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A-Z of thought: Volcanoes

Sam Berry


Alfred Russel Wallace (1823-1913) is best known for writing to Darwin about how animals and plants could adapt to their environment - the idea of natural selection which Darwin had arrived at independently and had been collecting evidence for. Wallace's letter precipitated a joint publication from the two of them, and the appearance a year later of Darwin's Origin of Species.

Wallace looked up to Darwin, and Darwin supported Wallace, getting him a government pension, but they disagreed about human evolution. Wallace argued that natural selection had acted in the earlier stages of human evolution, but as our intellectual and moral faculties developed, the body ceased to be subject to selection, and subsequent adaptation was solely 'through the action of the mind'. Wallace believed that brain size reflected mental capacity; his problem was that fossil humans and 'savages' had skulls of similar size to civilized people's, and consequently all must be presumed to have had the same mental capacity. He assumed that traits like mathematical ability and complex trains of abstract reasoning were useless, even harmful, in the struggle for existence in primitive cultures. As it was both unneeded and unused, the brain could not have evolved by natural selection alone.

Consequently, and influenced by his belief in spiritualism, he proposed that a 'Higher Intelligence' had guided human evolution in a 'definite direction and for special ends'. The need for a 'higher intelligence' horrified Darwin, but the two remained friends.

Wallace was a naturalist par excellence. Before going to South-East Asia he had spent five years collecting in Amazonia. (He lost his notes and most of his collections when the ship bringing him back to Britain caught fire and sank). He is often regarded as the founder of biogeography - the science of the distribution of animals and plants. He realized that a narrow sea channel was a boundary between the animals found in Asia and those in Australasia; this became known as Wallace's Line and was an early hint of continental drift, which was only generally accepted with the discovery of tectonic plates a century later.

Darwin concluded his book The Descent of Man, 'Man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creatures, with his god-like intellect which has penetrated into the movements and constitution of the solar system - with all these exalted powers - Man still bears in his bodily frame the indelible stamp of this lowly origin.'  On that point, Darwin, Wallace, and we can all agree.

Sam Berry