A Short History of Historical
Geology I I - Cuvier to Darwin
Georges Cuvier
(1769-1832)
Extinction and Fossil Vertebrates
• French comparative zoologist
• Expert on vertebrate skeletons
• Studied vertebrate remains being
excavated from secondary and tertiary
strata in the Paris Basin.
• Proved extinction by comparing fossil
and modern elephants
• Published “Discourse on the
revolutions of the surface of the globe”
describing a succession of prehistoric
worlds populated by extinct species.
"Such is the economy of nature,
that in no instance can be produced
her having permitted any race of
her animals to become extinct."
Thomas Jefferson collected fossils
found in Virginia and Kentucky, in
part to prove that the Americas
hosted animals as impressive as
anywhere else in the world.
Giant Ground Sloth
Jefferson assumed that these
animals would be found alive
elsewhere on the continent - he did
not accept the possibility of
extinction.
Contrary to Jefferson, Cuvier
proved that some species were
now extinct by comparing
fossil mammoth bones found in
Europe with modern elephant
bones.
Mammoth
Elephant
American Mastodon
Reconstructed by Cuvier
Cuvier showed that the bones of animals being found in
the Secondary strata were from giant marine reptiles.
Mosasaur jaw being excavated from the chalk at Maestricht,
Late 1700’s.
Mosasaur skull
circa 1790
circa 1870
British Isles
post-Diluvial
Diluvial
Tertiary
Secondary
Continental Europe
Cuvier used fossils to
prove the
existence of
Quaternary
gravels
Sicilian strata several unique ages in
Unusual mammals
Tertiary
the history of the Earth
London clay
Parisian gypsum beds
prior toCretaceous
the appearance
Parisian chalk
English chalk
of humankind.
Oolites
alluvium
Modern mammals
Extinct fish andJura
reptiles
Mt. strata
Jurassic
New Red Sandstone
Triassic
Lias
Muschelkalk - Trias
“Fossils alone reveal
Permian
successive epochs in
Coal Measures
Carboniferous
Mountain Limestone
Shelly fossils,the
butformation of the
Old Red Sandstone
Devonshire strata
Devonian
no vertebratesglobe.”
Magnesian Limestone Perm strata
Transitional
Wenlock Limestone
Silurian
Welsh Greywackes
Ordovician
Cambrian
Primary
No fossils
Crystalline (metamorphic) strata
Precambrian
William Smith (1769-1839)
surveyor, civil engineer
Smith’s work as a surveyor
and canal digger allowed him
to create the first accurate
geologic map of a large
region.
Time
His careful observations of
fossils allowed Smith to
identify strata that were
equivalent in age no matter
where he found them in
Great Britain.
Smith discovered that fossil
species occur in a unique,
non-repeating sequence
through time. Other
geologists picked up on this
observation and began using
the fossil record to correlate
rock formations.
Why species changed
through time was still an
open question.
By the early 1800’s geologists had established…
•
•
•
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A long history for the Earth
The existence of a fossil record of past, extinct, species
Methods for interpreting past events from rock layers
A way to date rocks and correlate them from place to place by
comparing their fossils.
• Missing was an explanation for the origin and extinction of life on
Earth through time.
Hutton
Cuvier
Lyell
Smith
Charles Darwin (1809-1882)
• Son of a wealthy doctor. Went to medical school but dropped out.
• Took geology with Professor Jameson, a neptunist. He did not
enjoy his lectures.
“The sole effect they produced on me
was the determination never as long
as I lived to read a book on Geology
or in any way to study the science.”
• Enrolled at Cambridge to study Divinity.
• Enjoyed classics and theology, but spent
most of his time hanging out with
zoologists, botanists, and geologists,
developing a keen interest in natural
history.
Charles Darwin
• Darwin began cultivating an active interest in geology at
Cambridge.
• He joined his geology professor, the Reverend Adam Sedgwick,
on a two-week expedition mapping the rock strata of Wales (part
of Sedgwick’s Cambrian project.
Grab your hammer
and clinometer
Charles - there’s
work to be done!
Darwin graduated and would have
entered the Anglican priesthood, but for
an unusual job offer….
The Voyage of the Beagle
• Darwin is offered the role of “captain’s
companion” on a survey voyage of the
HMS Beagle.
• Captain Fitzroy is looking for a gentleman
naturalist to join the crew on a survey of
the coast of South America.
• 1831 - Darwin sets sail on a two year
expedition aboard the Beagle.
•The Beagle spends 5 years circumnavigating South America
and the Southern Hemisphere.
•Darwin spends most of that time onshore - traveling, exploring,
collecting, and keeping detailed notebooks and a journal.
Voyage of the
Beagle
The Voyage of the Beagle
•Darwin observes and collects animals, plants, and fossils.
•He studies the geology of South America and of the islands
he visits.
•Carries with him Principles of Geology by Sir Charles Lyell.
Geologists in the 1800s were very concerned
with questions of origin: the origin of different
rock types, the origin of different sedimentary
formations, geologic features, etc.
Based on his observations on the Beagle voyage, Darwin
worked out the origin of coral atolls from volcanic islands.
Fossils Darwin found in S. America led him to question the origin of species.
Glyptodon
?
Megatherium
?
This wonderful relationship in the
same continent between the dead and
the living, will, I do not doubt,
hereafter throw more light on the
appearance of organic beings on our
earth, and their disappearance from it,
than any other class of facts.
Darwin observed two similar species
of ‘ostrich’ separated by the Rio
Negro in Argentina.
American Rhea
Darwin’s Rhea
He puzzled over why
there should be two
similar species of
this bird occupying
the same habitat in
20
adjacent regions.
Darwin experienced a powerful earthquake while ashore in
Chile. Exploring the coastline he saw areas where the sea floor
had been uplifted several meters above sea level.
Later, Darwin noted fossil seashells in the rock strata high up in
the Chilean Andes. He surmised that the rocks in the high peaks
had been uplifted from sea level over a very long time in a
manner analogous to the uplift he saw from the earthquake.
The power of small changes, added together
over geological spans of time, would become
an important theme in Darwin’s thinking.
One last stop in S. America: The Galápagos Islands
Pinta
Marchena
Genovesa (Tower)
0°
Santiago
Santa Cruz
Fernandina
Santa Fé
San Cristóbal
Isabela
Floreana
Espánola
The Galapagos Islands are named for the giant tortoises that live
there. Darwin was impressed by the large number of species unique
to these islands, including the tortoises.
Marine iguanas - unique to the Galapagos Islands
Galapagos land iguana - lives on the same islands as the marine
iguana, but feeds on cactus instead of seaweed.
The Galapagos penguin the only penguin that lives
near the equator!
The flightless cormorant almost identical to its
mainland cousins except for
the stubby, useless wings!
Opuntia cactus - we have them
growing on the Hofstra campus, but
not as trees!
After returning home, Darwin realized that some Galápagos
animals and plants were found showing uncommon variety, often
with each island populated by unique species.
“Seeing this gradation and diversity of
structure in one small, intimately
related group of birds, one might really
fancy that from an original paucity of
birds in this archipelago, one species
had been taken and modified for
different ends.”
Darwin was puzzled by what he saw on the Galápagos Islands
• Absence of native mammals and frogs in the Galápagos.
• Galápagos animals and plants were clearly similar to those he
had seen on the South American mainland, but they were
different species.
• Why should these small, similar islands, mostly within sight of
each other, have so many unique species of plants and animals,
many peculiar to a particular island?
“…it is the circumstance, that several
of the islands possess their own
species of the tortoise, mocking
thrush, finches, and numerous plants,
…that strikes me with wonder.”
Darwin was also impressed with the volcanic landscapes of the
Galápagos and realized that the islands were geologically very new.
“Seeing every height crowned with
its crater, and the boundaries of most
of the lava-streams still distinct, we
are led to believe that within a period,
geologically recent, the unbroken
ocean was here spread out.”
“[In the Galapagos], both in space and
time, we seem to be brought
somewhat near to that great fact–that
mystery of mysteries–the appearance
of new beings on this earth.”
After returning to England, Darwin
began a series of investigations into
the question of organic evolution
that would occupy him for the rest
of his life.
“ From this work I became
convinced that species are
not immutable. It is like
confessing a murder.”
By the end of 1838, Darwin had a working hypothesis for
explaining how species could change over time in a way that
left them adapted to their circumstances.
“This preservation of
favourable variations
and the rejection of
injurious variations, I
call Natural Selection.”
Individuals vary in their traits
This process
repeats itself
with each
generation
Reproduction
makes an excess
of offspring
(Malthus)
Evolution through
Natural Selection
Offspring with
traits well-suited
to the environment
survive and
reproduce.
Offspring with
unfavorable traits fail
to survive or reproduce
On the Origin of Species
• 1859 Darwin publishes On the Origin of Species by Means of
Natural Selection.
• The book is a sensation - by 1876 it has sold over 16,000 copies
in England and has been translated into every major language.
“There is grandeur in this view of life, with its
several powers, having been originally
breathed into a few forms or into one; and that,
whilst this planet has gone cycling on according
to the fixed law of gravity, from so simple a
beginning endless forms most beautiful and
most wonderful have been, and are being,
evolved.”
On the Origin of Species (1859)
• Marshaled a large body of evidence in
support of the fact of evolution (that
all species living and extinct are
descended from other species).
• Developed a materialistic (nonsupernatural) explanation for the
formation of new species and for the
appearance of design in adaptation.
• Mechanism of natural selection is
plausible and testable.
• In later books, Darwin argued that
Humankind could not be excluded
from his theory.