A brief history of biology

A brief history of biology

A brief history of biology Not to mention development, immunology, neuroscience, microbiology, ecology, …

A brief history of biology Not to mention development, immunology, neuroscience, microbiology, ecology, … Biology is recent …

European exploration stimulated interest in biological diversity e.g. Joseph Banks, naturalist on Cook’s voyage (1768-1771)

European exploration stimulated interest in biological diversity e.g. Joseph Banks, naturalist on Cook’s voyage (1768-1771) Geology revealed an ancient and changing Earth

European exploration stimulated interest in biological diversity e.g. Joseph Banks, naturalist on Cook’s voyage (1768-1771) Geology revealed an ancient and changing Earth Diverse ideas of evolution emerged in the early 19th C - Lamarck’s Philosophie Zoologique (1809) - Erasmus Darwin speculated in poetry and prose (~1790) - Chambers’ Vestiges of the Natural History of Creation (1844)

Charles Darwin (1809-1882)

Charles Darwin (1809-1882) A keen naturalist

Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle (1831-1836)

Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle (1831-1836) Lyell’s Principles of Geology

Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle (1831-1836) Lyell’s Principles of Geology Darwin explained coral atolls

Charles Darwin (1809-1882) A keen naturalist Voyage of the Beagle (1831-1836) Lyell’s Principles of Geology Darwin explained coral atolls Sought to explain the “mystery of mysteries” by current mechanisms: - fossils, geography ….

Thought of natural selection in September, 1838 If variation be admitted to occur occasionally in some wild animals, and how can we doubt it, when we see thousands of organisms, for whatever use taken by man, do vary. If we admit such variations tend to be hereditary, and how can we doubt it when we remember resemblances of feature and character… . If we admit selection is steadily at work, and who will doubt it, when he considers amount of food on average fixed and reproductive powers act in geometric ratio. If we admit that external conditions vary, as all geology proclaims, they have done and are now doing—then, if no law of nature be opposed, there must occasionally be formed races, slightly differing from the parent races. (from an 1842 sketch of the theory)

Thought of natural selection in September, 1838 If variation be admitted to occur occasionally in some wild animals, and how can we doubt it, when we see thousands of organisms, for whatever use taken by man, do vary. If we admit such variations tend to be hereditary, and how can we doubt it when we remember resemblances of feature and character… . If we admit selection is steadily at work, and who will doubt it, when he considers amount of food on average fixed and reproductive powers act in geometric ratio. If we admit that external conditions vary, as all geology proclaims, they have done and are now doing—then, if no law of nature be opposed, there must occasionally be formed races, slightly differing from the parent races. (from an 1842 sketch of the theory) Spurred to publish by a letter from Wallace (1858)

The Origin of Species (1859) led to wide acceptance of evolution Brought many phenomena together in one framework Natural selection was not widely accepted as the key mechanism of evolution until a century later. Huxley, Galton emphasised the importance of 'sports’ Spencer, Haeckel … invoked some directed tendency or force Only two empirical studies of natural selection in the 19th century Bumpus (sparrows), Weldon (crabs)

Natural selection faced real difficulties: origin of complex adaptations age of the Earth - William Thomson (Lord Kelvin) blending inheritance Fleeming Jenkin, 1867. "The Origin of Species". North British Review 46:277-318.

Natural selection faced real difficulties: origin of complex adaptations age of the Earth - William Thomson (Lord Kelvin) blending inheritance Fleeming Jenkin, 1867. "The Origin of Species". North British Review 46:277-318.

Rediscovery of Mendel's work in 1900 strengthened the dispute 15 years of experiments: 22 true-breeding lines of pea, 30,000 plants Results read at the Brunn Natural History Society in 1865, published 1866

Rediscovered in 1900 by Correns, de Vries and von Tschermak Classical genetics developed by Bateson, Morgan, .....

Rediscovered in 1900 by Correns, de Vries and von Tschermak Classical genetics developed by Bateson, Morgan, ..... applies to all sexual organisms linkage, multiple alleles .... genes are on chromosomes

Mendelian inheritance was seen as incompatible with Darwinian selection: Mendelian variation distinct from continuous variation : Wilhelm Johannsen: selection cannot have any effect on pure lines selection on a mixed population can only sift amongst existing variation

Alleles of small effect + random variation -> continuous variation Understood by Mendel, Bateson, Pearson, Yule (1902)

Alleles of small effect + random variation -> continuous variation Understood by Mendel, Bateson, Pearson, Yule (1902) Nilsson-Ehle (oats & wheat)

Selection builds up favourable combinations of genes, step-by-step

Artificial selection (maize, hooded rats)

Artificial selection (maize, hooded rats) Fisher, R. A. 1918. The correlation between relatives on the supposition of Mendelian inheritance. Proceedings of the Royal Society of Edinburgh 52:399-433.

Population genetics established in 1920s Fisher, Haldane, Wright

Population genetics established in 1920s Fisher, Haldane, Wright Evolutionary Synthesis ~ 1930 - 1948 Theodosius Dobzhansky, E.B. Ford

Population genetics established in 1920s Fisher, Haldane, Wright Evolutionary Synthesis ~ 1930 - 1948 Theodosius Dobzhansky, E.B. Ford Simpson (paleontology), Mayr (taxonomy), Stebbins (botany)

“Evolutionary Synthesis” Mendelian genetics is conducive to natural selection Heritable variation is preserved Variation is not influenced directly by environment Mutation is random with respect to adaptation

“Evolutionary Synthesis” Mendelian genetics is conducive to natural selection Heritable variation is preserved Variation is not influenced directly by environment Mutation is random with respect to adaptation Adaptation is solely due to natural selection Many processes contribute, but only NS tends to produce organisms with better survival and reproduction Minor differences are influenced by selection, and weak selection is effective