Charles Darwin: The Galapagos Finches and the Emergence of Evolutionary Theory

Charles Darwin:
Galapagos Finches &
the Emergence Evolutionary Theory
Prepared for BIO 110
“Ecology and Biodiversity”
University of the West

“Charles Darwin certainly did not invent the idea of evolution, that is, of the continuous
change in time of the state of some system as a fundamental property of that system,
or even the idea that a process of evolution had occurred in the history of life. The
study of the evolution of the cosmos itself was founded in Kant's Metaphysical
Foundations of Natural Science in 1786 and Laplace's nebular hypothesis of 1796. Sadi
Carnot's second law of thermodynamics, the principle that over time all differences in
energy between bits and pieces of the universe decrease, was published in 1824. The
idea that the various geological formations observed on earth were not the result of a
unique catastrophe or Great Flood, but the consequence of repeated and continual
geological processes still going on at present, was postulated before the turn of the
nineteenth century by James Hutton and long since accepted by 1859.
“By the time of the appearance of the Origin, the physical sciences had become
thoroughly evolutionary. Living beings were not seen as an exception. In 1769, Diderot
had his dreaming philosopher d'Alembert wonder what races of animals had preceded
us and what sorts would follow. He provided the motto of evolutionism as a worldview:
"Everything changes, everything passes. Only the totality remains." Darwin's
grandfather, Erasmus, in his epic The Temple of Nature of 1803, invokes his Muse to tell
"how rose from elemental strife/Organic forms, and kindled into life," and the Muse
completes the evolutionary story by telling him that even "imperious man, who rules
the bestial crowd,/...Arose from rudiments of form and sense." By the younger Darwin's
time, the idea of organic evolution had become a common currency of intellectual life.
“
‘
-- Richard Lewontin, “Why Darwin?”
NYRB Volume 56, Number 9 · May 28, 2009
“EVOLUTION”???

https://blog.oup.com/2011/10/ussher/

Thomas Malthus
"In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus
on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-
continued observation of the habits of animals and plants, it at once struck me that under these circumstances
favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be
the formation of a new species. Here, then I had at last got a theory by which to work".
-- Charles Darwin, from his autobiography. (1876)
“This often quoted passage reflects the significance Darwin affords Malthus in formulating his theory of Natural Selection. What
"struck" Darwin in Essay on the Principle of Population (1798) was Malthus's observation that in nature plants and animals
produce far more offspring than can survive, and that Man too is capable of overproducing if left unchecked. Malthus
concluded that unless family size was regulated, man's misery of famine would become globally epidemic and eventually
consume Man. Malthus' view that poverty and famine were natural outcomes of population growth and food supply was not
popular among social reformers who believed that with proper social structures, all ills of man could be eradicated.
“Although Malthus thought famine and poverty natural outcomes, the ultimate reason for those outcomes was divine institution.
He believed that such natural outcomes were God's way of preventing man from being lazy. Both Darwin and Wallace
independently arrived at similar theories of Natural Selection after reading Malthus. Unlike Malthus, they framed his
principle in purely natural terms both in outcome and in ultimate reason. By so doing, they extended Malthus' logic further
than Malthus himself could ever take it. They realized that producing more offspring than can survive establishes a
competitive environment among siblings, and that the variation among siblings would produce some individuals with a
slightly greater chance of survival.
“Malthus was a political economist who was concerned about, what he saw as, the decline of living conditions in nineteenth
century England. He blamed this decline on three elements:
The overproduction of young;
the inability of resources to keep up with the rising human population;
and
the irresponsibility of the lower classes.
To combat this, Malthus suggested the family size of the lower class ought to be regulated such that poor families do not produce
more children than they can support. Does this sound familiar? China has implemented a policy of one child per family
(though this applies to all families, not just those of the lower class).”
http://www.ucmp.berkeley.edu/history/malthus.html

US Census Bureau:
Population Clock
https://www.census.gov/popclock/

Jean-Baptiste LaMarck
“If Darwin (and Wallace) did not invent the idea of evolution or its
application to the history of life, then at least it might be claimed
that they invented a natural historical theory of the cause of that
evolution. But they were not the first to do so. Jean-Baptiste
Lamarck, in a succession of works between 1801 and 1809,
provided a biological theory of adaptive organic evolution based on
the supposed inheritance of changes acquired by organisms in the
course of their individual lives. The example often cited is the
roughly six-foot increase in the length of giraffes' necks from their
ancient origin as deer-like animals. If giraffes in any generation
stretched their necks, even slightly, to feed on leaves higher up in
trees, and if that slight increase in length were passed down to their
offspring, then over many generations the cumulative effect would
be the extraordinary shape of the modern giraffe.”

Cuvier and “Extinction”
“A few earlier naturalists, such as Buffon, had argued that species might
become extinct. But for some people in Cuvier's day, the idea of extinction
was religiously troubling. If God had created all of nature according to a
divine plan at the beginning of the world, it would seem irrational for Him
to let some parts of that creation die off. If life consisted of a Great Chain
of Being, extending from ocean slime to humans to angels, extinctions
would remove some of its links. A 1798 paper by Cuvier contained this
drawing showing the differences between the lower jaws of a mammoth
(top) and an Indian elephant. These differences supported the idea that
mammoths were indeed extinct.
“Cuvier carefully studied elephant fossils found near Paris. He discovered that
their bones were indisputably distinct from those of living elephants in
Africa and India. They were distinct even from fossil elephants in Siberia.
Cuvier scoffed at the idea that living members of these fossil species were
lurking somewhere on Earth, unrecognized—they were simply too big.
Instead, Cuvier declared that they were separate species that had
vanished. He later studied many other big mammal fossils and
demonstrated that they too did not belong to any species alive today. The
fossil evidence led him to propose that periodically the Earth went through
sudden changes, each of which could wipe out a number of species. “
“A 1798 paper by Cuvier
contained this drawing showing
the differences between the
lower jaws of a mammoth (top)
and an Indian elephant. These
differences supported the idea
that mammoths were indeed
extinct.”http://evolution.berkeley.edu/evolibrary/article/history_08

Sedimentary Schema
https://opentextbc.ca/geology/chapter/6-3-depositional-environments-and-sedimentary-basins/

Lyell: Principles of Geology
Lyell, Principles of
Geology Vol. 1
Chpt.5

Some Basic Principles of Geology
(as described by James Hutton, Charles Lyell and others)
Uniformitarianism
Original horizontality
Superposition
Cross-cutting relationships
Inclusions
Faunal Succession

“Uniformitarianism”
“The ‘present is the key to the past’ ”
“processes operating on earth today have
always operated in the past, sometimes at
different rates.”
http://tornado.sfsu.edu/Geosciences/classes/lwhite/notes3.htm

“Uniformitarianism”
https://www.nps.gov/articles/geologic-principles-uniformitarianism.htm

“Superposition
and Original
Horizontality”
https://www.nps.go
v/articles/geologic-
principles-
superposition-and-
original-
horizontality.htm

Law of Cross-cutting Relationships
https://imnh.iri.isu.edu/exhibits/online/geo_time/geo_principles.htm#cross

https://www.nps.gov/articles/geologic-principles-cross-cutting-relationships.htm

Law of Inclusions
https://imnh.iri.isu.edu/exhibits/online/geo_time/geo_principles.htm#inclusions

Law of Faunal Succession
https://imnh.iri.isu.e
du/exhibits/online/g
eo_time/geo_principl
es.htm#faunal

https://www.nps.
gov/articles/geolo
gic-principles-
faunal-
succession.htm

The Burgess Shale
“The Burgess Shale is found in an area of the Canadian Rocky Mountains known as the Burgess
Pass, and is located in British Columbia's Yoho National Park. Part of the ancient landmass
called Laurentia, centered in Hudson Bay, the Burgess Shale represents one of the most
diverse and well-preserved fossil localities in the world. These fossils have been gathered
from shales of the Stephen Formation in two quarries opened between Mount Wapta and
Mount Field. The upper quarry is known as Walcott's quarry and contains the most famous
fossil-collecting site, the Phyllopod Bed. The lower quarry is known as Raymond's quarry,
named after Professor Piercy Raymond of Harvard, a visitor of the site who opened the
quarry in 1924. It is now appreciated that the Burgess Shale is a site of exceptional fossil
preservation, and records a diversity of animals found nowhere else. In 1981, to protect
the site from overgathering, UNESCO designated the Burgess Shale as a world heritage site.
“The Burgess Shale contains the best record we have of Cambrian animal fossils. The locality
reveals the presence of creatures originating from the Cambrian Explosion, an evolutionary
burst of animal origins dating 545 to 525 million years ago. During this period, life was
restricted to the world's oceans. The land was barren, uninhabited, and subject to erosion;
these geologic conditions led to mudslides, where sediment periodically rolled into the
seas and buried marine organisms. At the Burgess locality, sediment was deposited in a
deep-water basin adjacent to an enormous algal reef with a vertical escarpment several
hundred meters high.”
– UC Berkeley Museum of Paleontology
http://www.ucmp.berkeley.edu/cambrian/burgess.html

“Wiwaxia”
from the Burgess Shale
https://www.bbc.co.uk/programmes/p03t939l/p03t8yvs

Thomas Henry Huxley
“Man’s Place in Nature”

The Tangled Bank…
“It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with
birds singing on the bushes, with various insects flitting about, and with worms crawling
through the damp earth, and to reflect that these elaborately constructed forms, so different
from each other, and dependent on each other in so complex a manner, have all been
produced by laws acting around us.
“These laws, taken in the largest sense, being
-- Growth with Reproduction;
-- Inheritance which is almost implied by reproduction;
-- Variability from the indirect and direct action of the external conditions of life,
and from use and disuse
-- a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence
to Natural Selection, entailing
-- Divergence of Character
and
-- the Extinction of less-improved forms.
“Thus, from the war of nature, from famine and death, the most exalted object which we are
capable of conceiving, namely, the production of the higher animals, directly follows. 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.” -- Charles Darwin, Origin of the Species

DARWIN-WALLACE: 3 PRINCIPLES
“The Darwin-Wallace explanation of evolution, the theory of natural
selection, is based on three principles:
1) Individuals in a population differ from each other in the form of
particular characteristics (the principle of variation).
2) Offspring resemble their parents more than they resemble unrelated
individuals (the principle of heritability).
3) The resources necessary for life and reproduction are limited. Individuals
with different characteristics differ in their ability to acquire those
resources and thus to survive and leave offspring in the next generations
(the principle of natural selection).”

“Darwin collected and documented a
dazzling array of species in the Galapagos. He
studied these organisms when he returned home.
Eventually, Darwin focused his study on his
collection of finches, a species of small bird. The
finches were very similar, but had beaks of
different sizes and shapes. Darwin theorized that
the beaks were adaptations that helped each
species of finch eat a different type of food, such
as seeds, fruits, or insects. ”
https://www.nationalgeographic.org/thisday/sep15/darwin-explores-galapagos-islands/

“Divergence of Character”
“Natural selection, also, leads to divergence of character; for
more living beings can be supported on the same area the
more they diverge in structure, habits, and constitution, of
which we see proof by looking at the inhabitants of any
small spot or at naturalised productions. Therefore during
the modification of the descendants of any one species,
and during the incessant struggle of all species to increase
in numbers, the more diversified these descendants
become, the better will be their chance of succeeding in
the battle of life. Thus the small differences distinguishing
varieties of the same species, will steadily tend to increase
till they come to equal the greater differences between
species of the same genus, or even of distinct genera.”
Charles Darwin The Origin of Species (1859) Pp. 127–128)

http://ecoevoevoeco.blogspot.co
m/2015/05/the-adaptive-
radiation-of-darwins.html

“One representation of the
Darwin's finch radiation (Grant
1986: Ecology and Evolution of
Darwin's finches)”
http://ecoevoevoeco.blogspot.com/2015/05/the-
adaptive-radiation-of-darwins.html

Some of the Darwin’s finches I first encountered. Clockwise from upper left: medium ground finch (Geospiza fuliginosa),
medium ground finch (Geospiza fortis), large ground finch (Geospiza magnirostris), cactus finch (Geospiza scandens),
small tree finch (Camarhynchus parvulus), vegetarian finch (Platyspiza crassirostris), and woodpecker finch
(Camarhynchus pallida).

“The birds Darwin collected in the Galapagos
inspired him and later scientists to develop the
evolutionary principle of natural selection—the
idea that animals evolve particular traits to suit
their lifestyles.”
Illustration courtesy National Geographic
https://blog.education.nationalgeographic.org/201
5/05/12/one-of-darwins-finches-struggles-to-
survive/

“Crude depiction of the distribution of different finch species on the different islands.”
(From A Field Guide to the Birds of Galapagos by Michael Harris. Collins.}
http://ecoevoevoeco.blogspot.com/2015/05/the-adaptive-radiation-of-darwins.html

“Different finches sing songs with different vocal properties.”
From Podos (2001 - Nature).

“David Lack's classic demonstration of character displacement.”
(Image from Ricklefs' (1996) Economy of Nature. )

EVOLUTION OF THE PAPER CLIP
https://space-hippo.net/photos/paperclips1.jpg

https://commons.wikimedia.org/wiki/File:BirdBeaksA.svg
BIRD BEAKS

“What Darwin's Finches Can Teach Us about the
Evolutionary Origin and Regulation of Biodiversity”
“Darwin's finches on the Galápagos Islands are particularly suitable for asking
evolutionary questions about adaptation and the multiplication of species:
how these processes happen and how to interpret them. All 14 species of
Darwin's finches are closely related, having been derived from a common
ancestor 2 million to 3 million years ago. They live in the environment in
which they evolved, and none has become extinct as a result of human activity.
Key factors in their evolutionary diversification are environmental change,
natural selection, and cultural evolution. A long-term study of finch
populations on the island of Daphne Major has revealed that evolution occurs
by natural selection when the finches' food supply changes during droughts.
Extending this finding to the past, we discuss how environmental change has
influenced the opportunities for speciation and diversification of finches
throughout their history: The number of islands has increased, the climate has
cooled, and the vegetation and food supply have changed.”
“What Darwin's Finches Can Teach Us about the Evolutionary Origin and Regulation of
Biodiversity,” Rosemary B. Grant Peter R. Grant
BioScience, Volume 53, Issue 10, 1 October 2003, Pages 965–975
https://academic.oup.com/bioscience/article/53/10/965/254944

https://www.youtube.com/watch?v=iA0NF41tLn8&feature=youtu.be

“Daphne Major”
“By virtue of its small size (0.34 square kilometers [km]),
moderate degree of isolation (8 km from the nearest
island), undisturbed habitat, and resident populations of
finches, Daphne Major is a particularly favorable location
for studying Darwin's three essential ingredients of
adaptive evolution: variation, inheritance, and selection.
We accomplished this by capturing and measuring many
finches to determine phenotypic variation, comparing
offspring with their parents to determine inheritance, and
following their fates across years to detect selection. We
found pronounced heritable variation in beak size and body
size within populations of the medium ground finch
(Geospiza fortis) and the cactus finch (Geospiza scandens).
We also found that when the environment changes, some
of the variants in each population survive while others die.
This amounts to a vindication of David Lack's views on
adaptation.”

“Annual Variation in Finch Numbers, Foraging and Food Supply on Isla Daphne Major,
Galfipagos” P.R. Grant and B.R. Grant. Oecologia (Berl.) 46, 55-62 (1980)

“What Darwin's Finches Can Teach Us
about the Evolutionary Origin and Regulation of Biodiversity”
Rosemary B. Grant Peter R. Grant
“Abstract: Darwin's finches on the Galápagos Islands are particularly suitable
for asking evolutionary questions about adaptation and the multiplication
of species: how these processes happen and how to interpret them. All 14
species of Darwin's finches are closely related, having been derived from a
common ancestor 2 million to 3 million years ago. They live in the
environment in which they evolved, and none has become extinct as a
result of human activity. Key factors in their evolutionary diversification
are environmental change, natural selection, and cultural evolution. A
long-term study of finch populations on the island of Daphne Major has
revealed that evolution occurs by natural selection when the finches' food
supply changes during droughts. Extending this finding to the past, we
discuss how environmental change has influenced the opportunities for
speciation and diversification of finches throughout their history: The
number of islands has increased, the climate has cooled, and the
vegetation and food supply have changed.”

“Four Points of the Darwin’s Finches ‘Compass” “
“The most curious fact is
the perfect gradation in the
size of the beaks of the
different species of
Geospiza.… Seeing this
gradation and diversity of
structure in one small,
intimately related group of
birds, one might fancy that,
from an original paucity of
birds in this archipelago,
one species has been taken
and modified for different
ends”
Charles Darwin
Journal of Researches into the
Geology and Natural History of the
Various Countries Visited during the
Voyage of H. M. S. Beagle, under the
Command of Captain FitzRoy, R.N.,
from 1832 to 1836. London: Henry
Colburn 1842.(p. 458).

Related Darwin’s Finches
https://academic.oup.com/bioscience/articl
e/53/10/965/254944

Beak Gradations of Darwin’s Finches
“The intergradation of beak
sizes and shapes, illustrated
with outlines of the six species
in the genus Geospiza. 1–3,
Geospiza magnirostris; 4–7,
Geospiza conirostris; 8–13,
Geospiza fortis; 14–15,
Geospiza fuliginosa; 16–21,
Geospiza difficilis; 22–24,
Geospiza scandens. Illustration
by Swarth (1931), from Abbott
and colleagues (1977).”

Beak Depth and Seed Hardness
“As the average beak depth of a population of granivorous Geospiza species increases, so does the
maximum size and hardness of the seeds they can crack. Based on Schluter and Grant (1984).”

BioScience, Volume 53, Issue 10, 01 October 2003, Pages 965–975, https://doi.org/10.1641/0006-3568(2003)053[0965:WDFCTU]2.0.CO;2
The content of this slide may be subject to copyright: please see the slide notes for details.
“Figure 5. Evolutionary change in beak
depth in the population of Geospiza fortis
on the island of Daphne Major. The upper
panel shows the distribution of beak
depths in the breeding population in 1976,
with the survivors of the 1977 drought that
bred in 1978 indicated in black. The
difference between the means, indicated
by a caret, is a measure of the strength of
natural selection. The middle and lower
panels show the distributions of beak
depths of fully grown offspring hatched in
1976 and 1978, respectively. Evolutionary
change between generations is measured
by the difference in mean between the
1976 population before selection and the
birds hatched in 1978.”

https://biologos.org/blogs/guest/david-lack-and-darwins-finches

Gregor Mendel
“Unknown to Darwin, Wallace, or any of the enthusiasts for the claim of evolution by
natural selection, work by an obscure monk in the Königenkloster at Brno in
Moravia would turn out to save the theory. Mendel's experiments on peas
demonstrated that inheritance was not based on the blending of some fluid-like
material, but by the passage of particles that maintained their individual
properties even when mixed together in a hybrid. Thus, in future generations,
variant properties would reappear even though what we now call the genes for
those variants were temporarily mixed with the normal gene forms in hybrids.
“The journal of the Brünn Society of Natural Science in which Mendel's research was
published would never have been read by the English scientific establishment, nor
indeed by anyone in the major centers of nineteenth-century natural science. It
was not until 1900 that Mendel's work was rediscovered as a consequence of the
appearance of new scientific results on crossing plants. In full historical justice, if
we are to personalize our modern explanation of evolution we should call it not
"Darwinism," nor even "Darwin-Wallacism," but "Darwin-Wallace-Mendelism."

https://press.princeton.edu/titles/84
86.html

https://press.princeton.edu/titles/
10282.html

“Finch Beaks” (a lab exercise)
Coral Levi February 14 2017
http://rstudio-pubs-
static.s3.amazonaws.com/250190_1f8459822b0d4183b4cd756486cce5dd.html

https://faculty.uca.edu/johnc/introdarwin.htm

Charles Darwin: The Galapagos Finches and the Emergence of Evolutionary Theory

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