How did people find out that animal testing existed?

Animal testing has been documented for centuries, with its roots traceable to ancient civilizations such as Greece and India, where animals were used to study anatomy and disease. The formalization of animal experimentation as a scientific method began in the 19th century, as researchers published findings in medical journals, showcasing the use of animals in developing vaccines and surgical techniques. Public awareness grew with the rise of animal rights movements in the 20th century, which highlighted ethical concerns surrounding the practice and led to greater scrutiny and regulations.