Biological Clocks and God’s Good Creation

One thing I find surprising, and more than a little amazing, is that even though so many wildly different types of living things have clocks, they all have many of the same basic parts. They all share pigments that detect light, a way to keep track of how long the light is present each day, and a method for knowing whether there was the same amount of light the day before. In insects, the group of animals that I use for my research, the circadian clock includes two interacting feedback loops that, in my opinion, are as intricate and awesome as any human designed timepiece.

Clocks are not included in the creation narrative, so we don’t know exactly when they first appeared. But scientists think clocks originated more than a hundred million years ago.

The mechanics of biological clocks

Proteins with names like Clock, Cycle, Timeless, Period, Clockwork Orange, and Takeout form complexes that work together in several interacting feedback loops. One thing I find really cool is that one complex of proteins, made up of Clock and Cycle, controls production of a second protein complex (Timeless and Period) that, in turn, regulates production of itself by interfering with the on/off switch for the first complex. There is also a light–sensing pigment that degrades the Timeless part of complex 2 when light is present and keeps it from interfering with the first complex. Together these protein complexes create an elaborate, repeated rhythm of protein production and degradation that marks the passing of time.

Examples of biological clocks

Diapause is a type of dormancy that is internally regulated by networks of hormones and proteins, including circadian and photoperiodic clocks. Diapause allows insects, and other animals, to survive seasons when food and water are limited, and temperatures are dangerously low. In many ways insect diapause is like hibernation in mammals, frogs, and turtles. Both types of dormancy include changes in energy use, increased protection against hostile environments, and other adaptations that allow them to survive until winter is over and the environment regains enough resources to sustain life.

A key difference between diapause and hibernation is that diapause begins well before winter starts in response to a cue, often a specific number of daylight hours in a 24-hour period, that tells each species that it is time to get ready for a change in the seasons. The amount of daylight is detected and processed by the circadian clock and its interaction with the photoperiodic timekeeper. Together these clocks send a signal from the brain to other parts of the body that, ultimately, leads to changes in physiology, like turning off processes that consume a lot of energy, like growth and reproduction, and ramping up production of protective chemicals that prevent ice formation and limit tissue damage. Scientists don’t completely understand the nature of the relationship between the circadian clock and photoperiodic timekeeper. But laboratory experiments on mosquitos have shown that interfering with proteins in the clock causes females to enter diapause even though their environment indicates that it is a season to remain active.