Removing the appendix could reduce the risk of Parkinson's disease (PD), research has suggested.
Its importance to the human body - if any - has long been the subject of speculation, but now scientists believe the tiny organ could be a contributor to the onset of the neurodegenerative disease.
A study of more than a million people found removing the appendix could be linked to a 20% decrease in the condition.
Researchers with the American Association for the Advancement of Science investigated the connection between Parkinson's and the appendix, which has been shown to act as a reservoir for the protein alpha-synuclein which collects in the brains of patients with PD.
They studied an epidemiological dataset containing demographic information and PD statistics on 1.6 million people in Sweden, and found that appendectomy - the procedure to remove the appendix - reduced the overall risk of developing PD by 19.3%.
Analysis of a second dataset of 849 PD patients revealed that appendectomy was associated with a delayed onset of PD by an average of 3.6 years later in life.
But removal of the appendix after the disease process starts had no effect on disease progression.
"Our results point to the appendix as a site of origin for Parkinson's and provide a path forward for devising new treatment strategies that leverage the gastrointestinal tract's role in the development of the disease," said Dr Viviane Labrie, senior author and assistant professor at Van Andel Research Institute.
"Despite having a reputation as largely unnecessary, the appendix actually plays a major part in our immune systems, in regulating the makeup of our gut bacteria and now, as shown by our work, in Parkinson's disease."
Around 9,000 people in Ireland are thought to have PD, according to the Parkinson's Association of Ireland, with one in every twenty of those under 40.
The research was published in the Science Translational Medicine journal.
The findings build on previous research indicating that for some patients Parkinson's starts in the gut.
But experts say removing the organ is unlikely to eliminate the illness as it could also start its onset in other parts of the body or in the brain.
New therapy could potentially stop progression of PD
Meanwhile, a new therapy has been developed by scientists at Irish based company Inflazome, Trinity College Dublin and in Australia which has the potential to stop the progression of PD.
A small molecule known as MCC950 worked to effectively cool the brain of a disease sufferer in a number of animal models, preventing the loss of brain cells, researchers said.
University of Queensland scientists hope human clinical trials of the molecule, which has so far only been tested on mice, can begin in 2020.
Associate Professor Trent Woodruff said: "The disease is characterised by the loss of brain cells that produce dopamine, which is a chemical that co-ordinates motor control, and is accompanied by chronic inflammation in the brain.
"We found a key immune system target, called the NLRP3 inflammasome, lights up in Parkinson's patients, with signals found in the brain and even in the blood.
"MCC950, given orally once a day, blocked NLRP3 activation in the brain and prevented the loss of brain cells, resulting in markedly improved motor function."
Professor Matt Cooper, chief executive of Inflazome, said current therapies focus on managing symptoms rather than stopping the disease.
"We have taken an alternative approach by focusing on immune cells in the brain called microglia that can clear these toxic proteins," he said.
"With diseases of ageing such as Parkinson's, our immune system can become over-activated, with microglia causing inflammation and damage to the brain.
"MCC950 effectively 'cooled the brains on fire', turning down microglial inflammatory activity, and allowing neurons to function normally."
The study, also published in Science Translational Medicine, was supported by The Michael J Fox Foundation for Parkinson's Research and Shake it Up Australia Foundation.