Tag Archives: evolutionary psychology

High fidelity

Arms races have been a big engine of evolutionary progress, both in biological evolution and in the evolution of human societies. Another big driver has been improvements in the fidelity of inheritance. We see this in the evolution of genetic systems, including the evolution of life itself, and of the eukaryotic chromosome. And we’ll see it in human social evolution, including the evolution of language, of writing, of the alphabet, and printing.

Both arms races and improved information transmission may have been factors in the evolution of braininess.

jerison brain race

The figure above is from the classic work of Harry Jerison, one of the pioneers in studying the evolution of brain size. It’s several steps away from the raw data, but what it shows is how mammalian Encephalization Quotients (EQs), a measure of brain size relative to body size, evolved over the Cenozoic. The figure might be read as the record of a brainy arms race between prey and predators, leading to increased variance in the EQ bell curve for both.

Primates of course are particularly brainy mammals. One popular explanation for this is a series of arms races within species, with bright monkeys and apes outwitting dimmer ones. This has been called the Machiavellian Intelligence hypothesis (or, in the case of macaques, macachiavellian intelligence).


This hypothesis may not hold up too well, however. One complication is that, contrary to what a lot of modularist evolutionary psychology might suggest, social intelligence in primates is not separate from other sorts of intelligence. The same primate species that are good at solving social problem (e.g. tricking other group members) are also clever about things like tool use and other complex foraging skills. Variation in intelligence across primate species mostly boils down to a single general factor, rather than a bunch of domain-specific aptitudes.

Also, the latest research suggests that variation in diet and ecology, such as the distinction between fruit eaters (brainy) and leaf eaters (not-so-much), accounts a lot of variation in brain size, while differences in social complexity (measured by group size) don’t seem to matter.

An alternative to the Machiavellian Intelligence hypothesis is the cultural intelligence hypothesis, with brainier animals more likely to innovate and more likely to learn others’ innovations. The first part pf this equation holds up: across various groups of organisms, including birds and primates, brainy animals are more flexible in their behavior, more likely to discover new adaptive behaviors, and more successful in colonizing novel environments. The second part is trickier. In recent years we’ve learned that learning useful information by observing others (go ahead, call it culture, if you want to annoy cultural anthropologists) is extremely widespread, and found in organisms like guppies and honeybees that no one thinks are terribly bright. So learning from others doesn’t take special smarts.

Where bigger brained animals may excel is not in how much social learning they do, but in how accurately they do it – in copying fidelity. Theoretical models of the evolution of copying suggest that accurate copying makes a big difference. Small changes in copying fidelity can lead to large changes in the persistence of cultural traits. Of course this will crucially important for human evolution: more on this in days to come.

copying fidelity

For a wide-ranging introduction to this rapidly advancing area of research, written by a leader in the field, try Darwin’s Unfinished Symphony: How Culture Made the Human Mind.

Dead baby monkeys

There’s a dark side to being a primate. A few years back a review article summarized data on rates of lethal aggression in non-human animals. The figure below shows some of the results. Several clusters of especially violent species stand out in the figure, including primates (redder is more violent). Bats are pretty nice, though (too bad about all the viruses).

dead monkeys

Much of the lethal aggression in primates involves infanticide. Sarah Hrdy demonstrated back in the 1970s that infanticide occurs regularly in Hanuman langurs, monkeys in India. A male who takes over a group of females will systematically kill offspring sired by the previous male. If you think evolution is about the survival of the species, this is hard to explain. But it makes sense given the logic of the selfish gene. Females who lose an infant return more quickly to breeding again, and the father of the next infant is likely to be the killer of the previous one.

Primates may be particularly vulnerable to this grim logic, because they spend a long time as infants. Among primates, commonly,


That is to say that the time, L, a female spends lactating for an infant (during which she is unlikely to conceive), is usually greater than the time, G, she spends gestating an infant. This puts particular pressure on males to hurry things along by eliminating nursing infants fathered by other males.


Death of Astyanax

As a result, infanticide is relatively common among primates, and females under particularly strong pressure to find ways to avoid it. Hanuman langurs live in one-male units, where a female has little choice about who she mates with. In other species, by contrast (most baboons, chimpanzees), multiple males reside with multiple females. In these species females are often sexually promiscuous, sometimes actively soliciting multiple males for sex. This is probably mostly a matter of confusing paternity sufficiently to suppress the threat of infanticide. There’s a general lesson here: females are not always monogamously inclined, but female promiscuity generally has different evolutionary roots than male promiscuity.

Leaves of grass

Not as dramatic as the evolution of Triceratops or T. rex, but of more lasting consequence, is the evolution of grasses (Poaceae). We know from coprolites – fossil feces — that grass was around by the Late Cretaceous, so the coevolution of grass and grazers had already begun with dinosaurs. These early grasses were not widespread. It would take climate shifts and more evolution (toward using carbon dioxide more efficiently) to create the sort of grasslands we are familiar with.

Grasses have played a central role in human evolution and human history. Human beings evolved in tropical grasslands, and some evolutionary psychologists think we still have an instinctive affinity for this environment. The domestication of grasses (wheat, barley, oats, millet, rice, corn) was one of the great revolutions in human prehistory, and grasses provided most of the calories people ate for most of recorded history. Contact along the frontier between grasslands supporting pastoralists and grain growing lands supporting peasants is one of the great engines of historical dynamics.

Grasses grow from the base of the leaf, not the tip of the stem, which is what allows them to recover from being grazed. This makes them a recurring symbol both of the transitoriness of life (“All flesh is grass, and all the goodliness thereof is like the flower of the field,” Isaiah 40:6) and its resilience.

Brahms used another verse about grass in the second movement of his German Requiem “For all flesh is as grass, and all the glory of man as the flower of grass. The grass withereth, and the flower thereof falleth away,” 1 Peter1:24. (Here is the German text and English translation.)

And the most famous poem about grass, by Walt Whitman, perhaps strikes the right elegiac note for the dinosaurs, who meet their doom today:

A child said, What is the grass? fetching it to me
with full hands;
How could I answer the child?. . . .I do not know what it
is any more than he.

I guess it must be the flag of my disposition, out of hopeful
green stuff woven.
Or I guess it is the handkerchief of the Lord,
A scented gift and remembrancer designedly dropped,
Bearing the owner’s name someway in the corners, that we
may see and remark, and say Whose?

Or I guess the grass is itself a child. . . .the produced babe
of the vegetation.

Or I guess it is a uniform hieroglyphic,
And it means, Sprouting alike in broad zones and narrow
Growing among black folks as among white,
Kanuck, Tuckahoe, Congressman, Cuff, I give them the
same, I receive them the same.

And now it seems to me the beautiful uncut hair of graves.
Tenderly will I use you curling grass,
It may be you transpire from the breasts of young men,
It may be if I had known them I would have loved them;
It may be you are from old people and from women, and
from offspring taken soon out of their mother’s laps,
And here you are the mother’s laps.

This grass is very dark to be from the white heads of old
Darker than the colorless beards of old men,
Dark to come from under the faint red roofs of mouths.

O I perceive after all so many uttering tongues!
And I perceive they do not come from the roofs of mouths
for nothing.

I wish I could translate the hints about the dead young men
and women,
And the hints about old men and mothers, and the offspring
taken soon out of their laps.

What do you think has become of the young and old men?
What do you think has become of the women and

They are alive and well somewhere;
The smallest sprouts show there is really no death,
And if ever there was it led forward life, and does not wait
at the end to arrest it,
And ceased the moment life appeared.

All goes onward and outward. . . .and nothing collapses,
And to die is different from what any one supposed, and

2019 RIP

Some deaths in 2019

Napoleon Chagnon

There will never again be anything like the twentieth century for cultural anthropology, a time when still-surviving tribal societies were studied in depth by several generations of fieldworkers. Napoleon Chagnon is among the great ethnographers. Even in this company he is exceptional for the range and depth of quantitative data he collected. He is exceptional as well for his interest in bringing evolutionary theory to bear on understanding human behavior – including violence and revenge. This made him a figure of controversy in cultural anthropology, where the duumvirate of Blank Slate and Noble Savage still have a strong hold. Here’s a post on Chagnon, and the controversy.


Jessye Norman

Just this


Immanuel Wallerstein

Wallerstein’s World Systems Theory is a spatialized version of Marxism: a prosperous Core of developed nations grows rich by glutting themselves on an exploited, underdeveloped Periphery. As a historical-sociological Theory of Everything, it probably ultimately doesn’t work better than classical Marxism. But it’s not entirely wrong either. Silver from Potosi, sugar from Haiti, corn from Wallachia, rubber from the Congo; Wallerstein and World Systems Theory have forced our attention on one of the dark sides of the making of the modern world.


Gene Wolfe

Thus I became acquainted with all the thoroughfares and with many an unfrequented corner – granaries with lofty bins and demonic cats; windswept ramparts overlooking gangrenous slums; and the pinakotheken, with their great hallway topped by a vaulted roof of window-pierced brick, floored with flagstones strewn with carpets, and bound by walls from which dark arches opened to strings of chambers lined – as the hallway itself was – with innumerable pictures.

Many of these were so old and smoke-grimed that I could not discern their subjects, and there were others whose meaning I could not guess. … After I had walked at least a league among these enigmatic paintings one day, I came upon an old man perched on a high ladder. …

The picture he was cleaning showed an armored figure standing in a desolate landscape. It had no weapon, but held a staff bearing a strange, stiff banner. The visor of this figure’s helmet was entirely of gold, without eye slits or ventilation; in its polished surface the deathly desert could be seen in reflection, and nothing more.

This warrior of a dead world affected me deeply, though I could not say why or even just what emotion it was I felt. In some obscure way, I wanted to take down the picture and carry it … into … mountain forests. … It should have stood among trees, the edge of its frame resting on young grass.

A remembrance of things past from Severian, born into the guild of torturers but now exiled, on a weary, war-torn Earth perhaps a million years in the future, under a dying sun. He is looking, all unknowing, at the picture of an Apollo astronaut, one of the few relics left of our forgotten age. (See picture at the top of this page, under December.)

Gene Wolfe is one of the finest literary artists the field of science fiction has produced. His tetralogy, The Book of the New Sun, bears reading and rereading. (This quotation is from Book One, The Shadow of the Torturer.)

About Wolfe. And more.

“My nights were sour, spent with Schopenhauer”

February 1997 – March 1999

In December 1998, Bill Clinton is impeached by the House of Representatives, only the second US President to be impeached, after Andrew Johnson in 1868. The charges are perjury and obstruction of justice. Clinton has a long record of philandering going back to his days as governor of Arkansas and continuing to the White House. His attempts to cover this up give Republicans in the House an opening for impeachment. Clinton also pays a $90,000 fine for lying about his relations with Paula Jones, an Arkansan who accused him of sexual harassment. He eventually settles out of court with Jones for $850,000.

In 2000, the Presidential campaign of Al Gore keeps its distance from Clinton. In polls, an exceptionally high percentage of potential voters list “moral character” as an important issue in the election, and these voters mostly favor Gore’s opponent, George W. Bush. Gore believes that the Clinton scandals cost him the election.

Here’s a quote from the great pessimistic philosopher Schopenhauer (my translation):

Sexual love … next to the love of life … shows itself as the strongest and most active of motives, and constantly lays claim to half the powers and thoughts of the younger portion of mankind. It is the ultimate goal of almost all human effort. It exerts an unfavorable influence on the most important affairs, interrupts every hour the most serious occupations, and sometimes confuses for a while even the greatest minds. It does not hesitate to intrude with its trash, interfering with the negotiations of statesmen and the investigations of the learned … It devises daily the most entangled and the worst actions, destroys the most valuable relationships, breaks the strongest bonds, demands the sacrifice sometimes of life or health, sometimes of wealth, rank and happiness. Indeed, it destroys the conscience of the otherwise honest, makes traitors of the once loyal … One is forced to cry: Why all this noise? Why the strain, turmoil worry and effort? … Why should such a trifle pay so important a part, and constantly introduce disturbance and confusion into the well-regulated life of man? But to the earnest investigator the spirit of truth gradually reveals the answer: it is no trifle that is in question here; on the contrary, the importance of the matter is quite proportionate to the seriousness and ardor of the effort. The ultimate aim of all love affairs … is actually more important than all other aims in human life, and is therefore quite worthy of the profound seriousness with which everyone pursues it. What is decided by it is nothing less than the composition of the next generation … This is the key to the problem.

Schopenhauer actually anticipated a lot of Darwin’s theory of sexual selection – for example, how differences in men’s and women’s sexuality derive from differences in potential rates of reproduction. However he got there with the help of a lot of high-flown Germanic idealist talk about the Will to Live, rather than with scientific arguments.

Schopenhauer’s greatest disciple is Richard Wagner. If most of Mozart’s operas are about the triumph of monogamy in the face of obstacles, then most of Wagner’s operas are about the destructive antisocial nature of sexual love.

Europe of nations

May 1989 – September 1992

The 1991 disintegration of the Soviet Union was not widely anticipated. Academic Sovietologists were probably less likely than knowledgeable non-academics to anticipate that the Union was not going to last. One of the small number of people who got it right was public intellectual (and long-time Senator from New York) Daniel Patrick Moynihan. He argued a decade earlier that the Soviet system faced serious economic problems and that ethnic divisions were likely to lead to a collapse of the Union, as they had to earlier colonial empires like the British.

Being of Irish ancestry helped Moynihan to appreciate the continuing importance of ethnicity and nationalism under the cover of universalist ideologies. As warfare diminished in importance over the later twentieth century, the earlier Orwellian nightmare of a world divided into a few warring super-states receded, and an older vision of a Europe of nations revived. In 1900, neither Ireland, nor Poland, nor the Czech Republic was an independent country; by 2000 they were all running their own affairs – not because they built unstoppable military machines, but because they mobilized feelings of imagined community.

However there was a dark side to the return to nationalism. The newly independent nations of Eastern Europe were successful in resolving older border conflicts partly owing to a wave of mass killing and mass expulsions during and after the Second World War that tidied up the ethnic map. In Yugoslavia, where different nationalities were still heavily intermingled, the return to nationalism resulted in a civil war that killed about 130,000 people, and introduced the phrase “ethnic cleansing” to the language.

At the time, the fall of the Soviet Union and the Warsaw pact, and of communism is Eastern Europe, was widely seen as the decisive victory of one ideology – liberal capitalist democracy – over another. As it has turned out however, the fall of communism in Eastern Europe did not represent The End of History, even European history. Nationalism helped finish off the Soviet Empire; more recently it has emerged as a challenge to the multinational institutions of the West, NATO and the European Union.

On a scholarly note: Is ethnic nationalism an expression in the modern world of an evolved human psychology, a psychology shaped by the process of kin selection, as some scholars have argued? I considered the matter in an article, Kin selection and ethnic group selection (and here’s a blog post). The short answer: it’s complicated. Here’s my conclusion to the paper

Both the study of prehistory and political psychology are changing rapidly in the face of new evidence from biology, especially genetics. It would be intellectually satisfying if we could integrate these findings under the heading of an already existing theory, by equating ethnicity with kinship and applying kin selection theory. But we’ve seen that this won’t work. Ethnicity, like kinship, may have to do with shared genes. There may even be such a thing as ethnic nepotism. But an evolutionary theory of ethnicity – even the barebones theory presented here – has to be something more than the theory of kin selection, because of the way ethnicity is entangled with some of the most complicated aspects of human sociality: norms, rules, and political ideals, and their connection with large-scale population processes.

The modern synthesis and the blank slate

August 1938 – November 1943

We’re now dividing time finely enough to include months as well as years.

For most of the later nineteenth century after the publication of On the Origin of Species. biologists were skeptical of Darwin’s proposed mechanism of evolutionary change – natural selection. It was only in the twentieth century that this began to change. When Mendel’s work on heredity was rediscovered in 1900, it was originally seen by many as antithetical to Darwinism. But with the pioneering theoretical work of Fisher, Haldane, and Wright, and the subsequent empirical work of Mayr, Dobzhansky, Simpson, Huxley, Stebbins, and others, Darwin’s theory of natural selection and Mendel’s theory of heredity were combined in what came to be called “the modern synthesis.” Julian Huxley’s book Evolution: The Modern Synthesis marked the coming of age of the theory.

In an earlier post I noted how Lyell’s and Darwin’s embrace of gradualism in explaining the past (as well as George Eliot’s celebration of Dorothea Brooke’s “unhistoric acts” and “hidden life”) had something to do with the political climate in England in the years after the French Revolution and Napoleon. Evolution: The Modern Synthesis was first published in 1942. It’s no surprise that the modern synthesis too was a product of its time, when Nazi Germany and the Soviet Union offered gruesome antithetical demonstrations of how not to think about evolution, genes, and behavior.

Not coincidentally, at the same time that biologists in England and the United States were advancing the modern synthesis, social scientists – cultural anthropologists, behaviorist psychologists – were coming to embrace a strong blank slate view of human nature. (Carl Degler tells the American side of the story in In Search of Human Nature: The Decline and Revival of Darwinism in American Social Thought.) There grew up something amounting to a peace treaty between evolutionary biology and the social sciences, with the two fields agreeing to respect each others’ spheres of influence. Social scientists would leave biology to the biologists, accepting, for example, that neither a good upbringing nor acquired skills can improve your genes. Biologists in turn would largely steer clear of addressing social behavior. For example, the theory of sexual selection, which Darwin developed, and Fisher elaborated, was mostly dropped from the modern synthesis as it matured. Huxley argued (pretty unconvincingly in retrospect) that the elaborate mating dances and ornaments found in so many species were not a product of sexual selection, but merely helped to get individuals to choose the right species of mate. Westermarck’s pioneering work on the evolutionary psychology of incest avoidance and the incest taboo was largely shelved in favor of the shakier theories of Freud and Lévi-Strauss. Even Darwin’s work on emotional expression, which might have seemed fairly anodyne politically, was largely rejected by anthropologists. And the study of prehistory was affected as well.

It was only beginning in the 1960s and 1970s, with the rise of sociobiology, that evolutionary biologists returned to seriously addressing social behavior. Sociobiology: The New Synthesis (1975), by E. O Wilson, made a nod to Huxley in its subtitle. It also announced the end of an intellectual peace treaty, and the opening of an intellectual war that persists up to the present.