Discredited evolutionary theories

Scientists who study evolution come in many varieties, with conflicting theories about the nature and causes of evolution. Many theories eventually fall by the wayside, but can provide ammunition for the more scattershot of creationists who think that any attack on evolution by a biologist undermines evolutionary theory as a whole.

Jean-Baptiste Lamarck (1744-1829)
Lamarck theorised that organisms evolve through passing on characteristics acquired in life. In the years before Darwin, Lamarck's ideas were favoured, but eventually drifted from their previous esteem for lack of supporting evidence. Only in France did Lamarckism survive in academic circles, and then only through misplaced patriotism. Lamarckism was also an influence on Lysenkoism.

Étienne Geoffroy Saint-Hilaire (1772-1844)
An early 19th-century naturalist, theories on evolution had far to go before they could be accepted. In fact his lack of evidence for his ideas (which relied in part on non-materialist thinking), in the face of attack by brilliant rivals such as Cuvier, meant that evolutionary theory was slow to take hold in scientific circles at the start of the century.

Herbert Spencer (1820-1903)
Spencer originally based his evolutionary ideas on Lamarck's until the works of Charles Darwin were published, which Spencer incorporated into his own writings. Spencer is considered to be one of the most prominent exponents of social Darwinism.

Francis Galton (1822-1911)
A half-cousin of Charles Darwin, Galton was a staunch proponent of Darwinian evolution. However, he also originated the concept of eugenics by applying it to society and politics.

Nils Heribert Nilsson (1883-1955)
While Nilsson's works, in particular a short article in German, have been used to discredit evolution, his outlandish theory of emication cannot be taken seriously these days. Only the most badly-informed and foolhardy of creationists would use him as a weapon against the evil Darwinian baby-eaters.

Trofim Lysenko (1898-1976)
Lysenko propounded a Lamarckian-derived version of evolution and denounced Mendelian genetics as a "bourgeois pseudoscience." He was the recipient of Josef Stalin's political favoritism and helped to cause famine in the Soviet Union.

Stuart Pivar (1930-)
Pivar holds that there is an archetypal substance, a self-organized pre-embryonic structure, which shapes the form of all living organisms. He has no evidence of such a substance, and likes to sue people who say it ain't so.

Christian Schwabe (1930-)
Christian Schwabe denies common descent, partly because there are no intermediate forms between molecules. Or something.