Modern conventions such as work and school schedules dictate the daily lives of city dwellers. But a new study shows that sunrise and sunset still influence urban activity.
Like many other organisms, humans have an internal biological clock that helps them adapt to different environmental cues, such as light and darkness. In modern cities, people also must adhere to a social clock of daily activities, including professional duties, leisure time, and schooling.
“How does the daily rhythm of humans pan out under the simultaneous ticking of these two clocks?” asked Daniel Monsivais of Aalto University School of Science, Finland, who led the new study.
Monsivais’ team tracked cell phone use for about 1 million people living in the same time zone in southern Europe over the course of one year. They obtained anonymous records of call times for each person and inferred their individual sleep/wake cycles by noting daily periods when calling activity started and stopped.
The call records revealed that, despite a shared time zone, the timing of sunrise and sunset at people’s respective longitudes still guided the start and end of their daily activities. Over one year, changes in the timing of daily activities corresponded to seasonal variations in the timing of sunrise and sunset.
These findings could have implications for human health, the economy, power consumption, and public transportation—all of which are influenced by the timing of human activity.
“The next step in our study is to use this type of big data approach to understand the difference in behavior between urban and rural populations, as it pertains to the role of social and biological clocks in their daily routines,” Monsivais says.
Monsivais D, Ghosh A, Bhattacharya K, Dunbar RIM, Kaski K (2017) Tracking urban human activity from mobile phone calling patterns. PLoS Comput Biol 13(11): e1005824.
Sunrise by Daniel Monsivais