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Jan 1, 1145
The Great Chain of Being
[Caption: A visual representation of the great chain, with heaven at the top, hell at the bottom, and humans in between.] Upon being re-introduced to ancient Greek ideas by Islamic scholars, Christian thinkers, beginning with Peter Abelard, began creating the Great Chain of Being. Here, they organized all animate, inanimate, and living beings into one system. Here, everything was a hierarchy. This was used as a foundation for evolutionary thought in Biology during the 17th and 18th centuries. -
Jan 1, 1220
Akhlaq-i-Nasri puts forth a basic theory of Evolution
Islamic scholar Nasīr al-Dīn Tūsī wrote Akhlaq-i-Nasri, which puts forth a basic theory of evolution 600 years before Darwin was even born. He also explains how all living things have certain characteristics that help them survive in their environment, such as strength, intelligence, claws, tools, etc. He also believed that lower beings evolved to become more advanced ones, such as animals becoming humans. -
Jean-Baptiste Lamarck precedes Theory of Evolution
[Caption: Lamarck believed that as giraffes began reaching for higher leaves, their necks grew long. This was a way they would adapt to their environment, or so he believed.] Lamarck did not believe that all organisms shared a common ancestor, but he did believe that all life forms were created by spontaneous generation. He stated that species became more complex over time, and that they adapted to their environment.
Early Concepts of Evolution: Jean Baptiste Lamarck. (n.d.). Retrieved March -
The Voyage of the Beagle
[Caption: By R. T. Pritchet, the HMS Beagle in the Straits of Magellan.] Darwin began a journey, going all over from places like Brazil all the way to New Zealand. Here, Darwin took notes on his changing views and the development of his theory of evolution. He observed the world around him and studied biology, geology, and anthropology. -
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The Voyage of the Beagle
From 1831 to 1836, Darwin traveled the globe on the HMS Beagle. -
John Phillips publishes the first geological time scale
Phillips created a geological time scale based on the correlation of fossils. Here, he named three major eras: the Paleozoic, in which the world was dominated by marine invertebrates and fish, the Mesozoic, the age of reptiles, and the Cenozoic, the age of mammals. -
The publication of The Origin of Species
[Caption: The diagram is a visual representation of how natural selection works with mutations. Those that survive and reproduce are not selected against.] This book is where Darwin argues about how natural selection is the driving force behind evolution. He talks about how the fittest, those who reproduce, will be the ones to survive, and the weak will become extinct. Darwin, C., & Beer, G. (1996). The origin of species. Oxford: Oxford University Press. -
Heredity experimentation
[Caption: A visual representation of Mendel's pea experiment.] With pea plants, Mendel's experiment sets up the basis of Natural Selection. Mendel bred short and tall pea plants together to see which trait would come out dominant and recessive. This is also where punnet squares came from. MENDEL'S EXPERIMENTS. (n.d.). Retrieved March 8, 2015, from http://www.indiana.edu/~p1013447/dictionary/mendel.htm -
he Variation of Animals and Plants under Domestication
[Caption: A visual representation of Darwin's theory, from parents to offspring.] In this book, Darwin introduces his first theory of heredity, known as pangenisis. He states that an organism's cells can shed gemmules (minute particles of inheritance) so that they can circulate throughout the body and congregate in the gonads.He believed cells contained hereditary materials and created this theory to describe the units of inheritance between parents and offspring. -
The Descent of Man
Darwin continues his theory here, except this time, he applies it specifically to humans. This brought outrage because his claims that humans shared origins with even the simpler, "lesser" beings, was considered to contradict many religious beliefs. He states that humans share an origin with apes and, in turn, with all forms of life. Darwin, C. (1981). The descent of man, and selection in relation to sex. Princeton, N.J.: Princeton University Press. -
The Expression of the Emotions in Man and Animals
[Caption: Illustrating human facial expressions.] In this book, Darwin seeks to find the evolutionary origins of human expressions of emotion (such as smiling, for instance). This book was considered more attractive to readers than his other more controversial works. -
James Clerk Maxwell's lecture of "Molecules"
"No theory of evolution can be formed to account for the similarity of molecules, for evolution necessarily implies continuous change, and the molecule is incapable of growth or decay, of generation or destruction." Here, he claims that molecules themselves do not evolve; however, there are other things that do. -
Rediscovery of Mendel's work
[Caption: A punnet square is a way to find out the likelihood of traits the offspring will inherit.] Initially, many scientists rejected Mendel's work. They believed that the characteristics passed down to offspring were averaged together, something known as blending inheritance. Hugo de Vries and Carl Correns duplicated his work in the early 20th century, which led to rediscovery of his ideals. Mendelian genetics were combined with Darwin's theory of natural selection. -
Alfred Wedneger and Plate Tectonics
Alfred Wegener (1880-1930). (n.d.). Retrieved March 8, 2015, from http://www.ucmp.berkeley.edu/history/wegener.html Upon seeing that certain fossils, the same fossils, would be found in numerous continents, this supported his theory about all continents once being one super-continent known as Pangea because these organisms could not have gone across oceans from one continent to another. They must have been together, at some point. -
Neutral Theory of Molecular Evolution
Proposed by Motoo Kimura, he states with this theory that at the molecular level, it's not natural selection that causes the most change but the drift of neutral, mutant alleles. This theory caused much controversy. Kimura used to theory in an attempt to explain the high rate of evolutionary change and large amount of intraspecific molecular variability. -
Evolution by Gene Duplication
Written by Susumu Ohno, this book states that the creation of the creation of vetebrates and mammals from a unicellular organism by natural selection alone was impossible, because this kind of leap requires the creation of gene loci. Ohno, S. (1970). Evolution by gene duplication. Berlin: Springer-Verlag.
