Question: briefly describe two ideas about evolution that were proposed in the 18th century

title: History of evolutionary thought
text: In 1858 Charles Darwin and Alfred Russel Wallace published a new evolutionary theory , explained in detail in Darwin 's On the Origin of Species ( 1859 ) . Unlike Lamarck , Darwin proposed common descent and a branching tree of life , meaning that two very different species could share a common ancestor . Darwin based his theory on the idea of natural selection : it synthesized a broad range of evidence from animal husbandry , biogeography , geology , morphology , and embryology . Debate over Darwin 's work led to the rapid acceptance of the general concept of evolution , but the specific mechanism he proposed , natural selection , was not widely accepted until it was revived by developments in biology that occurred during the 1920s through the 1940s . Before that time most biologists regarded other factors as responsible for evolution . Alternatives to natural selection suggested during `` the eclipse of Darwinism '' ( c. 1880 to 1920 ) included inheritance of acquired characteristics ( neo-Lamarckism ) , an innate drive for change ( orthogenesis ) , and sudden large mutations ( saltationism ) . Mendelian genetics , a series of 19th - century experiments with pea plant variations rediscovered in 1900 , was integrated with natural selection by Ronald Fisher , J.B.S. Haldane , and Sewall Wright during the 1910s to 1930s , and resulted in the founding of the new discipline of population genetics . During the 1930s and 1940s population genetics became integrated with other biological fields , resulting in a widely applicable theory of evolution that encompassed much of biology -- the modern synthesis . 

Answer: answer: Unlike Lamarck, Darwin proposed common descent and a branching tree of life, meaning that two very different species could share a common ancestor.
 Alternatives to natural selection suggested during `` the eclipse of Darwinism '' (c. 1880 to 1920) included inheritance of acquired characteristics (neo-Lamarckism), an innate drive for change (orthogenesis), and sudden large mutations (saltationism .