The human body clock is shaped by the weather as well as the changing seasons, according to scientists. Edit
The researchers said they hope their findings will help tackle problems experienced by people doing shift work and those affected by jet lag.
A team led by University of Edinburgh scientists used computer models to show how a person's internal clock is shaped by the seasons and the weather.
Carl Troein, of the University of Edinburgh's school of biological sciences, who carried out the study, said: "By better understanding why biological clocks are so complex, we stand a better chance of controlling them.
"Our study goes some way to explaining how and why these in-built rhythms have developed.
"We hope it will be useful in informing treatments for sleep disorders, as well as helping scientists develop crops that can survive in the long term."
Researchers created models of internal clocks and looked at how they worked in a variety of environments. They found that the biological timekeepers, known as circadian clocks, deal with the effects of varying amounts of light from hour to hour and day to day, as well as the changing seasons.
The findings give researchers a greater understanding of what drives the internal rhythms of people, animals and plants.
Environmental signals, such as hours of daylight, affect the daily rhythms which many plants use to control flowering and ripening. The research may also help scientists develop crops that can adapt to climate change.
The study involved researchers from the California Institute of Technology and University of Warwick and was funded by the Biotechnology And Biological Sciences Research Council and published in the scientific journal Current Biology.