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The Astounding Differences in Chimp Y-Chromosomal Structure Add Weight to Bill Banning Ape Research


Originally published at This Dish is Veg
September 12, 2011

Before the Human Genome Project, epidemiological study of human populations, cellular and tissue research, clinical trials, and innumerable technological advances, scientists had few resources to understanding the progress of disease or injury in a living being.  In recent decades, scientific progress has provided resources of incalculable benefit.  For these reasons, many (as in, most of the developed world) have abandoned, or restrictively legislated, research involving humankind’s closest evolutionary relative, the chimpanzee. 


Today, the United States remains the only advanced nation of which still condones medical and scientific research involving chimpanzees.  Representative Roscoe G. Bartlett of Maryland is looking beyond antiquated animal-based studies by introducing H.R. 1513, the Great Ape Protection and Cost Savings Act of 2011, prohibiting medical and scientific study on chimps in the United States.   


H.R. 1513 seeks to ban chimpanzee research based upon the proposals that such research is too expensive, no longer in tandem with current scientific progress, yields poor results, and does not consider the unreasonable cruelty to the chimpanzee.  In a letter published in the NY Times in August 2011, Representative Roscoe discusses his experience as a naval physiologist during the Space Program,

At the time, I believed such research was worth the pain inflicted on the animals. But in the years since, our understanding of its effect on primates, as well as alternatives to it, have made great strides, to the point where I no longer believe such experiments make sense — scientifically, financially or ethically. That’s why I have introduced bipartisan legislation to phase out invasive research on great apes in the United States.

Representative Roscoe appropriately timed H.R 1513, as the Institute of Medicine of the National Academies (IOM,) upon request from the NIH & National Research Council, is currently weighing whether continued scientific and medical research warrants the use of chimpanzees.  The IOMs Board on Health Sciences Policy expects to release their report at the end of 2011. 

The chimpanzee is said to share 98% of DNA with humans—but what are the implications of such a “slight” difference in genetic material?

The small physiological difference between genders has many implications in terms of medical treatment. One such example is the how men and women process pain, or respond to pain treatment. According to a 2003 Tufts University study, women require higher levels of morphine to achieve the same level of anesthesia. The National Institute of Drug Abuse notes that certain opioid compounds affect the brain’s two pain receptors in differing levels—kappa and mu opioids. The male brain has a greater concentration of mu opioid pain receptors, and women respond better to pain medication of which targets kappa opioids. Even identical twins have different gene-expressions (how genes behave) studies revealing that where both twins have genetic predispositions to a disease but only one ultimately develops the condition. Researchers at the American College of Rheumatology have shown such examples in the development of rheumatoid arthritis.

What is the relevance? Men and women, even identical twins, cannot accurately predict response to disease or drugs. The Human Genome Project gave science insight into the substantial differences in X-chromosome activation between men and women (European Journal of Human Genetics, 2003.) Identical twins possess 100% of each other’s DNA, as they develop from the same zygote, men and women share over 99% of DNA. Small differences create entirely different outcomes in disease and humans response to medical treatment.

These differences expand to an ocean of genetic diversity when comparing humans to chimpanzees, of who possess the estimated 98% genetic similarity. Scientists who argue for continued medical testing involving chimpanzees do so with the rational that they are the closest genetic relatives to humans. Today, medical and scientific research has progressed to the level of which small genetic variations make the possibility of accurate results similarly minute.

Advocates for continued testing link chimpanzee research to successes in AIDS research/ treatment, hepatitis and cancer therapies, but the ratio of failure is high and alternative methods have succeeded,
  • Despite decades of chimpanzee research, there is still no HIV cure or vaccine effective in humans. HIV does not infect or interact with the chimpanzee physiology with the same behavior as human—chimps can carry the virus, but in research have not progressed into AIDS. Animal models continue to hider the future of vaccine development.
  • AZT, the first treatment for AIDS, synthesized in-vitro in 1964 as an anti-cancer treatment, proved ineffective in humans (after showing promise in animal cancer-studies) until another in-vitro study in 1986 showed it effectiveness as an anti-retroviral in HIV. With this in-vitro research and bypassing animal models, AZT moved directly to human trials. Seven months later, the NIH recommended AZT use to treat AIDS in the public.
  • In 1985, protease inhibitors developed using computer and in-vitro models, also bypassing animal-models, proceeding directly to human trials.
  • In hepatitis research, the principle explanation for the use of chimpanzees is that they are the only non-humans capable of carrying the hepatitis virus—not unlike their ability to carry HIV. The hepatitis virus does not affect liver enzymes in chimpanzees, and does not lead to liver disease. The use of chimpanzees as carriers of the virus, due to the inability to develop a hepatitis cell-culture, is no longer necessary. In 2005, Rockefeller University developed the first hepatitis viral strain created in cell-culture, allowing study of the hepatitis virus progression in human context.

In January of 2010, a study published in Nature revealed previously unknown differences between humans and chimpanzee at the genetic level. The chimpanzee contains a 44% larger density of genes in the male-specific regions of the Y-chromosome. Until 2010, the chimpanzee DNA had not been fully sequenced, and thus, the assessment of 98% likeness to human DNA was made without the ability to “see” chimp DNA in its entirety. This is not unlike judging whether currency is counterfeit or genuine based strictly upon whether it “looks right.” With the entire chimp DNA sequence revealed, an accurate comparison of their Y-chromosomal structure is possible.

The differences in chimpanzee Y-chromosomal structure are astounding—not only did this reveal a larger number of genes, but entirely different gene categories than humans (a little over 30 %.) Genetic variations in humans who share over 99% of their DNA have innumerable outcomes—and yet the argument of chimps as necessary for medical advancement persists.

Medical and scientific advancement has revealed vast differences between human’s closest genetic relative. If there were to be an instance of a non-human genetic relative responding to research that so benefits humankind, sufficient to outweigh its ethical implications, the chimpanzee would be such an example. However, chimpanzee research is expensive, inadequate, and unjustifiable for its cruelty to, as Representative Roscoe states, “these magnificent and innocent animals.”

To do more to support Representative Roscoe’s bill, H.R. 1531, which is currently in the House Subcommittee of Health, contact your local representative.

The study in Nature (“Chimpanzee and human Y chromosomes are remarkably divergent in stru...,”) is fascinating! The abstract is available to the public, but feel free to write to for a PDF version of the study in its entirety.


Nathan Rivas at ThisDishisVeg
Nathan is a passionate animal advocate and vegan in the Seattle-area, and a contributor to This Dish is Veg.  He lives with his partner, Troy, and a band consisting of: a defiant dachshund, an ginormous Maine coon and a judgmental short-haired black cat. Nathan graduated with a Bachelors of Science (summa cum laude) from Northeastern University last spring, and is currently in his Masters of Science program.  Nathan is at any time, 17% coffee, a slave to his Kindle, and a lover of science and mathematics.  Twitter | Facebook.

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