So far life has been divided into three phases by biologists, which are: development, aging and late life. Now biologists have come up with a fourth stage, which they term as "death spiral". And new research has shown that there is a similarity in this fourth phase of life in fruit flies and humans.
Scientists claim that this fourth phase of life comes prior to death. The research was conducted on fruit flies and it's believed that details regarding the last stage of human life can also be traced with this research.
A website named yourgenome.com revealed that 75% of the ailment-causing genes in humans are present in fruit flies too.
"We believe this is part of the process of, basically, genetically programmed death," said Laurence Mueller, chair of the Department of Ecology and Evolutionary Biology at the University of California, Irvine, as reported by Live Science.
Various research conducted on fruit flies over the past decade by Mueller and other researchers, revealed that the spiral towards the death in fruit flies was observed by the drop in fecundity or reproductive rate.
A research was conducted in 2015 in which researchers detected that the first day a female fly laid no eggs began her journey towards death.
A decline in the reproductive rate acted as a crucial indicator towards the death of female fruit flies. The researchers came to a conclusion that whatever causes the death of these female fruit flies impacts their fecundity rate too.
Mueller stated that the timing of reduction in the reproductive rate of these fruit flies matches another previously conducted study.
"Relative to the average life span of a fruit fly, 10 days could be as much as a third of a fly's life," Mueller stated, as reported by Live Science.
Research carried out in 2002 on a species of male Mediterranean fruit flies called medflies, revealed that the male fruit flies started lying upside down 16 days before their death; this was a potential indicator towards their death, as well as a reduction in fecundity rate.
Research was also conducted in which fruit flies, zebrafish and nematodes or roundworms, were analysed by researchers to figure out if the intestines of these species portrayed a rise in leakiness prior to their death. This leakiness is called permeability and researchers tested it by feeding food dye to these creatures. The reason behind using the food dye was to detect excess intestinal leakage as it would change the colour of the body of these creatures.
The colour of the fruit flies and zebrafish would change to blue whereas the colour of the nematodes would change to fluorescent green. It was concluded that the leakiness was a marker of death in all species. This research was reported by Scientific Reports, published on March 22.
Researchers are hoping that the findings about the death spiral in other organisms could help in revealing more about the decline taking place in humans just before their death.
A research from 2008, published in the journal, Proceedings of the National Academy of Science, about 'humans might experience spiral death too' was reviewed by Mueller and his colleagues.
This research was conducted on 2,262 Danes belonging to the age group of 92 to 100 years. The research was carried out from 1998 to 2005. The cognitive and physical scores of people who died in the first two years of the research was analysed and found to be remarkably lower than those who were still alive in 2005.
Ability to complete daily tasks such as eating and using the toilet, grip strength and exams which aided in calculating cognitive impairment were evaluated in this research.
According to Mueller, the death spiral in people is likely to be responsible for spiked disability prior to their death. The study subjects are being challenged for biological and ethical reasons, but analysing death spiral in other organisms could help scientists understand this phenomenon in humans.
According to Mueller, the next step in this research will likely be breeding fruit flies selectively in different groups based on the death spirals they face over different timespans.
"Once you create populations that are genetically different in that way, you can ask, 'What genes were changed in order to reduce the length of the death spiral?'" Mueller said.
"Researchers could use the knowledge about fruit flies and research on the human genome for similar genetic markers, as humans and fruit flies are genetically alike," he explained.
"The research isn't about stopping or even delaying death. Rather, it is as a way to improve people's quality of life when they are reaching the end, and potentially save immense amounts of money in end-of-life health care," Mueller told Live Science.
"Even if we don't affect when you die, we'd like to make you fully functional up to the day you die," he said further.