates, and hominoids.
BUT – they have a different genus and species
Primate Brain Capacity
Primate Bone Structure
Homo habilis = handy human Homo erectus
1.5 to 2 mya 1.6 mya
35,000 to 40,000 ya
35,000 to 100,000 ya
Evolution & Diversity
Charles Darwin – Darwin’s Theory of Evolution
Darwin’s main points include:
1. Variations – Individual members of a species vary in physical
characteristics, & these characteristics can be passed from generation to
2. Struggle for existence – The members of all species compete with
each other for limited resources with certain members being able to
capture these resources better than others
3. Survival of the fittest – Natural selection by the environment
determines which organisms will survive & reproduce
4. Adaptation – Natural selection causes a population of organisms &
ultimately a species to become adapted to the environment. The
process is slow, but each subsequent generation includes more
individuals that are better adapted to the environment
Evidence for Evolution
1. Fossil record – the remains & traces of past life, or any other direct
evidence of past life.
2. Geographical Distribution -
3. Embryonic/Developmental – common structures in embryonic form
shows closely related species and common ancestors.
4. Homologous structures – structures that are similar because they
were inherited from a common ancestor; generally have a different
A. Vestigial structures – anatomical features that are fully developed
in one group of organisms but are reduced & may have no function
in similar groups.
5. DNA Evidence - genetic evidence shows just how closely related
species are. This has shed even more light on the concept of common
Transitional forms in the
evolution of whales.
Evolution in Action - Antibiotic Resistance in “TB Bacteria”
(example of microevolution)
First round of
Initial population incomplete
has rare resistant antibiotic treatment
Most cells are resistant
After second round of
antibiotic treatment Antibiotic
population expands Second round of treatment
and all cells are antibiotic treatment discontinued
Surviving cells are
in absence of
Genetic drift is random fluctuation in allele frequency between
generations. Its effects are pronounced in small populations.
A Genetic Bottleneck
A genetic bottle neck is one form of genetic drift in which a
population “crashes” then rebounds.
Animals known to be affected by genetic bottlenecks include
the northern elephant seal, cheetah, and some human
A Genetic Bottleneck
The Founder Effect
• The founder effect is another form of genetic drift in which a
small portion of a population migrates to a new area then
expands in number.
• In this case, the allele frequencies in the expanded population
are often very different from those of the founder population.
• The Founder effect accounts for the high frequency of Ellis-van
Crevald syndrome in Amish characterized by short-limb
dwarfism, polydactyly (additional fingers or toes), malformation
of the bones of the wrist, dystrophy of the fingernails, partial
hare-lip, cardiac malformation, and often prenatal eruption of
the teeth; colourblindness, and other genetic recessives
Gene Flow or Migration
Gene flow makes separate populations more similar genetically.
The effects of gene flow are seen in many human
Why?……….ease of transportation.
Gene flow in plants –
Natural selection leads to adaptation – an increase in the fitness
of a population in a particular environment.
Natural selection works because some genotypes are more
successful in a given environment than others.
Successful (adaptive) genotypes become more common in
subsequent generations, causing an alteration in allele
frequency over time and a consequent increase in fitness.
There is only one force that changes allele frequency so that
populations become better adapted.
Types of selection
1. Stabilizing selection
Occurs when an intermediate phenotype is favoured over the two extremes
Birth weight of human infants – Death rates are highest for those extremely low (1
kg) & those extremely high (5-6 kg)
2. Directional selection
Occurs when an extreme phenotype is favored & the distribution curve shifts in
Industrial melanism with moths
Pesticides & antibiotics selecting for “super” insects & bacteria
3. Disruptive selection
Two or more extreme phenotypes are favored over any intermediate phenotypes
British land snails have wide habitat range– Light banded survive in one area, dark
banded in another, mixtures of the bands get consumed
Forms of Natural Selection
Stabilizing Selection for the Sickle Cell Allele
In heterozygous form, the sickle cell allele of beta globin confers
resistance to malaria. Therefore, the allele is maintained, even
though its harmful in homozygous form.
Does Selection Create the Perfect Organism?
No, only better organisms as
evolution is constrained by history
and buffeted by random events.
Mimicry (Nash, 2009)
For 150 years scientists have been trying to explain
convergent evolution. One of the best-known examples of
this is how poisonous butterflies from different species
evolve to mimic each other's color patterns -- in effect
joining forces to warn predators, "Don't eat us," while
spreading the cost of this lesson.
It has been discovered that a single gene controls the red
colour patterning across distantly related species of passion
Biologists have been asking themselves, 'Are there really so
few genes that govern evolution?'" Reed said. "This is a
beautiful example of how a single gene can control the
evolution of complex patterns in nature. Now we want to
understand why: What is it about this one gene in particular
that makes it so good at driving rapid evolution?“
(Science Daily, 2011)
This treehopper insect has
developed an absolutely insane
helmet that looks like an aggressive
species of ant.
• Mimicry can take several forms.
• Many cases of mimicry involve
organisms which have evolved to
look like inanimate objects.
• In this case, mimicry is a form of
camouflage and the evolutionary
advantage may be an increased
ability to escape detection.
For example the Camo moth looks like a dead
leaf and of course stick insects resemble sticks.
• In some cases mimicry is used by predators to help them ambush their prey.
• Praying mantis are famous for this, one of the best examples are the flower mantis.
• Many insects have evolved defense mechanisms against predators which make
them distasteful or even toxic to eat. This type of defense is only useful if the
predator knows in advance not to try and eat the distasteful species.
• Natural selection has, therefore, favored the evolution of bright, warning coloration.
• Predators learn to associate distastefulness with the colour pattern and avoid eating
things that have that pattern.
• Many distasteful individuals are still killed by naïve predators., decause they have to
learn this association.
• Many distasteful species which occur in the same habitats have, therefore, evolved
similar colour patterns, which is called Müllerian mimicry.
• The yellow and black stripes common to bees and wasps give one example.
• The selective advantage favoring the evolution of this sort of mimicry comes from the
predator's having to learn only a single colour pattern, which it does more quickly
through encountering a greater number of distasteful prey all with the same colour
• In some cases non-toxic species have taken advantage of Müllerian
• Hoverflies for example are not toxic or distasteful; they don’t
invest any energy in maintaining this expensive defence mechanism.
Instead many species have evolved yellow and black bands so they
mimic wasps and bees. Their predators will associate the hoverfly
colour pattern with the horrible taste of truly toxic species and so
avoid them, even though they are perfectly edible. This is called
• Batesian mimicry can disrupt the stability of Müllerian mimics as
predators no longer learn to associate the colour pattern with the
distastefulness if the Batesian mimic becomes too common. When
this happens selection drives the evolution of new colour patterns
in the truly toxic species.
Mimics bird droppings!
Beetle looks like a fungus
• This colour pattern mimicry is also
accompanied by convergence in the
habits of the co-mimics.
• Races of each species involved in
the mimicry ring have more similar
ecologies than non-mimetic races.
• This suggests they have not only
evolved to look similar, but also to
behave in similar ways and occupy
• All of these factors work together
to increase the rate at which
predators learn not to target these
butterflies as prey!