The rhythms of life–biological clocks and a new season

We’re almost midway through the semester at my university. It’s a busy time for students and professors alike: assignments, exams, and projects seem to pile up… and so we all anticipate a few days of welcome respite during the upcoming fall break. Meanwhile, the days shorten, the leaves fall, the insects quiet down, and festive celebrations of autumn pop up across the city. These familiar rhythms provide a predictable framework for moving through the year, both in the academic and astronomical senses.

The changing of the seasons, the rising and setting of the sun, the moon’s gravity and phases: environmental rhythms such as these guide the metabolism and behavior of many different types of species. Daily, or circadian, rhythms are perhaps the most well understood. These biological events, following a roughly 24-hour cycle that is calibrated by light, help keep cells and organisms functioning in harmonious rhythm each day. It’s easy to experience times when our own bodies’ rhythms feel out of synch: jet lag, early school start times for night-owl teens, the winter blues of seasonal affective disorder, the phone screen that may disrupt your sleep, among others. Scientists have been busy exploring the rhythms of humans: sleep, hormones, organ function, metabolism, and so much more. They’re even studying circadian rhythms in space. The human brain uses light detected by the eyes to set (and reset) tiny molecular clockwork in the brain and throughout the body. Many of these molecular processes are similar in very different organisms. It’s a fascinating topic with seemingly endless questions and applications.

The Nobel Prize in Medicine was awarded this week to three researchers—Jeffrey Hall, Michael Rosbash, and Michael Young—who helped discover some of the key molecules of biological clocks. Using fruit flies as a model organism, they were able to identify genes and the proteins they encode that provide the steady oscillation that ticks away in the cells of many organisms, including our own. Circadian rhythm research isn’t a new field of study; researchers have been studying the curious rhythms of life in plants and animals for centuries. Karl von Frisch, famous for deciphering the “waggle dance” of bees, which helps bees communicate and navigate to food sources, was an early investigator of circadian rhythms. But by pinpointing the molecular apparatus of the clocks themselves, the Nobel winners and their many collaborators and successors have opened our eyes to the intricacies of these systems across life’s diversity.

Mimosa plant

Mimosa plants fold up their leaves at night. Their daily rhythms were first studied in the 1700s! By Abubiju – Own work, CC0,

A few years ago, I chose circadian rhythms as a topic for a senior seminar course I was teaching. I’m not an expert in this field–far from it. But I was drawn to the theme out of personal curiosity and the hope that any student, no matter what their area of interest in biology was, could find something intriguing to explore in their independent investigations into the published scientific literature in this area. It’s an amazingly interdisciplinary topic. I got to learn right alongside my students as we explored questions about bacteria, fungi, bees, plants, human biology, molecular biology, biochemistry, human medicine, and behavioral ecology, among other topics. I’ve become a big fan of these ubiquitous circadian rhythms, and I’m glad some of the pioneers in the field are being recognized for their contributions.

The Nobel Prizes in areas of science traditionally honor a person or persons who have done outstanding work in their field that sets them apart from the rest. It’s seemingly becoming more and more difficult to choose a seminal figure in science for these awards, as the highly specialized and technical work of many areas of science is carried out by extensive teams of collaborators, and as new findings build on the ever-widening scaffolding of prior knowledge. Some observers have also raised questions about the fairness of the selection, or its representation of gender, geography, or other factors. But at its heart, by highlighting exciting topics each year, the Nobel Prizes provide us with an opportunity to ponder breakthrough ideas that change how we think about our world. Learning and teaching about circadian rhythms has certainly been a topic that has changed how I think about the world. Everywhere I look, I see evidence of the influence of the rhythms that makes us tick. Each day and each season, we participate in the rhythms of life.


Further reading:

Bilder, D. 2017. “Another Nobel Prize for the fruit fly.”

Callaway, E and Ledford, H. 2017. “Medicine Nobel awarded for work on circadian clocks.”

Foster, R. and Kreitzman, L. 2005. Rhythms of Life: The Biological Clocks that Control the Daily Lives of Every Living Thing

Fox, M. 2017. “Body clock researchers win Nobel Prize.”

National Institute of General Medical Sciences. “Circadian rhythms fact sheet.”

ScienceBlogs. 2008. “Clock classics: It all started with the plants.”

Yong, E. 2017. “The absurdity of the Nobel Prizes in science.”



4 thoughts on “The rhythms of life–biological clocks and a new season

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