Darwin, Wallace and natural selection explained

Inheritance, variation and evolution • The development of understanding of genetics and evolution

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Who is Alfred Russel Wallace and what does he contribute?

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Alfred Russel Wallace is a naturalist who independently formulates the theory of natural selection and sends his findings to Darwin in 1858, prompting joint publication and providing biogeographical evidence such as the Wallace Line .

Key concepts

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Definition and steps of natural selection

Natural selection is the process by which individuals with traits better suited to an environment survive and reproduce more successfully, passing those traits to offspring. Key steps: (1) variation exists within a population; (2) more offspring are born than can survive, producing competition; (3) individuals with advantageous variations survive and reproduce; (4) advantageous traits increase in frequency across generations, and, over long timescales, may produce new species. This summary follows Darwin’s original formulation of the mechanism .

Darwin’s observations and mechanism

Charles Darwin bases his ideas on observations from many species, including finches from the Galápagos Islands, and on analogies with artificial selection (selective breeding). Darwin links struggle for existence, variation and inheritance to explain how species change over time. He delays publication while collecting evidence and refines arguments about competition, variation and inheritance before publishing On the Origin of Species in 1859 .

Alfred Russel Wallace’s contribution

Alfred Russel Wallace independently formulates the theory of natural selection after extensive fieldwork in South America and the Malay Archipelago. Wallace sends a paper to Darwin in 1858 describing a mechanism similar to Darwin’s; their work appears jointly, which accelerates Darwin’s publication. Wallace provides additional evidence from biogeography, including the pattern now called the Wallace Line showing species differences across a narrow strait of water .

Examples and evidence cited by Darwin and Wallace

Darwin uses differences in beak shape among Galápagos finches to illustrate adaptation to different food sources and habitats. Darwin predicts biological relationships such as a moth pollinator with a long proboscis for an orchid with a long spur; later discovery of the moth confirms the prediction and supports co-evolution. Wallace supplies biogeographical evidence from island distributions and species colouration patterns in the Malay Archipelago .

Reasons for gradual acceptance

Three main factors slow acceptance: (1) incomplete evidence about the mechanism of inheritance - genes, chromosomes and Mendelian genetics are not understood until decades later; (2) religious and cultural opposition that conflicts with literal creation beliefs; (3) public controversy and ridicule, illustrated by heated debates such as Huxley versus Bishop Wilberforce, which make immediate scientific consensus unlikely. These factors combine to delay wide scientific and public adoption of natural selection despite strong explanatory power .

Key notes

Important points to keep in mind

Natural selection requires variation, differential survival/reproduction, and heritability.

Artificial selection demonstrates that selective breeding can change traits quickly and illustrates the principle of selection by humans rather than nature .

Wallace independently formulates natural selection and provides crucial biogeographical evidence (Wallace Line) .

Acceptance of Darwin’s ideas is delayed because inheritance mechanisms remain unknown until later genetics research .

Public debates and religious objections create social resistance even when scientific arguments are strong .

Predictions that lead to discoveries (for example, Darwin’s orchid prediction) count as strong tests of theory .

Speciation often follows geographical isolation and different selection pressures in separated populations .

Multiple independent lines of evidence (fossils, biogeography, comparative anatomy, genetics) together support evolution by natural selection .