EvolutionEvolutionThe Unifying Theory of BiologyThe Unifying Theory of Biology

EvolutionEvolutionThe Unifying Theory of BiologyThe Unifying Theory of Biology

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Contemporary Scientific History of the UniverseContemporary Scientific History of the Universe

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13.7 billion years in 30 volumes-each volume = 450 pages

-each page = 1 million yearsBig Bang, p. 1

Origin of Earth

Life Begins Complex Animal Life Dinosaurspp. 215-385

Modern Humansp. 450,

last sentence

What is Evolution?What is Evolution?

Evolution = Descent with ModificationEvolution = Descent with Modification

• Species originate as modified descendants of other species.

• Biological evolution is the origin of new species from previously existing ones over time.

“As many more individuals of each species are born than can possibly survive, and as consequently there is a frequently recurring struggle for existence, it follows that any being, if it vary in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of survival and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.”

Charles Darwin, The Origin of Species

Darwin’s TheoryDarwin’s Theory

• If there is a struggle for existence…

• If heritable variations exist among members of a population…

• If these variations affect survival and/or reproduction…

• Then species will change over time.

There is a struggle for existence.There is a struggle for existence.

• Species tend to produce more offspring than the environment can support.

Darwin calculated that even one slow-breeding female elephant could give rise to 19,000,000 elephants after 750 years if all of her young survived and reproduced at the same rate. Obviously, the environment cannot support all elephants that are born.

Heritable variations exist.Heritable variations exist.

• An impressive amount of variation exists within living species.

Breeders of animals and plants use these diverse characteristics to establish new varieties of dogs, cats, pigeons, wheat, cotton, corn, and other domesticated organisms.

Variations affect survival & reproduction.Variations affect survival & reproduction.

• Certain individuals possess inherited traits that make them more likely than other individuals to survive and/or reproduce.

• “Differential survival and reproduction”

Species will change over time.Species will change over time.

Evolution in Action

Populations evolve, not individuals.Populations evolve, not individuals.• Individuals may change throughout their

lifetimes, but this is not evolution.

• Evolution occurs across many generations.

• Over time, populations acquire new characteristics that enhance their ability to survive and/or reproduce in a given environment.

Variations are “Random”Variations are “Random”

• Mutation and sexual recombination occur randomly.

• The variations that occur do not anticipate the “needs” of the organism.

• In this sense, “random” does not mean that anything can happen.

Natural Selection is NOT RandomNatural Selection is NOT Random• Genetic variation occurs randomly, but

natural selection is NOT random.• Genetic variations that aid survival and

reproduction are more likely to become common than variations that do not.

Nature imposes a direction to evolutionary development. Though dolphins are more closely related to humans than they are to sharks, they have evolved bodies adapted to an aquatic environment.

Evolution is About ConsequencesEvolution is About Consequences

• Evolution is historically contingent, that is, “windows of opportunity” constantly open and close.

• Once certain changes have occurred, the range of possible future changes is permanently altered.

““Windows of Opportunity”Windows of Opportunity”

The earliest turtles could not retract their necks.

Proganochelys220 million years ago

Proganochelys220 million years ago

side neck turtles(southern hemisphere)

side neck turtles(southern hemisphere)

vertical neck turtles(northern hemisphere)

vertical neck turtles(northern hemisphere)

Later, two distinct forms of neck retraction evolved.

With the extinction of the turtles that could not retract their necks, the possibility that another form of neck retraction would evolve was lost.

Evolution is PredictiveEvolution is PredictiveTiktaalik roseaeTiktaalik roseae

IchthyostegaIchthyostega

EusthenopteronEusthenopteron

PanderichthysPanderichthys

AcanthostegaAcanthostega

TiktaalikTiktaalik

385 million years ago385 million years ago

365 million years ago365 million years ago

??

Evolution is TestableEvolution is TestableHuman & Ape Chromosome NumbersHuman & Ape Chromosome Numbers

Hypothesis:Hypothesis: Human Human chromosome 2 resulted chromosome 2 resulted from the fusion of two from the fusion of two chromosomes present in chromosomes present in the common ancestor of the common ancestor of humans and the other humans and the other great apes.great apes.

19581958 H

uman chrom

osome num

ber is 46

Hum

an chromosom

e number is 46

19601960 C

himpanzee chrom

osome num

ber is 48.

Chim

panzee chromosom

e number is 48.

19611961 G

orilla and orangutan chromosom

e numbers are 48.

Gorilla and orangutan chrom

osome num

bers are 48.

19751975 D

etailed analysis confirms that four species share ancestry.

Detailed analysis confirm

s that four species share ancestry.

19801980 Banding patterns of hum

ans and chimpanzees m

atch.

Banding patterns of humans and chim

panzees match.

19821982 Telom

eres in the middle of hum

an chromosom

e 2.

Telomeres in the m

iddle of human chrom

osome 2.

centromere

telomeres

Evolution is TestableEvolution is TestableHuman & Ape Chromosome NumbersHuman & Ape Chromosome Numbers

19581958 H

uman chrom

osome num

ber is 46.

Hum

an chromosom

e number is 46.

19601960 C

himpanzee chrom

osome num

ber is 48.

Chim

panzee chromosom

e number is 48.

19611961 G

orilla and orangutan chromosom

e numbers are 48.

Gorilla and orangutan chrom

osome num

bers are 48.

19751975 D

etailed analysis confirms that four species share ancestry.

Detailed analysis confirm

s that four species share ancestry.

19801980 Banding patterns of hum

ans and chimpanzees m

atch.

Banding patterns of humans and chim

panzees match.

19821982 Telom

eres in the middle of hum

an chromosom

e 2.

Telomeres in the m

iddle of human chrom

osome 2.

19911991 Sub-telom

eric sequence confirmed by D

NA analysis.

Sub-telomeric sequence confirm

ed by DN

A analysis.

20022002 Precise fusion point sequenced.

Precise fusion point sequenced.

20052005 C

himpanzee genom

e sequenced.

Chim

panzee genome sequenced.

centromere

telomeres

19921992 Second centrom

ere discovered.

Second centromere discovered.

Evolution is TestableEvolution is TestableHuman & Ape Chromosome NumbersHuman & Ape Chromosome Numbers

• These scientists were not limited to simply noting the similarities in the chromosomes.

• They were able to use evolutionary theory to consistently predict what they would later confirm to be correct.

Video

Is Evolution a Theory or a Fact?Is Evolution a Theory or a Fact?

• Evolution is both a fact and a theory.

• Scientists no longer really question the basic fact that evolution has occurred. The concept of common descent has withstood nearly 150 years of extensive testing.

• There are various competing theories used to explain HOW evolution happens.

Is Evolution Controversial?Is Evolution Controversial?

• The socio-political controversy stems from the notion science is trying to explain phenomena that some religions have already explained.

• The genuine scientific disagreements concern technical points about how evolution happens, not whether it has occurred.

ConclusionConclusion

“Nothing in Biology makes sense except in the light of evolution.”

Theodosius Dobzhansky

(1900-1975)