In 1935, renowned anthropologist Joseph Daniel Unwin tried to prove the opposite: that marriage was an irrelevant and even harmful cultural institution. He was forced by the evidence to conclude that only marriage with fidelity, what he called absolute monogamy, would lead to the cultural prosperity of a society. Anything else, such as “domestic partnerships” would degrade society.
In his address to the British Psychological Society, Unwin said this:
The evidence was such as to demand a complete revision of my personal philosophy; for the relationship between the factors seemed to be so close, that, if we know what sexual regulations a society has adopted, we can prophesy accurately the pattern of its cultural behavior…
Now it is an extraordinary fact that in the past sexual opportunity has only been reduced to a minimum by the fortuitous adoption of an institution I call absolute monogamy. This type of marriage has been adopted by different societies, in different places, and at different times. Thousands of years and thousands of miles separate the events; and there is no apparent connection between them. In human records, there is no case of an absolutely monogamous society failing to display great [cultural] energy. I do not know of a case on which great energy has been displayed by a society that has not been absolutely monogamous…
If, during or just after a period of [cultural] expansion, a society modifies its sexual regulations, and a new generation is born into a less rigorous [monogamous] tradition, its energy decreases… If it comes into contact with a more vigorous society, it is deprived of its sovereignty, and possibly conquered in its turn.
It seems to follow that we can make a society behave in any manner we like if we are permitted to give it such sexual regulations as will produce the behavior we desire. The results should begin to emerge in the third generation.
”Sexual Regulations and Cultural Behavior,” Joseph Daniel Unwin, Ph.D., in an address given to the Medical Section of the British Psychological Society. Library of Congress No. HQ12.U52