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Pascals’ wager

The animal experimentation community sells animal use to society based on their claim that animals can predict human response to drugs and disease. Want to cure cancer? Study mice. Want to understand HIV? Study monkeys. For example, according to the BBC May 31, 2010: American scientists say they have developed a vaccine which has prevented breast cancer from developing in mice. The article quotes Vincent Tuohy, from the Cleveland Clinic as saying:

We believe that this vaccine will someday be used to prevent breast cancer in adult women in the same way that vaccines have prevented many childhood diseases. If it works in humans the way it works in mice, this will be monumental. We could eliminate breast cancer. (Emphasis added.)

An editorial in Nature May 20, 2010 is titled Still prime time for primates. It states:

Rats turn out to be surprisingly useful for research on cognition [see Neuroscience: The rat pack]. But if the goal is to understand the human brain and its many disorders, then primate studies remain essential . . . But the rodent researchers have never argued that rats could or should replace primates in research that is ultimately directed at understanding how the human brain works — and thus what goes wrong in neurological and psychiatric conditions . . . This approach — combined with the low cost of rearing and keeping rodents and the wide availability of genetic tools for studying them — promises to help scientists to reach these basic cognitive components with unprecedented speed and rigour. Rodent research is also a less ethically sensitive issue than primate research, so the more information that can be wrung out of rats and mice the better. However, scientists will not be able to extrapolate directly from the rodent brain to the human brain to work out what has gone wrong in complex disorders such as schizophrenia. (Emphasis added.)

Clearly the editors are saying neuroscience research in nonhuman primates can be directly translated to humans in terms of diseases. In other words, nonhuman primates can predict human response.

Gad, in his textbook Animal Models in Toxicology:

Biomedical sciences’ use of animals as models [is to] help understand and predict responses in humans, in toxicology and pharmacology . . . by and large animals have worked exceptionally well as predictive models for humans . . . Animals have been used as models for centuries to predict what chemicals and environmental factors would do to humans . . . The use of animals as predictors of potential ill effects has grown since that time . . . If we correctly identify toxic agents (using animals and other predictive model systems) in advance of a product or agent being introduced into the marketplace or environment, generally it will not be introduced . . . The use of thalidomide, a sedative-hypnotic agent, led to some 10,000 deformed children being born in Europe. This in turn led directly to the 1962 revision of the Food, Drug and Cosmetic Act, requiring more stringent testing. Current testing procedures (or even those at the time in the United States, where the drug was never approved for human use) would have identified the hazard and prevented this tragedy. (1) (Emphasis added.)

Michael F. Jacobson, executive director of the Center for Science in the Public Interest noted in 2008: “We must test animals to determine whether a substance causes cancer (2).” Similarly, Huff et al. observe: “Chemical carcinogenesis bioassays in animals have long been recognized and accepted as valid predictors of potential cancer hazards to humans” (3).

Such examples can be easily multiplied. No reasonable person can deny that the animal experimentation community as whole wants society to equate response in animals with response in humans. (See Animal Models in Light of Evolutionfor more on the above).

A familiarity with evolutionary biology, complex systems, and or the empirical evidence unmistakably refutes the notion that one species can predict drug or disease response for another. (I again remind the reader that one correlation or even a series of correlations does not make a modality predictive.) If researchers want to use animals to make discoveries about the species being experimented on, that is viable science. If they want to use animals to seek new knowledge in general, that is also scientifically viable. But promising society cures for cancer or safer drugs based on animal experimentation is disingenuous.

Further, society has better options for spending its research dollars. According to Sleeman and Steeg who published in the European Journal of Cancer 2010;46(7):1177-1180, only five percent of cancer research funds are spent on studying metastases, despite the fact that metastases are what actually kill 90% of all cancer patients. All admit that the big difference between human cancers and cancers of commonly used lab animals is that humans are unique in the metastasis problem. If scientists are going to find cures for human cancers they will have to study humans and human tissues. Not mice.

A press release from the University of Wisconsin-Madison titled Powerful Genome Barcoding System Reveals Large-Scale Variation in Human DNA describes, “Variation on the order of thousands to hundreds of thousands of DNA's smallest pieces -- large swaths varying in length or location or even showing up in reverse order -- appeared 4,205 times in a comparison of DNA from just four people.”

The press release continues:

"I've got a whole folder of papers on diseases that are ascribable to these structural differences," he says. "If you can see the genetic basis for those diseases, you can figure out the molecular differences in their development and pick drug targets to treat or cure or avoid them altogether. We fit into that storyline right up at the front."

Even individual humans differ in their response to drugs and disease because of their unique genetic makeup. If all you understand about medical research is this, you should understand why research with animals is not going to predict human response.

Maintaining that “the only reason to oppose the work [vaccine development using animals] is if you know this effort is certain to be a failure” is similar to Pascal’s wager. Blaise “Pascal [maintained] that even though the existence of God cannot be determined through reason, a person should wager as though God exists, because living life accordingly has everything to gain, and nothing to lose.” There is actually much to lose when one rejects science and reason and bases one’s decisions on faith and hope.


1. S. Gad, in Animal Models in Toxicology, S. Gad, Ed. (CRC Press, 2007),  pp. 1-18.

2. CSPI. 2008.Longer Tests on Lab Animals Urged for Potential Carcinogens. CSPI 2008 [cited November 17. Available from

3. J. Huff, M. F. Jacobson, D. L. Davis, Environ Health Perspect116, 1439 (Nov, 2008).


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