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Darwin and Evolutionary Theory
1) What is evolution?
2) Do humans come from monkeys?
3) Is it possible to “believe” in evolution?
Why?
4) Is there any evidence of evolution? If
yes, give evidence
What is a theory?
• A theory is a thoroughly tested idea based on
evidence
• A theory in science is not the same as theory in
everyday language
• Theories are NOT guesses
• Theories are accepted until someone else provides
evidence that the theory needs to be changed
• Theories are NOT beliefs
Greeks-first evolutionists?
• Greeks thought all living things originated
from water and air.
• Aristotle suggests a transition between the
living and the nonliving, and thought that in
all things there is a constant desire to move
from the lower to the higher, finally becoming
the divine.
Great chain of being (Pre-Darwinian
thought)
• Medieval times
• Early ideas were based on the church’s
philosophy which is descended from God.
• Suggests that there is a hierarchy created by god
for all beings
• Dirtmineralsplantsanimalshumans
angelsGod
• Spontaneous generation
• All current species have been here since creation,
and have changed little to none since then.
Carolus (1707-1778) Linnaeus
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Father of animal classification
Devout Christain
Divine creator
God had a plan for all things
Erasmus Darwin (1731-1802)
• Charles Darwin’s grandfather
• “all life could have a single common ancestor”
• Believed that competition and sexual selection
were important force for organisms changing
• Adaptations come from the “use or non-use of
body parts”
• Also that adaptations come from organisms
constantly striving to be better.
Jean Baptiste Lamarck (1744-1829)
• Organisms are in a constantly changing state
• All organisms wanted to adapt to their environment,
suggesting that they had to think about it happening
• Adaptations are use or non use of body parts, just like
Erasmus Darwin
• Inheritance of acquired characteristics-organism could
pass on to its offspring any characteristics it had
acquired in its lifetime.
• For example, if a man exercised and thus developed
strong muscles, his offspring would then have strong
muscles at birth.
Thomas Malthus (1766-1834)
• According to Malthus, populations produce
many more offspring than can possibly survive
on the limited resources generally available.
• poverty, famine, and disease were natural
outcomes that resulted from overpopulation.
• However, Malthus believed that divine forces
were ultimately responsible for such
outcomes, which, though natural, were
designed by God.
Alfred Wallace and Charles Darwin
• Together proposed Natural Selection-the
process by which traits become more or less
common in organisms due to survivability
• Best fit individual will survive better, so its in best
interest of organisms to develop better fitness
• For ex: moths that are dark colored live better on
dark colored trees, if trees become light colored,
then it would be advantageous for moths to
become light colored.
Their findings were criticized by the church
Their findings are still criticized by many people today.
Charles Darwin
• Born from wealthy medical professionals in
Pennsylvania
• First entered college to be a doctor/surgeon
• Then quit that and entered into divinity school
• Finally decided to become a naturalist
• Later planned a journey to Galapagos islands in
search of some answers.
• Found that finches on different islands had
striking similarities, and that each island had its
own unique species of finches.
While at the Galapagos, he found 13 varieties of finch
on different islands, some that ate insects, others that
ate seeds. He realized they were descendants of a
single ancestor species that dispersed across the
islands then adapted to the different foods available
on each island.
Darwin cont
• Darwin some 20 years later published his findings in On the Origin of
species.
• He was forced into publishing, because other people had begun to work
on papers just like his, so he decided to go ahead and publish his own.
Microevolution
Macroevolution
Definition of microevolution
• Change in gene frequency within a
population
• For ex: If you have a population of
squirrels, and the smaller squirrels get
eaten more often because they can’t
defend themselves as well, then there will
be more large squirrels left to mate with
other large squirrels, therefore the
percentage of large squirrels will become
more common.
4 methods of microevolution
• Mutation
• Selection
• Gene flow
• Genetic drift
Selection
• Selection is the process by which heritable
traits that make it more likely or less likely for
an organism to survive and successfully
reproduce become more common in a
population over successive generations.
• Natural Selection is one type, artificial (by
humans) is the other type.
• Natural selection acts on a characteristic, that
trait will become more common in a
population. Over time, this process can
result in adaptations that benefit the
organism.
Selection
Types of Selection
• Stabilizing
• Directional
• Disruptive
Stabilizing Selection
•When the extremes are selected against, and the preferred
is in the middle.
•For example: Plant Height If a plant is too short, it will
have to compete for photosynthesis, and most likely lose to
the taller plants. If a plant is too tall, it is more likely to be
eaten, and more likely to die from weather damage. Best
survival comes from plants that are of medium height.
Survival
rate
Plant height
Directional Selection
• When one extreme is preferred over another
• Ex: Giraffe necks. Short necks are not good for
eating leaves from tall trees, so short necks were
selected against, and tall necks are preferred.
Length of neck
Disruptive
• Selection against the middle of the range.
• Can create two separate species over time
• Ex: A species of bird in SC can nest in trees, bushes, or on
the ground. If all the bushes in SC got cut down, the birds
would have to choose ground or trees. Eventually this would
cause two different species of birds.
Genetic Drift
• Genetic drift is when an allele occurs in a
population due to random sampling and
chance.
• Unlike selection, is not driven by
adaptation.
• The effect of genetic drift is larger in
small populations, and smaller in large
populations.
Example
Mutation
• Alterations in DNA can cause changes in
frequencies of alleles in a population
• Mutations result in alternate forms of phenotypes,
and some phenotypes have an advantage over
another
• For example: A mutation occurs in a dog that
enables it to survive in the heat better. It is likely
that It will produce offspring with the same
phenotype, and they will produce offspring, etc.
• After several generations, this would result in an
increase in the number of dogs with this mutation.
For example:
• A butterfly may produce offspring with new
mutations. The majority of these mutations
will have no effect; but one might change the
color of one of the butterfly's offspring,
making it harder (or easier) for predators to
see. If this color change is advantageous, the
chance of this butterfly surviving and
producing its own offspring are a little better,
and over time the number of butterflies with
this mutation may form a larger percentage of
the population.
Gene Flow (gene migration)
• When genes are transferred from
one population to another
• Usually in the form of migration
• If both populations are migrating
back and forth, they will become
more like each other.
• Can be between same species or
between two different species
Example
• Humans- Mexican immigrants come to US,
and begin to interbreed with White (of
European descent).
• This makes them more like each other
• Hypothetically speaking, if Mexicans had a
gene that allowed them to fly, then their
offspring are more likely to have this gene
also. So, if they are interbreeding, then more
white people are going to have this same
gene. So this advantage has spread to other
populations, without mutations to the original
population.
Sexual Selection
• Natural selection between opposite sex
• A male has to do certain things to
“impress” the female
• When traits are selected that give one
male an advantage over another to court
the female
• Ex: Fireflies, crickets, pheromones
Sexual Selection
• Intrasexual Selection
• Intersexual Selection
• Rams butting heads
to compete with each
other
• Within same sex
• Competition
• Peacocks display
bright colors to look
attractive for mates
• Impress opposite sex
• Non-competitive
Sexual Selection a bad thing?
• Bats
– Larger testes=female mating, but larger
testes=smaller brain=less food
– Larger brain=smaller testes=less females
• Widow Birds
– Longer tail=more mates=increase in predators
• Crickets chirping
– Louder chirp=more mates=increase in predator
locating cricket
Macroevolution
Macroevolution
• Evolution on a large scale
– When species changes
– Two or more species sharing a common
ancestor
• Much less evidence for than
microevolution…easier to find fault in
• Microevolution is more widely accepted
than macroevolution
Speciation
• The rise of two or more species from one
existing species:
• When most people think of evolution, they
think of speciation…the two words are often
confused.
– Ex: humans and monkeys derived from a
common ancestor.
– Alligators and birds are both derived from
dinosaurs
• Speciation usually comes from a catastrophe
or from a barrier
Different types of barriers
• Isolation when two or more species are
unable to contact each other in order to
reproduce, compete, or to interact with
each other.
• Types or barriers or isolation:
– Reproductive
– Behavioral
– Temporal
– Geographical
Reproductive
• Species when two things are able to
reproduce, and those offspring are viable and
able to produce also
– Two frogs are different species if they cannot
reproduce.
– Different breeds of dogs are still the same species,
because they can reproduce with each other.
• Reproductive isolation when two species,
once considered one species, can no longer
reproduce with each other, or they do not
produce offspring that can reproduce
– Horse and donkey are separate species, mule is an
additional species separate from both.
Behavioral barriers
• Difference in courtship, or mating rituals
that no longer allow the species to mate
with each other
• Caused by changes in courtship, dances,
chemicals, and mating calls
• Fireflies recently have been dividing
species rapidly
Geographical barriers
• Most commonly studied type
• When a physical barrier divides a population
into two or more groups.
– Rivers, mountains, dried lakebeds, deserts,
dense forest, etc.
• These can also come from flooding and other
natural disasters such as earthquakes,
tsunamis, and volcanoes.
• Two species become isolated, and adapt to
their new environment, and over time, are
unable to reproduce with the same species
even after re-exposure
Temporal Barriers
• Temporal=time
• When two or more species are able to
mate at different times.
– Ex: some tree species only flower for certain
months, and other similar species flower for
other months, and the two cannot mate.
– More common in plants than in animals.
Patterns in evolution
• Convergent evolution when two unrelated
species seem to be related, and often share
similar characteristics
– Ex: dolphins and whales are mammals, but
sharks and fish are not, yet they have very similar
characteristics, and often are seen together in the
same habitat, and share the same ecosystem
• Very common
• Often seen as a counterargument against
speciation
Divergent Evolution
• When closely related species often have very
different characteristics
• Two different types of foxes kit fox (desert fox)
and the red fox (mountain, cold region fox)
• Look very different, live in different
environments, yet they share a common
ancestor
• Sort of how humans are more similar to a rat
than to a dog.
Comparative Evolution
Comparative Embryology
Make Observations.
Comparative Embryos cont.
• They all look the same at the beginning
• Same size and shape
• They all have gill slits, a two-chambered heart,
and a tail with muscles to move it
Comparative Anatomy
• Jean Baptiste Lamarck was the first person to
look at the bone structure of organisms
• He noticed a striking similarity
• Still used as a technique today to provide
evidence for evolution
• Even if things have different functions, they
still have very similar structure
Comparative Genetics
• Comparing traits, genes, and DNA within
species, and between multiple species
• Humans and Chimps share 99% of DNA
• Humans and Dogs share 75% the same DNA
• Humans and Bananas share 30% the same
DNA
• Humans and Flies share 50% the same DNA
• Humans share 99.998% the same DNA as each
other
Everyone Stand UP
• Have a seat if…
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You do not have polydactyly
You have hair on your head
You have attached earlobes
You have a hitchiker thumb
You have a cleft chin
You have a widow’s peak
You have blue eyes
Right over left thumbs clasping
Left over right arm crossing
Phylogenetics
Items to look at with organisms
• How they move walking, swimming, other
• How many legs look carefully (magnifying
glass)
• Do they have eyes? Antennae? (magnifying glass)
• Hard surface exoskeleton or endoskeleton
• Other observations such as color, size, activity,
Symmetry
• Bilateral symmetry
• Radial symmetry
• asymmetry
Cladogram
• Used to show relationships based on
differences in characteristics
• Also traces the sharing characteristics by
different organisms
• Traces common ancestors
• More reliable than phylogenetic tree
Phylogenetic tree
• Shows degree of similarity
• Does not show what is a shared character just the
similarities.
• Does show what is similar at a specified point in
time
• Phylogenetic trees are used more in high school,
but clagograms are used more in the real world.
• But for all intents and purposes, both types of
diagrams are used interchangeably.
Common Ancestors
Parts
Character
Wiley
Road
Runner
Bugs
Daffy
Tweety
Happy
Gloves:
N
N
Y
N
N
N
Long Ears
Y
N
Y
N
0
N
Beak
N
Y
N
Y
Y
N
Tail
Y
Y
Y
Y
Y
N
Appendages Y
Y
Y
Y
Y
N
Feathers
N
Y
N
Y
Y
N
Thumb
Y
N
Y
Y
Y
N
Cladogram
Daffy Duck
Bugs bunny
gloves
Wiley
Coyote
Tweety
Roadrunner
Long
ears
beak
feathers
Happy
Beak
Thumb
Tail
Appendages
Evolution Unit
Human Evolution
Apes Hominoidea
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Primate all apes, true monkeys, and humans
More recently evolved primates
Do not possess a tail like a traditional monkey
Go through menstrual cycle just like humans
Much more intelligent than monkey
Gibbons lesser apes
Great Apes
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Chimps
Gorillas
Orangutans
Bonobo
Humans
Gibbons lesser apes
• No tail
• Not as smart as
other Apes
• More closely
related to true
monkeys than
others
• Do not build nests
Orangutans
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Highly intelligent-more so than gibbons
More closely related to chimpanzee than gibbon
Large head
Prominent mouth-jaws
Reddish fur
Longer arms than most other primates
Can walk on two legs, but mostly hang from tree
branches
• Use tools to extract insects from trees and the
ground.
• Use tools to scrape branches for berries and leaves
• Use tools to crack nuts or hard fruits
Gorillas
• Very intelligent
• Very large group of primates-Apes
• Typically have broad chests, large core
muscles, sharp teeth
• Have extended care for young
• Share 97% of DNA with humans
• Musculature is unrivaled for primates
• More similar to humans than orangutan, but
not as much as bonobo or chimpanzee
• More closely related to
other greater apes
more specifically, more
related to chimpanzee
or human than to true
monkey
• Even greater care for
young.
• Very social, docile
primates
• Use many tools to
perform everyday tasks
• Use mushroom stalks
as feminine menstrual
products
Bonobos
Chimpanzee
• Most advanced primate
• Most closely related to humans
• Closer to human than to gorilla genetically and
internally
• Most intelligent Primate other than human
• Spend large amounts of time on two legs-bepedalism
• Have pelvis more shaped for two legged primate
instead of four
• Feet more similar to human than to gorilla
Four themes of Human Evolution
• Bipedalism walking on two legs
– As primates evolve, move to more advanced walking patterns such as
bipedalism
• Increase in braincase size space inside of skull or cranium
volume of space that brain could be
• Changes in tooth and jaw morphology How do the jaw and
teeth change as humans begin to evolve?
– Reduced canines, more teeth, more durable, longer lasting teeth
• sexual dimorphism difference between males and females
– Roles as parents, physical appearance, aggressiveness, hunting ability
• Skeletal features
– Elbow joint differences, Knee differences, Pelvic bone differences,
Foramen mangum differences, Spine differences, Foot differences,
Femur size, differences, Arm size differences
Hominid
• True Apes
• Gorillas, Chimps, Bonobos,
Gibbons, Orangutan
• Knuckle-walk not true
bipedal creatures
• Smaller brain size
• More protruding tooth row
• Canine teeth are quite
sharper and project out of
mouth more
• More sexual dimorphism
– Territorial males fight for
mates and for food for his
family
vs.
Hominin
• Prehistoric or modern
humans
• Many different forms
evolved over time
• Older hominin forms still
knuckle-walked
• More modern hominins
were bipedal
• Smaller and shorter tooth
row
• Canines are reduced
• Decrease in sexual
dimorphism
Hominin skeleton features
• Longer femur
• Flat foot
• Locking elbows for
knuckle walking
• Bowl shaped pelvis
• S shaped spine
• Short arms
• Foramen mangum,
where brainstem
enters skull, points
down
Evolution of homo sapiens
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Sahelanthropus Tchadensis7 million years ago
Orrorin Tugenensis 6 MYA
Ardipithecus ramidus 4.5-5.5 MYA
Australopithecus Afarensis Lucy 3-4 MYA
Paranthropus1-2 MYA
Homo Habilius 1.9 MYA
Homo Erectus 1.7 MYA
Homo Heidelbergensis 500,000-1MYA
Homo Neanderthalensis 500,000 YA
Homo Sapiens
Sahelanthropus Tchadensis
• 7 million years ago
• Fossil Evidence:
– “Toumai”
– Found in African desert
– Oldest known hominin?
– We do not know enough information
– Probably knuckle-walked
– Smaller braincase size-slightly larger than chimp
– Foramen mangum near rear of skull suggesting four
legs
Orrorin Tugenensis
• 6 Million Years Ago
• Same size as chimp
• Did not find complete specimen…
– Femur fragments, humorous fragments, and teeth
– Based on fossil evidence:
• Smaller brain
• lower jaw and teeth
• First bipedal hominin?
– possible
Ardipithecus ramidus
• 4.5-5.5 Million Years Ago
• First known bipedal
hominin
• Grasping big toe
• Small braincase
• Height=1.2m
• IMPT age and tooth
morphology
• Perfect blend of human
and chimp
Ardipithecus Ramidus
Why such a big change between this and
previous two???
• Change in selective pressures
– Reduced male/male combat-aggression
– Bipedalism not good for combat
• Free hands for gathering foods, etc.
• Weapons 2Million years later-no combat
anymore, so weapons are developed for
fighting
Australopithecus Afarensis
• 3-4 Million Years Ago
• Fossil Specimen: Lucy
– Bipedalall features
– Braincase slightly smaller than ardipithicus
ramidus
– Height 1m - slightly smaller than AR
– Flat feet
– Smaller canines suggesting even less combat
– Again, perfect blend between human and chimp
Paranthropus
• 1-2 Million Years Ago
• Very robust-first one with large numbers
• Fossil evidence: “nutcracker man”
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40% brain size of ours
Large jaw
Large cheekbones
Very flat teeth
Probably plant eaters?
Flatter face
Dental structure very different
1.2m tall
Homo Habilius
• 1.9 Million Years
Ago
• Fossil evidence:
“handy man”
– 1.7m tall 5ft
– Many tools
– Bigger brain, over
50% size of ours
– Africa
Homo Erectus
• 1.7 Million Years Ago
• Fossil evidence: “java man”
– Bigger brain than habillus
– More sophisticated tools than habillus
– 5ft or taller
– Started in Africa, then moved to Asia and Europe
• Most scientists believe this is the most direct
ancestor between other apes and humans
Homo Heidelbergensis
• 500,000
years to 1
Million Years
Ago
• Cave-man
like
• Used tools
extensively
Homo Neanderthalensis
(Neanderthal)
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500,000 years ago
Went extinct about 35,000 years ago
Larger than brain than H. Sapiens
Shorter
Stronger brow ridge
Culture: bury dead
Hyoid bone: Bone connecting tongue to voicebox
– More language?
– No chin: allows for change in sounds by muscle attachment from lower
lip to chin
– FOXP2 gene: complex speech, more developed than other hominins
Homo Sapiens