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).

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,

           L/G>1

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

71.5 – 67.7 million years ago

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 tomorrow:

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
zones,
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
mothers,
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
children?

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
luckier.

Reuben, Reuben

Reuben, Reuben, I’ve been thinking
What a fine world this would be
If the men were all transported
Far beyond the northern sea.

Oh, my goodness, gracious, Rachel,
What a strange world this would be
If the men were all transported
Far beyond the northern sea.

Reuben, Reuben, I’ve been thinking
What a great life girls would lead
If they had no men about them
None to tease them, none to heed.

Rachel, Rachel, I’ve been thinking
Life would be so easy then
What a lovely world this would be
If you’d leave it to the men.

Reuben, Reuben, stop your teasing
If you’ve any love for me
I was only just a-fooling
As I thought, of course, you’d see.

Rachel, if you’ll not transport us
I will take you for my wife
And I’ll split with you my money
Every pay day of my life!

(Traditional song, many versions)

I once heard William Hamilton, the evolutionary theorist, give a talk where he suggested, among other things, that human beings might give up sexual reproduction in the future. He was building on a familiar evolutionary puzzle: sex, or more exactly the division between female (large, expensive gametes) and male (small, cheap, mobile/motile gametes) is a very expensive proposition. Imagine a sexually reproducing population in which females average two offspring each, one female, one male. On average, each female is replacing herself in the next generation with one daughter. Now imagine a mutant asexual female. She also gives birth to two offspring, but the offspring are both daughters, clones of their mother. The numbers of this mutant lineage will initially double in every generation, and they will eventually replace the sexually reproducing type entirely. 

Unless … There must be some advantage to sexual reproduction to make up for this huge disadvantage. One possibility is that sex somehow makes it easier to avoid the accumulation of deleterious mutations. Another possibility, which Hamilton was pushing, is that sex gives an advantage to host species in their evolutionary arms races with parasites. A species consisting of lots of genetically uniform clones is more vulnerable to pathogens. 

However … (and this is where Hamilton was going) a species that has developed medical technology to the point that it no longer has to worry so much about infectious disease might be able to dispense with sexual reproduction. So Hamilton pondered a germ-free hygienic future in which the clonal offspring of one or more fit, fecund, philoprogenitive females replaced the rest of the human race.

And … minus the evolutionary theorizing, some science fiction writers have imagined futures without a division between men and women. John Wyndham, writing back in the 1950s imagined a world in which a plague had wiped out men, and the surviving women carried on high tech reproduction without men in an ant-like caste society. Wyndham thought this was a bad thing, but for some feminist science fiction writers in the 1970s – Joanna Russ, James Tiptree, Jr. – a world without men was imagined as a utopia.

The most sustained piece of world-building of a society without “men” and “women” comes from Ursula Le Guin. The aliens on the planet Winter are much like humans on Earth, but they are hermaphrodites. Most of the time they are neuter, with underdeveloped male and female organs. But during kemmer (estrus, the breeding season), two individuals will pair off and develop complementary sexual characters and sexual desires. One member of the pair will temporarily develop as a female, the other as a male. They will copulate much as we do, and the female member of the pair will conceive and eventually give birth. The next time kemmer rolls around, the former female may develop as a male, and her former (and formerly male) partner (or another) may develop as a female.

Le Guin, the daughter of two anthropologists, gives us a richly developed thick description of the culture of Winter, not a utopia, but just another world, different from our own in some ways, similar in others. But what’s missing from her story is much consideration of the evolutionary dynamics underlying the exotic (to us) reproductive biology. In Le Guin’s scheme, the female member of a pair is still putting more energy than the male into producing a child. We have to expect that there will be considerable jockeying, both physiological and psychological, over who, in each reproductive episode, takes on the more burdensome role. On Winter, the Battle of the Sexes will still be fought, albeit on different terrain.

Meanwhile, back on Earth, Reuben, Reuben is a comic novel about the Battle of the Sexes in 1950s suburban Connecticut. The novel centers on the priapic poet Gowan MacGland, (obviously modeled on Dylan Thomas), who takes advantage of an American tour to enjoy the opportunities available to an alpha small-gamete-producer. Up to a point, anyway: the terrible lesson he learns is never, ever, ever cuckold your dentist.

“My nights were sour, spent with Schopenhauer”

October 1998 – January 2001

In December 1998, Bill Clinton is impeached by the House of Representatives. He is one of only three US Presidents to be impeached, preceded by Andrew Johnson in 1868 and followed by Donald Trump in 2019 and 2021. The charges against Clinton are perjury and obstruction of justice. He 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. Curiously, 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

December 1990– August 1993

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 way and the word, continued

Continuing yesterday’s post: What accounts for the differences between classical Greek and early Chinese intellectual traditions? Below are a few things that might be involved; this is hardly a complete list.

Non-degenerate limit random variables

Here’s a nice little puzzle involving probability:

Take a bag with two marbles in it, one red and one green. Draw a marble at random. Put it back in the bag, and add another marble of the same color. Repeat: randomly draw one of the (now three) marbles in the bag, put it back, and again add a marble of the same color. Continue, adding a marble every time. What happens to the frequency of red marbles as the number of marbles in the bag goes to infinity?

Answer: When you carry out this procedure, the frequency approaches a limit. As the number of marbles grows larger, you sooner or later get, and stay, arbitrarily close to the limit. Now carry out the same infinite procedure a second time. This time you also approach a limit. But the limit this time is different! The first time, the limiting frequency might be .23748… . The second time it might be .93334… . If you keep on doing the infinite experiment a bunch of times, you’ll approach a different limit every time, with the various limits uniformly distributed over the interval [0,1]. These are non-degenerate limits. This is different from what you get when you flip a fair coin infinitely many times. The frequency of heads will always approach the same “degenerate” limit, .50000… .

A chance element like this is probably involved in the intellectual traditions of major civilizations. The first few great thinkers to come along have a massive influence on the direction of intellectual life, just as picking a red or green ball on the first round makes a big difference to the final limit. So Pythagoras’ and Plato’s obsessions with numbers and geometry as the keys to the universe have a disproportionate influence on later Western thought (allowing that the “Pythagoras” we know is encrusted with legends). Subsequent thinkers have progressively less and less influence, just as picking a green or red ball when there are already a hundred balls in the bag doesn’t make much difference in the ultimate limiting frequency.

Temperament

But there may be more systematic things going on. Daniel Freedman was a psychologist, white, married to a Chinese-American woman. While awaiting the birth of their first child, the couple found that relatives on the two sides of the family had very different ideas about how newborns behave. Freedman was sufficiently intrigued that he carried out an investigation of assorted newborns in a San Francisco hospital, including babies of Chinese and European origin.

It was almost immediately apparent that Chinese and Caucasian babies were indeed like two different breeds. Caucasian babies started to cry more easily, and once started they were more difficult to console. Chinese babies adapted to almost any position in which they were placed.. … In a similar maneuver … we briefly pressed the baby’s nose with a cloth, forcing him to breathe with his mouth. Most Caucasian and black babies fight this … by immediately turning away or swiping at the cloth. However … the average Chinese baby in our study … simply lay on his back, breathing from his mouth. … Chinese babies were … more amenable and adaptable to the machinations of the examiners. p. 146

This might seem like a minor curiosity, but it fits neatly with later work demonstrating East-West differences in adult cognitive styles. This raises the possibility that differences in temperament evident at a very early age might influence the evolution of intellectual traditions.

Coinage

Coined money apparently initially appeared in Lydia, in Asia Minor, around 600 BCE. It was quickly taken up by the Lydians’ Ionian Greek neighbors. And it is in Ionia too that we find the earliest philosophers. In Money and the Early Greek Mind, Richard Seaford argues that these developments are connected. The monetization of the Greek economy accustomed Greeks to the idea that a common impersonal material measure of value, relatively independent of individual control, underlay the multifarious goods and services produced by the polis economy. This led in turn to the pre-Socratic philosophers, who were obsessed with finding the one impersonal natural element – water, air, number – of which the whole heterogeneous variety of the natural world was made.

In Athens, the expansion of a monetary economy led to a curious insult – opsophagos, or fish-eater. What made this an insult is that fish were sold in the marketplace. They were a mere commodity, free of the ritual and taboos that surrounded the sacrifice and distribution of animal flesh. The fish-eater was a rich man indulging the pleasures of consumption free from the constraints of tradition and decorum. And his conspicuous consumption offended not only tradition but the spirit of democracy. Better that he spend his wealth on the public good.

In traditional China, by contrast, coins, and later paper money, would challenge but never break the hold of state patriarchy. And Spartans too recognized the subversive potential of money. Sparta used iron bars for money, precisely because they were inconvenient.

The goodness paradox

205 – 195 thousand years ago

We’re now doing history at ten thousand years a day.

Earth Abides is an early (1949) entry in the genre of post-apocalyptic science fiction, with some haunting reflections on what it takes to keep a civilization going, or just a human community. In this case the apocalypse takes the form of a lethal infectious disease that wipes out well over 99% of Earth’s human population, leaving scattered survivors to try and put things back together.

The drama is low-key. If you want to read about the remnants of civilized humanity defending themselves against zombies, or venomous man-eating walking plants, or a horde of cannibal anti-nuke zealots, you’ll have to look elsewhere. The threat to civilization in Earth Abides is more subtle. The generation born after the die-off has no understanding of what they have lost, of what the collapsing factories and powerlines and machines around them really were, or how they worked, or how to get them back up and running. The older generation, without the institutions of a complex society backing them up, can’t supply enough discipline and punishment to pass on the arts of civilization. The young will grow up as illiterate scavenger-foragers, skilled with bow and arrow, well-adapted in their own way to a rewilding Earth. Ish, the protagonist, will end his days as the Last American (a fictional counterpoint to the real-life Ishi, the last Yahi Indian).

The community is nonetheless capable of reacting decisively when their survival is threatened.

One day a newcomer enters the scene. Charlie is talkative, forceful, charismatic. The kids adore him. It looks like he might even take over as leader of the little group. But it becomes clear that there is something off about him, even sociopathic. He can turn on the charm, but when thwarted he is menacing. He always carries a gun, which he keeps hidden. He is sexually abandoned. And, in a world without antibiotics, he is infected with a slew of venereal diseases.

Something has to be done about Charlie, and the elders of the group meet to decide what. Their options are limited. Keeping him locked up is not a practical possibility for this tiny community. They could banish him. But who is to say he won’t find a gun, and come back, looking for revenge? They could execute him. But what actual harm has he done, so far? They decide to settle the matter with a vote.

Em located four pencils. Ish tore a sheet of paper into four small ballots.

…

This we do, not hastily; this we do, not in passion; this we do, without hatred. …

This is the one who killed his fellow unprovoked; this is the one who stole the child away; this is the one who spat upon the image of our God; this is the one who leagued himself with the Devil to be a witch; this is the one who corrupted our youth; this is the one who told the enemy of our secret places.

We are afraid but we do not talk of fear. … We say, “Justice”; we say, “The Law”; we say “We, the people”; we say, “The State.”

…

Ish sat with his pencil poised … He could not be sure. Yet, at the same time, he knew that The Tribe faced something real and dangerous and even dreadful, in the long run threatening its very existence. … In that final realization, he knew that he could write only the one word there, out of love and responsibility for his children and grandchildren. …

“Give me your slips,” he said.

They passed them in, and he laid them face up before him on the desk. Four times he looked, and he read: “Death … death … death … death.”

Keith Otterbein is an anthropologist who did a study of capital punishment across cultures. He expected to find that capital punishment is limited to complex societies, used to enforce social hierarchy. Instead he found that capital punishment is a universal, present in societies from the simplest to the most complex. It is an option that even the smallest, most easy-going communities – like The Tribe of Earth Abides – may find themselves resorting to. We can infer that for tens or even hundreds of thousands of years, our ancestors have been carrying out group-sanctioned executions of individuals deemed anti-social and a threat to group harmony and survival. This is long enough to have had evolutionary consequences. Long before we domesticated the wolf, the wild sheep and goat, the aurochs, we may have been domesticating ourselves, weeding out the wildest and most dangerous from our midst, replacing the old tyranny of the alpha male with the new tyranny of Custom and The Law.

The idea that human beings are in some ways like domesticated animals is an old one. It has recently returned to the spotlight. The extraordinary long-term experiment in artificial selection for tameness in foxes carried out by Nikolai Belyaev, Lyudmila Trut, and their coworkers in Russia has demonstrated that selection for tameness ends up selecting for a whole suite of anatomical characteristics as byproducts. Strikingly, many of the features that differentiate Homo sapiens hundreds of thousands of years ago from Homo sapiens today are also features that distinguish tame from wild foxes, and dogs from wolves.

Richard Wrangham’s recent book, The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution connects the dots, setting out one long argument that an evolutionary history of capital punishment has reduced our disposition for reactive aggression (the hot-blooded, spur-of-the-moment, volatile, antisocial kind), while leaving intact our capacity for calculated, cold-blooded, proactive killing (“not hastily, … not in passion, … without hatred”).

Perhaps this explains a very recent finding in human evolution. Apparently 200,000 years ago, we were about evenly matched with Neanderthals, sometimes replacing them, sometimes being replaced by them. By 40,000 years ago however, Neanderthals lose out decisively to modern humans. It may be that what changed in the interim to give us the edge is that we improved our ability to get along peaceably with insiders (including distant insiders we don’t know personally) without losing our ability to apply lethal aggression to outsiders.

It’s a small world after all

475 – 450 thousand years ago

The story of human origins is partly a story of Big Things like The Taming of Fire and  The Dawn of Speech. But it’s also the story of some odd byways and quiddities. A nice introduction to some of these is Chip Walter’s book Thumbs, Toes, and Tears: And Other Traits That Make Us Human. (His more recent Last Ape Standing is good too.) Walters considers funny bits of anatomy like our unique big toes and thumbs, and funny bits of behavior like our habits of laughing, weeping, and kissing. Toes and thumbs fossilize, but behaviors can be hard to date, evolutionarily. Presumably these behaviors appeared sometime before modern humans evolved and spread, so let’s pick today’s date. It’s also hard to figure out the exact evolutionary rationale for some of these behaviors. Humor, for example, is not a simple phenomenon: intellectually appreciating a joke, actually finding it funny and enjoying it, and finally laughing, each involve separate areas of the brain.

Laughter, specifically, is a minor human oddity that sheds an interesting light on some big events in human evolution. Robert Provine, a leading laughter researcher, spells out the argument in “Curious Behavior: Yawning, Laughing, Hiccuping, and Beyond.” Chimpanzees have a kind of laugh, a modified vocalized panting synchronized with inhalation and exhalation. Presumably laughter first resulted when panting-during-play evolved into a play signal. But the short bursts of human laughter go further, having freed themselves from synchrony with the inhalation/exhalation cycle. Laughter, in other words, is just one instance of the more general phenomenon of humans having separate controls for vocalization and for respiration. Interestingly, the most prominent examples of complex vocalization – songbirds and some other birds, whales, bats, and humans – are all found in non-quadrupeds. In quadrupeds, breathing is tightly coupled with locomotion: lungs need to be full to stiffen the thorax when the forelimbs hit the ground. Giving up quadrupedalism seems to have allowed for an “adaptive release” in the evolution of vocal abilities in a number of unrelated lineages. So the study of laughter (and other vocalizations) suggests that two key human adaptations – bipedalism and spoken language – are more closely linked than one might have expected.

Another and overlapping set of human particularities involves facial expressions of the emotions. Darwin got a whole book out of this. He concluded (admittedly based on somewhat anecdotal evidence) that different emotional expressions are largely innate. It’s an interesting illustration of his ability to reason from small facts to large conclusions that he also drew a big conclusion about human evolution from this. In Darwin’s day, there were scientists who believed that different human races had evolved from very different prehuman progenitors: one prehuman species giving rise to Europeans, another to Africans, and so on. But Darwin reasoned that the very close similarity in facial expressions (and he had traveled a lot, and witnessed a lot of expressions in a lot of places) and the very similar emotional makeup of humans around the world was evidence that human populations shared a fairly recent common ancestry. Here as in several other cases, a mixture of close reasoning and sheer luck led Darwin to the correct conclusion about evolution long before there was much solid evidence.

Darwin’s work on emotions was neglected for most of the twentieth century by anthropologists favoring a blank slate view of human behavior, but was eventually largely vindicated by a number of researchers, notably Paul Ekman. There is now good evidence for six basic facially expressed emotions: Fear, Disgust, Joy, Anger, Sadness, and Surprise.

If you’re a movie watcher, this list may seem familiar. These emotions (all except for Surprise) are all depicted as little homunculi living inside the head of an 11 year old girl in the animated feature “Inside Out.” Somebody at Pixar Studios knew their Ekman.

So the sappy song is right: There is just one moon and one golden sun, and a smile means friendship to everyone.

Heather erectus, or Women Gotta Stick Together

(Here’s a link to the song, “Women Gotta Stick Together”, a satirical take on female solidarity from the musical sitcom “Crazy Ex-Girlfriend”)

Because boys are much louder and less private than girls, it took me a while to begin to focus on girls’ behaviors. When I did, I was quite surprised to see that the stereotypes that apply to girls’ behavior around the world, such as “sugar and spice and everything nice,” did not fully describe what I was actually seeing girls do. … Girls spend a lot of time talking about other people in their lives … These discussions, however, are not composed simply of saying “nice” things about their family and friends. Often, they are dissecting the most negative aspects of another’s behavior. … Paradoxically, I … found out that two girls or two women talking do not typically help one another, other than to be reassuring. In fact, two unrelated females often can become fast enemies. Because they have so much in common, they need similar physical resources, and beginning in adolescence they may compete for the same men. This creates an inherent conflict in unrelated human females’ relations with one another. … How this plays out leads to some very confusing relationships.Warriors and Worriers: The Survival of the Sexes. Joyce F. Beneson

As Darwin noted, adaptive evolution involves nsexual selection as well as the struggle for existence. Sexual selection is not simply about A surviving and reproducing, but more specifically about A reproducing at the expense of B. This may involve mate choice: A may succeed at the expense of B because he or she is more attractive to the other sex. Mate choice may have shaped both female and male traits in our species. Sexual selection can also involve contests within one sex over who mates with the opposite sex. There have been epochs in the history of our species when some men have acquired many more mates, and left many more offspring, than others, most likely by wielding violence, typically as part of a gang. 

Female-female sexual competition is less conspicuous, but still very real.It may have left its mark on women’s sexual physiology and behavior. One argument goes like this:

Ovulation is less conspicuous in our species than among many other primates. Unless we know them very well, we generally don’t have much idea who among the young women we run into is ovulating. The evolution of concealed ovulation at some point in the human line has been the subject of a lot of theorizing. Most of the theories invoke male mate choice: maybe men were more likely to stick around and provide for women who didn’t reveal when they were and weren’t ovulating. But recent work suggests that, in addition to male provisioning, female-female sexual rivalry and aggression may have been crucial. In an agent-based simulation in which females could secure mateships and provisioning by aggressing against rivals, “concealers” were able to out-reproduce “revealers” because they avoided aggression from other females. In other words, the concealment of ovulation in our species may reflect a long evolutionary history of estrus-shaming (my phrase, not the authors’).

Calories and curves

1.31 -1.24 million years ago

This figure is from a neat recent paper comparing energy expenditure (TEE or Total Energy Expended) and fat among humans and our closest relations: chimpanzees (genus Pan), gorillas (Gorilla), and orangutans (Pongo). (The numbers are adjusted for differences in overall body mass.)

What stands out here is that humans are a high energy species. Also we carry a lot more body fat than the other great apes. This applies particularly to women, who need a lot of extra fat to meet the high energy demands of human infants. But it even applies to men. For both sexes, a high energy life style means you want to carry around an extra reserve of fat in case of emergencies.

We don’t know how long ago our ancestors decided to crank up their energy consumption. Maybe back with the rise of Homo erectus (just a few days ago on Logarithmic History). Or maybe later, when the typical modern human pattern of slow maturation was more firmly in place. At some point in the near future, we’ll actually nail down the specific genetic changes leading humans to accumulate more fat, and be able to put a date on the change. It may be that the distinctively human mating system also arose back then, with human females concealing ovulation (no chimp-style monthly sexual swellings) but advertising nubility (with conspicuous fat deposits appearing at puberty).

A high energy life-style also goes with extensive food sharing and changes in human kinship. (Here’s me, on beating Hamilton’s rule through socially enforced nepotism.)