THE moon, according to the playwright Christopher Fry, "is nothing but, a circumambulating aphrodisiac, divinely subsidised to provoke the world into a rising birth rate". There are parts of creation, indeed, that might lead one to believe that this is so. The Californian grunion, for example, times its procreative activities to coincide exactly with the new or the full moon.
The key to the grunion's amorous behaviour lies in the very high tides, spring tides, that occur when the moon, the sun, and the earth all lie in a straight line - when the moon is new or full. With spring tide at appropriate times of the year, the 6 inch fish start to "run": thousands of them struggle ashore at high water to dig little troughs in the sand in which male and female intertwine before the latter deposits her fertilised eggs. Then both return to the sea with the next wave. Thus carefully buried above the highest possible water line, the eggs remain until they hatch exactly two weeks later just in time to be swept out to sea by the next spring tide.
Other creatures also look to the moon for family planning. Nightjars, for example, have been found to lay their eggs most frequently in the last quarter of the lunar cycle, so that the young will hatch at the next full moon when the adults can hunt more easily all night to feed them. And many organisms like barnacles and periwinkles that live in the intertidal
Zone have had to develop complex rhythmic reactions to allow them to cope with the dramatically varying conditions they encounter during a 24 hour period: thanks to the moon, twice each day they may be completely covered with water, and twice they must emerge into the air, perhaps to endure highly desiccating sunny or windy conditions.
There was a time when the similarity between the lunar tidal cycle of around 28 days and the rather similar menstrual pattern in the human female was considered too close to be coincidence. Such notions, for example, are reflected in Cleopatra's determination to end it all by the application of the "Nilean worm":
My resolution's placed and
I have nothing
Of woman in me, now from head to foot
I am marble constant, now the fleeting moon,
No planet is of mine.
It was thought at one time that the connection might lie in some dependence of our prehistoric ancestors on seafood and shellfish, but the observation that the estrous cycles of our evolutionary cousins, the apes and monkeys, are widely varied has led to the prosaic conclusion that the human 28 day cycle is, only coincidentally similar to that of the moon and tides.