THE ORIGIN OF TRADITION 419
(1) Supposing other things to be equal, we have to study the
influence of differences in fertility and contact upon
tradition. (2) Fertility is a purely relative term. (3) The
greater the fertility, the greater the incentive to increase in
skill and to the transmission of skilled processes. (4) Since
fertility is relative there is a shifting of the centres of
progress. (5) Contact varies in quantity and quality, and
facilitates the transmission and encourages the formation of
skill. (6) Contact is hindered by isolation by sea, deserts, and
mountains, and is facilitated by rivers. Importance of location
and language. (7) Contact also influenced by economic factors
which have brought about (8) the evolution from the segmentary
to the organic form of social organization. (9) Thus the origin
and transmission of tradition have been very greatly encouraged
in the third period, (10) though certain influences work against
the full realization of the organic type in modern communities.
(11) Differences in economic organization are correlated with
other differences in social organization.