On the contrary, The first reason why many people support the animal-testing’s existence is animals are suitable in experiment. It is because animals and human beings are very similar to each other in many ways, especially in biology. They have the same set of organs; heart, lungs, etc. that function similarly and tend to have the same reaction with humans. For instance, chimpanzees’ DNA is 99% similar to humans, and the genetics of mice are 98% similar to humans.13 Accordingly, animals have many chances to get the same illness with humans such as heart disease, cancer, and diabetes. In addition, thanks to the shorter life cycles than human beings, animals are better in making research subjects. For example, mice and rats are appropriate to long-term cancer research, partly because the lifespan of laboratory mice on average is only two or three years, so the researchers can study the effects of treatments, or medicines for a whole lifespan, or even for generations, which obviously would be impossible using human subjects in the experiments.14
Another reason why animals are appropriate with the experiment is that there’s no any other option which is good enough to test a living whole-body system. According to Nature, science journal, more than 90% of 1,000 biomedical scientists "agreed that the use of animals in research is essential."15 Neither using computer model nor laboratory experiments could replace animal-testing because the systems of human beings and animals are greatly complex, so the laboratory experiments, such as studying cell culture in a Petri dish, don’t always provide the opportunity for researchers to study the processes that occur in the central nervous system, endocrine system, and immune system. To give an example, blindness, and high blood pressure obviously cannot be studied in tissue culture. Additionally, evaluating side effects of drugs needs a circulatory system to bring the medicine to every organ of the body, so non-animal experiments literally can’t play the animal-testing’s role. With these evidences and examples, it is enough to say that using animals in experiments is irreplaceable, and animals are really fit for the experiments.