This state of descents which can be traced back to the Middle Status
of savagery, as among the Australians, remained among the American
aborigines through the Upper Status of savagery, and into and
through the Lower Status of barbarism, with occasional exceptions.
In the Middle Status of barbarism the Indian tribes began to change
descent from the female line to the male, as die syndyasmian family
of the period began to assume monogamian characteristics. In the
Upper Status of barbarism descent had become changed to the male
line among the Grecian tribes, with the exception of the Lycians,
and among the Italian tribes, with the exception of the Etruscans.
Between the two extremes, represented by the two rules of descent,
three entire ethnical periods intervene, covering many thousands of
years.

As intermarriage in the gens was prohibited, it withdrew its members
from the evils of consanguine marriages, and thus tended to increase
the vigor of the stock. The gens came into being upon three
principal conceptions, namely, the bond of kin, a pure lineage
through descent in the female line, and non-intermarriage in the gens.
When the idea of a gens was developed, it would naturally have taken
the form of gentes in pairs, because the children of the males were
excluded, and because it was equally necessary to organize both
classes of descendants. With two gentes started into being
simultaneously the whole result would have been attained, since the
males and females of one gens would marry the females and males of
the other, and the children, following the gentes of their
respective mothers, would be divided between them. Resting on the
bond of kin as its cohesive principal the gens afforded to each
individual member that personal protection which no other existing
power could give.