MAN IN THE MODERN WORLD
The maritime expansion continued into the next millennium, and
so did the dry climate, which was especially marked in north-western
Europe. Sea trade reached Ireland and Scandinavia. Ireland
attained a very high level of culture, which was probably only made
possible by this dry and bracing climate, before the excessive moisture
of later centuries damped the energies of her inhabitants.
About 1800 B.C. there was again a change. The climate became
gradually moister and cooler. From about 1200 B.C. to A.D. 200 there
was a new cycle of wet and cold, reaching its maximum about 400 B.a
and then gradually falling off, to pass over to drought about A.D, 500.
The belt of storm-tracks again passed through the Mediterranean,
giving opportunity for the rise of Babylonia and Assyria, Canaan and
Phoenicia, of latter-day Crete and Egypt, of Mycenae and Troy,
Greece, Carthage, and Rome. North Africa was then the granary of
the world. The Mediterranean was the focus of human energy, and,
since the nomads could live comfortably on their steppes while the
wet time continued, could pursue its destiny little troubled by bar-
But the change of climate was disastrous to the northern lands,
On them, cold and wet descended; the peat bogs spread; the forests
died off as the swampy moors extended. There was a marked falling
off of culture in Ireland and Scandinavia; and the worst cold spell,
in the fifth and fourth centuries B.C., has apparently left its permanent
trace in the northern legend of the Twilight of the Gods, which pic-
tures a disastrous world bound in the grip of snow and ice.
After this, the classical Mediterranean civilization began to fail.
Jones, some twenty-five years ago, suggested in a remarkable book
that the downfall of Greece was due to malaria imported from Africa.
Now that we know that a progressive desiccation was in progress at
the time, the idea gains in probability. The rivers, drying up to a
series of pools in summer, would afford countless new breeding-places
for the larvae of the malaria-carrying mosquitoes. Malaria probably
contributed to the downfall of Rome as well; but since Italy has more
rainfall than Greece, the malaria-spreading change would have struck
her later. But in addition the yield of agriculture in the Mediter-
ranean began to grow less; and about the same time the first of a new
series of barbarian invasions poured in.
For the period from A,D. 500 to 1000 was definitely a dry one. This
it seems to have been which in the South drove the Huns and Goths
to the limits of Europe, and stimulated the expansion of Islam from
drought-stricken Arabia. But it brought new life to the swampy
North. The culture of Ireland revived. In Scandinavia this was the