How far back?


In most clannish cultures, it has been revealed by y DNA tests that frequently, clans which technically perceived themselves as agnatic kinship structure, had accepted to (probably in the beginning only to 'cadet-sort') clan membership people who were not agnates,
and it is thought that many of ties in such acceptances, were (or became) cognatic.

Also it is known that pure male lines are not at all easy to procreate over remarkable lengths of time.
Any agnatic lineage has seen times when its major branches 'daughter out'

When non-warlike civilization settles in, ideal of the male line loses some of its practical significance.
Ability to read and write, as well as peaceful culture, usually empowers to have other means of governance than pure raw warlike method.

Now, to talk about adoption in a clan setting: yes, a head of a clan is bound to know who are his close male-line cousins and who of his close cousins are cognatic as in not at all agnatically descended from the same root.
But, in cases of much remoter cousinages within a clan, the precise descent of cadet branches may have become obscured when a greater length of time has passed.
Of course, a clan membership has a ceremonial meaning - and, depending on which sort of relatives had been in the past accepted to the clan membership, may lend ceremonial beliefs upon genealogy.





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