Opinion - Medical journals critical

  Animal Experiments Scrutinized:  

New Studies Yield Disturbing Evidence


Two respected scientific journals have recently published disturbing new evidence demonstrating that:


1.       Animal experiments are not generally useful in contributing toward advancements in human healthcare, or predictions of human toxicity; and,


2.       Despite most closely modeling human beings, chimpanzee experiments have contributed minimally toward the development of cures for human diseases.


The evidence provided by these controversial new studies is strongly contrary to more traditional scientific opinion that animal experiments are essential during the development of cures for human diseases. Although opinions have been passionately expressed on both sides of the debate, hard evidence about the merits of animal experimentation for these purposes has generally been lacking, until now.

Stated study author, London-based veterinary scientist Andrew Knight: “These combined results from thousands of animal experiments[1] prove they rarely, if ever, contribute toward advances in human healthcare. Furthermore, they do not reliably predict human toxicity. Continuing to rely on animal models in denial of scientific evidence of such strength risks human lives.”

Experiments on chimpanzees have proven particularly controversial. Their advanced sensory, cognitive, communicative and social abilities confer upon them a profound ability to suffer when born into unnatural captive environments, or captured from the wild—as many older research chimpanzees once were—and when subsequently subjected to confinement, social disruption, and involuntary participation in potentially harmful biomedical research. Significant public concern has already led to legislative or policy bans on great ape experimentation in seven European countries and New Zealand, and the US is now almost completely isolated internationally, in continuing chimpanzee experimentation.

Stated Dr Knight: “None of the chimpanzee experiments examined made an essential contribution, or, in most cases, a significant contribution of any kind, toward the development of human medical techniques. The approval of large numbers of experiments of such dubious scientific merit demonstrates a widespread failure of the ethics committee system. Chimpanzee experiments should be banned in those very few remaining countries—notably the US—that persist in conducting them.”


STUDIES (available on request)

1.                    Knight A. Systematic reviews of animal experiments demonstrate poor human clinical and toxicological utility. ATLA: Alternatives to Laboratory Animals 2007;35(6):641-659. ,

2.                    Knight A. The poor contribution of chimpanzee experiments to biomedical progress. Journal of Applied Animal Welfare Science 2007;10(4):281-308. .


In September 2007, such issues were thrown into sharp relief by the signature of 433 Members of the European Parliament—a rarely precedented total—of Parliamentary Written Declaration 40/2007, which calls for urgent action to end the use of great apes and wild-caught monkeys in experiments, and for the establishment of a timetable for the cessation of all European primate experiments. Of particular significance, the Declaration calls for these measures to be taken into consideration during the formal revision of Directive 86/609/EEC on the Protection of Animals used for Experimental and other Scientific Purposes, which presently allows experiments on all non-human primates.


The decreasing use of chimpanzees within biomedical research within the US—by far the leading global user—is increasingly the subject of debate, as evidenced by several recent articles in leading scientific journals such as Science and Nature. Fuel was recently added to this fire by a 2007 US National Institutes of Health National Center for Research Resources decision to make permanent a funding moratorium on chimpanzee breeding. This decision may very well signal the beginning of the end of chimpanzee experimentation within the US, and thereafter, worldwide.


Stated Dr Knight: “Because these studies examine very large numbers of animal experiments, selected systematically using randomization or similar means, and because they have been conducted to a standard sufficient to achieve publication in peer-reviewed scientific journals, they provide the strongest scientific evidence about the human utility of animal models that is available to date. They clearly demonstrate that animal experiments contribute little toward advances in human healthcare, and predictions of human toxicity. Given their generally substantial animal welfare and financial costs, this evidence provides a strong case for ending animal experimentation in favor of methods able to deliver advances in human healthcare with considerably greater efficiency, such as lifestyle improvement and education, preventative healthcare, and the non-animal research methods techniques that featured prominently during the development of human medical techniques highlighted within these studies.”


The abstracts of these studies are provided below. Abstracts and some complete texts of related systematic reviews of animal experiments are freely downloadable from www.AnimalExperiments.info.



Knight A. Systematic reviews of animal experiments demonstrate poor human clinical and toxicological utility. ATLA: Alternatives to Laboratory Animals 2007;35(6):641-659.

The assumption that animal models are reasonably predictive of human outcomes provides the basis for their widespread use in toxicity testing and in biomedical research aimed at developing cures for human diseases. To investigate the validity of this assumption, the comprehensive Scopus biomedical bibliographic databases were searched for published systematic reviews of the human clinical or toxicological utility of animal experiments. In 20 reviews in which clinical utility was examined, the authors concluded that animal models were either significantly useful in contributing to the development of clinical interventions, or were substantially consistent with clinical outcomes, in only two cases, one of which was contentious. These included reviews of the clinical utility of experiments expected by ethics committees to lead to medical advances, of highly-cited experiments published in major journals, and of chimpanzee experiments—those involving the species considered most likely to be predictive of human outcomes. Seven additional reviews failed to clearly demonstrate utility in predicting human toxicological outcomes, such as carcinogenicity and teratogenicity. Consequently, animal data may not generally be assumed to be substantially useful for these purposes. Possible causes include interspecies differences, the distortion of outcomes arising from experimental environments and protocols, and the poor methodological quality of many animal experiments, which was evident in at least 11 reviews. No reviews existed in which the majority of animal experiments were of good methodological quality. Whilst the effects of some of these problems might be minimised with concerted effort (given their widespread prevalence), the limitations resulting from interspecies differences are likely to be technically and theoretically impossible to overcome. Non-animal models are generally required to pass formal scientific validation prior to their regulatory acceptance. In contrast, animal models are simply assumed to be predictive of human outcomes. These results demonstrate the invalidity of such assumptions. The consistent application of formal validation studies to all test models is clearly warranted, regardless of their animal, non-animal, historical, contemporary or possible future status. Likely benefits would include, the greater selection of models truly predictive of human outcomes, increased safety of people exposed to chemicals that have passed toxicity tests, increased efficiency during the development of human pharmaceuticals and other therapeutic interventions, and decreased wastage of animal, personnel and financial resources. The poor human clinical and toxicological utility of most animal models for which data exists, in conjunction with their generally substantial animal welfare and economic costs, justify a ban on animal models lacking scientific data clearly establishing their human predictivity or utility.


Knight A. The poor contribution of chimpanzee experiments to biomedical progress. J Appl Anim Welf Sci 2007;10(4):281-308.

Biomedical research on captive chimpanzees incurs substantial nonhuman animal welfare, ethical, and financial costs that advocates claim result in substantial advancements in biomedical knowledge. However, demonstrating minimal contribution toward the advancement of biomedical knowledge generally, subsequent papers did not cite 49.5% (47/95), of 95 experiments randomly selected from a population of 749 published worldwide between 1995 and 2004. Only 14.7% (14/95) were cited by 27 papers that abstracts indicated described well-developed methods for combating human diseases. However, detailed examination of these medical papers revealed that in vitro studies, human clinical and epidemiological studies, molecular assays and methods, and genomic studies contributed most to their development. No chimpanzee study made an essential contribution, or, in most cases, a significant contribution of any kind, to the development of the medical method described. The approval of these experiments indicates a failure of the ethics committee system. The demonstrable lack of benefit of most chimpanzee experimentation and its profound animal welfare and bioethical costs indicate that a ban is warranted in those remaining countries—notably the United States—that continue to conduct it.


Dr Andrew Knight

Director, Animal Consultants International

               Multi-disciplinary expertise for animal issues



ph: +44-(0)7876436631

London, UK