Charles Darwin and
Biological Evolution
Part I - Creation to
Evolution
Charles Darwin and Evolution
The modern theory of evolution was first developed
by Charles Robert Darwin (1809-1882).
• But Darwin began his adult life an avowed
Creationist who was studying for the Anglican
clergy!
The logic of (Paley’s
‘Evidences of Christianity’)
and, as I may add, of his
'Natural Theology,' gave me
as much delight as did
Euclid.
What happened?
Dr. Robert Darwin
Charles Robert Darwin
• Born February 12th, 1809
• The Mount, Shrewsbury, England
• Son of a gentleman physician in a
wealthy family.
• Did not show any strong aptitudes
as a child.
• His father decided Charles would
study medicine.
• Attended University of Edinburgh for medical school.
• Charles did not enjoy the heavy emphasis on lectures at Edinburgh.
• He was very put off by the two surgical operations he observed.
• After two years he left Edinburgh.
“Dr. Munro made his lectures on
human anatomy as dull, as he was
himself, and the subject disgusted
me.”
• Enrolled at Cambridge to prepare for a
career as an Anglican clergyman.
• Studied classics and theology, but spent most of
his time hanging out with zoologists, botanists,
and geologists, developing a keen interest in
natural history.
• Darwin began cultivating an active interest in botany and geology
at Cambridge.
• He joined a 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 Cambridge and
would likely have entered the Anglican
priesthood, but for an unusual 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
11
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
“In the morning (17th,) we landed
on Chatham Island, which, like
the others, rises with a tame and
rounded outline, interrupted only
here and there by scattered
hillocks—the remains of former
craters.”
The small bay where Darwin first
came ashore in the Galápagos on
Chatham (San Cristobal) Island.
Espánola
Sierra Negra (Isabela)
The Galapagos Islands are named for the giant tortoises that live
there. Darwin was told that each island had its own variety of
tortoise, although he did not make much of that at first.
“My attention was first called to this
fact by the Vice-Governor, Mr. Lawson,
declaring that the tortoises differed
from the different islands, and that he
could with certainty tell from which
island any one was brought.”
This one is shaped
like a burrito!
Geochelone elephantophus hoodensis
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!
Darwin collected many types of birds from the Galapagos,
including a number of species that all turned out to be types of
finches.
Daphne Major
“The remaining land-birds form a most
singular group of finches, related to
each other in the structure of their
beaks, short tails, form of body, and
plumage: there are thirteen species,
which Mr. Gould has divided into four
sub-groups.”
Woodpecker finch
Large ground finch
Mangrove finch
Medium ground finch
You mean
Darwin’s finches!
Seed Eaters
Small ground finch
Vegetarian finch
Cactus finch
Sharp billed
ground finch
Large cactus
finch
Large tree finch
Medium tree finch
Small tree finch
Ground finches
Warbler finch
Tree finches
Warbler-like
finch
Mainland finch ancestor
Woodpecker finch
Large ground finch
Mangrove finch
Medium ground finch
Cactus flower
eaters
Small ground finch
Vegetarian finch
Cactus finch
Sharp billed
ground finch
Large cactus
finch
Large tree finch
Medium tree finch
Small tree finch
Ground finches
Warbler finch
Tree finches
Warbler-like
finch
Mainland finch ancestor
Woodpecker finch
Large ground finch
Mangrove finch
Medium ground finch
Small ground finch
Vegetarian finch
Cactus finch
Sharp billed
ground finch
Large cactus
finch
Large tree finch
Medium tree finch
Small tree finch
Insect
eaters
Ground finches
Warbler finch
Tree finches
Warbler-like
finch
Mainland finch ancestor
Woodpecker finch
Large ground finch
Mangrove finch
Medium ground finch
Small ground finch
Vegetarian finch
Cactus finch
Sharp billed
ground finch
Large cactus
finch
Large tree finch
Medium tree finch
Small tree finch
Ground finches
Warbler finch
Tree finches
Warbler-like
finch
Mainland finch ancestor
Vampire Finches
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.”
After returning to England, Darwin was informed by an
ornithologist that most of the small land birds he brought back
from the Galápagos were actually different species of finch.
“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.”
“[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.”
Darwin does not directly question
creationism in The Voyage of the
Beagle, but he drops hints that show
he was seriously thinking about the
origin of new species when he wrote it.
Within a year of returning from the
Beagle voyage, 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.”