Evolution and Systematics

• EARLY THEORIES OF EVOLUTION• DARWIN, WALLACE, & THE ORIGIN• DARWIN’S THEORIES OF EVOLUTION• WHAT EVOLUTION IS NOT• MODERN SYNTHESIS• BIOGEOGRAPHY• SCHOOLS OF SYSTEMATICS

Early theories of natural history and classification treated living things as immutable and were essentialistic. From the end of the 18th century and the early part of the 19th century the study of the diversity of life developed into four forms:• Progress by catastrophes (e.g. Cuvier)• Progressive transmutation (e.g. Lamarck)• Natural Theology (e.g. Paley)• Naturphilosophie (e.g. Goethe)

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck

• Though others had suggested it, Lamarck gave the first clear theory of the mutability (transmutation) of species

• Came to this view after trying to organize the invertebrate collection in the Natural History Museum in Paris

• Theory of two parts:– A generating force pushed living

things up the scala naturae – Acquired characters allowed them to

become adapted to local conditions

1744-1829, France

Natural Theology• Teleology inserted into natural

history in the tradition of Thomas Aquinas

• This evolved into the search for the purpose intended by the creator

• Mainly British and American proponents (~1750-1850)

• William Paley (1743-1805, Britain) most well known for his teleological argument for the existence of God

• Best known is his watchmaker argument

Naturphilosophie• German movement in natural history

begun by Johann Christoph Friedrich von Schiller (1759-1805, Germany)

• Search for the ur-plant and the ur-animal• Study the parts but interpret them as in a

holistic way (e.g. plant parts all modifications of the leaf and skeletal elements all modifications of the vertebra –Goethe)

• Most famous of the Naturphilosphen was Johann Wolfgang von Goethe (1749-1832, Germany) work on light and flowers

• Fit well with embryology and the idea that species could change toward an ideal

Monument of Goethe(L) and Schiller(R) in Weimar

The rise of paleontology, global explorations, and uniformitarianism suggested a gradually changing world versus the periodic catastrophes of Cuvier. Still Charles Lyell accepted the immutability of species.

Charles Robert Darwin• Born 12 February 1809, Britain• Unmotivated student with poor

aptitude for languages• Sent to Edinburgh to study

medicine with his older brother Erasmus

• Entered Cambridge and studied under Adam Sedgwick (1785-1873) and John Stephens Henslow (1796-1861)

• Avid beetle collector

Second Voyage of the H.M.S. Beagle• Introduced to ad for a naturalist by Henslow• Robert Fitzroy (1805-1865)• 27 December 1831-2 October 1836

Returned to England a Celebrity Among Scientists

• Initially lived in London and Cambridge• Became active in scientific societies

there• Wrote his Journal for publication, sold

very well unlike Fitzroy’s journal• Within a year, Darwin was speculating

about the mutability of species• He married his cousin, Emma

Wedgwood• Moved to the village of Downe

Malthusian Crisis

Thomas Robert Malthus (1766-1834, Britain)

From Darwin’s Autobiography

"In October 1838, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being 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 result would be the formation of a new species.“

Breeding and Domestication

All pigeon and dog breeds must have come from just one and differences through selective breeding or artificial selection

Darwin found his mechanism for change:Natural selectionVariationStruggle for existence

Darwin spent the next 20 years gathering evidence from:– Domestication– Examples of Variation– Classification– Complex Organs– Rudimentary Organs– Instinct– Hybrids– Geological Record– Succession of Life through Geologic Time– Geographical Distribution– Embryology

Robert Chambers & The Vestiges of Creation

• Published anonymously 1844• Argued for a progressive

evolution of life and the cosmos

• Similar to Lamarck and Naturphilosophie

• The strong reaction caused Darwin to set aside his developing manuscript on the Species Book

1802-1871, publisher and naturalist, Britain (Scotland)

Naturalists inspired to explore (a short list)• Henry Walter Bates

(1825-1892)

• Alfred Russel Wallace (1823-1913)

• Joseph Dalton Hooker (1817-1911)

• Thomas Henry Huxley (1825-1895)

Wallace in Amazonia• 1848 left England with Bates• Collected near Belem and then they separated• Wallace spent 4 years on the Rio Negro & returned in 1852

Wallace in Moluccas• 1854 to Moluccas (the Spice Islands)• Cataloged >126,000 specimens• Noted differences in island taxa• Returned in 1862

Letter from Ternate

• In malarial fever, he mulled over why so many species after having read Malthus.

• He had already published the Sarawak Law, an exploration of why related species occupy nearby but not identical spaces

• Sent letter with a manuscript to Charles Lyell via a naturalist whom he had met briefly before traveling to the Spice Islands and with whom he had corresponded, Charles Darwin

The Origin, Published 1859• Living things have changed over time– The fact of evolution

• Common descent of all living things– The unifying principle of biology

• Multiplication of species– Theory of the origin of biological diversity

• Gradualism– Applies theory of uniformitarianism to the history of life

• Natural selection– Theory of change in species over time in response to local

conditions

Living things have changed over timeThe fact of evolution

Common descent of all living thingsThe unifying principle of biology

• The genealogy of all living organisms can be traced back to a single common ancestor.

Theobald, Douglas L. "29+ Evidences Macroevolution: The Scientific Case for Common Descent." The Talk.Origins Archive. Vers. 2.83. 2004. 12 Jan, 2004<http://www.talkorigins.org/faqs/comdesc/>

Multiplication of speciesOrigin of biological diversity

Sato et al. 1999. Phylogeny of Darwin's finches as revealed by mtDNA sequences. Proc Natl Acad Sci U S A. 96 (9): 5101–5106

GradualismApplies theory of uniformitarianism to the history of life

• Charles Lyell- changes in history of the Earth occurred gradually

• Influenced Darwin’s thinking on how changes in the history of life occurred

• Problem with Lord Kelvin’s estimate for the age of the earth (~100,000,000 years)

Natural selectionTheory of change in species over time in response to local conditions

• Organisms exhibit variation in particular traits• There is a heritable basis to this variation• Organisms produce more offspring than can survive • Organisms with favorable traits produce more

offspring than those with unfavorable traits

What Evolution Is NOT

• The origin of life

• Anthropocentrism

• Progressionism

• Purpose of life (teleology)

Darwin’s Books Following Origin1862: On the various contrivances by which British and foreign orchids are fertilised by insects1865: The Movements and Habits of Climbing Plants (Linnean Society paper, published in book form in 1875)1868: The Variation of Animals and Plants under Domestication1871: The Descent of Man, and Selection in Relation to Sex1872: The Expression of Emotions in Man and Animals1875: Insectivorous Plants1876: The Effects of Cross and Self Fertilisation in the Vegetable Kingdom1877: The Different Forms of Flowers on Plants of the Same Species1879: "Preface and 'a preliminary notice'" in Ernst Krause's Erasmus Darwin1880: The Power of Movement in Plants1881: The Formation of Vegetable Mould through the Action of Worms

Abuses of evolutionary theory• Fraud– Piltdown man

• Political movements– Social Darwinism– Lysenkoism– Creation science

De Vries Theory of Mutationism

• Though Darwin convinced the scientific community of change over time, few supported natural selection

• Mutations gave rise to jumps (hopeful monsters)

• Early period of the Mendelian renaissance seemed to support mutationism

Modern Evolutionary Synthesis• Mutations -> variation• Natural selection operates on the variation• Developed 1936-1947• Julian Sorell Huxley (1887-1975)• Others: Ronald Aylmer Fisher (1890-1962);

Theodosius Grygorovych Dobzhansky (1900-1975); John Burdon Sanderson Haldane (1892-1964); Ernst Walter Mayr (1904-2005); George Gaylord Simpson (1902-1984); George Ledyard Stebbins (1906-2000), et al.

Julian Huxley

Modes of Speciation

Molecular clocks• Theory after Emile Zukerkandl

(1922- Austria & USA) and Linus Pauling (1901-1994, USA) in 1962

• Motoo Kimura (1924-1994, Japan & USA) developed neutral theory of molecular biology

• Assumption- change in molecules or genomes over geological time is constant

• “Molecular clocks” can be used to determine evolutionary relationships among taxa

• Reliability depends on constancy of molecular change!– Non-coding regions vs genes subject to

selection

Wallace and BiogeographyThe Geographical Distribution of Animals (1876)

Island Biogeography by Wilson and MacArthur

Theory that explores the relationship between evolution and extinction relative to area

Robert Helmut MacArthur (1930-1972), USA

Edward Osborne Wilson (1929), USA

Major Implications for Landscape Ecology and Wildlife Management

Schools of Evolutionary Reconstruction

• Evolutionary Systematics (generate phylogenetic trees)

• Numerical Systematics (Phenetics, generate phenograms)

• Phylogenetic Systematics (Cladistics, generate cladograms)

Rise of Cladistics• Founded by Willi Hennig• Difference between primitive

and derived characters very important

• This system is very powerful when coupled with molecular data

1913, Germany

Character-Taxon

Cladogram

Interpretation of Cladogram

Biodiversity