The Seasons Of You
BBC Earth|March - April 2021
The calendar year follows the pattern of spring, summer, autumn, winter. But perhaps it shouldn’t…
Susan D'Agostino

Ancient Egyptians identified three seasons based on cycles of the Nile River: inundation, emergence, and harvest. In tropical countries, it’s the rain that tends to divide the year in two: a wet and a dry season. Elsewhere the calendar demarcates four seasons: autumn, winter, spring, and summer.

But now, researchers at Stanford University have found that human biology, rather than rivers, rainfall, or calendars, could be used to determine the seasons. In their study, published in the journal Nature Communications in October 2020, the Stanford researchers discovered our bodies seem to set their own rhythm, splitting the year into two seasonal time periods. Or at least that’s the case if you live in California, where the study was carried out. Since every geographical location has unique environmental conditions, their approach may be used the count the seasons in other parts of the world too.

“People say there are four seasons of three months each. But why four? There could be 15 or could be 2. Why don’t we let biology tell us?” asks Prof Michael Snyder, principal investigator of the study.

To determine the human seasons, Snyder’s team profiled the biology of 105 volunteers in the San Francisco Bay area over a period of four years. They regularly sampled and measured tens of thousands of molecules and microbes from the participants’ blood, noses, and guts. This type of study is called ‘deep longitudinal multi-omics profiling’.

On sample days, the researchers also collected meteorological data (such as air temperature and solar radiation) and airborne pollen counts.

This massive effort was undertaken to create a better picture of how the changing seasons might be affecting our physiology and health.

MAKING SENSE OF THE SEASONS

After four years of testing poo, taking blood samples, and logging the weather, the team used powerful computational tools to try and find patterns between the volunteers’ biology and their environment. What they found surprised them.

There were two signals. One was a group of molecules that seemed to peak in December – a season the researchers dubbed late fall/early winter. This included markers related to immune responses such as the complement system, a collection of proteins that work together to eliminate infectious microorganisms, which peaked during this time. Unsurprisingly, this correlated with the period we know viral infections are also high. The second signal however did come as a surprise.

“I thought the other [season] would be in June or July when it’s pretty hot, but that wasn’t true,” Snyder says. Instead, the second season peaked in late April – a season they called ‘late spring’. This season’s peak made sense in hindsight, as late April also corresponded with a time of high pollen counts at the end of California’s rainy season. The pollen caused a reaction in a large enough subset of people to contribute to the seasonal peak in the immune response.

Continue reading your story on the app

Continue reading your story in the magazine

MORE STORIES FROM BBC EARTHView All

Who is Britain's greatest prime minister?

Three hundred years ago this month, Robert Walpole became Britain’s first PM. To mark this huge moment in political history, we asked five historians to nominate the 10 leaders who they believe accomplished most during their residency in Number 10

10+ mins read
BBC Earth
May - June 2021

HOW YOUR BRAIN CREATES REALITY

DO WE SEE THE WORLD AS IT REALLY IS, OR ARE WE CREATING OUR OWN REALITY? HERE, WE DELVE INTO THE NEUROSCIENCE BEHIND THE WORLD THAT WE EXPERIENCE

9 mins read
BBC Earth
May - June 2021

WASTE NOT, WANT NOT

MEET THE COMMUNITIES FORGING THE WAY TO ATRASH-FREE FUTURE, BY RESHAPING UNWANTED BY-PRODUCTS INTO VALUABLE RESOURCES

5 mins read
BBC Earth
May - June 2021

Inside the world's first airport for drones and flying cars

Plans to build the world’s first off-grid transport hub for drones and air-taxis have just received government funding. The Urban Air Port, located in Coventry, will offer flying electric vehicles a place to charge and load up. The project aims to lay the groundwork for a web of transport hubs that could provide a green, clean remedy to our cities’ groaning infrastructure. Daniel Bennett talks to Ricky Sandhu, the founder and CEO of Urban Air Port, to see if the idea could take off.

5 mins read
BBC Earth
May - June 2021

A SCIENTIST'S GUIDE TO LIFE - HOW TO GET FIT AT HOME

DUE TO THE CORONAVIRUS, MORE PEOPLE ARE EXERCISING INDOORS. THIS MONTH, WE ASK EXERCISE RESEARCHERS MATT COCKS AND KATIE HESKETH HOW TO GET FIT AT HOME

3 mins read
BBC Earth
May - June 2021

PUMAS IN THE PEAKS

Living secretive lives against the spectacular backdrop of Chile’s Torres del Paine, Patagonia’s pumas are proving a conservation success.

4 mins read
BBC Earth
May - June 2021

Living lightbulbs

From the ocean depths to remote rainforests, bioluminescent organisms light up the natural world. We take an illuminating look at the species that glow in the dark.

8 mins read
BBC Earth
May - June 2021

ALEXA, TELL ME A STORY

Dr Lara Martin wants to teach artificial intelligence how to tell a tale and tell it well. She reveals to Amy Barrett why we need to train machines how to be storytellers and what Dungeons & Dragons has to do with it all….

7 mins read
BBC Earth
May - June 2021

A UNIVERSE FULL OF SEE-THROUGH STARS

Mysterious discoveries around the globe have opened up a tantalising possibility: the cosmos could be full of ghostly stars that are invisible to our most sensitive detectors

9 mins read
BBC Earth
May - June 2021

A SAFE SPACE

Intrusive social media and online shouting matches have left people seeking the internet hideouts that allow them to be themselves

2 mins read
BBC Earth
May - June 2021