Why did Charles Darwin oppose slavery after visiting Brazil?

Charles Darwin’s opposition to slavery was deeply rooted in his personal background and moral convictions. While visiting Brazil during the voyage of the HMS Beagle, Darwin was profoundly revolted by the practice of slavery he witnessed there.1

His stance was heavily influenced by his family’s history, as he possessed what have been described as "Wedgwood-abolitionist characteristics"—a reference to his family's long-standing commitment to the abolitionist movement. Darwin viewed the institution of slavery as a moral evil that contradicted the fundamental equality of mankind. He later reflected on this in his private notes, questioning the hypocrisy of slaveholders who sought to dehumanize enslaved people to justify their subjugation, writing: "Animals—whom we have made our slaves we do not like to consider our equals.—Do not slave holders wish to make the black man other kind?"12

Ultimately, Darwin’s antislavery views were an integral part of his broader understanding of human nature and equality, which he maintained throughout his life and scientific work.2