Some animals have biological similarities to humans that make them particularly good models for specific diseases, such as rats for cancer, rabbits for atherosclerosis and monkeys for polio. If human beings had chosen to stop using animals for medical research 100 years ago, the world would be a very different place today. Many of us are here because neither our parents nor ourselves died from diseases that have now been controlled through the knowledge gained from animal research. Even the animals that we keep as pets would live shorter, less healthy lives were it not for many of the vaccines and treatments that have become standard in today's veterinary medicine. Imagine being the first to try a drug that had not been tested on any living system.
Controlled experiments necessitate introducing only one variable at a time.
Animal populations are easily controlled in a laboratory setting. Humans' environments and genetic backgrounds vary widely, which makes it difficult to control variables. There is no substitute for the living systems necessary to study interaction among cells, tissues and organs. Animals are the best surrogates because of their similarities to humans, both in structure and function of their organs and biological systems. Shorter life spans of animals enable scientists to study effects over shorter time periods.