Nothing in biology makes sense, except in the light of evolution Theodosius Dobzhansky

Nothing in biology makes sense, except in the light of

evolution

Theodosius Dobzhansky

1. Introduction and historical notes2. The discovery of the past3. The reconstruction of phylogeny4. Early times5. History of life I: From Proterozoic to Paleozoic6. History of life II: From Mesozoic to Cenozoic7. Genetic basis of evolutionary change I8. Genetic basis of evolutionary change II9. Genetic basis of evolutionary change III10.Genetic variation and fitness11. Patterns of speciation and extinction12.Selection, adaptation, and the rise of biological complexity13.Altruism and sociality14.Human evolution I15.Human evolution II

Lecture outline

Pre Darwinian Views on Evolution

The classical view

Anaximander of Milet (610-546 BC)

„Anaximander of Miletus considered that from warmed up water and earth emerged either fish or entirely fishlike animals. Inside these animals, men took form and embryos were held

prisoners until puberty; only then, after these animals burst open, could men and women come out, now able to feed themselves” (Centorinus, 238 AC)

Empedocles(494?-434? BC)

According to Aristotle Empedocles proposed a struggle for life in the animal kingdom

Platon (427-347 BC) developed the essentialism in which the concept of eidos as an ideal

form that is imperfectly imitated by organisms (Timaios).

Variation of organisms is therefore accidental imperfection.

The allegory of the cave

7 book of Politeia

Aristoteles (384-322 BC) developed the concept of the scala naturae, the great chain of life.

Starting from inanimate objects and ending by humans and spititual beings the scala naturae gives every object and organism its

permanent place that is unchangeable.

There are three main levels:

Minerals

Plants

AnimalsFrom Didacus Valadus

Rising empiricism

Vesalius (1514-1564)

Founded modern anatomy from dissections of corpses.

He corrected the classical work of Galen who dissected Barbary apes instead of humans.

He was the first to describe organs in a mechanical way.

William Harvey (1578-1657)

Rediscovered the blood circularly system from dissections of living animals.

He also proposed that mammals have eggs and he worked on embryology.

The mechanization of the world

René Descartes (1596-1650)Descartes was the first to develop a theoretical framework for the natural sciences.

Descartes suggested that the body works like a machine, that it has the material properties of extension and motion, and that it follows the laws of physics.

He paved the way to a mechanistic study of the living world.

On the other hand he believed that only humans have a mind and animals lack souls.

Essentialism (eidos)

Importance ofobservations

Mechanistic explanation

Carolus Linneus (1707-1778) His Systema naturae (10. edition 1758) established the framework of

modern classification. While initially believing that species were ‘created’ and fixed, he changed this view in the last edition of the Systema naturae.

Described plant sexuality

Critised Descartes for his mechanistic view of animals

Georges-Louis Leclerc, Comte de Buffon (1707 – 1788) In his Histoire Naturelle he questioned the biblical view of earth history

and proposed that organism can undergo evolutionary change although he lacked a precise theory of change.

Immanuel Kant (1724-1804) The Allgemeine Naturgeschichte und Theorie des Himmels (1755) is

surely the first explicit evolutionary treatment on the basis of Newton’s mechanic.

He also speculated about the origin of life as a natural process.

Jean Baptiste Lamarck (1744-1829) As the director of the Muséum National d'Histoire Naturelle he

developed the concept of transmutation while studying molluscs.

Lamarck developed two ‘laws’ to explain evolution: the law of use and disuse, and the law of inheritance of acquired characteristics.

Use and disuse: A frequent and continuous use of organs gradually strengthens, develops and enlarges them. This gives it a power

proportional to the length of time of use. The permanent disuse of organs imperceptibly weakens and

deteriorates them, and progressively diminishes its functional capacity, until it finally disappears.

Inheritance of acquired characteristics: All the acquisitions or losses, through the influence of the environment and through the influence of the predominant use or permanent disuse of any organ are preserved

through reproduction.

Modern biology proved both ‘laws’ to be wrong.

TimeSpontaneous origin of simple life forms

Sca

le o

f org

aniz

atio

n

Scala naturae

The rise of Geology

Georges Cuvier (1769-1832)founded palaeontology and comparative anatomy.

His work on fossil elephants (mammoths) convinced him that species get extinct.

He explained extinction from the theory of catastrophism.

His discovery of the remains of Pterodactylus and Mosasaurus convinced him that they were older than 6000 years.

He was sceptical about evolutionary theories.

Charles Lyell (1797-1875)expounded the principle of uniformitarianism, holding that the same geological processes operated in the past as in the present:

The present is the key to the past.

He rejected the theory of catastrophism and supported Darwin’s view on evolution.

Alfred Russel Wallace (1823-1913)Travelled through the Amazon rainforest and the Malayan archipelago.

Developed in parallel with Darwin the concept of gradually evolving species: Every species has come into existence coincident both in space and time with a pre-existing closely allied species.

In 1958 he and Darwin presented their views on evolution in a joint meeting of the Linnean Society of London.

Wallacea

Charles Robert Darwin (1809-1882)

The voyage of the Beagle (1831-1836)

Comparative beak sizes of Darwin finches

Darwin’s Galapagos tortoise Harriet

(ca 1830-2006)

Thomas Robert Malthus(1766-1834)

020406080

100120

0 2 4 6 8 10Time

Population

Food production

The principle of population

Population growth and resources

Malthus thought that population growth is a geometric process and food production a linear.

From this conclusion Darwin took his principle of the ‘struggle for existence’:

Today we know that population growth is an exponential process.

Food availability is more or less constant.

The number of progenies exceeds the capacity (the amount of resources).

Only some individuals survive.

Surviving probabilities differ due to inherited individual variability.

All species in a focal evolutionary tree have a common ancestor

Characters of lineages change over time (evolution)

AB

CCharacter change is a gradual process

Each node represents a common ancestor of

the lineages above

Lineages that do not reach the top represent extinct lineages

Extinction results from interspecific competition

DE

F

Evolution occurs by change in the proportion of individuals that carry certain characters

(population level)

Changes of proportions are caused by differential

survival and reproduction of individuals due to their natural variation (natural

selection)

Darwin’s theory of evolution

Differentialial survival and reproduction means that individuals are differentially

adapted to their environment.The cumulation of different adaptations

causes the split of lineages.Variation is hereditary

The same evolutionary mechanisms work at all taxonomic level

All species in a focal evolutionarytree have a common ancestor

Characters of lineageschange over time (evolution)

AB

CCharacter change is a gradual process

Each node representsa common ancestor of

the lineages above

Lineages that do not reach the top representextinct lineages

DE

F

Evolution occurs by change inthe proportion of individualsthat carry certain characters

(population level)

Changes of proportions arecaused by differential

survival and reproductionof individuals due to theirnatural variation (natural

selection)

Darwin’s theory of evolution

Differentialial survival and reproductionmeans that individuals are differentially

adapted to their environment.

The cumulation of different adaptationscauses the split of lineages.

Variation is hereditary

Can we identify common ancestors?

Are there evolutionary brushes, networks, or rings ?

How fast do characters change? (tempo of evolution)

How common are speciation and extinction?

Is evolution saltatorial?

Are there ‘hopeful monsters’?

(mode of evolution)

Are nodes always bifurcations?

Basic questions of evolutionary research

Do different evolutionary

processes operate at different

taxonomic levels?

How do proportions

change?

What is variation?(material basis)

Does evolution proceed directional (orthogenesis) or is it a blind process?

Can adaptations be acquired?(mechanistic basis)

Are lineages optimally adapted?

From: University of California Museum of Paleontology

The origin of species

Vegetable

mould

and

Earth-worms

The voyage of the MS Beagle

toms

Domestication of plants and

animals

Today’s literature

Darwin Ch. 1859. The origin of species by means of natural selection, or the preservation of favored races in the struggle for life. http://www.human-nature.com/darwin/origin/contents.htm

The voyage of the Beagle. http://home.att.net/~p.caimi/darwin.html

Platon. Timaios. http://en.wikipedia.org/wiki/Timaeus_%28dialogue%29

Aristoteles. De Anima. http://ccat.sas.upenn.edu/jod/texts/aristotle.soul.html

Immanuel Kant. Allgemeine Naturgeschichte und Theorie des Himmels. http://www.mala.bc.ca/~johnstoi/kant/kant2e.htm

Evolution. Selected papers and commentary. http://post.queensu.ca/~forsdyke/evolutio.htm

A concise history of evolutionary theories since Darwin. http://www.uni-kassel.de/fb19/plantphysiology/niklas.pdf

History of Science. http://biology.clc.uc.edu/courses/bio104/hist_sci.htm

Some biographies. http://www.ucmp.berkeley.edu/help/topic/history.html

General literature