376 | Medical Research with Animals use of animals in such a fashion, and may speak of alternatives for numbers 3–9 For example, aortic valve replacement can be performed with artificial or synthetic valves instead of obtaining them from pigs, and physicians rarely prescribe insulin from pigs and cows, since human insulin can be synthesized Instead of using animal tissue to study basic physiological processes, human tissue is plentiful and better, if what the scientists actually want is more knowledge about humans These are all alternatives to using animals They are scientifically valid, and acceptable to the animal protection community The way veterinary students and researchers study animals can also be made less harmful to animals The same criteria used in research involving humans can be applied to research designed to find cures for diseases in dogs and cats Instead of creating models of cancer, researchers can study cancers that occur naturally in dogs They can even break this down further and study the same cancer in different breeds, as there will be genetic differences between breeds just as there are differences between groups of humans A final consideration is the use of animals that lack either a central nervous system or a highly organized peripheral nervous system These animals not appear to be sentient, which is the basis of the animal rights and welfare arguments Therefore their use should be acceptable to all Some of the great breakthroughs in biological science are now coming from the study of invertebrates and organisms like yeast The level of examination has changed since the 18th and 19th centuries As our examination of living systems has become increasingly fine-grained, we have found that, when it comes to explanations of biologic activity, subtle differences between organisms tend to outweigh gross similarities Science could use animals to shed light on shared functions when we were struggling to understand living systems at the level of the organ; for example, the functions of the liver and heart are similar between species But today we are studying drug response and disease at a level that defines not only a species, but in many cases the individual Today, science studies human disease and drug response in light of complexity theory, evolutionary biology, gene expression, and gene regulation Arguments about ethics have been around for centuries Ethics are somewhat subjective, but science should be less so Scientific questions are eventually answered with more or less unanimous agreement Such is the nature of studying the material world In the final analysis, society will have to decide what role animals will play in scientific pursuits, indeed in all pursuits But hopefully all sides will be able to agree on the scientific principles outlined above and use that knowledge to make intelligent decisions See also Alternatives to Animal Experiments: Reduction, Refinement, and Replacement Further Reading Americans for Medical Advancement at www curedisease.com Associated Press 2008 Gene map shows no two cancers alike http://www.msnbc.msn.com/ id/26546943/ Bourne v E.I.DuPont de Nemours and Company, 189F Supp 2d 482 (S.D W.Va 2002) Daubert v Merrell Dow Pharms., 509 U.S 579, 584 (U.S., 1993) Flintoft, Louisa 2005 Identical twins: Epigenetics makes the difference Nature Reviews Genetics 6, 667; doi:10.1038/nrg 1693