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Classificatory and descriptive systems of kinship

Lineal and collateral descendants

The distinction between classificatory and descriptive systems of kinship is easily made but widely misunderstood. In the end, it draws on Lewis H. Morgan’s legal background and the distinction between lineal and collateral descendants in mid-19th century inheritance law.

Parallel and cross cousins

In my previous post I showed and told how to create a basic kinship diagram allowing for the easy distinction of parallel and cross cousins.

Fig. 1. Parallel and cross cousins.

A cousin is parallel to Ego when that cousin’s parent is of the same gender as Ego’s parent.

Classificatory systems

The diagram below shows a typical classificatory system. Any sister of anyone Ego calls mother is also called mother, and any child of anyone called mother is called sister or brother. Any brother of anyone Ego calls father is also called father, and any child of anyone called father is called sister or brother.

In other words, the parallel cousins and their parents are “classed” together.

Fig. 2. A typical classificatory system.

It’s as simple as that.

Descriptive systems

The diagram below shows a typical descriptive system. Ego calls one individual mother and one individual father. Only the children of mother or/and father are called sister or brother.

Fig. 3. A typical descriptive system.

It’s as simple as that.

The “So what?” question

In discovering and elucidating the classificatory/descriptive distinction, Lewis H. Morgan was able to demonstrate the internal coherence of so-called primitive social life and psychology. As was the case after Saussure’s and Sapir’s discovery of the phoneme, no one had good standing anymore to claim that “they’re just talking gibberish.”

I do believe that there are reasons that the classificatory/descriptive distinction should not be relegated to mere great moment in the history of science status. About which more later; blog posts needn’t be book length.

The origin of the names

The origin of the terms classificatory and descriptive apparently stem from Morgan’s practice of inheritance law within a system in which the primacy of ‘lineal’ relatives (such as mother and father) over ‘collateral’ relatives (such as aunt and uncle) was the de jure standard.1 Morgan seems to have taken this to be the correct understanding of things, and to have taken kinship systems reflecting the same as more descriptive of that understanding.

Morgan’s ethnocentric terminology is a reflection of Victorian era society’s obsession with lineal descent as the sine qua non of parenting and inheritance. Lest Morgan and his work be dismissed out of hand due to this fact, I would point out that modern-day American society is, as well, as evidenced by the Supreme Court’s pending judicial referendums on same-sex marriage and the Indian Child Welfare Act. It is to this subject which I plan to turn in my next post.


1. See Elisabeth Tooker, “Another view of Morgan on kinship,” Current Anthropology 20, no. 1 (March 1979): 131–34. doi:10.1086/202219.

Author information

Matthew Timothy Bradley




  1. […] Classificatory and descriptive systems of kinship. […]


  2. […] or marriageable or not (ex., see Matthew Bradley’s site Consanguinity and Affinity). For example, some societies refer to aunts and uncles as ‘mother’ or ‘father.’ There are also many examples of people […]


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