Most scientists in Darwin’s day thought: Earth was young (6000 years old) Earth was populated by millions of unrelated species Darwin’s book challenged that, and was radical for its time Anazimander (Greek philosopher) had idea that life arose in water, and simpler forms of life preceded more complex ones. Aristotle (Greek philosopher)held that species are fixed or permanent, and do not evolve (are static). Darwin, 1859 Darwin, 1874

A cartoon of Charles Darwin - his book and beliefs were radical for its time

Buffon (1700’s) (French naturalist) studied fossils - said Earth may be much older than 6000 years. Proposed that a species in a fossil could be an ancient version of a living species Lamarck (1800’s) (French naturalist) said that life evolves through adaptation; ex: a powerful bird’s beak. However, he had an erroneous views of how adaptations evolve: He said “Inheritance of Acquired Characteristics” - by using or not using body parts, one can develop certain characteristics, which can pass on to offspring. Ex: if you exercise beaks and get stronger you can pass that trait down to offspring. (Use & Disuse Theory) Incompatible with modern genetics. Lamarck

Lyell (Scottish geologist) - said ancient Earth was sculpted by gradual geologic processes that continue today. (Mountains, earthquakes, erosion.) Earth was very old. Gradualism principle. Wallace (British naturalist) (1850’s) developed a concept of natural selection identical to Darwin - both were presented to the scientific community. Darwin’s book evidenced 2 major points: Organisms on Earth today descended from ancestral species, accumulating different modifications or adaptations - “descent with modification.” History of life is analogous to a tree. Natural selection is the mechanism for descent with modification Lyell Wallace

Elephant family: Example of “descent with modification”