Rhythms of Life: Biological Clocks

Originally published in Disciple, June 13, 2011.

Biological science has taken great notice of the cyclical nature of all life on earth. Not only is there a definite rhythm to heartbeats, breathing, sleeping, and waking, but also rhythms have been found in mating cycles, growth periods, hunting/resting times, and many other activities of life in both the plant and animal kingdoms.

Most of these cyclical activities appear to be regulated by the sun or the moon, and scientists speak of "biological clocks" which operate on 24-hour days, or 28-day lunar months, or 12-month years. But there is also strong evidence that something resident within each creature or plant exercises even more basic control of the rhythms of life-something that works in conjunction with the external stimuli, but which can function independently if need be.

For example, a Dutch botanist discovered in 1929 that certain bean seedlings that had been grown in constant artificial light could be trained to adapt their sleep/wake cycle to a 16-hour "day." But when returned to continuous light-still without ever being exposed to sunlight-the bean sprouts returned to a normal 24-hour rhythm.

Another variety of bean was found to have no regular rhythm when the sprouts were kept in constant light conditions-either fully lighted or fully dark. Those grown entirely in the dark developed a normal rhythm when a mere flash of light was allowed in their darkness.

An example of a lunar biological clock is that of the grunion. This small fish invariably mates on southern California beaches a quarter-hour after the peak tide-following the two highest tides of the summer months. It is so predictable that newspapers have carried announcements in advance, not only of the day but also of the approximate minute the fish will swarm ashore.

An experiment with oysters from the Eastern Seaboard of America, which were moved to a mid-continent laboratory almost 1,000 miles from the sea, showed that they kept their accustomed lunar clock setting for about two weeks. But after that they adjusted to lunar time in their new environment-they opened their shells widest to feed when it would have been high tide in the laboratory, if it had been on a beach.

Many migratory birds use the sun as both a timekeeper and a reference point for their flights. They can even adjust their built-in "compasses" for the passage of the sun across the sky, according to the time of day! In a test of this ability, a starling was trained to fly east for food in the morning, toward the sun. But when tested in the afternoon, with the sun westering, the bird flew unerringly toward the east feeder and its reward. It had adjusted for the time of day.

Warblers and other night-migrating birds use the stars as navigation aids. But they do this instinctively. It has been found that warblers do not migrate in flocks but individually; and even young birds, which have never made the trip, arrive at their winter feeding grounds as surely as more experienced birds.

One warbler variety begins its fall migration in Scandinavia and ends in southern Africa-almost one-third of the way around the world. Another requires a major mid-course adjustment in its flight: from Germany, the white-throat warbler flies southeast across the Balkans, then shifts to a more southerly course to its destination near the headwaters of the Nile River in Africa.

But an even more amazing demonstration of their built-in navigation ability lies in the fact that young warblers, raised in the laboratory from eggs and isolated from each other as well as all other birds, instinctively followed the same flight orientation when they were placed in a planetarium, under a replica of the stars they would normally see en route.

Equally amazing is the young adult bronzed cuckoo of New Zealand. This bird flies 1,200 miles northeast across the Tasman Sea to Australia, and then an additional 1,000 miles north across the Coral Sea to tiny wintering areas in the Bismarck Archipelago and the Solomon Islands. The young birds have never flown this course, but nevertheless do so alone, for they leave at least a month after their parents' departure.

And then there is the lowly potato: were it not verified under laboratory conditions, its ability to predict changes in the weather would be almost unbelievable. But an American scientist, who measured the rate at which potatoes consume oxygen, found that the rate varies according to barometric pressure-but does so two days in advance. The scientist, Frank A. Brown Jr., further stated: "everything studied in our laboratory-from carrots to seaweed, and from crabs and oysters to rats-has shown this capacity to predict, very safely beyond chance, the barometric pressure changes, usually two days in advance."

So there are many strange and wonderful controls built into probably all of life on earth, including man-controls that establish the rhythms of life and keep each species "on track" and regular. Science seeks eagerly to learn more about how and why these controls work. But science by itself will never be able to explain them all. Science is merely following in the footsteps of God, who long ago caused it to be written: "To everything there is a season, and a time to every purpose under the heaven" (Eccl. 3:1).

"To everything there is a season," and so it is. So it has been, and so it shall be, until time shall be no more. Because that is the way the One, who is far greater than man, created life.

It is as the German poet-philosopher Goethe wrote: "What more can man profit from life than to apprehend how God reveals Himself through nature, and how constant nature is, imbued with the Spirit." Amen!

The Old Scot (Ted Kyle) served as managing editor for Pulpit Helps magazine (Disciple's predecessor publication) from 1993-2008. He was always fascinated by the natural world, and readily saw God's hand in every detail. Ted went to be with His Creator and Savior in April 2013.

Sources: The Living Clocks, Ritchie R. Ward, Alfred A. Knopf, NY, 1971, p. 96. Frank A. Brown Jr., "The Rhythmic Nature of Animals and Plants," American Scientist, Vol. XLVII (June 1959), pp. 164-186.

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