Growth and Development of Social Groups 
are found. In Africa, for example, many tribes went directly 
from the Neolithic to the Iron Age without the intervening use 
of bronze, and straight from simple hunting and gathering to 
herding cattle. In India primitive monkey hunters and root 
diggers hid in the forests for millenia while a parade of successive 
civilizations passed by on the plains below. In Africa the iron- 
working Bantu, having obtained new sources of food, exploded 
eastward and southward, from their West African home, by- 
passing the Pygmies, while in India some of the simple hunters 
and grubbers came down from their leafy retreats to become 
specialists in humble occupations, and also outcastes. 
In the well-known history of the Germanic invasions and the 
terminal history of the Roman Empire a similar upset took 
place, for a number of reasons, one of which was the export 
of technical skills from Rome to the colonies, which came to 
need contact with the capital less and less. When the political 
institution weakened, the church took over and a degree of 
equilibrium was restored in a new way. It took several centuries 
for western society to get back into the semblance of a well- 
balanced web of institutions. 
THE RELATIVE FLEXIBILITY OF SOCIAL SYSTEMS 
Old-established systems which have had the advantages of a 
steady, balanced growth tend to be resilient and flexible. They 
absorb and recover from blows. The state does not usually 
dominate the church, nor is everyone madly passionate about 
games or war. A multitude of optional occupations and of 
voluntary associations gives room for the varied outlets of 
different kinds of personalities, and a class system, overt or 
covert, permits the growth of a sometimes inconspicuous ¢lite. 
What preserves the serenity of such civilizations is a harmony 
between the duration of the individual life cycle and the rate 
of cultural changes. The culture must change or it will rot. On 
the other hand, as people grow older they may wistfully note 
that things are not as they were before, but in a well-modulated 
society the rate of change is not swift enough to cause more 
than a little sadness associated with diminishing energy and 
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