Perrin Davidson is a scientist, a bluegrass banjo player, and - at his core - a builder.
He spent his youth roaming around his family's farm just outside of Freeport, Maine, a small coastal community near Portland. Although the town is close enough to the city to feel connected, he recalls a childhood filled with memories and adventures that felt worlds apart.
Both of Davidson's parents figure prominently in those singular experiences. Davidson's mother, a painter and creative, helped build and care for the farm, ran the milk delivery business, and made the goods they sold. "She's really an incredible woman," he says.
Alongside her, Davidson's father was integral to all of it. A carpenter by trade, he built the farm's barns himself. Yet his interests and talents go way beyond that title. He once converted a dilapidated World War II-era ambulance into a milk delivery truck. Although the farm has been sold, he now owns Maine Craft Distilling, which produces spirits, canned cocktails, and agricultural beverages, and he manufactures some textile products in his free time.
As a kid, Davidson tinkered alongside his dad. When he was 5 or 6, they milled aluminum themselves and used it to build a miniature steam engine. They did the same with a vertical wind turbine. These projects, Davidson recalls, were never just about building; they were about energy, sustainability, and how to remake the systems around you.
"My dad is a true Renaissance man and a very smart individual," Davidson says. "He passed on that interest in me - in building. I build less physical things than he does. I build ideas."
From early on, those experiences shaped Davidson into someone curious not just about how the world works and why, but about how to understand a system well enough to improve it.
Now, in his day-to-day research in the MIT Department of Earth, Atmospheric and Planetary Sciences, Davidson gets to chip away at his long-held childhood interests. His theoretical work on the carbon cycle explores the powerful mechanisms that keep our planet habitable.
Davidson analyzes microscopic shifts in the ratios of carbon and oxygen isotopes in ancient oceanic sediments to understand the impact of disturbances on global environment systems. Photo: Gretchen Ertl
Understanding How the Earth “Damps”
Davidson's approach is theoretical in that he works with equations, rather than with the massive simulation models commonly used in climate science. "Theory can be a picture," he says. "It doesn't have to be a complicated model or the most high-precision number in the world." Rather than simulate every variable in Earth's climate system, Davidson's goal is to find simple mathematical descriptions of how a system behaves and validate them.
His recent research centers around one such description: identifying the fundamental features of global environment systems that allow the Earth to respond to disturbances - for example, lurching global temperatures, or changes in carbon concentrations in the oceans and atmosphere - across timescales, while remaining apparently stable. In physics, this tendency to return to a steady state after a push is called "damping." Davidson, in essence, is trying to better understand how the Earth damps.
To do this, he relies on the Earth's natural chemical fingerprints preserved in ancient oceanic sediments. He examines microscopic shifts in the ratios of carbon and oxygen isotopes following disturbances to formulate working theories for how the system responds.
The key driver of his recent work is the insight that the system's damping mechanisms appear to be scale-invariant. Whether you zoom in on processes occurring across thousands of years or zoom out to millions of years, the same basic principles apply.
"What we're positing," Davidson says, "is that all of these different time scales, the rate at which fluctuations are damped, saturates. The dominant damping mechanism saturates."
Because the rate of damping hits a ceiling, rather than the fluctuations themselves, the system can explore a wider range of extreme events than conventional models predict: A 100-year flood event, in this framework, may occur far more frequently. Davidson argues that understanding this saturating damping mechanism is crucial to understanding how Earth has maintained the conditions necessary for sustaining life.
From Bluegrass to MIT
Davidson came to MIT through somewhat unconventional means. His first virtual interview with his now-advisor, Professor Daniel Rothman, did not go the way he expected: Davidson had mistakenly submitted the wrong CV, one that included a section about his deep musical roots, particularly bluegrass.
He started playing music at 4. By 8, he'd become enamored by the banjo after hearing a local bluegrass band play at a barn party hosted on his family's farm. Soon after, Davidson was playing gigs with his band at local bars and festivals throughout New England, earning enough to call it his middle- and high-school job. At 13, he traveled to China to play at the country's international youth cultural festival. He was even offered a scholarship to the Berklee College of Music. Instead, he decided to attend the University of Chicago, where he studied math and physics.
The advice he received at the time was incisive: "You can always play the banjo, but you can make money too." He laughs. "Clearly, I've chosen a very lucrative path."
During that initial interview about an MIT PhD program, Rothman commented on the pegheads of a banjo and guitar subtly sticking up in the background of Davidson's apartment.
"The only thing that we talked about was music," Davidson recalls. "Science was kind of by-the-by. And then, by the end of it, he said, 'You'll be hearing from me.' And that was it."
Years later, it's clear that Davidson's addition to Rothman's research group has been productive for both of them.
"Perrin's thesis uses tools and concepts of statistical physics to reveal how the carbon cycle works. Very few students have the ability to combine such disparate fields," says Davidson's advisor, Professor Daniel Rothman. Photo: Gretchen Ertl
Rothman values Perrin's unusual preparation for graduate work, which includes research expertise in chemical oceanography, as well as his math and physics background. "Perrin's thesis uses tools and concepts of statistical physics to reveal how the carbon cycle works. Very few students have the ability to combine such disparate fields," Rothman says.
He also cites Perrin's creativity and imagination to make connections. "But there's an added ingredient here," he notes. "Perrin approaches his work with a certain humility, and an innate understanding that progress comes from an interest in learning from others and a willingness to make small steps as one seeks deeper results. And his results have indeed been profound."
In parallel, Davidson appreciates the kind of concentrated attention he receives from Rothman. "It's really a mentoring relationship," he says. "My dad's a carpenter, I'm an apprentice. I'm constantly learning how to do things. And Dan is giving me the time to do that."
In addition to their research partnership, Davidson and Rothman play music together almost weekly. They have even formed a band with two of their colleagues. "I lost playing music when I was in college," Davidson says. He's thankful MIT has afforded him time to pursue both his bluegrass roots and scientific interests.
Scaling Down to the Microbial Level
As Davidson wraps up his PhD, he is naturally thinking about next steps. He believes his academic future may lie at the cellular scale of the processes he has so far only studied at the systems level - and that the tools he has built to understand climate on geological timescales can be scaled down.
The scale-invariant nature of his climate work suggests the same damping mechanisms may also operate in microbial cells living in extreme, energy-starved conditions - populations that, by some accounts, have persisted for tens of millions of years with little to no energy input, even as individual organisms turn over.
Understanding microbial persistence in those conditions, Davidson says, is a question of deep personal curiosity, with implications ranging from combating climate-caused biodiversity loss to antibiotic resistance.
Davidson seems to be in no hurry to figure out exactly what comes next. For now, he is content to keep focusing what comes naturally to him: building ideas.