Argument: Animal environments can be better controlled for research than humans
"Why do scientists use animals in research?". The American Physiological Society. Retrieved May 3rd, 2008 - "In addition, scientists can easily control the environment around the animal (diet, temperature, lighting, etc.), which would be difficult to do with people. However, the most important reason why animals are used is that it would be wrong to deliberately expose human beings to health risks in order to observe the course of a disease."