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Part I
Historic Perspective
Summary
• Fixity of Species• Lamark: The first cohesive theory• Darwin: Natural Selection• Mendel: factors of inheritance• Modern Synthesis: Connected Darwin and
Mendel
Popular Beliefs up through the 1800s
Commonly held beliefs were not based on looking at the world, or examining nature.
They were based on stories handed down from generation to generation, in both oral and written forms. The Bible and Catholic dogma was the most influential force on thought.
Therefore, when the world and nature was examined, anything that was observed was interpreted according to what was already believed.
Beliefs based on these forces:The earth was young.Species were made and did not change.
When observations were made that did not fit what was already believed, new theories were contrived to fit the data into the context of what was already believed.
Popular Beliefs up through the 1800s
Commonly held beliefs were not based on looking at the world, or examining nature.
They were based on stories handed down from generation to generation, in both oral and written forms. The Bible and Catholic dogma was the most influential force on thought.
Therefore, when the world and nature was examined, anything that was observed was interpreted according to what was already believed.
Beliefs based on these forces:The earth was young.Species were made and did not change.
When observations were made that did not fit what was already believed, new theories were contrived to fit the data into the context of what was already believed.
Jean-Baptiste Lamarck (1744-1829)A major contributor to Cell TheoryOne of the first to use “biology” in its modern senseStarted out as an “essentialist” who believed species did not change. But his own work on mollusks convinced him that change had to have occurred.Was the first to propose a cohesive theory of evolution (inheritance of acquired characteristics)
George Cuvier (1769-1832): paleontologist, father of comparative anatomyHe worked with fossils (he found and named pterodactyl in Bavaria).
He thought Lamark’s ideas were ridiculous, and firmly believed in the fixity of a species.
He came up with the principle of “correlation of parts” – The notion that comparative anatomy was so accurate that after inspecting a single bone, the class and sometimes genus of an animal could be inferred.
This is because the number, direction, and shape of the bones composing each part of a body are always in a necessary relation to all parts such that a great deal can be inferred with only a few bones.
That was in 1798.
He believed (because he was really left with no other choice) that the fossil remains he worked with must be that of extinct species.
He had to fit his observations into the context of the creationist account that the earth was young.
He proposed that “All of these facts, consistent among themselves, and not opposed by any report, seem to me to prove the existence of a world previous to ours, destroyed by some kind of catastrophe”
Catastrophism was developed, which is sometimes called “Cuvier’s Compromise”.
It’s the idea that a young earth’s history was defined by an accumulation of brief yet violent natural catastrophes. Localized natural disasters would wipe out all life in one region, and new species from other regions would repopulate the barren area.
All extinct forms of life found in the fossil record were formed in a dark mysterious antediluvian period (before the flood).
Due to his protestant beliefs, Cuvier carefully described his antediluvian period having multiple floods of the last being the biblical flood.
Abraham Gottlob Werner separately proposed the theory that all rocks and sand precipitated out of an enormous flood. This theory was called Neptunism.
People studying nature were fitting their observations into a predetermined theory – that the earth was young and that the Biblical accounts were literal.
James Hutton (1726 – 1797) founder of modern geology
His geological observations suggested that the earth was very, very old. Neptunism – and therefore, catastrophism – could not be correct.
They called his theory Plutonism. The earth was hot inside, which was the only way to explain the observed geology. (Pluto was god of the underworld)
The notion of “deep time” arose from his work.So did Uniformitarianism: The assumption that the
natural processes operating in the past are the same as those that can be observed operating in the present – “the present is key to the past”
He wasn’t a very good writer, and his ideas didn’t catch on until others popularized his work (mostly, Lyell, see below)
He believed that species could adapt, but the notion of selection giving rise to new species was a “romantic fantasy”
Deep TimeYosemite Valley, Half Dome
Sir Charles Lyell (1797 – 1875)
His father was a lawyer and botanist. So he followed his father into law. Until his eyes started to get bad; then he took up his passion of geology (he spent a lot of his childhood at a famous hunting lodge)
He worked under William Buckland, at Exeter College in Oxford, who did NOT like Hutton’s work on Uniformitarianism, as it countered the existence of the flood. Buckland developed a theory to reconcile the biblical account – Flood Geology -- in 1820. This was found in “the Connexion of Geology with Religion”. In this he reconciled Hutton’s theories with the notion that the word “beginning” in Genesis meant an undefined period of time. Old World Creationism is born.He also wrote the first full account of a fossil dinosaur.
Lyell was rare in that he managed to support himself by writing books (how this helped his eyesight, I have no idea). He wrote Principles of Geology , in which he popularized the theory from 30 years ago (Hutton’s) that the earth was very old, based on geographical data.
Aside
• Freethought is a philosophical viewpoint that holds that beliefs should be formed on the basis of science and logic and not be compromised by emotion, authority, tradition, or any dogma. The cognitive application of freethought is known as freethinking, and practitioners of freethought are known as freethinkers
Charles Darwin (1809 – 1882)Dad was a doctor. Darwin was an apprentice, then went to college for medicine – but didn’t
like how brutal surgery was.He joined a society of naturalists, the Plinian Society, while in college, and studied under a
biologist who advocated Lamarck’s ideas.(Darwin’s grandfather Erasmus, wrote a book that advocated a common descent as well)Darwin’s early work examined marine animals, and his work led to evidence supporting
homology, the ‘radical’ theory that all animals have the same organs, but differ in complexity, thus showing common descent.
Dad didn’t like any of this; he enrolled Charles at Christ’s College, in the hopes his son would make good money as an Anglican parson. But Darwin liked to ride and shoot, more than study.
He studied botany, collected beetles, and studied (and enjoyed) the writings of William Paley (who argued for the divine design in nature- “the watchmaker” idea).
He graduated 10th in his class of 178, and did not rush to take his orders to be ordained as a parson (similar to a priest). Instead, he wanted to go to the Madeira islands with some classmates, to study its natural history (Alexander von Humboldt wrote a book talking about biogeography that excited young Charles)
To prepare, he took a course in geology (by one of the founders of modern geology who initially proposed the Cambrian and Devonian periods), and later helped assist mapping the geological strata in Whales.
Charles hung out with some friends for a “fortnight”, and upon returning home, found a letter waiting for him.
Video
Charles Darwin (1809 – 1882)It was from Henslow, his university professor. It basically said that
Darwin was “suitable (if unfinished)” for the position of naturalist for the unpaid position of “gentleman’s companion” to Robert Fitzroy, captain of the HMS Beagle.
It was leaving in 4 weeks.
His dad originally objected to the idea, seeing it as a waste of time, but his wife’s brother convinced him to let his son go.
It’s five year mission was to chart the coastline of South America. (originally it was supposed to take 2. whoops.)
http://darwin.thefreelibrary.com/The-Voyage-of-the-Beagle/0-1
The second voyage of the Beagle
Darwin believed in a Creator during his initial voyage.
While in Australia…In the dusk of the evening I took a stroll along a chain of ponds, which in this dry country represented the
course of a river, and had the good fortune to see several of the famous Platypus, or Ornithorhyncus paradoxus... A little time before this I had been lying on a sunny bank, and was reflecting on the strange character of the animals of this country as compared with the rest of the world.
An unbeliever in every thing beyond his own reason might exclaim, "Two distinct Creators must have been at work; their object, however, has been the same, and certainly the end in each case is complete." While thus thinking, I observed the hollow conical pitfall of the lion-ant: first a fly fell down the treacherous slope and immediately disappeared; then came a large but unwary ant; its struggles to escape being very violent, those curious little jets of sand, described by Kirby * as being flirted by the insects tail, were promptly directed against the expected victim.
But the ant enjoyed a better fate than the fly, and escaped the fatal jaws which lay concealed at the base of the conical hollow.
There can be no doubt but that this predacious larva belongs to the same genus with the European kind, though to a different species.
Now what would the skeptic say to this? Would any two workmen ever have hit upon so beautiful, so simple, and yet so artificial a contrivance? It cannot be thought so: one Hand has surely worked throughout the universe.
It took many years before Darwin published his radical theory.
He stated it simply at the beginning of his book:
As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.
Modern Synthesis
• The modern synthesis solved difficulties and confusions caused by the specialisation and poor communication between biologists in the early years of the twentieth century. Discoveries of early geneticists were difficult to reconcile with gradual evolution and the mechanism of natural selection. The synthesis reconciled the two schools of thought, while providing evidence that studies of populations in the field were crucial to evolutionary theory. It drew together ideas from several branches of biology that had become separated, particularly genetics, cytology, systematics, botany, morphology, ecology and paleontology.
Part II
Natural Selection
Requirements of Natural Selection
• Phenotypic Variation– Environmental vs. genetic determinations
• Variation has a genetic basis – it is inheritable• Variants have differential fitness – some individuals
will survive better than others• Fitness: proportional genetic contribution to the
next generation (how many kids you have)• Differences in individual reproductive success leads
to greater adaptation of a population to its environment
1. heritable variation functional, phsical, behavioral variations. IT IS COMPLETELY RANDOM 2. more offspring are produced than the environment can support. Organisms struggle to exist. The work of Malthus: humans reproduction is
held in check by death and famine due to the fact that populations tend to increase faster than their food supply does. Darwin applied this concept to ALL of life.
reproductive potential of elephants: assuming 100 year lifespan with breeding
of 30-90 years, a single female would bear ~6 young. If all of these survive and reproduce at the same rate, after only 750 years, a single pair of elephants would produce 19 million.
3. some individuals survive better than others as a result of their variations the most fit capture a disproportionate amount of resources. This is
converted to a disproportionately larger number of offspring that also survive. What determines fitness differs for different populations (it depends on the environment)
Humans carry out artificial selection (breeding) THERE ARE OTHER MECHANISMS BESIDES NATURAL SELECTIION: gene flow,
nonrandom mating, genetic driftONLY natural selection leads to adaptation to the environment. the others
drive diversity.
Selection
This ultimately determines “fittness”.
Relative Fitness: Comparing the ability of one phenotype to reproduce better or worse than another.
http://www.biologyinmotion.com/evol/
http://www.truthtree.com/evolve.shtml
Part III
Sources of Genetic Variation
Origins of genetic variation
• Ultimately, all are derived from mutations– RANDOM, not arising from a ‘need’.
• Errors during DNA replication & Repair• Sexual recombination– Independent assortment– Crossing over– Key: new allele combinations– Demonstrate analogy of merging 2 different assembly lines
• Large-scale chromosomal mutations– Duplications, polypoloidy
Part IV
Lines of Evidencehttp://en.wikipedia.org/wiki/Evidence_of_common_descent
Lines of Evidence
Besides direct experimentation:Comparative anatomy (homologous vs. analogous
characters),Biogeography: The study of the distribution of different
species of organisms around the planet and the factors that influenced that distribution
fossil record, molecular biology (e.g., amino acid and nucleotide
sequencing, ubiquity of genetic code and fundamental biochemical pathways)
Embryology and development.
Human, Mouse, ChimpComparing human & chimpAnother article
Changes in chromosomes during evolution. During human evolution, two ancestral ape chromosomes fused to produce human chromosome 2 (shown in the diagram, green outline). Humans are more distantly related to other mammals than to chimps. The greater divergence of chromosomal contiguity for cats and rats is shown.
Part V
Controversies
Controversies
Short answer: there aren’t any.
Scientists argue about the mechanism, not underlying idea.
Of all Western Countries, Americans believe in evolution the least. The next country is Turkey.
Why?
It’s not just religionPoliticizing Evolution
In America, those who say they are pro-life, pro death penalty, and anti- gay marriage also do not believe in evolution.In Europe, there is no correlation between these and evolution belief.
• Christian fundamentalists have made evolution a political issue. Less people in America believe in evolution today than they did a few years ago.
The Exception of Evolution
Why is evolution so contested even today, when the last century of work has done nothing but deepen our confirmations of the underlying principles?
It is the one theory that directly impacts our personal identity. The very thing that makes us human causes strife.
Evolution leads many to ponder the core questions of our very existence – where did we come from, where are we going, why are we here – what is our purpose?
However, evolution theory does not address these questions, contrary to what popular belief states.
Controversies
• “Young Earth” Creationists• “Expelled” the movie– http://www.discovery.org/expelled/– http://www.rottentomatoes.com/m/expelled_no
_intelligence_allowed/
• The Creationist MUSEUM– http://www.creationmuseum.org/– http://www.discovery.org/– http://friendlyatheist.com/2007/09/18/video-of-
my-creation-museum-speech/
