Animal testing has a long and messy history of saving thousands of human lives through medical advancement, but also causing the suffering of innocent animals in cruel and unusual experiments. Ancient Greek and Arab physicians tested their surgical procedures on animals before using them on humans. Their experiments indicate that people have long recognized the physical similarities between humans and animals while also believing their lives to have less value. Given the heavy influence of religion on morality in early societies, the primary arguments in favor of animal testing came from the human-centric doctrines of Christianity, Islam and most other religions. However, medieval Catholic theologian Thomas Aquinas discouraged cruelty against animals because it often led to similar treatment of other people.
From a secular viewpoint, Renee Descartes advanced the idea that animals could feel pain and express that pain, but their inferior intelligence made them more like machines than people. The justification Descartes offered paved the way for a century of animal testing in Europe with almost no government oversight. Despite the scientific community’s general tolerance of animal testing, including live dissection, some members of the public reacted by forming Anti-Vivisection Societies or lobbying their governments. Animal testing increased in scope and popularity in the U.S. after an untested drug killed 100 people in 1937, leading to the passage of the Food, Drug and Cosmetics Act of 1938. The law required extensive animal testing before the approval of new medicines, beauty products and food ingredients.
Throughout history, the main tensions within the debate over animal testing have been in the degree to which animals’ similarities to humans granted them similar rights. The reason scientists and doctors turned to animal testing was because animals shared physical characteristics in common with humans, which allowed them to stand in for human subjects and advance our understanding of the human body. For opponents of animal testing, the similarities between animals and humans runs deeper than their external features. If animals had beating hearts, brains and eyes just like people, they could feel pain and suffer psychologically like we did.