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Nothing in biology makes sense, except in the light of evolution Theodosius Dobzhansky. Lecture outline. Introduction and historical notes The discovery of the past The reconstruction of phylogeny Early times History of life I: From Proterozoic to Paleozoic
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)
According to AristotleEmpedocles proposed astruggle for life in the animal kingdom
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
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:
From Didacus Valadus
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.
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.
Importance of observations
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.
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.
Scale of organization
Modern biology proved both ‘laws’ to be wrong.
Spontaneous origin of simple life forms
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.
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.
The voyage of the Beagle (1831-1836)
Comparative beak sizes of Darwin finches
Darwin’s Galapagos tortoise Harriet
Malthus thought that population growth is a geometric process and food production a linear.
Today we know that population growth is an exponential process.
Food availability is more or less constant.
Thomas Robert Malthus(1766-1834)
From this conclusion Darwin took his principle of the ‘struggle for existence’:
The number of progenies exceeds the capacity (the amount of resources).
Only some individuals survive.
Surviving probabilities differ due to inherited individual variability.
Changes of proportions are caused by differential survival and reproduction of individuals due to their natural variation (natural selection)
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
Evolution occurs by change in the proportion of individuals that carry certain characters(population level)
Lineages that do not reach the top represent extinct lineages
Extinction results from interspecific competition
Each node represents a common ancestor of the lineages above
Characters of lineages change over time (evolution)
Character change is a gradual process
All species in a focal evolutionary tree have a common ancestor
The same evolutionary mechanisms work at all taxonomic level
Does evolution proceed directional (orthogenesis) or is it a blind process?
Are lineages optimally adapted?
Can adaptations be acquired?(mechanistic basis)
How do proportions change?
Do different evolutionary processes operate at different taxonomic levels?
What is variation?(material basis)
How common are speciation and extinction?
Are nodes always bifurcations?
How fast do characters change? (tempo of evolution)
Is evolution saltatorial?
Are there ‘hopeful monsters’?
(mode of evolution)
Can we identify common ancestors?
Are there evolutionary brushes, networks, or rings ?
The voyage of the MS Beagle
Domestication of plants and animals
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