Human Cultural Evolution: A Letter Exchange

In a recent exchange of letters, hosted on the platform Letter.wiki, Massimo Pigliucci and David Sloan Wilson explored the question of whether multi-level selection theory, a school of evolutionary biology, could deepen our understanding of historical events, such as the Peloponnesian War (431–404 BC).

With doctorates in biology, genetics and philosophy of science and professional interests ranging from Stoicism (an enthusiasm we share) to ecology, Pigliucci has a longstanding interest in the relationship between the humanities and sciences. His scholarly works include Phenotypic Plasticity (2001), Making Sense of Evolution (2006), Nonsense on Stilts: How to Tell Science from Bunk (2010) and How to be a Stoic (2017). He is currently Professor of Philosophy at SUNY City College.

David Sloan Wilson is an eminent evolutionary biologist and the founder of the Evolution Institute at Binghamton University in New York. In his teaching and written work, Wilson uses evolutionary theory and, in particular, multi-level selection theory to illuminate questions in philosophy, sociology, medicine, bioengineering and religion. His scholarly works include Darwin’s Cathedral (2002), Evolution for Everyone (2007), Does Altruism Exist? (2015) and, most recently, This View of Life: Completing the Darwinian Revolution (2019).

Pigliucci and Wilson are both enthusiastic proponents of the controversial Extended Evolutionary Synthesis, a scholarly attempt to deepen our understanding of evolution by supplementing Mendelian genetics and Darwinian natural selection theory with explanatory models based on niche construction, evolvability, evolutionary development theory and epigenetics. Darwin himself arguably anticipated the expansion of his theory at the end of The Origin of Species, where he writes, “I am convinced that natural selection has been the main, but not the exclusive, means of modification.” A discussion of EES is well beyond my capabilities, but, crucially, one of the ideas many of those involved, including Pigliucci, take seriously is multi-level selection theory (MLS), of which Wilson is one of the best known champions.

Group Selection Theory

MLS offers an explanation of a phenomenon difficult to reconcile with classic evolutionary biology: altruism. If natural selection takes place only at the level of genes, and genes are selfish, to use Richard Dawkins’ metaphor, and are only concerned with ensuring their own proliferation by heightening an individual’s chances of surviving and reproducing, why do organisms so often co-operate with each other? Co-operation often requires generous individuals to make sacrifices on behalf of the group, sacrifices that may damage their own odds of leaving offspring. Traditional explanations invoke kin selection theory and game theory. MLS posits an additional mechanism: group selection. Groups with a large proportion of generous, co-operative individuals tend to be more successful than those with many slackers, cheaters and freeloaders. Proponents of group selection believe this operates either through genetic mechanisms (genetic group selection), cultural mechanisms (cultural evolution) or both.

Wilson gives the example of an egg farm. Let’s imagine the chickens are divided into separate enclosures of ten. You are asked to choose which ten chickens will lay the greatest number of eggs. Should you pick out the ten best individual layers from anywhere within the entire coop? No, Sloan Wilson argues, since the best layers are also the most aggressive birds: they manage to lay more by fighting their rivals and destroying their eggs. Put ten such birds together in a cage and they will peck each other to death. Instead, you should choose between groups of chickens and opt for the enclosure which has produced most eggs.

Other examples which may be amenable to group selection explanations include some slime moulds, which join together to form a mat, the exposed top layer of which may be destroyed by sunlight, but protects the rest; and emperor penguins, huddling together for warmth—everyone must take a turn on the frozen circumference of the huddle, to protect the group. Far from being always red in tooth and claw, not only is nature full of examples of co-operation, but complex life forms depend on it. Chloroplasts in plants and mitochondria in animals are both descendants of free-living bacteria, now bonded with their hosts. Some have even suggested that eukaryotic cells—the building blocks of animal and plant life—are the result of a co-operative partnership between a bacterium and an archaon, a hypothesis known as endosymbiotic theory, first proposed by Lynn Margulis in 1967.

Evolutionary Biology and Human History

“From the right perspective,” Wilson argues, “history provides a fossil record of human cultural evolution that puts the biological fossil record to shame!” Wilson bemoans the fact that history, like other humanities subjects, lacks an overarching theoretical framework. No first principles have been formulated; no equations can be applied. In this way, humanities scholars resemble naturalists before Darwin, who often observed patterns in nature and sometimes speculated as to their causes in ways that seem to anticipate a crude form of evolutionary theory. James Burnett, Lord Monboddo (1714–99), for example, famously suggested that men may have descended from apes. In his epic poem, The Temple of Nature (1802), Darwin’s own grandfather, Erasmus outlines a vision of natural history in which more primitive organisms gradually give rise to more complex ones, over the course of many generations:

Organic life beneath the shoreless waves
Was born and nurs’d in ocean’s pearly caves;
First forms minute, unseen by spheric glass,
Move on the mud, or pierce the watery mass;
These, as successive generations bloom,
New powers acquire and larger limbs assume;
Whence countless groups of vegetation spring,
And breathing realms of fin and feet and wing.

Such speculations do not detract from Charles Darwin’s originality or genius. Unlike his predecessors, Darwin formulated a coherent and falsifiable theory. His analytical framework unified a mass of diverse observations and enabled a paradigm shift in our understanding of nature: a shift from musings and guesswork to explanation. For Wilson, humanities scholars are still at the butterfly collector stage and lack their master theory:

I don’t think you sufficiently appreciate how much the study of humanity is in a pre-Darwinian “natural history” stage—mountains of information that need to be organized by the right theoretical framework. This is the theme of my newest book This View of Life: Completing the Darwinian Revolution.

Taking the study of religion as an example, Wilson proposes a model that would allow us to test hypotheses about historical events and cultural phenomena against six fundamental criteria:

Culturally evolved features of religion might or might not be adaptive. If adaptive, they might be a product of between-group selection, within-group selection, or cultural parasites harmful to both individuals and groups. If not adaptive, they might be byproducts of adaptations, adaptations to past environments mismatched to current environments, or products of drift. These six major hypotheses serve for the study of culturally evolved religious traits as well as for genetically evolved traits.

Wilson stresses the close relationship between culture and biology. For the proponents of Extended Evolutionary Synthesis, this connection is reciprocal. As Wilson points out, citing Niko Tinbergen, “a behavioral trait such as aggression can evolve in the same way as an anatomical trait such as a deer’s antlers.” Conversely, cultural developments can have an effect on human biology, as Kevin Laland argues in Darwin’s Unfinished Symphony: How Culture Made the Human Mind:

culture is not just the magnificent end product of an evolutionary process that produced a species unlike all others—it is also the key driving force behind that process … The truly unique characteristics of our species—such as our intelligence, language, teaching, and cooperation—are not adaptive responses to predators, disease, or other external conditions. Rather, humans are creatures of their own making.

Peter J. Richerson and Robert Boyd illustrate this thesis by suggesting that the history of honour culture in the American South has resulted in differences in typical hormonal responses between men from southern and northern states, such that “an insult that has trivial effects in a Northerner sets off a cascade of physiological changes in a southern male.” From this standpoint, evolutionary biology and cultural history are intertwined and one cannot be understood separately from the other. (I don’t have the expertise to evaluate these claims, but some evolutionary biologists have expressed scepticism about Laland’s and about Richerson and Boyd’s work.)

For Wilson, it is important to study history through the lens of group selection theory because history is the record of interactions between groups—such as the Athenians and Spartans fighting the Peloponnesian War. In Wilson’s view, history charts our steady progress towards an ability to peaceably co-exist in ever greater groups. It records “a process of cultural MLS resulting in a net increase in the scale of society”:

Our distant ancestors became exceptionally good at suppressing disruptive self-serving behaviors within groups so that between-group selection became the primary evolutionary force, favoring teamwork in all its forms. That’s what our moral psychology is all about. The capacity to learn from each other and to transmit learned information across generations is itself a form of teamwork.

For Wilson then, just as he who neglects to study history is doomed to repeat it, he who does not fully understand history cannot influence the future. Our survival and flourishing are dependent on our ability to live together harmoniously and to do that requires a deeper understanding of the nature of co-operation. History is not the record of the actions of specific individuals but a collection of object moral lessons on how we, as social animals, can suppress aggressive and destructive within-group dynamics and promote group harmony. As an example of this approach to history, he cites the advent of currency in ancient Greece. The shift from a barter and gift-based society to one centred on coinage caused, Wilson argues, a “revolution in thought,” as it altered the nature of relationships within the social group.

Levels of Explanation

Massimo Pigliucci’s objections to Wilson can be summarised in a single question: what do such theories have to do with the Peloponnesian War? In letter after letter, Pigliucci attempts to pin Wilson down to specifics—without success. They agree on the validity and importance of multi-level selection theory in evolutionary biology; they disagree as to whether it is relevant to recorded history.

Pigliucci has discussed the explanatory limits of science on a number of other occasions. In this talk, with Daniel Dennett and Lawrence Krauss, he argues against Sam Harris’ thesis in The Moral Landscape that it’s possible to derive ethical values from scientific facts. Science cannot bridge the is–ought gap, Pigliucci told Derek Colanduno in a podcast interview:

you need both empirical facts, you need an evidence-based approach to the world and you need to be able to reflect on the meaning of those facts … If you want answers to moral questions then you don’t ask the neurobiologist, you don’t ask the evolutionary biologist, you ask the philosopher.

Pigliucci is a sceptic and a staunch opponent of pseudoscience and quackery. That scientific explanations have limitations does not mean we should lend credence to mysticism, deepities or woo. Nor does he grant religion an exemption from critical scrutiny, as Stephen Jay Gould does, with his concept of non-overlapping magisteria. Pigliucci is more concerned that examining everything through the same theoretical lens invariably causes myopia. He alludes briefly, in Letter Two, to Stephen Jay Gould and Richard Lewontin’s famous paper “The Spandrels of San Marco and the Panglossian Paradigm.” Gould and Lewontin’s central example of this kind of short-sightedness is worth quoting in full:

The great central dome of St. Mark’s Cathedral in Venice presents in its mosaic design a detailed iconography expressing the mainstays of Christian faith. Three circles of 2 figures radiate out from a central image of Christ: angels, disciples, and virtues. Each circle is divided into quadrants, even though the dome itself is radially symmetrical in structure. Each quadrant meets one of the four spandrels in the arches below the dome. Spandrels—the tapering triangular spaces formed by the intersection of two rounded arches at right angles—are necessary architectural byproducts of mounting a dome on rounded arches. Each spandrel contains a design admirably fitted into its tapering space. An evangelist sits in the upper part, flanked by the heavenly cities. Below, a man representing one of the four biblical rivers (Tigris, Euphrates, Indus, and Nile) pours water from a pitcher in the narrowing space below his feet. The design is so elaborate, harmonious, and purposeful that we are tempted to view it as the starting point of any analysis, as the cause in some sense of the surrounding architecture. But this would invert the proper path of analysis. The system begins with an architectural constraint: the necessary four spandrels and their tapering triangular form. They provide a space in which the mosaicists worked; they set the quadripartite symmetry of the dome above.

Gould and Lewontin’s paper illustrates the fact that not every feature of an organism is an adaptation. The spandrels of San Marco are the result of a architectural design constraint: build round arches and you automatically get spandrels—which creative artists can then fill with decoration. More relevantly here, Gould and Lewontin also provide an example from the study of history: Michael Harner and E. O. Wilson’s argument that—despite its elaborate, mythical, religious and social functions—the real reason the Aztecs practised cannibalism was because it provided them with a good source of protein. Gould and Lewontin are sceptical:

We strongly suspect that Aztec cannibalism was an “adaptation” much like evangelists and rivers in spandrels … a secondary epiphenomenon representing a fruitful use of available parts, not a cause of the entire system. To put it crudely: a system developed for other reasons generated an increasing number of fresh bodies; use might as well be made of them. Why invert the whole system in such a curious fashion and view an entire culture as the epiphenomenon of an unusual way to beef up the meat supply? Spandrels do not exist to house the evangelists.

Speculations as to the real reasons for cultural practices are unfalsifiable. More importantly, they provide the wrong level of explanation. Jordan Peterson’s remarks on why women wear lipstick—because reddened lips signal proximity to orgasm and can therefore stimulate male sexual arousal—may be of interest to a visiting alien, who wonders why we usually colour our lips red, rather than green or blue. But it neither explains why blood is red to begin with nor why a particular woman might choose to wear lipstick on any particular occasion, nor is it of interest to a student of fashion and make-up history. Women’s fashions are designed to enhance female attractiveness: but this kind of general statement does nothing to explain—or even chart—the shifts in dress from the farthingale to the pencil skirt. “Culture is an outgrowth of biology. But that doesn’t mean that culture can be straightforwardly treated as yet another manifestation of human biology,” Pigliucci argues, “biology provides the boundary conditions for the emergence of culture, but that culture is its own beast, characterized by its own dynamics and modalities.”

It is characteristic of science, as Wilson points out, to seek underlying general principles, to formulate the laws that govern the myriad individual instances of phenomena. But, as Pigliucci points out, there is no reason to privilege this level of generalisation. “When you say that the humanities lack the conceptual unification provided in biology by the Darwinian theory you are assuming the sciences as the model for scholarship. Why?,” he asks Wilson. In the arts and humanities, we are interested in specific instances and how they differ from each other. We want to know not what the Peloponnese War had in common with every other armed conflict, but what was distinctive about it. Its ultimate causes may have been human tribalism and aggression—but what were its proximate causes? What sparked this specific conflict and what specific consequences did it bring? These are questions evolutionary biology cannot answer. Nor can it, as Pigliucci points out, explain the individual motivations of those involved, whose behaviour can be unpredictable and whose choices are influenced by cultural, as well as biological factors:

we can think about stuff before acting on it, and our thinking is influenced by many factors, including cultural institutions (states, ideologies), personal motivations (friendships, love), and so forth. Do we seriously contend that all of that can be satisfactorily captured by exactly four variables?

In his book, The Quark and the Jaguar: Adventures in the Simple and the Complex, Murray Gell-Mann asserts that “The world of the quark has everything to do with a jaguar circling in the night.” That is true: but, as he also points out, to speak meaningfully about the jaguar, which he describes as “a particular complex adaptive system,” requires a different level of explanation. As Pigliucci explains:

I see science as being in the business of providing a number of pertinent levels of description of various phenomena, none of which is intrinsically more important or fundamental. If I’m interested in cosmology, physics is relevant, biology and economics not at all. If I’m interested in history, psychology is relevant, physics not at all. And so forth. The disciplines that do not provide meaningful levels of description for a particular problem are then moved to the background. For instance, even if quantum mechanics provides no insight at all into human history, human beings (like everything else in the universe) are still made of quarks, and still abide by the laws of physics. It’s just that these latter two facts do not provide any additional meaningful insight to historians.

Pigliucci and Wilson’s own conversation reflects this mismatch. Wilson’s most specific example of a historical occurrence that can and should be interpreted using multi-level selection theory is the introduction of money to Greek society. This is an extremely broad, society-level change, not a single occurrence, involving known individuals, recorded conversations, datable events, etc.

Enthusiasm and Scepticism

Wilson talks in generalities because he thinks big and, in this, he is typical of a scientist-philosopher. In his book, The Disorder of Things, John Dupré writes that, “The great dream of philosophers and scientists has been to give a complete account of the order of things.” This is an ambition, incidentally, more often mocked than shared by humanities scholars and literary authors—think of Casaubon’s futile efforts to compile a “Key to All Mythologies” in George Eliot’s Middlemarch. Wilson believes that his theory can elucidate not just biology—but history and culture too—and that its insights can be used to change society: “the most important application is to guide our future cultural evolution, which is the main point of my new book.”

Such excitement is charming and contagious. Wilson’s talks on MLS are insightful and ingenious and I am looking forward to reading his new book, which has garnered considerable acclaim. But, like Pigliucci, I am sceptical of overarching theories, and I am mindful of the earlier meaning of the word enthusiasm, which once signified delusional fanaticism. In response to Wilson’s criticism that “the overall rhetorical impact of [his letters] is to ‘dampen enthusiasms,’” Pigliucci responds tartly: “Good! Because sometimes over-enthusiastic scientists go down rabbit holes.” Ambitious claims carry larger burdens of proof.

This letter exchange has failed to convince me of Wilson’s initial proposition: that multi-level selection theory might provide helpful insights into ancient Greek history. But it has left me eager to find out more about what insights the theory might provide, in other spheres of thought. And it has also left me with a heightened appreciation of the differences between the sciences and the humanities and the kinds of knowledge valued in both.

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