What is "neo-darwinism"

Weismannism \Weis"mann*ism\, n. (Biol.) The theories and teachings in regard to heredity propounded by the German biologist August Weismann, esp. in regard to germ plasm as the basis of heredity and the impossibility of transmitting acquired characteristics; -- often called neo-Darwinism.

n. The modern synthesis of (w: Charles Darwin)'s theory of natural selection with the modern genetic understanding of heredity.

Neo-Darwinism is the " modern synthesis" of Darwinian evolution through natural selection with Mendelian genetics, the latter specifying that evolution involves the transmission of characteristics from parent to offspring through the mechanism of genetic transfer, rather than the "blending process" of pre-Mendelian evolutionary science. Neo-Darwinism can also designate Charles Darwin's ideas of natural selection separated from his hypothesis of pangenesis as a Lamarckian source of variation involving blending inheritance.

As part of the disagreement about whether natural selection alone was sufficient to explain speciation, George Romanes coined the term neo-Darwinism in 1895 to refer to the version of evolution advocated by Alfred Russel Wallace and August Weismann with its heavy dependence on natural selection. Weismann and Wallace rejected the Lamarckian idea of inheritance of acquired characteristics that even Darwin took for granted. The term was first used to explain that evolution occurs solely through natural selection, and not by the inheritance of acquired characteristics resulting from use or disuse. The basis for the complete rejection of Lamarckism was Weismann's germ plasm theory. Weismann realised that the cells that produce the germ plasm, or gametes (such as sperm and egg in animals), separate from the somatic cells that go on to make other body tissues at an early stage in development. Since he could see no obvious means of communication between the two, he asserted that the inheritance of acquired characteristics was therefore impossible; a conclusion now known as the Weismann barrier.

From the 1880s to the 1930s, the term continued to be applied to the panselectionist school of thought, which argued that natural selection was the main and perhaps sole cause of all evolution. From then until around 1947, the term was used for the panselectionist followers of Ronald Fisher.