When you were a tadpole and I was a fish

1.17 – 1.11 billion years ago

And here’s a post (with a poem) that works for Valentine’s Day.

The Boring Billion rolls on. The atmosphere is one percent oxygen or so thanks to photosynthetic bacteria and algae. The ocean still largely anoxic and thick with sulfates and sulfate-eating bacteria. Eukaryotes have been around for a while, and are diversified, although still all single celled (as far as we know).

Sexual reproduction begins with eukaryotes, and by now some groups are presumably differentiated into male and female. And so here’s a poem for Valentine’s Day, by the biologist Langdon Smith. Martin Gardner has a nice account of the poem, in his book “When you were a tadpole and I was a fish,” and here’s a great video of the poem spoken by Jean Shepherd.

Evolution
By Langdon Smith (1858-1908)

When you were a tadpole and I was a fish
In the Paleozoic time,
And side by side on the ebbing tide
We sprawled through the ooze and slime,
Or skittered with many a caudal flip
Through the depths of the Cambrian fen,
My heart was rife with the joy of life,
For I loved you even then.

Mindless we lived and mindless we loved
And mindless at last we died;
And deep in the rift of the Caradoc drift
We slumbered side by side.
The world turned on in the lathe of time,
The hot lands heaved amain,
Till we caught our breath from the womb of death
And crept into life again.

We were amphibians, scaled and tailed,
And drab as a dead man’s hand;
We coiled at ease ‘neath the dripping trees
Or trailed through the mud and sand.
Croaking and blind, with our three-clawed feet
Writing a language dumb,
With never a spark in the empty dark
To hint at a life to come.

Yet happy we lived and happy we loved,
And happy we died once more;
Our forms were rolled in the clinging mold
Of a Neocomian shore.
The eons came and the eons fled
And the sleep that wrapped us fast
Was riven away in a newer day
And the night of death was passed.

Then light and swift through the jungle trees
We swung in our airy flights,
Or breathed in the balms of the fronded palms
In the hush of the moonless nights;
And oh! what beautiful years were there
When our hearts clung each to each;
When life was filled and our senses thrilled
In the first faint dawn of speech.

Thus life by life and love by love
We passed through the cycles strange,
And breath by breath and death by death
We followed the chain of change.
Till there came a time in the law of life
When over the nursing sod
The shadows broke and the soul awoke
In a strange, dim dream of God.

I was thewed like an Auroch bull
And tusked like the great cave bear;
And you, my sweet, from head to feet
Were gowned in your glorious hair.
Deep in the gloom of a fireless cave,
When the night fell o’er the plain
And the moon hung red o’er the river bed
We mumbled the bones of the slain.

I flaked a flint to a cutting edge
And shaped it with brutish craft;
I broke a shank from the woodland lank
And fitted it, head and haft;
Then I hid me close to the reedy tarn,
Where the mammoth came to drink;
Through the brawn and bone I drove the stone
And slew him upon the brink.

Loud I howled through the moonlit wastes,
Loud answered our kith and kin;
From west to east to the crimson feast
The clan came tramping in.
O’er joint and gristle and padded hoof
We fought and clawed and tore,
And cheek by jowl with many a growl
We talked the marvel o’er.

I carved that fight on a reindeer bone
With rude and hairy hand;
I pictured his fall on the cavern wall
That men might understand.
For we lived by blood and the right of might
Ere human laws were drawn,
And the age of sin did not begin
Til our brutal tush was gone.

And that was a million years ago
In a time that no man knows;
Yet here tonight in the mellow light
We sit at Delmonico’s.
Your eyes are deep as the Devon springs,
Your hair is dark as jet,
Your years are few, your life is new,
Your soul untried, and yet –

Our trail is on the Kimmeridge clay
And the scarp of the Purbeck flags;
We have left our bones in the Bagshot stones
And deep in the Coralline crags;
Our love is old, our lives are old,
And death shall come amain;
Should it come today, what man may say
We shall not live again?

God wrought our souls from the Tremadoc beds
And furnish’d them wings to fly;
He sowed our spawn in the world’s dim dawn,
And I know that it shall not die,
Though cities have sprung above the graves
Where the crook-bone men made war
And the ox-wain creaks o’er the buried caves
Where the mummied mammoths are.

Then as we linger at luncheon here
O’er many a dainty dish,
Let us drink anew to the time when you
Were a tadpole and I was a fish.

Between Darwin’s and Saint Valentine’s Day

1.23 – 1.18 billion years ago

Yesterday was Darwin’s birthday (and Lincoln’s). Tomorrow is Valentine’s Day. Here’s a post appropriate for either day.

Imagine sex worked like this:

You’ve been feeling bad lately, getting sick a lot. You’re not at your best. You find someone who seems to be in better shape. One thing leads to another and you wind up acquiring body fluids from the other party – and picking up some new genes from them. The new genes help a lot in fighting off infection. You’re feeling better now.

Reproduction? That’s another matter, nothing directly to do with sex. When you reproduce, your offspring will carry all the genes you happen to have at the moment. (Here’s one drawback, according to The Onion.)

Also, I forgot to mention that you’re neither male or female – the gene exchange could have gone in the other direction if you’d both been in the mood. And your partner in the adventure above might not even have been the same species as you. (Just what counts as a species here isn’t well-defined.)

This is more or less how bacteria work out sex. (Joshua Lederberg got the Nobel Prize for figuring this out.) Eukaryotes (you’re one of them) mostly do it differently, combining sex and reproduction. It’s the story you learned in high school about passing on half your genes to a gamete (sex cell), which joins with another gamete to make a new organism.

Most eukaryotes also have two sexes. The best theory we have about why that got started goes like this: Most of the DNA in a eukaryote cell is in the nucleus. But a small fraction is in the mitochondria, little powerhouses outside the nucleus that started out as bacteria, and got domesticated. Imagine that two gametes join together, and combine two sets of mitochondria. There’s a potential conflict here. Suppose your mitochondria have a mutation that lets them clobber your partner’s mitochondria. This is good (evolutionarily speaking) for the winning mitochondria, but very likely to be bad for the cell as a whole. Better for the cell as a whole is if one gamete, acting on instructions from the nucleus, preemptively clobbers all their own mitochondria, so that all the mitochondria come from just the other gamete. This is the beginning of what will eventually lead to a distinction between sperm and eggs, pollen and ovules, male and female. Which means you got all your mitochondrial DNA from your mom, something that will turn out to be important when we look later in the year at geneticists unraveling human prehistory. This is also an example of how selection at one level (within cells) can conflict with selection at another level (between cells). We’ll see such multilevel selection again and again, for example in the evolution of complex human societies.

Sex has to be highly advantageous, although we’re not sure exactly what the advantage is. The general answer is probably that an asexually reproducing organism almost never produces any offspring who have fewer harmful mutations than she has. But a sexually reproducing organism, passing on a random half of her genes to each of her offspring, can have some offspring with fewer harmful mutations, at the cost of having other offspring with more. There are various reasons (Muller’s ratchet, Kondrashov’s hatchet) why this could be evolutionarily advantageous.

In other words, with sexually reproduction, at least some of mum and dad’s kids can be less messed up than their parents; it’s asexually reproducing organisms that really embody Larkin’s dour verse …

Man hands on misery to man,

It deepens like a coastal shelf

Get out as early as you can,

And don’t have any kids yourself.

… insofar as, when eukaryote species give up sex, they don’t seem to last long. Dandelions reproduce asexually: based on what we see in other organisms, they probably won’t be around for long, evolutionarily speaking. There’s one mysterious exception, tiny animals called bdelloid rotifers which have been reproducing asexually for tens of millions of years . For readers who are not bdelloid rotifers: Happy Valentine’s Day tomorrow! We’ll have an appropriate evolutionary post up tomorrow

Evolution and broken symmetries

8.81 – 8.34 billion years ago.

No big news in the universe today. Some evolutionary thoughts: Species evolve. Do planets? stars? galaxies?

Charles Darwin didn’t use the word “evolution” often. But he did write a lot about “descent with modification,” which is pretty much what biologists mean by evolution. For example, the usual definition of genetic evolution is “change in gene frequency,” i.e. descent with (genetic) modification.

However, people sometimes talk about evolution that doesn’t involve descent with modification, in contexts that have nothing much to do with biological evolution – cosmic evolution or stellar evolution in the history of the universe, for example, or mineral evolution in the history of the earth. Another Victorian writer, the sociologist and philosopher Herbert Spencer, offered a definition of evolution that might cover these cases.

Evolution is an integration of matter and concomitant dissipation of motion; during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity.

It’s easy to make fun of this definition. It’s the sort of abstract word pile that style manuals tell you to avoid, and that gives sociology a bad name. For that matter, it’s easy to make fun of Herbert Spencer. He may be some of the inspiration for the character of Mr. Casaubon, the dried up, impotent pedant in George Eliot’s “Middlemarch.” (Spencer probably turned down a chance to marry George Eliot = Mary Ann Evans. You should be careful about offending a writer.) But it may be that Spencer was groping toward the important modern concepts of symmetry and symmetry breaking.

A simple example: imagine you’re holding a bicycle exactly upright. The bicycle is pretty much bilaterally (mirror image) symmetrical. (OK, not really, the gears are on the right side, so it’s not a perfect mirror image. But just pretend …) Now let go of the bike. It will fall to one side or the other. The symmetry is broken, and you need one extra “bit” of information to tell you which side the bicycle is on.

Symmetry breaking is a fundamental concept in physics. In the very early history of the universe, the four forces of nature — gravitational, strong, weak, and electromagnetic – were united, but then as the universe cooled, one by one, these forces broke the symmetry and turned into separate forces. More symmetry breaking generated elementary particles, and nuclei, and atoms. When atoms first formed, they were distributed symmetrically through the universe as a diffuse gas. But gravitation pulled atoms and other particles together into clumps, leaving other parts of space emptier, and the spatial symmetry was broken (a “translational” symmetry in this case).

Symmetry breaking will keep showing up throughout the history of the universe. Consider sexual reproduction. A simple early form of sex involved two equal sized gametes (sex cells) joining to produce a new organism. Some species still do it this way. But more commonly the symmetry is broken – some organs or organisms produce little gametes that move around easily (sperm or pollen), others produce big gametes that don’t move around so easily (eggs or ovules). We call the first sort of organs or organisms male and the second sort female. Sex in most multi-cellular organisms is a broken symmetry. This broken symmetry will go on to have a dramatic consequences for human social evolution. It entails, for example, that patrilineages can expand their size much more rapidly than matrilineages.

Or consider the rise of political stratification, the move from small-scale societies where “every man is a chief over himself” to large-scale societies of chiefs and commoners, rulers and ruled. Another broken symmetry. It may be more or less an accident (good or bad luck, Game of Thrones style) who ends up being king, but it’s not an accident that somebody is, past a certain social scale.

We don’t attach much moral significance to broken symmetries where the physical world is concerned. You’re being way too sensitive if you feel sorry for the poor weak nuclear force that missed its chance to be the strong nuclear force, or for the dwarf Gaia-Enceladus galaxy that got cruelly torn apart and cannibalized by the Milky Way. Broken symmetries in social life – males and females, kings and commoners – are another matter …

The veil

April 1977 –September 1980

From Persepolis: The Story of a Childhood by Marjane Satrapi.

Before the Iranian Revolution (1979), a number of Western scholars wrote books attempting to develop general theories of revolution. Barrington Moore’s Social Origins of Dictatorship and Democracy is an early classic in the genre, treating different political trajectories – liberal, reactionary, and communist – as the outcome of different bargains between landowners, peasants, and bourgeoisie. Theda Skocpol’s States and Social Revolutions covers some of the same ground with an added focus on states and war-making.

But the class-centered theories that these authors develop don’t do a very good job of accounting for the Iranian Revolution or broader political currents in the Islamic world. It’s difficult to map Middle Eastern political movements onto a Left-Right spectrum. And both democracy and communism made far less headway in the Middle East than in either Latin America or East Asia. Nor do the class-based theories have much to say about gender relations and patriarchy, major issues in Islamic politics.

One of our themes in the past few months of Logarithmic History has been how the major civilizations of Eurasia have found different ways of combining patrilineal clans, state formation, and major world religions. From this perspective, the Islamic world is distinctive in several respects. The custom of marriage within the patrilineage (stemming from a culture of honor long predating Islam in the Near East, but spread far and wide by Muslim conquests) probably contributes to making the Muslim Middle East exceptionally fragmentary and fissiparous. And Islam has been exceptionally successful in overriding alternative identities based on nationality and class. Today for example, according to surveys, most Pakistani Muslims think of themselves as Muslims first and Pakistanis second, while most Indian Hindus think of themselves as Indians first and Hindus second. Michael Cook’s Ancient Religions, Modern Politics makes the case for Muslim exceptionalism in some detail in comparing the Islamic world with Hindu India and Catholic Latin America.

Baby boom

June 1961 – September 1965

Malthusianism does a pretty good job of capturing the facts of life for our species before the Industrial Revolution. For example, Malthus plus standard economics helps account for some of the historic differences between wheat and rice growing societies. And Darwinism suggests the reason why Malthusianism holds for living things in general: within a population, variants with a higher intrinsic rate of increase tend to replace those with a lower rate, even if the eventual outcome is overpopulation and misery for all. So the field of human behavioral ecology, based on the assumption that people try to maximize fitness, does pretty well in accounting for behavior in pre-modern societies.

But Malthusianism, and the assumption that people are fitness-maximizers, don’t work very well for modern societies. Even as life expectancies and standards of living have been increasing around the world, fertility rates have been declining, falling below replacement levels even in many less developed countries (although rates remain quite high in Sub-Saharan Africa.) The United States mostly follows the general trend, with a long decline in fertility rates over several centuries.

And then there’s the Baby Boom: Birth rates in the United States went up dramatically following the Second World War, then reached a peak in 1957, and continued high into the early 1960s. Young people were marrying early, and having more children. Women were staying out of the workforce to take care of the kids.

Here are two popular theories of why the Baby Boom happened that don’t work:

Soldiers coming home. The return of soldiers from the Second World War contributed to an early spike in the birth rate (visible in the chart above in the late 1940s). But the boom lasted too long to be mostly explained this way, and involved a big increase in the total number of babies born, not just people getting around to having babies that they’d put off having earlier.

Women squeezed out of the labor force. Increasing employment and educational opportunities for women are one of the long-term drivers of the demographic transition. So were these factors operating in reverse during the Baby Boom? The data clearly rule this out. Women’s wages actually rose rapidly during this period, and older women, with their child-rearing years mostly behind them, responded by entering the labor market in large numbers. In other words, employers were eager to hire women, but young women, at least, thought they had better things to do.

Instead, the best account we have comes from Richard Easterlin. He proposes that the Boom happened because young men encountered an exceptionally favorable labor market, resulting from the conjunction of several factors. (1) Birth rates fell to low levels during the Great Depression, naturally enough. As a result, twenty years on, employers faced a shortage of native-born young men looking for entry level jobs. (2) In the nineteenth century, periods of high demand for labor in the United States saw increases in immigration; levels of immigration tracked the business cycle. But in the mid-twentieth century, legal restrictions made it difficult to increase the supply of labor through immigration. Employers instead had to offer higher wages for entry level workers. Young men felt they were doing well enough – both absolutely and relative to the older generation – to get an early start on marrying, and to support their wives while raising bigger families.

The Baby Boom would be its own undoing however. As the earliest Boomers grew up and started to crowd the job market and the universities, “The Sixties” took off.

Half the sky

December 1946 – January 1952

Chinese state patriarchy – the alliance of the Emperor and his officials with patrilineal extended families and clans and patriarchal authority, under the sign of Confucius – was extraordinarily resilient. Over the course of several thousand years, it bounced back again and again in the face of foreign invasions, and neutered potentially disturbing influences like Buddhism and Christianity and the growth of mercantile wealth. It was finally severely weakened, if not quite eliminated, in the twentieth century. Chinese intellectuals, including the student reformers of the May 4^th movement, regarded the traditional Chinese family system as a source of backwardness, which would have to be overthrown for China to take its rightful place among the world’s powers. After the Chinese Communists took over in 1949, they promulgated a revolutionary new marriage law (1950), which stated, in part

The feudal marriage system, which is based on arbitrary and compulsory arrangements and the superiority of man over women and ignores the children’s interests, shall be abolished.

The New Democratic marriage system, which is based on the free choice of partners, on monogamy, on equal rights for both sexes, and on protection of the lawful interests of women and children shall be put into effect.

Bigamy, concubinage, child betrothal, interference with the re-marriages of widows, and the exaction of money or gifts in connection with marriages, shall be prohibited.

Marriage shall be based on the complete willingness of the two parties. Neither party shall use compulsion, and no third party shall be allowed to interfere.

(The law, however, allowed traditional rules of exogamy to stand. These required people to marry outside their clan.) A campaign began, launched in 1953, to enforce the new law. The Communists in China would prove willing to use extraordinary violence to attack old ways, including a kinship system that stood in the way of new forms of state power.

Inbreeding depression

“Let others wage war. Thou, happy Austria, marry” (a description of Habsburg marriage policy). And here’s what “30 Rock” had to say about the Habsburgs, marriage and inbreeding. (Note: if Jenna Moroni, the blonde character in the clip, had managed to procreate with the miserably inbred last Habsburg heir, their kids would have turned out fine, not inbred at all.)

Human inbreeding has a genetic side, which favors outbreeding, at least within the species. Here’s a recent article showing that inbreeding is associated with a wide range of deleterious consequences, including reductions in stature, fertility, and mental ability. But inbreeding also has a political side, which may favor a balance between outmarriage (to make new alliances), and in-marriage (to conserve old alliances, and keep land and honor within the family).

The Habsburgs played the political game adroitly, putting together an enormous empire, partly by war, but partly by astute dynastic marriages. The Habsburg domains were so unwieldy that after the death of Charles V in 1558, they were divided between two branches of the family. Both sections were huge. The map below doesn’t even show the Habsburg possessions outside Europe, in Spanish America and the Far East.

By 1700, however, genetics caught up with the Habsburgs. The Spanish Habsburg line ended with Charles II, who was grossly disabled, physically and mentally. He was also impotent, and left no heirs. A recent calculation shows that, as a result of generation of in-marriage, Charles II had a coefficient of inbreeding of .254. For comparison, a child of full sibling incest will have a coefficient of inbreeding of .25!

Witches

1564 – 1589

It is putting a very high price on one’s conjectures to have a man roasted alive because of them.

Montaigne, “Of Cripples”

Among the Gebusi, a small tribal society on the edge of the New Guinea highlands, all the deaths that we would call natural were attributed to witchcraft. Most natural deaths led to an inquest to determine who the witch was. Children and young women were pretty safe from accusation; others were fair game. Witchcraft was a capital crime, and one third of all deaths of adults in the immediate pre-contact period were killings of suspected witches! The Gebusi are an extreme case, not typical of New Guinea, or of tribal societies in general. But witchcraft beliefs, and punishment of accused witches, have been widespread across cultures, including Europe in past centuries.

Some common notion about European witchcraft accusations and executions is that they’re “medieval,” both in the literal sense of happening in the Middle Ages, and in the figurative sense of expressing the spirit of a dim and barbarous age. Monty Python gave comic expression to both ideas. But neither idea is true. For much of the Middle Ages, the Church condemned the idea that people could fly through air on broomsticks, and similar beliefs, as pagan superstitions, unbefitting good Christians. It is only toward the end of the Middle Ages that the fear of witches starts to take off. And it is at the beginning of the Modern Age – the Age of Discovery, the time of the Renaissance, the Reformation, and the early Scientific Revolution – that the witch craze reaches its height. Most witchcraft trials and executions in the West happen between 1550 and 1700. The total number executed is probably in the high tens of thousands, with additional tens of thousands persecuted but not killed. About 80% of the victims are women.

And some of the most educated men in Europe contribute to the witch craze (although some are skeptics, like Montaigne). In the 1570s, Henri Bouget, a respected French jurist, calculates that there are 1,800,00 witches active in Europe. Slightly later, Jean Bodin, a major figure in early modern political theory, argues that witches are so dangerous and devious that normal judicial safeguards should be suspended: there can be no presumption of innocence for accused witches. King James VI of Scotland (=James I of England) writes a whole book on witches, Daemonologie, and organizes witchcraft persecutions in Scotland; the witches in Macbeth are Shakespeare’s nod to James.

A new information technology, the printing press, doesn’t just foster the Reformation and the Scientific Revolution. It also helps the witch craze go viral. The Malleus Maleficarum (Hammer of the Witches), a 400 page witchcraft treatise originally published in 1486, goes on to become a best seller, through multiple editions. (Here’s a book review.) It is just one of a number of treatises and tracts on witchcraft pouring out of the printing presses.

And the witch craze is also tied up with the religious struggles of the Reformation and Counter-Reformation. Witchcraft persecutions are strongly associated, both in time and space, with confessional battles between Protestants and Catholics. Where Protestants and Catholics are in competition with one another – especially southern and western Germany and neighboring areas – they try to outdo one another in their zeal for persecuting witches. Where one denomination or the other is securely in power – Catholics in Spain and Italy, Lutherans in Scandinavia – witchcraft persecutions are mild. Although the persecutors wouldn’t have admitted it, witches are innocent collateral damage in the great religious struggles of the age.

Mother-right

Like the traditional poetry of other peoples, the traditional poetry of the Greeks celebrated the Heroic Age. This was the time when men were bigger and stronger, and they performed marvelous feats of prowess. Their weapons were made of bronze and not of iron, and they were ruled by kings. … The Heroic Age came to an end in two great wars – the Theban and the Trojan. … This was how the Mycenaean Greek civilization of the second millennium BC was remembered in historic Greece.

Margalit Finkelberg. Greeks and Pre-Greeks

Classical Greek poetry concerned with the Heroic Age includes a lot of genealogy, with an emphasis on descent in the male line, much like the begats in the Bible. Modern readers familiar with the Iliad and Odyssey find this stuff pretty boring, but it mattered a lot to the Greeks, who would try to link their existing patrilineal clans to the legendary family lines of the Heroic Age.

An emphasis on patrilineal descent is a general feature of early Indo-European society and its later offshoots, including the Greeks; the Indo-European expansion is one phase of the Patriarchal Age, leaving its imprint particularly on the distribution of Y chromosome variants. But given this patrilineal focus, there is something odd about the legends of the Heroic Age. In virtually none of the surviving legends do we find kingship passing from father to son, even when there is a son around. Instead, the normal pattern is that the king’s successor is the guy who marries his daughter – in other words his son-in-law, not his son. Meanwhile, the king’s son has to marry elsewhere. (Although the legends seem to present some cases of rotating succession, where multiple patrilineages took turns marrying into a matrilineage. In these cases, a king’s grandson might marry back into the kingdom, marrying his father’s sister’s daughter.) The implication is that the line of succession to the throne ran from mother to daughter, although it was the husbands of these women who actually exercised power: kingship by marriage. The most notable case of a son succeeding to his father’s throne is the exception that proves the rule: Oedipus got to be king of Thebes because he married Queen Jocasta, not because he was King Laius’ son. (Spoiler alert: see below*)

In Greeks and Pre-Greeks: Aegean Prehistory and Greek Heroic Tradition, Margalit Finkelberg argues that legends of the Heroic Age are memories of a time when the patrilineal traditions of the Greeks coexisted with earlier matrilineal traditions. More specifically, she argues that matrilineal Pre-Greek cultures were associated with the Anatolian language family, the first branch off the Indo-European tree, which also includes Hittite. On her account, Greece looks like ancestral Polynesia, a society flipped from matrilineal to patrilineal by invaders.

Finkelberg is not the first person to notice possible survivals of matrilineal descent from before the coming of the Indo-Europeans and other folk. Such survivals led some nineteenth century scholars to theorize that matrilineality – tracing descent and succession through the female line – was a stage of social evolution that all societies passed through. Some scholars also believed that matrilineal societies were matriarchal – ruled by women. Neither of these theories has held up very well. And yet …

… based on reconstructions of cultural phylogeny and/or ancestral vocabulary a number of the great demic expansions that covered the world seem to have started out matrilineal and/or matrilocal. The list (labeled by associated language families) includes:

• Austronesian (ancestral to languages ranging from Malagasy to Malay to Hawaiian)
• East Bantu, and maybe Bantu as a whole
• Nilo-Saharan (ancestral to Nilotic groups like the Nuer and Maasai, who, however had switched to patrilineality)
• Na Dene (North American Indians, including Athabaskan, Navajo, Apache)
• Je, Tupi, and Carib (Amazonian Indians)

So although matrilineal/matrilocal organization is not a stage that every society passes through, it seems to be a phase in many demic expansions. (I wrote an article, The matrilocal tribe: An organization of demic expansion, about this.) This is actually not too surprising. One solid finding in the anthropology of kinship is that matrilocal societies, in which a man goes to live with his wife’s kin when he marries, tend to be internally peaceful, without a lot of feuding between neighboring villages in the same tribe. This makes sense, since the men are no more related to the men in their own village than they are to men in neighboring villages. At the same time, matrilocal societies are often quite war-like with respect to folks outside the larger tribe (just ask the surviving neighbors of the Iroquois or the Navajo). Since matrilocality is associated with internal peace and external aggression, this social organization is well-suited to life along an ethnic frontier. Matrilocality (which is strongly associated with matrilineality) is one way tribal societies generate the social solidarity that enables demic expansion, in a pre-state variant of asabiya.

But there are several limits to matrilocal solidarity. First, the introduction of stock herding tends to undermine matrilocality and matrilineality. (My late colleague Henry Harpending worked with a group, the Herero in southern Africa, who had taken up cattle herding, and were probably in the early stages of transition from matri- to patrilineal.) Also matrilocal/matrilineal societies rarely exceed a few tens of thousands of people. Beyond that size their internal unity tends to break down, and parents start insisting that married sons stick around to defend the homestead. So a lot of the later, better known population expansions, including Indo-European, Semitic, Turkic, and Han Chinese are heavily patrilineal. But even today, traces of earlier matrilineal social organization still survive in some places – in the matrilineal belt of Central Africa, and in some of Southeast Asia, where patrilineality, and mate guarding to secure the male line, mostly don’t reach the same intensity as in much of Asia.

* Oedipus didn’t know it, but Jocasta was his mom.

Weaving history

829 – 673 BCE

The association of particular plaid patterns (tartans) with particular Scottish highland clans is a phenomenon of the last several centuries. But the Celt-plaid connection goes back a lot farther than that.

This picture shows a scrap of fabric associated with the Iron Age Hallstatt culture of central Europe. The culture lasted from 800-500 BCE, and is ancestral to later historic Celtic cultures. In fact, traditions of plaid weaving seem to go back a lot further. We find similar plaids being woven at roughly the same time, but thousands of miles away, in what is now Xinjiang province in western China. Linguistic evidence (from later writing) and genetic evidence (from mummies) suggest that some of the inhabitants of Xinjiang at this point were speakers of Tocharian languages, a branch of Indo-European, deriving from the western steppes. (Both Tocharian and Celtic probably branched off the Indo-European tree long before Indo-European-speaking chariot riders rode south to Iran and India.) We know that Proto-Indo-European had words for weaving. The Celtic and Tocharian plaids are similar enough (according to those who know such things) that it seems likely that IE speakers were also weaving plaids from early on.

The Mediterranean developed its own culture of weaving. In Mycenaean Greece, slave women worked under factory-like conditions to produce cloth for ordinary wear, some of it exported. Aristocratic women too were weavers. They might work with spindles of bronze, silver, or gold, weaving story cloths – tapestries that illustrated family histories. The shroud that Penelope wove by day and unwove by night was presumably one such.

Mycenaeans used writing for bureaucratic record keeping, not story-telling. Remembering the past was the business of female weavers and male bards. When literacy disappeared during the Greek Dark Age, historic memory, such as it was, was kept going by weavers, and by bards – often called weavers of words.