Darwin on dating
Today, this concept remains in doubt, with the presentation of various punctuational models for speciation and for the origin of new designs.Although concepts of evolution were not uncommon in the first half of the nineteenth century, Darwin’s theory of modification through natural selection operating on expressed variability was radical in three of its foundational premises: In actuality, it is the theory of modification through natural selection, rather than the theory of descent with modification, that had these three radical components.(Although by the time of Darwin's death in 1882, the fact of evolution was almost universally accepted by his contemporaries, the mechanism for this evolution—the theory of natural selection—did not become an orthodoxy until long after his death, and particularly only after the rediscovery of Gregor Mendel's work in the early twentieth century and the inception of the modern synthesis.) The impact of Darwin's ideas on current teachings of evolutionary theory is readily visible.
Darwin also looked at speciation as a populational phenomenon; the population gradually changed until it became a new species.That is, the "pattern of evolution" is documented by the fossil record, the distribution patterns of existing species, methods of dating fossils, and comparison of homologous structures, among others.