• 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”