Social Exaptation

1 February 2009

One never knows from what quarter inspiration will strike nor what form it will take. (Perhaps this is one reason that, before an innovation in social technology appears, it is utterly unpredictable – something I recently suggested but made no attempt to demonstrate.) I was granted a moment of understanding, like an undeserved gift of grace, from a book on antiquity by a medievalist, although my insight had little to do with the content of the exposition.

A "light bulb moment" is inherently unpredictable.

A "light bulb moment" is inherently unpredictable.

When I was listening to a book on tape a few days ago, Alexander the Great: Journey to the End of the Earth, by Norman F. Cantor (posthumously published with the assistance of Dee Ranieri), I was struck with one of those “light bulb” moments. Cantor is better known as a medieval historian, and although specialists take issue with the details of his The Civilization of the Middle Ages, it has been the textbook that has introduced many to the period. Cantor is here out of his element, and at times it shows, but there were still flashes of narrative insight now and then of the sort one expects from a historian like Cantor.


Recently in Terrorism and the Evolution of Technology I noted the role of exaptation in terrorist’s use of technology. “Exaptation” is a term of evolutionary biology, subsequently itself exapted for non-biological uses, by which it is meant that traits evolved to serve one particular function subsequently can be adapted to serve another function. S. J. Gould uses an example of social exaptation in his enormous posthumously published The Structure of Evolutionary Theory, citing Nietzsche’s conception of punishment as an instance. Thus the idea of social exaptation is not new. I want to here comment on some particular social exaptations I have noticed.

Cantor in his book noted that the ancient Persians followed a matrilineal descent with their royal family, so that if Alexander were to marry one of the daughters of the defeated Persian King Darius III (Artashata) he would be the legal heir to the throne of the Persian empire. This started me thinking about matrilineal descent from an evolutionary perspective.

Systems of matrilineal descent are relatively common. Wikipedia gives this list: “examples of this cultural practice include many ancient cultures and continues in the contemporary cultures of those ancient origins such as Huron, Cherokee, Iroquois Confederacy (Haudenosaunee), Hopi, Navajo, and Gitksan of North America. In the Old World cultures it is found in Egyptian, Minangkabau, (West Sumatra); and Ezhava, Nairs, and Kurichiyas of Kerala, India, Bunts, Billavas and Mogaveeras of Karnataka, Pillai caste in Nagercoil District of Tamil Nadu; the Khasi, Jaintia and Garo of Meghalaya, India, the Naxi of China, and the Tuaregs.” Clearly this is not an unusual practice.

How matrilineal descent works

How matrilineal descent works: triangles for men and circles for women.

Upon reflection, the evolutionary advantage of matrilineal descent became obvious. Societies receive traditions handed down from antiquity, and for purposes of consistency and social coherence must often make the best of institutions that are not well-adapted to the changed conditions of later ages. By a clever use of tradition, however, the forms and appearances of tradition can be maintained even while greater flexibility and adaptability is built into slighted altered institutions in later ages.

For example, a society (such as any of those named among the above examples of matrilineal succession) can retain the biological and dynastic descent of their rulers, an arrangement that presumably can be traced back to prehistoric chieftainship, while leaving open the possibility of a far greater number of individuals from among whom their king or ruler can be chosen, by the use of the system of matrilineal descent. The royal blood is maintained through the mother’s line, but in each generation the daughter of the king can choose as a husband (and therefore as the future ruler of her people) the best qualified man. The people of a given society, under such arrangements, are not then stuck with whomever the king’s son happens to be. Matrilineal succession introduces choice into a process that would otherwise be at the mercy of chance. Thus meritocracy can be the reality perpetuated by the appearance of royal dynasty.

The Romans similarly adapted their tradition through adoption. Because, as with the previous example, family and kinship ties are the origins of most societies, but eventually cease to serve the interests of those societies as those societies evolve into something more complex than a band of hunter-gatherers, the appearance of family and kinship must be maintained. This the Romans did by having prominent men quite literally adopt as their own sons promising young men whom they would make their heirs. Such arrangements became family relationships over time, though they began as relationships of mentoring and inheritance.

Pliny the Younger was adopted by his uncle, Pliny the Elder. The Elder Pliny wrote on natural history and died observing the eruption of Vesuvius, which episode in preserved in the letters of the Younger Pliny.

Pliny the Younger was adopted by his uncle, Pliny the Elder. The Elder Pliny wrote on natural history and died observing the eruption of Vesuvius, which episode is preserved in the letters of the Younger Pliny.

This reminds me of another social exaptation that once puzzled me, and this is perhaps a better example because it appears to be a case of social success trumping biological success. It never made any biological sense to me that older men commonly marry younger women, but the custom is so widespread, and presumably ancient, that if it had a distinct biological disadvantage the practice would have disappeared or have become taboo. There are, of course, familiar economic arguments for this, but I want to give it a different spin.

It now seems to me that an older man, with experience of the world and fully formed in his character, with set ideas about the world and how it works, can be expected to inculcate and acculturate his less-experienced and less-formed young bride in the ways of a patriarchal society – and almost all societies to date (with some important exceptions) have been patriarchal. While this practice has no intrinsic biological advantage, it does foster social stability, and social stability in turn indirectly fosters health, longevity, and successful reproduction. Hence, at one remove there is a biological advantage to younger women marrying older men, at least within patriarchal societies.

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