The modern science of cultural evolution and gene-culture coevolution began, by some accounts, in the 1960s with the work of psychologist Donald T. Campbell and further developed by Cavalli-Sforza and Feldman in the 1970s and Boyd and Richerson in the 1980s to the present.  This all seems rather late.  Why didn’t an evolutionary science of cultural change get started earlier?

All the pieces were there.  For example, Darwin’s “inherited habits” in The Descent of Man can be as easily (if not more easily) interpreted as descriptions of cultural transmission than genetic transmission. (Remember, Darwin did not know anything about genes).  When population geneticists started integrate Darwinian evolution with Mendelian genetics in the 1920s and 1930s using mathematical models,* why were there not evolutionary social scientists, in concert or in parallel, using mathematical models to describe cultural inheritance and or develop models of gene-cultural coevolution?

A couple years ago, from a brief mention in Lippman’s Public Opinion, I came across a 1921 book by political scientist Graham Wallas called Our Social Heritage. Although there were no mathematical models, Wallas had the basic premises for what I would consider relatively modern ideas concerning cultural inheritance.

First, Wallace specifies the difference between what he calls “biological” inheritance and “social” inheritance. Today we distinguish between “genetic” and “cultural” inheritance (since both systems are inherently biological). He also discusses things in terms of the nature/nurture divide which seems antiquated today.  But given that the population genetics was only three years old and it was still 30 years before Lewis and Crick published the structure of DNA, his description seems remarkably modern.

Our nature consists of those facts of structure and instinct which are inherited by the biological process of begetting and birth. We inherit biologically, for instance, the viscera by which we digest certain kinds of food, and the instincts which make us desire them; a skin which resists bacterial infection, and an instinct to brush away a fly before he pierces our skin; a highly complex nervous system and an instinctive impulse to think.

He also distinguishes between what we call individual and social learning.

Our nurture may be divided into two parts. The first part consists of that which each one of us acquires for himself, without learning it from other human beings. The second part consists of the knowledge and expedients and habits which were originally the personal acquisition of individuals, but which have been afterwards handed down from one generation to another by the social process of teaching and learning. It is this second part of our nurture which I shall call our “social heritage.”

Humans rely more on social learning than other animals.

Men differ widely from all other animals by the extent of their social heritage and the degree of their dependence on it. Those insects among whom one generation dies out before another is born can obviously have no social heritage at all; nor can fishes, or any other species among whom parents do not associate with their offspring. A certain amount of social heritage apparently exists in some species of birds…

He actually goes on about social heritage in birds at some length.  This is interesting because birds are thought to be the only other taxa, besides possibly chimpanzees, that show clear signs of “cumulative cultural evolution.”  From a 1995 Boyd and Richerson paper, “cumulative cultural evolution resulting in behaviors that no individual could invent on their own is limited to humans, song birds, and perhaps chimpanzees.”  The sign of cumulative cultural evolution is when cultural traits are complicated enough that individuals organisms could not figure them out on their own.  For an extreme example, no one could, starting from scratch, invent an automobile or an mp3 player. In birds, cumulative cultural evolution is associated with bird songs.

In one of my favorite passages from the book, Graham Wallas makes an implicit distinction between normal social learning and cumulative culture evolution with a rather long science-fiction type story where (1) a comet strikes the earth, (2) somehow deletes all of our cultural inheritance, which (3) eventually kills everyone in Europe and North America. I think someone should pitch this as a premise for a new NBC television drama.

The process of social inheritance is, as far as I know, not necessary for the existence of any wild non-human or variety. The swallows or the London rats might if they forgot all that they had learnt from their parents, sink for a few generations to one half or one quarter of their present numbers. But the most important and progressive varieties of the human race would probably, if social inheritance were in their case interrupted, die out altogether. If the earth were struck by one of Mr Wells’s comets and if, in consequence, every human being now alive were to lose all the knowledge and habits which he had acquired from preceding generations, though retaining unchanged all his own powers of invention and memory and habituation, nine tenths of the inhabitants of London or New York would be dead in a month and 99 per cent of the remaining tenth would be dead in six months. They would have no language to express their thoughts and no thoughts but vague reverie. They could not read notices or drive motors or horses. They would wander about, led by the inarticulate cries of a few naturally dominant individuals, drowning themselves, as thirst came on, in hundreds at the riverside landing places, looting those shops where the smell of decaying food attracted them and, perhaps at the end stumbling on the expedient of cannibalism. Even in the country districts, men could not invent, in time to preserve their lives, methods of growing food, or taming animals, or making fire, or so clothing themselves as to endure a northern winter. An attack of constipation or measles would be invariably fatal. After a few years mankind would almost certainly disappear from the northern and temperate zones…

He also writes about what we would now call “gene-culture coevolution,” hypothesizing that cultural traits should influence genetic ones and comparing our genes to a parasitic barnacle. 

Man has been increasingly dependent on his social heritage since the beginning of conventional language and of the art of flint-chipping, that is to say, for perhaps half a million years. This fact has brought about important modifications in our biologically inherited nature. We have become biologically more fitted to live with the help of our social heritage and biologically less fitted to live without it. We have become, one may say, biologically parasitic upon our social heritage. Just as the parasitic crustacean sacculina, after living for unnumbered thousands of generations upon the body-juices of the crab, has evolved special organs and a special body of instincts which fit it to obtain that food and unfit it to live without that food; so man has evolved and is still evolving certain modifications of structure and instinct, which, while they increase his power of acquiring and using social heritage also increase his dependence on it.

Since these ideas were in the ether, why didn’t some enterprising researcher take them on and independently, or in concert with population geneticists at the time, develop a more complete Darwinian synthesis.  Perhaps Wallas could have inspired this effort.  As one of the founders of the London School of Economics, he was no slouch.  However, he wrote this book towards the end of his career and, perhaps, did not promote these ideas with the persistence of one establishing a career.

Although I would like to picture an alternate history where Fisher or some analogous person tackled cultural evolution with the drive of the early population geneticists, perhaps the history of science is just a road routed by the whims of path dependence.

But it is nice to have so much work ahead.

PS – In the later chapters of the book, Wallas applies his ideas about social inheritance to furthering cooperation and preventing conflict both within and between states.  Since this is a focus of my research, I find his ideas her interesting – at least from an historic perspective, but will save them for a later post.

* – Before population genetics, Darwinians and Medellians had considered themselves members of rival camps.