Humans Are Not Flies

| by Dr Ray Greek

I have discussed many times the perfidy of basic researchers who use animal models. Because they would never be able to coerce society into allowing most of their research involving animals, they must sell their product for something it is not: a fast track to cures and treatments. (See Is the use of sentient animals in basic research justifiable?) I read articles and press releases like the following almost daily and just ignore them, but every now and again I decide to refresh your memory. (I am not sure this is necessary as you probably see or read the same things on a regular basis.) But make no mistake; the animal model industry claims that basic research is synonymous with predictive value.

A press release from NSF dated September 14, 2011, states:

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Scientists have sequenced the genomes (genetic codes) of 17 strains of common lab mice--an achievement that lays the groundwork for the identification of genes responsible for important traits, including diseases that afflict both mice and humans. Mice represent the premier genetic model system for studying human diseases. What's more, the 17 strains of mice included in this study are the most common strains used in lab studies of human diseases. By enabling scientists to list all DNA differences between the 17 strains, the new genome sequences will speed the identification of subsets of mutations and genes that contribute to disease. . . . Results reveal striking variations in strain relationships across the genome. [1]

A similar press release from the University of WI-Madison, which participated in the research:

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“Mice are the premier model organism for human disease. We’ve made a lot of progress in understanding the genetics of common human diseases by studying mice,” says Payseur, an associate professor of medical genetics in the UW–Madison School of Medicine and Public Health. “Although we’ve been able to map genomic regions that contribute to disease risk, we haven't known the full spectrum of mutations involved.” [2]

On March 25, 2011, the following from Andrew B. Rudczynski, Yale University’s associate vice president for research administration, was published in the New Haven Register: “Contrary to claims in a letter to the editor, the basic research model used by Yale University and its peer institutions is scientifically valid and predictive of human disease.” I once again remind everyone that there are differences between research that advances science and research that advances medicine. In any event, here are some more examples of orchestrated duplicity.

A press release dated April 8, 2013, from the Genetics Society of America is titled: “A fly mutation suggests a new route for tackling ALS.” It states that: “Research presented at the Genetics Society of America's annual Drosophila Research Conference in Washington DC, holds clues to potential treatment for motor neuron diseases such as amyotrophic lateral sclerosis.” Technically, I suppose that is a true statement. But equally true would be the statement that: “Research presented . . . holds clues to reversing the orbit of the moon;” or, “Research presented . . . holds clues to cheap renewable energy.” Only if one holds that anythingis possible and that anything that is possible is likely can research on fruit flies be spun as offering hope to patients with amyotrophic lateral sclerosis (ALS). Basic research papers published in the highest ranked science journals lead to a new class of medication only 0.004% of the time.[3] Simply taking existing drugs and testing them for uses other than what they were approved for would offer better odds for helping patients. But such research brings in no overhead fees for the university.

The usual science-based rejoinders apply to the above press release. Just because a gene functions in a certain way in other species does not mean it will do the same in humans. Animals and humans are complex systems and subject to all the vagaries of such systems. Science does not support the claim in the press release and neither does critical thinking.

Another interesting aspect of this press release is the fact that it is describing research that reveals that, in some species, when a neuron is killed it is possible to regrow the axon. The longheld belief that anytime an axon was cut off from the body of the neuron, it would always die, is thus in dispute. (For more on Wallerian degeneration, see here.) So where did this notion that “the axon never regenerates,” come from? Research on frogs in 1850. The frog research was accepted as ultimate truth for over a century. What could society have had, in the form of treatments, if the mentality that “everything that comes from the animal lab must be correct,” had been rejected around the time that evolution was really beginning to be understood? It should not be surprising that different species respond to perturbations such as nerve injury differently. That is a characteristic of a complex system and especially an evolved complex system. Even if all species responded the same in terms of degeneration, it still would not follow that a treatment that is effective in one will be effective in another.

I hope that a treatment for nerve degeneration and or axon degeneration can be discovered in the near future. For the sake of argument, lets assume that this discovery is THE discovery that makes all that happen. Would that vindicate animal-based research? No. Lets not forget why science was on the wrong track to begin with: frogs. Also, regardless of what happens in the field of neuro-regeneration, the 0.004% figure still holds and those are very bad odds.

Another press release from the Genetics Society of America, dated April 6, 2013, is titled: “Flies model a potential sweet treatment for Parkinson's disease.” Mannitol is a sweetener and a diuretic. It was administered to fruit flies with a Parkinson’s-like disease and shown to improve motor functions. It is hoped to do the same in patients with Parkinson’s disease. The usual science-based rejoinders apply to this press release as well.

An article regarding coughing mice was published by PLoS One. As the news articledescribing this research was posted on April 1, 2013, I really thought it might be a prank. But, as I searched the Internet and read the article again, I decided that it was no worse than most of the articles that herald cures based on animal models so here it is. If it is a prank, they got me, but I swear I see no relevant differences between this one and almost all the others I read on a daily basis. The title of the LiveSciencearticle is: “Of mice and phlegm: Scientists prove a mouse can cough, which will help discover treatments for colds in humans,” and the author is Damien Gayle. The subtitle states: “Discovery means mice could soon be used to test cough medicines.” It essentially touts technological developments that allowed researchers at Guangzhou Medical College in China to “hear” a mouse cough. We apparently did not know that mice cough before this research. So, assuming this is real, we once again see a trait apparently shared by humans and animals (cough) and researchers assuming about a hundred things are also shared and then announcing that this new animal model will cure whatever (in this case a cough). My response: evolved complex systems, convergent evolution, and so on and so on.

Another press release from the Genetics Society of America, this one dated April 5, 2013: “Skin deep: Fruit flies reveal clues to wound healing in humans.” The release states:

A person's skin and a fruit fly's exoskeleton, called a "cuticle" may not look alike, but both coverings protect against injury, infection, and dehydration. The top layers of mammalian skin and insect cuticle are mesh-works of macromolecules, the mammal version consisting mostly of keratin proteins and the fly version predominantly of the carbohydrate chitin. . . . And because of these signaling similarities, the fruit fly Drosophila melanogaster serves as a model for wound healing.

I received hate mail the last time I said researchers should study stars to look for cures because, in the final analysis, we are all composed of stardust. Yet, here again we essentially see researchers saying the same thing. On some level, all animals are similar. While fascinating in its own right, this is irrelevant in terms of searching for cures. At the level where disease and drug response occur, the differences outweigh the similarities. Very small differences in initial conditions, or other aspects of a complex system, invalidate the animal model when it is being used for its predictive value. For drug and disease response, the animal model has no predictive value. So, despite claims to the contrary, this research does not“suggest new targets for wound-healing drugs.” Nor should it inspire the researcher, Ms. Patterson, a PhD candidate, to state: “My fiancé is a firefighter and a member of the U.S. military. Maybe one day our work will influence his medical treatment if he sustains burns or injury wounds.” She continues:

The fly is an excellent model to dissect skin repair at a cell and molecular level. "Many of the key molecules and proteins involved in Drosophila wound healing are involved in mammalian wound healing. The genetics of Drosophila is not as complicated as mammalian genetics, so it's easier to attribute specific biological functions to individual genes," explained Ms. Patterson. During healing, molecular signals bind to receptors on the cells that line a wound, influencing the cell division, growth, and migration that restores the barrier.

Once again we see a researcher touting similarities while ignoring the more important differences.

Once again I state for the record that basic biomedical research is important. Moreover, basic research on fruit flies has yielded fascinating facts and some of these facts have been important heuristics for human-based research. But small differences still exist hence fruit flies have no predictive value for human response to drugs and disease. Basic research can stand on its own merit without exaggerating the facts. Claiming new cures will come from basic research using animals is dishonest in addition to being damaging for science in general.


1. National Science Foundation (2011) Press release: Of Mice and Men. NSF, October 6

2. University of Wi-Madison (2011) Mouse genome sequences reveal variability, complex evolutionary history. UW-Madison, October 15

3. Crowley, WF, Jr. (2003) Translation of basic research into useful treatments: how often does it occur? Am J Med 114:503-505. S0002934303001190 [pii].