Life, Death, and Fruit Flies

by Mike James

I read an interesting fruit fly study that got me thinking about how stress may impact humans. The study was conducted by Christi Gendron, a neurobiologist at the University of Michigan.

Gendron conducted a study on how living fruit flies respond to the sight of dead fruit flies. The research was published in the journal PLOS Biology. Apparently, neurons in the flies' brains make them age faster after seeing dead flies. Scientists believe this relates to perceptions within the brains of animals causing physical reactions in their bodies.

Dr. Gendron and Scott Pletcher, who is a biologist at the University of Michigan, discovered how flies deal with death unintentionally. They were trying to see whether flies would show a behavioral or physiological response, like a heightened immune system, after being around other flies that had been made sick with a disease. "The only types of responses we saw happened after the flies that we infected died," Dr. Pletcher said.

Flies that had seen dead flies were avoided by other flies as if they'd been marked by death (how this works is still a mystery). The flies that viewed the dead flies quickly lost stored fat and died sooner than flies not viewing their dead counterparts.

"Our lab has long been interested in how the brain controls aging," Dr. Pletcher said, so they decided to investigate how the sensory perception of dead flies was being translated into a shorter life for living flies.

The scientists placed living flies in vials with dead flies for two days and tracked their brain activity with a fluorescent green dye. Dissecting these death-exposed flies revealed activity in their body, which integrates sensory information in the brain.

Dr. Gendron and Dr. Pletcher then identified the key neurons in the body. When these were shut off, seeing dead flies did nothing to the life span of the living. When the researchers activated those neuron clusters, flies died sooner, even if they had never been exposed to dead flies.

"They show that a specific set of serotonin-receptor-possessing neurons are used" by living flies to perceive dead ones, said Marc Tatar, a biologist at Brown University who was not involved with the study. "That is the beauty of this paper."

It's not clear why seeing dead flies would cause those still alive to die sooner. One theory is that the shorter life span results from stress caused by perceiving death. Chronic stress in animals leads to health problems and shortens life spans, and flies have a stress response, too. "If we suddenly found ourselves in a sea of dead humans, that would be very stressful," Dr. Pletcher said.

After reading about this study, I thought about what we know about human health. Negative emotions can weaken your body's immune system. This makes you more likely to get colds and other infections during difficult times. Also, when you are feeling stressed, anxious, or upset, you may not take care of your health as well as you should. Many diseases (not all) can be impacted by stress on our bodies.

Another thought that came to mind is that religious people, according to some research data, appear to live longer than secular people. Could this be due to less stress for religious people (at least some religious people)?

Several studies have shown associations between attending religious services and living a long time. One of the most comprehensive published in JAMA Internal Medicine in 2016 found that women who went to any kind of religious service more than once a week had a 33 percent lower chance than their secular peers of dying during the 16-year study-follow-up period. Another study, published in 2017 in PLOS One, found that regular service attendance was linked to reductions in the body's stress responses and even in mortality—so much so that worshippers were 55 percent less likely to die during the up to 18-year follow-up period than people who didn't frequent a religious meeting location.

So what can we learn from all this? Those of us who believe in God need to rejoice in that belief and be joyful. We know when this life ends, it is not the end. There are religious people I've encountered who seem to exude negative thoughts and emotions.

Knowing God's truth should give us a positive outlook and attitude about life. This attitude and outlook may have an impact on your physical health. Most importantly, we will be following the admonition in God's Word: "Be glad in the Lord, and rejoice, O righteous, and shout for joy, all you upright in heart!" (Psalm 32:11).

"Rejoice in the Lord always; again I will say, rejoice" (Philippians 4:4).

Sources: "These Flies Age Faster After Witnessing Death," by Darren Incorvaia, The New York Times, June 14, 2023.

"Mind/Body Connection: How Your Emotions Affect Your Health," https://familydoctor.org/mindbody-connection-how-your-emotions-affect-your-health/#:~:text=Poor%20emotional%20health%20can%20weaken,as%20well%20as%20you%20should.

"You Asked: Do Religious People Live Longer?" by Jamie Ducharme, Time magazine, February 15, 2018, https://time.com/5159848/do-religious-people-live-longer/#:~:text=Another%20study%2C%20published%20last%20year,frequent%20the%20temple%2C%20church%20or