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• Posted April 5, 2026

What Sea Creatures Reveal About How Fast People Age

This is no ordinary fish story.

Researchers who videotaped every moment in the lives of 81 African turquoise killfish gleaned intriguing insights into the aging process that may also apply to humans.

Though killfish live just four to eight months, they share important biological features with people, including a complex brain. That makes them a valuable model for studying aging, according to geneticist Anne Brunet, whose Stanford University lab collaborated on the study. 

By monitoring killfish 24/7, researchers found that simple habits in midlife, like staying active and sleeping, can predict lifespan.

Fish that stayed active and slept mostly at night tended to live longer, while those who slowed down lived shorter lives, the study found.

"Behavior is a wonderfully integrated readout, reflecting what’s happening across the brain and body," Brunet said in a news release. "Molecular markers are essential, but they capture only slices of biology. With behavior, you see the whole organism, continuously and non-invasively."

The study — recently published in the journal Science — found that aging didn’t happen in a neat or smooth fashion. Instead, there were sudden leaps between stages, researchers found.

They said the findings suggest that using wearable devices to track everyday behaviors like movement and sleep could provide valuable insight into the human aging process.

Typically, studies of aging compare young animals to older ones. Though useful, this can miss how individuals age over time and how differences among them arise, researchers pointed out.

Lead authors Claire Bedbrook and Ravi Nath wanted to follow aging across a lifetime.

The reason: Even when they are raised under nearly identical conditions, animals age differently and have very different lifespans. Researchers wondered whether natural behavior could reveal when the differences kick in.

For the study, they rigged up an automated system in which each fish was under constant video surveillance in its own tank. Frame by frame, researchers were able to analyze the animals’ posture, speed, rest and movement.

In all, the basic elements of how they moved and rested broke down into 100 brief, repeating actions.

By 70 to 100 days of age — early midlife — fish that would have shorter or longer lives were already behaving differently, the videos revealed.

Those who would have shorter lives tended to sleep increasingly during the day. Those who lived longer slept mostly at night.

Those destined for longer lives also swam faster and more vigorously and were more active during the day. Researchers noted that this type of spontaneous movement has been linked to longevity in other species, too.

And, the study found, only a few days of behavior data from middle-aged fish were needed to estimate life-span.

"Behavioral changes pretty early on in life are telling us about future health and future lifespan," Bedbrook said in a news release.

The study also revealed that aging doesn’t happen in a steady fashion.

Most fish had two to six rapid shifts in behavior, each lasting a few days, followed by longer periods of stability. 

"We expected aging to be a slow, gradual process," Bedbrook said. "Instead, animals stay stable for long periods and then transition very quickly into a new stage."

This meshes with studies in people, which suggest that molecular changes in aging occur in waves. Researchers compared it to a Jenga tower, where many blocks can be removed with little effect until one critical change triggers a sudden shift.

"Behavior turns out to be an incredible sensitive readout of aging," Nath said. "You can look at two animals at the same chronological age and see from their behavior alone that they’re aging very differently."

Bedbrook and Nash plan to continue this work as they establish labs at Princeton University later this year, with an aim to uncovering new ways to support healthier, longer lives.

The study was supported by the Knight Initiative for Brain Resilience between the labs of Brune and Dr. Karl Deisseroth.

More information

The University of Florida College of Medicine details five factors affecting how people age.

SOURCE: Stanford University, news release, March 26, 2026