Darwin was a long-time abolitionist who had been horrified by slavery when he first came into contact with it in Brazil while touring the world on the "Beagle" voyage many years before (slavery had been illegal in the British Empire since 1833). Darwin also was perplexed by the "savage races" he saw in South America at Tierra del Fuego, which he saw as evidence of man's more primitive state of civilisation. During his years in London, his private notebooks were riddled with speculations and thoughts on the nature of the human races, many decades before he published "Origin" and "Descent".