London: The inner clock that regulates the behaviour of all life forms has existed for millions of years - unchanged.
The finding could shed light on a range of human conditions such as depression, cancer and diabetes and provide relief to workers such as pilots or nurses who do odd hours.
The studies from the Universities of Cambridge and Edinburgh examined the circadian clock which controls patterns of seasonal activity in everything from sleep cycles to butterfly migration, a newspaper reported.
The first study, led by Cambridge University scientist Akhilesh Reddy, found that red blood cells (RBCs) have a 24-hour rhythm, according to a Cambridge statement.
The second study found a similar 24-hour cycle in marine algae suggesting that internal body clocks have always been important, even for ancient forms of life.
Scientists had previously thought the circadian clock was driven by gene activity, but both the algae and the RBCs kept time without it, meaning other factors were at play.
Akhilesh Reddy, neuroscientist with Cambridge, said: "The implications of this for health are manifold. We already know that disrupted clocks - for example, caused by shift-work and jet-lag - are associated with metabolic disorders such as diabetes, mental health problems and even cancer.
"By furthering our knowledge of how the 24-hour clock in cells works, we hope that the links to these disorders - and others - will be made clearer."
Prof Andrew Millar of the University of Edinburgh`s School of Biological Sciences, who led the second study, added: "This ground-breaking research shows that body clocks are ancient mechanisms that have stayed with us through a billion years of evolution.
"They must be far more important and sophisticated than we previously realised."