Evolution Evolution

Evolutionary ProcessEvolutionary ProcessHuman EvolutionHuman Evolution

EvolutionEvolution• Evolution = progressive change in Evolution = progressive change in

characteristics of organisms as a characteristics of organisms as a result of changes in genetic result of changes in genetic compositioncomposition

• Two important aspects Two important aspects – Descent from a common ancestorDescent from a common ancestor– Adaptation to the environmentAdaptation to the environment

• Adaptation = characteristic that makes it Adaptation = characteristic that makes it more likely that an organism will survive more likely that an organism will survive and reproduce in its environmentand reproduce in its environment

Evidence for Common DescentEvidence for Common DescentFrom the Fossil RecordFrom the Fossil Record

Living Organisms resemble extinct fossil forms.Living Organisms resemble extinct fossil forms.

Evidence for Common DescentEvidence for Common DescentFrom the Fossil RecordFrom the Fossil Record

Progressive changes from simpler to more complex Progressive changes from simpler to more complex organisms can be seen in the fossil record.organisms can be seen in the fossil record.

Biogeographical Evidence Biogeographical Evidence for Common Descentfor Common Descent

Plants and animals of each continent are distinctive.Plants and animals of each continent are distinctive.

BiogeographicalBiogeographicalEvidence for Evidence for Common DescentCommon Descent

Different island species resemble each other.Different island species resemble each other.

Biogeographical Evidence for Biogeographical Evidence for Common DescentCommon Descent

Island Populations resemble Island Populations resemble those on nearby land.those on nearby land.

The Galapagos finches resembled the The Galapagos finches resembled the grassquit found on the coast of Ecuador.grassquit found on the coast of Ecuador.

Anatomical Evidence for Common Descent: Homologous Structures

FlyingFlying SwimmingSwimming RunningRunning GraspingGrasping

Anatomical Evidence:Anatomical Evidence: Vestigial Structures Vestigial Structures

Functional hindlimb Functional hindlimb in salamanderin salamander

Remnants of Remnants of hindlimb seen in hindlimb seen in boa and whaleboa and whale

Evidence for Common Descent Evidence for Common Descent from Biochemistryfrom Biochemistry

Evidence for Evolution from BiochemistryEvidence for Evolution from Biochemistry

Similarities in sequence measured by Similarities in sequence measured by ease of separating DNA strands by heat ease of separating DNA strands by heat

A Flowchart of Evolutionary Reasoning

Potential forrapid reproduction

Relatively constantresources and

population over time

Variability instructures and

behaviors

Some variability is inherited; adaptations

increase in future generations

(observations)

(conclusions)

Competition for survival and reproduction (1)

NATURAL SELECTIONOn average, the fittest

organisms leavethe most offspring (2)

EVOLUTION:The genetic makeup of the

population changes over time, driven by natural selection (3)

Formation of new genotypes leads to

phenotypic variation

Adaptation

Originally, giraffe neck length varied.

Competition for resources causes long-necked giraffesto have the most offspring.

Due to natural selection, most giraffes nowhave long necks.

Darwin’s proposal

Natural Selection Natural Selection as the Mechanism as the Mechanism

for Evolutionfor Evolution

Applying Your KnowledgeApplying Your Knowledge

A.A. The mechanism for evolution is The mechanism for evolution is B.B. A progressive change in the A progressive change in the

characteristics of organisms is characteristics of organisms is C.C. A trait that makes a species A trait that makes a species

survival more likely is calledsurvival more likely is called a(n)a(n)

1.1. AdaptationAdaptation2.2. EvolutionEvolution3.3. Natural selectionNatural selection

Primate Primate Evolutionary Evolutionary

TreeTree 3

2

1

4

Pro

sim

ian

sA

nth

rop

oid

sH

om

ino

ids

Lemur

Gibbon

Orangutan

Gorilla

Chimpanzee

Hominid

Angiospermsevolve 199.6 MYAand forests spread.

Primateancestorenters trees.

70 60 50 40 30 20 10Millions of Years Ago (MYA) PRESENT

Old World Monkey

New World Monkey

Tarsier

Common ancestor may have resembled a

tree shrew

~45 MYA: There wasa common ancestor for monkeys, apes

and hominids

~15 MYA: There wasa common ancestor

for all apes and hominids

~7 MYA: There wasa common ancestor for African apes and

hominids

bipedalposture

Adaptations of PrimatesAdaptations of Primates

• Opposable thumbOpposable thumb

• Well-developed brainWell-developed brain

• Nails instead of clawsNails instead of claws

• Single birthSingle birth

• Extended period of Extended period of parental careparental care

• Emphasis on learned Emphasis on learned behaviorbehavior

Australopithecus afarensis Australopithecus afarensis An early hominid An early hominid

Hominid EvolutionHominid Evolution

Homo erectus

Homo habilis

Australopithecines

Genus Homo

0

1.0

2.0

3.0

4.0

5.0

5.5

Homosapiens

Homoneandertalenis

Australopithecusrobustus

Homoergaster

Australopithecusboisei

low foreheadprojecting face400 cm3 brain

Australopithecusafricanus

Australopithecusafarensis

distinct foreheadflat face700–1,300 cm3 brain

Ardipithecusramidus

Ardipithecusramidus kadabba

Mill

ion

s o

f Y

ears

Ag

o (

MY

A)

Possible ancestor of both A. africanus and

Genus HomoPossible ancestor of

modern humans

In Asia

In Africa

Human EvolutionHuman Evolution• Genus Genus AustralopithecusAustralopithecus

– walked uprightwalked upright– product of mosaic evolution = different body product of mosaic evolution = different body

parts change at different ratesparts change at different rates• Smaller brain resembles apesSmaller brain resembles apes• Bipedal locomotion resembles humansBipedal locomotion resembles humans

– ancestors of genus ancestors of genus HomoHomo(not certain which species led to(not certain which species led to Homo Homo habilis)habilis)

Human EvolutionHuman Evolution• Genus Genus HomoHomo

– Homo habilisHomo habilis = “handy man” = “handy man”• produced toolsproduced tools• teeth supported omnivorous dietteeth supported omnivorous diet• enlarged speech area in brainenlarged speech area in brain

– Homo ergaster Homo ergaster (in Africa)(in Africa)• advanced tools, use of fire advanced tools, use of fire • larger brain, taller bodylarger brain, taller body• striding gaitstriding gait

– earlyearly Homo sapiens Homo sapiens(based on Cro-Magnon fossils)(based on Cro-Magnon fossils)• compound toolscompound tools• larger brainlarger brain• language and culture, language and culture,

including artincluding art

neck of femur

femur

femur neck is longer than in modern humans

Homo ergaster

Two Hypotheses for the Two Hypotheses for the Origin of Modern HumansOrigin of Modern Humans

1

0.1

2

1

0.1

2

interbreeding

interbreeding

EUROPE

Homo ergaster

Homo sapiens Homo sapiens Homo sapiens

EUROPE

Homo ergaster

Homo sapiens

Homo sapiens Homo sapiens Homo sapiens

Out of AfricaMultiregional continuity

migration ofHomo ergaster

migration ofHomo ergaster

migration ofHomo ergaster

migration ofHomo ergaster

ASIA AFRICA ASIA AFRICA

Mill

ions

of Y

ears

Ago

(M

YA

)

Mill

ions

of Y

ears

Ago

(M

YA

)

Homo ergaster evolves into modern humans in Asia, Africa, and Europe.

Modern humans evolvein Africa and migrateto Asia and Europe.

DNA Analyses Related to DNA Analyses Related to Human OriginsHuman Origins

Visit Visit http://www.geneticorigins.orghttp://www.geneticorigins.org and choose and choose Mitochondrial Control Region Mitochondrial Control Region Media and Animations Media and Animations Solving the Mystery of the Neanderthals Solving the Mystery of the Neanderthals

Other Applications of DNA Analysis can be Other Applications of DNA Analysis can be found at found at http://www.dnai.orghttp://www.dnai.org Choose Applications, then Human OriginsChoose Applications, then Human Origins

A Newly-Discovered A Newly-Discovered (but extinct)(but extinct)

Species of Genus Species of Genus HomoHomo

Homo erectusHomo floresiensis

Homo sapiens

Applying Your KnowledgeApplying Your Knowledge

A.A. Which species is the closest ancestor Which species is the closest ancestor to Homo sapiens? to Homo sapiens?

B.B. Which species was the first to use Which species was the first to use tools? tools?

C.C. Which species is the earliest hominid?Which species is the earliest hominid?

1.1. Homo habilisHomo habilis2.2. Australopithecus afarensisAustralopithecus afarensis3.3. Homo ergasterHomo ergaster