The original biological timepiece may not have resembled the precision body clocks that scientists study today.
Just as Rolex, Timex, Swatch and Seiko make their own versions of a wristwatch, organisms including cyanobacteria, fungi, plants and insects have all invented their own varieties of circadian clocks.
There’s no doubt that today’s circadian clocks are must-have accessories for most organisms living on Earth’s surface. Some of the same protein cogs that drive the circadian clocks are also involved in DNA repair, further solidifying the connection.
Several lines of evidence argue against flight from light as the common force propelling the evolution of circadian clocks, says O’Neill, one of the scientists rewriting the circadian clock origin story.
Circadian rhythms can happen in a test tube without DNA. A type of cyanobacteria, or blue-green algae, known as Synechococcus elongatus has one of the simplest known circadian clocks.
The finding shook up circadian researchers because it showed that clocks can operate without DNA. It also revealed that they don’t need to switch messenger RNA and protein production on and off to keep time.