<P> Until the early 19th century, the prevailing view in Western societies was that differences between individuals of a species were uninteresting departures from their Platonic ideals (or typus) of created kinds . However, the theory of uniformitarianism in geology promoted the idea that simple, weak forces could act continuously over long periods of time to produce radical changes in the Earth's landscape . The success of this theory raised awareness of the vast scale of geological time and made plausible the idea that tiny, virtually imperceptible changes in successive generations could produce consequences on the scale of differences between species . </P> <P> The early 19th - century zoologist Jean - Baptiste Lamarck suggested the inheritance of acquired characteristics as a mechanism for evolutionary change; adaptive traits acquired by an organism during its lifetime could be inherited by that organism's progeny, eventually causing transmutation of species . This theory, Lamarckism, was an influence on the Soviet biologist Trofim Lysenko's antagonism to mainstream genetic theory as late as the mid 20th century . </P> <P> Between 1835 and 1837, the zoologist Edward Blyth worked on the area of variation, artificial selection, and how a similar process occurs in nature . Darwin acknowledged Blyth's ideas in the first chapter on variation of On the Origin of Species . </P> <P> In 1859, Charles Darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation . He defined natural selection as the "principle by which each slight variation (of a trait), if useful, is preserved". The concept was simple but powerful: individuals best adapted to their environments are more likely to survive and reproduce . As long as there is some variation between them and that variation is heritable, there will be an inevitable selection of individuals with the most advantageous variations . If the variations are heritable, then differential reproductive success leads to a progressive evolution of particular populations of a species, and populations that evolve to be sufficiently different eventually become different species . </P>

How does natural selection work as a mechanism of evolution