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Ask a NEET aspirant who discovered natural selection and the answer is "Darwin". The real story has two discoverers, a letter from an island in the Moluccas, and a special meeting in London. Knowing it helps you write sharper answers, and it shows how a scientific idea goes from private notes to public record. Here is what happened, the argument both men made, and the arithmetic at its heart.
What happened on 18 June 1858?
That day Darwin received a letter from Wallace containing an essay that, as the Linnean Society puts it, "formulated the same hypothesis that Darwin had worked on for the last twenty years but had never published". Wallace had written it at Ternate in February 1858 and asked that it be passed to the geologist Charles Lyell.
Darwin forwarded it the same day. His letter to Lyell reads: "Your words have come true with a vengeance that I shd. be forestalled." And: "I never saw a more striking coincidence."
What was read at the Linnean Society on 1 July 1858?
Lyell and the botanist Joseph Hooker arranged for three documents to be read at a special meeting. The Society's proceedings list them: an extract from Darwin's manuscript on species, "sketched in 1839 and copied in 1844"; an abstract of a letter from Darwin to the American botanist Asa Gray; and Wallace's essay "On the Tendency of Varieties to depart indefinitely from the Original Type". The Gray letter was dated September 1857; an early printing said October, which Darwin Online notes was corrected.
Neither author attended. According to the Linnean Society, Darwin was unwell and grieving the death of his son, and Wallace was still in the Moluccas. The papers were printed in the Society's journal later that year.
What argument did both men make?
The core is a mismatch between growth and food. In his 1844 extract, Darwin wrote that "the amount of food for each species must, on an average, be constant, whereas the increase of all organisms tends to be geometrical". He then gave a worked example with birds, which is worth doing yourself.
Start with 8 pairs, 16 birds. Suppose only half the pairs, 4 of them, rear 4 young each year. That is 16 new birds, so the population doubles every year: 16, 32, 64, 128, 256, 512, 1,024, 2,048. After seven years there are 16 × 2⁷ = 2,048 birds "instead of the original sixteen". Since bird numbers do not explode like this, Darwin concluded that most young must die or that birds do not live that long. Something is checking the numbers, and whatever survives that check leaves the next generation.
Wallace reached the same mechanism from varieties. His essay rejects the idea that animals change by wanting to: "Neither did the giraffe acquire its long neck by desiring to reach the foliage of the more lofty shrubs, and constantly stretching its neck for the purpose." Instead, varieties that happened to have longer necks gained fresh pasture and survived where others did not.
Why does Darwin's name come first?
Darwin had the larger body of evidence and turned it into a book quickly. *On the Origin of Species* was published on 24 November 1859, in a first printing of 1,250 copies. In his letter to Lyell, Darwin had already said where he thought his value lay: "all the labour consists in the application of the theory".
Neither man knew how variations were inherited. That piece arrived with the rediscovery of Mendel's work in 1900.
Common mistakes in exam answers about natural selection
Lamarckian wording. "The giraffe stretched its neck and passed it on" is the very idea Wallace rejected in 1858.
"Fittest" as "strongest". In the 1858 argument, what counts is surviving the checks on population and leaving offspring.
Individuals evolving. An individual does not change its traits by selection. The proportions of variants in a population change over generations.
Skipping the numbers. The geometric-growth step is the engine of the argument. A one-line calculation like Darwin's shows you understand it.
What can a student take from how they worked?
Both men built the idea on years of observation, and both checked it with simple arithmetic. Darwin also shows the cost of waiting: he had a written sketch from 1844 but had not published it when Wallace's essay arrived. Write your ideas down clearly and show them to someone.
Explaining selection in your own words is the real test. Fermi's AI tutor checks understanding as it goes, so you can practise the argument out loud and find where it slips. For the chapter itself, our guide to using NCERT for NEET covers how to read the textbook closely.
Next step: redo Darwin's bird calculation with 10 pairs and a different breeding rate, and write two sentences on what it tells you.
