A battle line has been drawn in one of the most controversial scientific disputes of our time, with prominent researchers from around the world taking sides over the issue of using nonhuman primates for neuroscience experiments.

The topic of animal testing has always been hugely divisive, and as we continue to develop our understanding of the cognitive and emotional capacities of some of our closest evolutionary relatives – as well as how they can help us to alleviate the suffering of millions of humans – scientists are divided over where to draw the line between improving our own healthcare and protecting the welfare of other primates.

The blue touchpaper was lit earlier this month when an international group of 21 scientists including David Attenborough published an open letter in The Independent calling for the bodies that fund and license neuroscience research on primates to bring an end to the practice, due to the suffering this causes the animals. In particular, they criticize those experiments that involve “fluid deprivation and movement restraint.”

However, a response has now appeared in the form of another open letter, this time published in The Guardian and signed by some 400 researchers. While the authors insists that “the use of primates [in neurological research] is not taken lightly,” they maintain that the benefits that these experiments bring to mankind outweigh the harm caused to the animals involved.

^{Nonhuman primates have been used in scientific research for many years, although as attitudes change many are calling for an end to the practice. Everett Collection/Shutterstock}

“We, the undersigned, believe that if we are to effectively combat the scourge of neurodegenerative and other crippling diseases, we will require the careful and considered use of nonhuman primates,” state the signatories.

For instance, they point out that experiments conducted on a few hundred monkeys in the 1980s and 90s led to the development of deep brain stimulation surgery, which has helped to alleviate the symptoms of over 200,000 Parkinson’s disease sufferers.

Yet those who oppose the use of these animals will be hard to convince. Among them is Sir David Attenborough, who told The Independent that many non-human primates “have mental lives comparable to ours, and sensitivities, and pain and deprivation mean things to them, just as they mean things to us.” This knowledge, he says, “has transformed our attitude, or should have transformed our attitude, to using them for our own benefit.”

Similarly, renowned primatologist Jane Goodall said: “I can state categorically that [chimpanzees] have a similar capacity for suffering, both mental and physical, and show similar emotions to many of ours.” She therefore labelled all experiments involving these apes as “inhumane”.

The thrust of the opposition to the use of primates is derived from a study published in the journal Alternative to Laboratory Animals, which concluded recent advancements in brain imaging techniques, such as MRI and electrocorticography, mean that we can now safely use human brains for this research, thereby “rendering nonhuman primates approaches redundant.”

^{Many species of non-human primate have been shown to be highly emotionally intelligent. Bokeh Blur Background Subject/Shutterstock}

In contrast, those who support the continued use of these animals claim that there are some hugely necessary experiments that can only be conducted on nonhuman primates. For instance, Sir Colin Blakemore, who signed the open letter defending animal testing, told The Guardian that “in the past year alone, research on monkeys has helped efforts to create new vaccines and treatments for Ebola, Zika and Aids.”

Naturally, the signatories of the letter accept that efforts must be made to reduce the suffering of all research animals, writing that “given that primates are intelligent and sensitive animals, such research requires a higher level of ethical justification. The scientific community continues to work together to minimize the suffering of primates wherever possible. We welcome the worldwide effort to replace, refine and reduce the use of primates in research.”