History of Evolution

• Just as life has a history, science has also its own story.
• Andreas Vesalius


  • Comparative Anatomy
  • Started out his career as a defender of "Galenism" at the University of Paris
  • Began dissecting corpses for himself to show his students fine details of anatomy at the University of Padua
  • Drew charts for the students to study, and the exquisite quality of the charts made him famous – so famous that the criminal court judge of Padua made sure he had a steady supply of cadavers from the gallows
• As Andreas Vesalius grew more familiar with the human body


  He began to notice that here and there, Galen had made mistakes
• Galen's mistakes


  • The human breastbone is made of three segments; Galen said seven
  • Galen claimed that the humerus (upper arm bone) was the longest bone in the body, save only the femur; Versalius saw that the tibia and fibula of the shin pushed the humerus to fourth
• Over the centuries, anatomists sometimes had minor quibbles with Galen, but Versalius began to suspect that there was something seriously wrong with his work
• Versalius' approach

  1. Widened his scope, dissecting animals

  2. Reading over Galen more carefully

  3. Realised the source of mistake was that Galen had never dissected a human
• Versalius' actions

  • At the age of 25, he launched a full assault on Galen
  • Lecturing at Padua and Bologna, he rigged up skeletons of humans and of Barbary macaques, and showed the assembled students how wrong Galen had been
  • He then set out to put together a new anatomy book that included his discoveries
  • He named his book De humani corporis fabrica libri septem, or "The Seven Books on the Structure of Human Body" – commonly known as Fabrica
• Nicholas Steno


  • Fossils and the Birth of Paleontology
  • In 1666, two fisherman caught a giant shark off the coast of Livorno in Italy
  • The local duke ordered that this curiosity to be sent to Niels Stensen (better known as Steno)
  • As he dissected the shark, he was struck by how much the shark teeth resembled "tongue stones", triangular pieces of rock that had been known since ancient times
• Steno's discovery


  1. Declared that the tongue stones indeed came from the mouths of once-living sharks

  2. Showed how precisely similar the stones and the teeth were

  3. Proposed the Law of Superposition – his greatest contribution to geology
• John Ray


  • First scientist (in the modern sense of the word) to carry out a thorough study of the natural world
  • Ray's particular interests lay with plants, for which he developed an early classification system based on physiology and anatomy
  • Established the modern concept of species, noting that organisms of one species do not interbreed with members of another
  • Used species as the basic unit of taxonomy
  • Studied fossils, recognizing them as having formed from once-living organisms, and grappled with contradictions between the biblical account of creation and the evidence of change and extinction that he saw in his fossils
  • Deeply religious, he rejected any possibility of an old and changing Earth, as did all scholars of his time
• Thomas Robert Malthus


  • Made his groundbreaking economic arguments by treating human beings in a groundbreaking way. Rather than focusing on the individual, he looked at humans as groups of individuals, all of whom were subject to the same basic laws of behavior
  • Used the same principles that an ecologist would use studying a population of animals or plants
  • Pointed out that the same forces of fertility and starvation that shaped the human race were also at work on animals and plants
• Carl Linnaeus


  • Fascinated by plants, paying botany much more attention than was required for his medical studies at the university, and took up the new idea that plants reproduced sexually, using differences in reproductive structures to develop a system for classifying plants
  • Moved on to study animals and to help make sense of the huge volume of data accumulated during his teaching and research that gave all his specimens a descriptive Latin binomial, or two-word name
• Georges-Louis Leclerc, Comte de Buffon


  • Set out the current knowledge of the whole of natural history in the 44-volume "Natural History" ("Histoire Naturelle"), a series that greatly increased popular interest in science
  • Contributed to the debate over the age of the Earth (begun by Isaac Newton), suggesting that our planet had formed in a molten state and that its gradual cooling must have taken far longer than the 6000 years
• Erasmus Darwin


  • Charles was not the first in his family to consider the concept of evolution. His grandfather, Erasmus Darwin (1731-1802) was a successful country doctor who published widely in many scientific fields
  • Wrote the book "The Loves of the Plants" which introduced the public to the intricacies of plant taxonomy and reproduction
  • In his book "Zoonomia", set out Erasmus' idea on evolution. He was aware that modern species were different to fossil types, and also saw how plant and animal breeders used artificial selection to enhance their products
  • Knew that offspring inherited features from their parents, and went so far as to say that life on Earth could be descended from a common ancestor
  • Believed in the original creation of life, but his God was "hands-off" from that point
• Georges Cuvier


  • Interested in Biology from childhood, an interest that he developed further while living in the French countryside during the Revolution
  • Read both Linnaeus and Buffon and worked on his own ideas on classification and taxonomy, before joining the Museum of Natural History in Paris, studying and writing on comparative anatomy
  • His work was extremely useful in interpreting the remains of the fossil animals and relating them to living species
  • Classified animals according to their body plan (as vertebrates, molluscs, those with exoskeletons and those with radial symmetry), which is a major advance in thinking about relationships
  • His extensive studies of fossils gave rise to the science paleontology, and he recognized that particular groups of fossil organisms were associated with certain rock strata
• Cuvier's Catastrophism Model of Earth's History


  • His paleontological studies told him that large numbers had become extinct
  • To explain this, he used the concept of catastrophism: a series of catastrophes, one of which was recorded in the Biblical story of the flood, had caused repeated waves of extinction
  • Areas were then repopulated by migration from unaffected areas
  • There was no room in this model for the evolution of new species. In his view, life had existed unchanged on Earth for hundreds of thousands of years, ever since the Creation
• Jean-Baptiste Lamarck


  • Worked at the Natural History Museum in Paris, but his views on species were the opposite of Cuvier's
  • His model of evolution proposed that individuals were able to pass to their offspring characteristics acquired during their own lifetimes
  • Proposed that species did not go extinct, but instead evolved into another form
  • Stated that evolution produced more complex organisms from simple ancestors, and that this process of change took time
• Etienne Geoffroy Saint-Hillaire


  • Elaborated Lamarck's views
  • Felt that the environment could produce changes in living things, and that if these changes were harmful, then the organism would die; only those well-adapted to the environment would survive
  • This is a foretaste of Darwin's theory of natural selection, but Geoffroy never went on to develop his idea further
  • Both his suggestions, and Lamarck's ideas about inheritance of acquired characteristics, were thoroughly ridiculed by Cuvier
• James Hutton


  • Made significant contribution to the understanding of the geological processes that shaped the Earth
  • Recognized that the Earth was extremely old
  • Saw that there was no need for global catastrophes to shape the surface of the Earth. Instead, given sufficient time, the gradual ongoing processes of erosion, sedimentation, and uplift could produce the geological features he saw
  • This concept became known as the principle of uniformitarianism
  • Without the concept of an extremely old and slowly changing Earth, Darwin would not have had the time available for his model of evolution to work
  • Darwin specifically applied Hutton's concept of gradual change, or gradualism, to his model of how species evolved
• Charles Lyell


  • Went to Oxford to study mathematics and law but turned to geology after being introduced to Hutton's work
  • Met Gideon Mantell, who had discovered several different dinosaurs in English rocks, and this led him to the serious study of the geological history
  • Travelled widely in Europe, where he observed ancient raised seabeds separated by lava flows, and became convinced that Hutton's model of gradual geological change was correct
  • Collected a large amount of supporting evidence of uniformitarianism and set this out in the "Principles of Geology", a book that had a tremendous influence of Darwin
  • While he believed in the special creation of all species now in existence, he also recognized that many species had become extinct and been replaced by others
• Charles Robert Darwin: Theory of Evolution
• Gradualism

  Gradual change
• Charles Lyell


  • Went to Oxford to study mathematics and law but turned to geology after being introduced to Hutton's work
  • Met Gideon Mantell, who had discovered several different dinosaurs in English rocks, and this led him to the serious study of the geological history
  • Travelled widely in Europe, where he observed ancient raised seabeds separated by lava flows, and became convinced that Hutton's model of gradual geological change was correct
  • Collected a large amount of supporting evidence of uniformitarianism and set this out in the "Principles of Geology", a book that had a tremendous influence of Darwin
• Charles Robert Darwin


  • One of the six children born to Robert and Susannah Darwin
  • Fascinated by science, particularly natural history, from a young age
  • Rejected becoming a doctor due to traumatic experience of observing an operation on a non-anaesthetized child
  • Took classes in geology and natural history, particularly marine biology
  • Ignored official studies at Cambridge and took classes reflecting his interest in the natural world, including botany and geology
• Charles Robert Darwin


  • Received a letter that was to change his life, from his botany professor John Henslow, who had put his name forward to join the crew of HMS Beagle, on a surveying expedition to South America
  • The Beagle's captain, Robert FitzRoy, required a "gentleman companion" to provide company and conversation on the voyage
  • Darwin's thinking was enormously influenced by the work done by previous scientists, particularly Charles Lyell's "Principle of Geology"
• Charles Robert Darwin


  • Made extensive fossil collections and noticed that these fossils were found in regions now occupied by their slightly different descendants
  • Found evidence supporting Lyell's theory of gradual geologic change, such as fossils and ancient sea beds now far from the sea, and witnessed first-hand how a large earthquake could raise the land
  • Visited the Galapagos Islands and noted how the finches and iguanas there resembled those of the South American mainland
• Charles Robert Darwin


  • Greeted with considerable scientific acclaim on returning home, due to the quality and quantity of the scientific specimens he brought with him
  • Began to develop his theory of evolution by natural selection as a coherent explanation for his observations on the form and distributions of species, tying it into the concepts developed by other thinkers such as Lyell, Lamarck and Malthus
  • Spent the next 25 years refining his theory and amassing still more supporting evidence
• Alfred Russel Wallace


  • Did not have the same advantages in life as Charles Darwin
  • Largely self-taught, he had always had an interest in natural history but do not have the funds to indulge it
  • Managed to save enough money to fund a trip to South America, with the intention of collecting specimens and selling them to wealthy private collectors
• Alfred Russel Wallace


  • While on a major expedition to South East Asia, began to give a serious consideration to how the species he was observing might have evolved
  • Quite independently of Darwin, came up with the idea that the best-adapted organisms in a population would survive to breed, passing on their adaptations to their offspring
• Natural selection


  • Differential reproductive success
  • Occurs as a result of interaction between the environment and genetic variability in the population
  • The outcome is the adaptation of populations to their environment
• The two documents by Darwin and Wallace were read together at a meeting of the Royal Society, but it is Darwin's contribution that we remember today
• "On the Origin of Species by Means of Natural Selection, or the preservation of favored races in the struggle for life" was published in 1859
• Observations leading to the theory of evolution by natural selection

  • Organisms of all species can produce so many offspring that their population size would increase exponentially if all individuals that are born reproduce successfully
  • Populations tend to remain stable in size, except for seasonal fluctuations
  • Environmental resources are limited
  • Individuals of a population vary extensively in their characteristics; no two individuals are exactly alike
  • Much of this variation is heritable
• Inferences leading to the theory of evolution by natural selection


  • Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of offspring surviving each generation
  • Survival in the struggle for existence is not random, but depends in part on the hereditary make-up of the surviving individuals. Those individuals whose inherited characteristics best fit them to their environment are likely to leave more offspring than less-fit individuals
  • This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over the generations