Choice is an interesting question for the ethicists, but there are also many more reasons to use mice, rats, fruit flies and other animals: you can easily get t

Choice is an interesting question for the ethicists, but there are also many more reasons to use mice, rats, fruit flies and other animals: you can easily get thousands of genetically similar ones, you can get ones bred with specific properties, they have shorter life cycles, so you can test what happens during life time, you can test to destruction/death, you can test before consent be given, you can test multiple generations, you can keep them in controlled conditions. All of those are things that are either impossible to get consent for or prohibitively time consuming or expensive with humans. There are other reasons why test animals are not that useful, mostly because they aren't human, and what works in them might not work on people, and what doesn't work in them won't be tested on people. Over time animal testing has been decreasing and will continue to decrease while cell cultures become easier to create and closer to the cell structures that need to be tested, but for now they are needed in many fields of science.