Major Contributors to Modern Evolutionary Theory. even this theory evolved from something!

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1 Major Contributors to Modern Evolutionary Theory even this theory evolved from something!

2 Throughout history there have been many contributions to theories involving the origin and evolution of species and the earth

3 The Ancient Greeks: they believed in the transmutation of forms: Aristotle: proposed the ladder of gradual transition, from inanimate objects to perfect Greek men Christian Europeans: believed that all animals were created by God and then saved by Noah

4 Irish Archbishop James Ussher of Armagh declared the earth was created on Sunday, October 23rd, 4004 BC based estimate on astronomy, history, and biblical sources

5 Ussher cont d Early beliefs held that organisms and the earth were immutable Immutable: unchanged and unchanging

6 Leonardo Da vinci (15 th century) Found fossils of sea shells in the mountains of Tuscany He postulated that they were deposited in an ancient sea Concluded that the earth s surface changed dramatically over time

7 Nicolas Steno (Danish scientist in Anatomy and Geology) 1669 analysed fossils, showed that they were in fact mineralized remains of living organisms the idea that the earth s surface changed over time was burgeoning

8 Baron George Cuvier (French zoologist/palaeontologist)18 th Century One of the earliest palaeontologists, he studied differences in species composition between sedimentary strata He found that all strata contained fossils of simple organisms but only younger strata contained fossilized complex organisms Further

9 The Baron cont d Further, fossils contained in younger strata resembled living organisms In addition, each layer contained fossilized species distinct from the layers above and below Catastrophism: local catastrophes cause extinctions; extinct species are then replaced by newly created species This did not account for the progressive complexity of species throughout time

10 James Hutton (Scottish scientist and medical doctor) 1795 Formally proposed his theory of Actualism which countered Cuvier s Catastrophism Actualism: the same geological processes occurring in the present also occurred in the past

11 Charles Lyell (English Lawyer and Geologist) 1830 Built on Hutton s Actualism with his principles of Uniformitarianism In his now-famous book, The Principles of Geology he proposed the following arguments: 1. Wait for it.

12 cont d 1. The earth has been changed by the same processes in the past as can be observed in the present 2. Geological change is slow and gradual rather than sudden and catastrophic 3. Natural laws are constant/eternal and operated with the same intensity in both the past and the present

13 So, the earth is really old, and things can change dramatically over long periods of time as the result of ongoing, slight processes got it. The work of Hutton and Lyell provided the foundation on which other scientists could build theories about the history of life on earth

14 Georges-Louis Leclerc, Comte de Buffon 18 th century Proposed that species could change over time and that these changes could lead to new organisms

15 Carl Linnaeus 18 th century The founder of biological nomenclature Proposed that relatively few species had formed many new species through interbreeding

16 Erasmus Darwin 18 th century Proposed that all life originated from a single cell Believed that humans may be closely related to primates but could not suggest a mechanism to explain how evolution might have occurred

17 Jean Baptiste Pierre Antione de Monet, Chevalier de La Marck 19 th century Recognised the influence of the environment on evolution Proposed that species must be able to adapt to the changing environment if they are to survive

18 Lamarck cont d Building on others ideas, he postulated on inheritance of acquired traits (or did he?) E.g.: over a giraffes lifetime, reaching high for food may cause a slight elongation of the neck he believed this trait could be passed on We now know this to be false but it paved the way for future theories

19 Thomas Malthus late 18 th century His Principle of Population Growth stated: Populations increase geometrically while food sources increase arithmetically; these environmental conditions create competition

20 Charles Darwin 19 th century collected and observed species mainly from South America and the Galapagos islands Incorporating elements from many of his predecessors, including Lamarck, Malthus, etc. he recognised that inheritable traits which resulted in increased survival rates contributed to the evolution of species

21 Darwin cont d Darwin entitled his theory, Natural Selection

22 Alfred Russel Wallace 19 th century Simultaneously to Darwin postulated the evolutionary theory: Survival of the Fittest The theory was fundamentally the same as Natural Selection however, Darwin s extensive research elevated his work to prominence