How rhythms become a vital part of us | A neuroscientist explains

Whether its the physiological monthly cycle of a woman or a plants seasonal cycle, the external world influences biology, says Daniel Glaser

This column has run weekly for more than two years but, from a biological view, that is a bizarre rhythm. Cells and systems in the brain and body have built-in mechanisms to enforce a 24 -hour sleep-wake cycle. And light-sensitive cells in the eye and elsewhere keep that synched to the earth’s rotation.

Animals and plants govern specific activities on an annual cycle, becoming frisky in springtime and hibernate over the winter. Again, intrinsic mechanisms tend towards an annual cycle and sensors of various kinds nudge it to keep track of the earth’s rotation around the sun.

The physiology of women proves a monthly periodicity in almost all aspects, although it’s not known whether that has more than a coincidental relation to the orbit of the moon.

But it is culture, especially religious culture, that has illuminated upon the seven-day cycle as an organising structure for our lives. Once something is in the external world, however, it starts to invade our biology, particularly our neurobiology. That’s why it’s so hard to wake up on Sunday morning even if you were silly enough to have set your alarm clock. In the end, science is an example of culture.

Dr Daniel Glaser is director of Science Gallery at King’s College London

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