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Fruit flies anomaly in the evolutionary theory of aging 0

Ashleigh Gehl/Kingston This Week

Adam Chippindale is an associate professor in the Biology department at Queen's University.

Adam Chippindale is an associate professor in the Biology department at Queen's University.

Twenty years ago Adam Chippindale, a Queen’s University biology professor, researched the evolution of aging in fruit flies.

At the time, he was a PhD student at the University of California, Irvine, working in the lab of renowned evolutionary biologist Michael Rose.

Today, the tables have turned.

Chippindale has his own lab at Queen’s and PhD student, Chris Kimber, under his wing. Kimber revisited Chippindale’s research and conducted similar experiments. The results were the same.

“You’ve got 35 days of lifespan for these little insects,” said Chippindale. “You think they buzz around your kitchen and they only live a few days. We’re talking about 35 days of lifespan. That’s Methuselah.”

Surprised by what they found, these researchers consulted past records. Together they discovered an anomaly in the evolutionary theory of aging. After going through 30 years of data, they put this information into a single analysis and looked for evidence of lifespans being eroded.

“We thought it should be [eroding],” said Chippindale. “Maybe slowly, but it should be going down bit by bit, as the odd mutation does accumulate in the population that we’re studying. But there’s no evidence for that. It’s flat line. It’s stable. That really suggested to us that there must be a positive force here. That the steady erosion is not happening, so something must be keeping the genome clean.”

Using evolutionary techniques, a fruit fly can live three times its normal lifespan. It can also revolve to shorter ages of reproduction, causing the lifespan to fall.

“But what we found was at a certain point it stops going down,” he said. “There seems to be limit to how far we can reduce the lifespan of this organism. And we wanted to know why that limit exists.”

To understand this, they looked at the impact of mutation early in life and its impact for later life survival. That’s where they found a positive connection.

“Selection has been keeping those genomes very clean early in life and those genomes tend to have extended beneficial effects on individual survival,” he said. “Robust individuals seem to enjoy a greater lifespan. Robust individuals at an early age show an extended survivorship, whereas individuals that are weakened by mutations die faster.”

When it comes to studying the evolution and genetics of aging, the fruit fly is the insect of choice. Chippindale describes them as “a real workhorse.” They’ve been studied for over a hundred years, since the pioneering days of Thomas Hunt Morgan, a Nobel Prize winner who, in 1911, created the “Fly Room.” In this room, Morgan documented how the species changed over time.

“We know a lot about their ecology, their life habits,” said Chippindale. “We know how to maintain them very easily in the lab. They have rapid generation so we can easily measure total lifespan and reproductive output really easily. They make a great model system for people doing experiments on aging and how aging evolves.”

With the fruit fly’s “live fast, die young” lifespan, it’s living 30 days longer than necessary.

This research can be applied to humans when asking, why is evolution making an organism live longer than it needs to?

Evolutionarily speaking, humans have a long post-reproductive lifespan, perhaps living longer than needed. There are many reasons for this. Chippindale points to extended childcare. But with the fruit fly, once the egg is laid, that’s where parental care ends.

 

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