Now You See It, Now You Don’t - The Stones and the Stars: Building Scotland's Newest Megalith - page 17

rotation to change the position of something in the sky by a single
degree. How could a true understanding of such slow processes be
reached? Indeed, what could move one to the attempt?
Well, first there is the alternation of day and night. Awareness
of that cycle is programmed into us at a very basic level - in isola-
tion, without external clues, human beings tend to drift towards
a 20 h rhythm that goes back 600 million years, to the time when
life crawled from the sea onto the land. It is hard to say whether
the dominant factor here was the day/night cycle or the ebb and
flow of the tides. But it is the braking effect of the tides that has
slowed down Earth since then, and it is the perception of the day/
night cycle that resets our biological clocks.
The monthly orbit of the Moon around Earth has its biologi-
cal tie-ins, too. The link with the menstrual cycle has been noted
from very ancient times. Even today, for all the barriers we have
put between nature and ourselves, outbreaks of crime and admis-
sions to asylums tend to peak around the full Moon - for no obvi-
ous reason. The Moon does affect the weather, as the old proverbs
say, although the effect is so subtle that it took computer analysis
of a century's records to prove the point.
However, to the nomadic hunters who comprised the human
species for almost all of its existence, the phases of the Moon were
crucial. The amount of light to be expected after sundown was a key
survival factor, to be taken into account at the start of the day, and
there are notched bones to suggest that the monthly cycle was being
plotted 20,000 years ago or more. It must have seemed fortunate
indeed that, when the days were shortest and game hardest to find,
the Moon rode higher in the sky and shone brighter for longer.
The evidence suggests that the beginnings of agriculture did
not come directly from the annual cycle of plants but from the
movements of the great herds of game. From moving with the
herds, as the Lapps do even today, domestication and nomadic
herding comprised the next step and led to the first attempts at
agriculture and fixed settlements. The very oldest towns, such as
Jericho (c. 8000 b.c.), came before the first crop farming. The move
to an annual cycle obviously required a true calendar, even if none
had previously been attempted.
The year is harder to calibrate than the month, however. Even
today, a week is a long time in politics - and most societies, if not