Seasonal cycles favor internal biological clocks that keep running on their own

Changing photoperiods may be sufficient environmental pressures to select for self-sustained circadian oscillators.

• Circadian clocks are mechanisms that help organisms anticipate daily changes in their environment.
• Self-sustained oscillations are a key characteristic of circadian clocks, allowing them to function in constant conditions.
• Damped circadian oscillators can adapt to daily light/dark cycles, while hourglass timers can also maintain temporal order.
• An extensive modeling analysis suggested that environmental variability demands self-sustained clocks.
• Experimental findings indicate that seasonal changes in light duration alone can drive the selection for self-sustained circadian oscillators.

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