Tag Archives: arms races

Plagues and peoples

206-305

Every day on Logarithmic History we cover an interval 5.46% shorter than the preceding day. From covering the first 754 million years after the Big Bang on January 1, we’re down to one century worth of history today.

And it’s a bad century for both Rome and China. Rome goes through an economic crisis, with a huge currency devaluation. Political life goes to hell too. From 235-284 there are 20 Emperors; 18 of them die violently. The Roman Empire experiences multiple, destructive invasions by barbarians. Previously under the Pax Romana, most of the cities of the Empire, including Rome, had been unwalled; now there is a spate of wall-building. The empire recovers toward the end of the century, but in a more heavily militarized and authoritarian form. And in China the Han dynasty disappears entirely after 220, to be replaced by three kingdoms of barbarian origin.

This coincidence of catastrophes may be more than just bad luck. Put it this way: If we look at the Big Picture, going way back on our calendar, and turning for a moment from human history to the evolution of life, we can summarize biological evolution since the Cambrian as:

but …

  • Now and then, a physical catastrophe punctuates the history of life, causing mass extinctions, from which living things slowly recover.

Returning to human history, we can summarize social evolution since the adoption of agriculture as:

  • A process of escalation, in which conflicts between rival groups (matrilineal and patrilineal kin groups, empires, and – we will see – major religions) are drivers of increasing social complexity …

but…

  • Now and then, a biological catastrophe – in the form of an epidemic of some new disease – punctuates human history, causing major population losses, and often political and social collapse as well (i.e. the “germs” in Guns, Germs and Steel).

One such catastrophe contributed to the collapse of New World societies in the face of Old World diseases after 1492. But the Old World too must have had its own earlier catastrophes as the great killer diseases – the diseases of civilization that need a minimum population to keep going – established themselves.

Epidemic disease may have made a major contribution to the fall of Rome and of Han China. Rome suffered two massive epidemics, one from 165-180, another from 251-266. It’s plausible (and some day geneticsts will tell us whether it’s true or not) that these epidemics represent the arrival of smallpox and measles in the West. There is also evidence from the current distribution of tuberculosis strains that the expansion of the Roman Empire, and trade across borders, helped to spread this disease. And we’ll run into bubonic plague in a few days time (Saturday, October 13). There may be a similar story to tell about China, also stricken by epidemics at this time. The opening of the Silk Road and of trade across the Indian Ocean allowed precious goods and new ideas to travel between civilizations. It also opened the way for lethal microorganisms.

In addition to “Guns, Germs and Steel,” a classic book here is William McNeill’s Plagues and Peoples. For the Roman empire, more up-to-date, and with a wealth of information, is The Fate of Rome: Climate, Disease, and the End of an Empire.

The Great American Interchange

3.03-2.87 million years ago

For most of the last 100 million years, South America was an island continent, like Australia, with its own peculiar mix of species, largely isolated from other continents (although monkeys, and guinea pig relations, rafted across.) By contrast, North America was intermittently connected with Eurasia and exchanged species off and on. South America supported a rich array of marsupials, including a marsupial version of a saber-toothed tiger. It also had predatory flightless “terror birds” that seemed bent on reoccupying the two-legged predatory dinosaur niche.

terror bird

There was also a profusion of notoungulates (probably distantly related to hoofed animals in North America and Eurasia), and liptoterns. (Below is a reconstruction of a late surviving liptotern, Macrauchenia, looking like a Dr. Seuss invention.)
macrauchenia

South America was close enough to North America for the two continents to start exchanging species by 14 million years ago, but the really massive exchange began with the establishment of the Isthmus of Panama, and climate changes, about 3 million years ago. 38 genera of land mammals walked north from South America. 47 genera walked south from North America. So the initial exchange was unbalanced; the subsequent evolution was even more so. Only a handful of South American invaders – notably armadillos and (for a while) ground sloths – succeeded in establishing themselves in North America, while North American invaders generated a profusion of new species. Many of the really distinctive South American forms would go extinct over the next millions of years.

Paleontologists dispute the causes of the turnover, but it looks an awful lot like North American species had a competitive edge. This is one instance of a phenomenon we’ve seen already in animal evolution, and will see again in human history, of large land areas generating more competitive forms.

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).

macachiavellian

This hypothesis may not hold up too well, however. One complication is that, contrary to what a lot of 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, like 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 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

The expected lifetime, measured in generations, of a cultural trait as a function of the efficiency of social learning (p). Each learning trial uses a new cultural parent drawn from the parent population (see text). Parameter value: n 1⁄4 2.

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.

Strange relations and island continents

59.4-56.3 million years ago

We’ve seen a great many catastrophes in the history of life, and been reminded of the role of sheer chance in evolution. But the Cenozoic also sees a dramatic adaptive radiation and the steady progress of arms races among survivors of the great dinosaur die-off. Four large scale groupings of placental mammals have already appeared: Afrotheres (aardvarks, hyraxes, elephants, and sea cows), Xenarthrans (anteaters, armadillos, and sloths), Laurasiatheres (shrews, hedgehogs, pangolins, bats, whales, hoofed animals, and carnivores), and Supraprimates (aka Euarchontoglires, including rodents, tree shrews, and primates). This grouping of mammals is anything but obvious – it’s only with DNA sequencing that it has emerged. What’s noticeable is the association with different continents: Afrotheres with Africa, Xenarthrans with South America, and the others with the monster content of Laurasia (Eurasia and North America). Looking beyond placental mammals we see other continental associations: marsupials flourish in South America and Australia, and giant flightless “terror birds” carry on rather like predatory dinosaurs in South America.

mammal tree

There is a pattern here. Evolutionary arms races are most intense in the supercontinent of Laurasia (eventually joined by India and Africa). The island continents of South America and Australia stand apart, and they fare poorly when they start exchanging fauna with the rest of the world. We’ll see a similar pattern – large areas stimulate more competition, and more intense evolution, isolated areas are at a disadvantage – when we look at modern history, with ocean voyages effectively reuniting Pangaea. (This is a major theme of Alfred Crosby’s Ecological Imperialism and Jared Diamond’s Guns, Germs, and Steel.)

Nature red in tooth and claw

339-321 million years ago

You’re trying to live without enemies. That’s all you think about, not having enemies.

Isaac Babel, Red Cavalry

Enemies are the most important agencies of selection.

Geerat Vermeij, Evolution and Escalation

Much of what we’ve been seeing since the onset of the Cambrian, Wednesday, February 27, is the outcome of evolutionary arms races, leading to steady improvements in teeth, claws, armor, and mobility. It may well be that the onset of predation is what triggered the Cambrian explosion in the first place. The paleontologist Geerat Vermeij argues that arms races and escalation – not adaptation to the physical environment – are the greatest cause of progressive evolution.

We’ll see when we start getting into human evolution, biological and social, that enemies – other people especially – and arms races go on being a major motor of change. But arms races and escalation are going to look different in human evolution than they do in most non-human evolution. People are super-cooperators, and violent competition in humans tends to involve more group-against-group competition, with rival groups monopolizing and competing over territory. And in the human analog of predation – the formation of stratified societies, where elites live off the mass of the population – the human “predators” commonly band together under the aegis of the state to regulate their competition. At their best, human elites are less like wolves and more like sheepdogs.

Arms races operate with greater intensity in some environments than others. Races are more intense on large landmasses than small. Hence the common pattern in both biological evolution and human social evolution that isolated small continents and islands are especially vulnerable to invasion when their isolation ends. And arms races may be more intense, and the pace of evolution correspondingly greater, in the (more or less) 2-D terrestrial environment compared to the 3-D oceans.

Yet there may be something else involved in the initial move onto land – it’s sometimes among refugees from arms races that the greatest evolutionary advances arise. Fish moving onto land may have been doing it partly to get to someplace where enemies were weak or scarce. Human analogs might be the early Ionian Greeks fleeing the Dorian invasions, the settlers of Polynesia lighting out for the territories to escape a lowly position in a social order of ranked lineages, or the New England Pilgrims fleeing an un-Godly England. Or Vermeij himself – he is competitively handicapped, having lost his sight at three years old, but has made a distinguished career studying shelled invertebrates by touch.

On the Origin of Seafood by Means of Natural Selection

Or the Preparation of Favorite Dishes in the Struggle for Dinner.

562-532 million years ago

The Cambrian explosion — shells and skeletons, and all the major animal phyla of today — is one of the major events in the history of life. It’s hard to miss – Darwin was well aware of it – because for the first time you have abundant well-preserved fossils of animals with hard parts. From now on, if I miss a tweet one day or another, it’s because I didn’t get to it, not because the evidence isn’t there.

Genetic evidence seemingly clashes with the fossil evidence. A “molecular clock” based on rates of gene divergence suggests that major animal phyla had begun diverging from one another long before the Cambrian explosion. But maybe the genetic evidence is wrong, and the “molecular clock” was running faster in the past than more recently. Or maybe complex organisms evolved long before the Cambrian, but left little or no fossil evidence. Or maybe the ancestors of today’s animals really did diverge early, but didn’t get complex until the Cambrian.

And why the explosion happened when it did is unresolved. Here’s a recent review. The early Snowball Earth episodes probably contributed in some way, and the rise of oxygen in the atmosphere must have been important. Or maybe there was some dramatic biological event that triggered the explosion: the origin of eyes, and/or the beginning of predation, setting off an arms race between predators and prey that’s been going on ever since.

If this last possibility is correct, then the transition from an Edenic, predator-free Ediacaran world to the Cambrian is a form of “symmetry breaking.” There is maybe an analogy here in human social evolution to the transition from an egalitarian society to a world of inequality, of rulers and ruled  (which also followed a – much milder – glacial episode).

Speaking of predation: the Logarithmic History blog is partly about commemorating great events in the past. It seems fitting to celebrate the Cambrian as the origin of seafood. If you take your time machine back to any time before the Cambrian, pickings will be slim – algae mostly, although we don’t really know what the Ediacara would have tasted like. The time-traveller’s menu gets a lot better with the Cambrian (although wood for a fire is still a problem). Nowadays you can’t hope to dine on trilobite, alas. (Check out March 12 last year for more of this sad story.) But sometime in the next few days why not have some mussels for dinner? (The recipe below has some non-Cambrian ingredients. It will be a few more days, incidentally, before the evolution of anything kosher.)

Steamed mussels, 4 servings

Wash and debeard:
4 to 6 pounds mussels
Place them in a large pot and add:
½ cup dry white wine
½ cup minced fresh parsley or other herbs
2 tablespoons chopped garlic
Cover the pot, place it over high heat, and cook, shaking the pot occasionally, until most of the mussels are opened, about 10 minutes. Use a slotted spoon to remove mussels to a serving bowl, then strain the cooking liquid over them. Drizzle over the mussels:
1 tablespoon extra-virgin olive oil
Juice of 1 lemon
Serve with:
Plenty of crusty bread (invented< 15,000 years ago, but who’s counting?)

Uneven development

1931-1937

If much of the history of Eurasia between 1000 BCE and 1600 CE was shaped by the clash between farmers and city folk, and pastoral nomads from the steppes and deserts, then much of the history of the twentieth century was defined by the collision between Western and non-Western societies. This is one way to see the rise of communism. Traditional Russia and China had developed autocratic institutions that allowed them to cope, more or less, with military threats from the steppe. But these institutions proved desperately unequal to coping with a new set of military challenges from the West and Japan.

Steven Pinker’s book The Better Angels of Our Natures portrays the march of history as a process of diffusion of enlightenment ideals. On a long enough time scale he may be right. But on a medium time scale we see something different – the formation of powerful totalitarian states on either side of the meta-ethnic frontier dividing industrialized societies from independent but militarily vulnerable peasant societies. Chance and individual personalities played a role in the bloodshed of the twentieth century, but there were also larger forces at work in The World Revolution of Westernization.

Here is a short piece of mine (not from the blog) on History and Group Consciousness relating this topic to arguments about group selection. I argue that taking group selection seriously as an engine of historical dynamics may give us a better understanding of recent history.

Marxism is not very successful as a scientific theory, but in its heyday it was enormously successful as an ideology involved in subordinating masses of individuals in larger collective projects. Here’s a famous speech by Stalin to industrial managers in 1931, in the midst of the first Five Year Plan and the collectivization of agriculture, and on the eve of mass starvation in the Ukraine

It is sometimes asked whether it is not possible to slow down the tempo somewhat, to put a check on the movement. No, comrades, it is not possible! The tempo must not be reduced! On the contrary, we must increase it as much as is within our powers and possibilities. This is dictated to us by our obligations to the workers and peasants of the USSR. This is dictated to us by our obligations to the working class of the whole world.

To slacken the tempo would mean falling behind. And those who fall behind get beaten. But we do not want to be beaten. No, we refuse to be beaten! One feature of the history of old Russia was the continual defeats she suffered because of her backwardness. She was beaten by the Mongol khans. She was beaten by the Turkish beys. She was beaten by the Swedish feudal lords. She was beaten by Polish and Lithuanian gentry. She was beaten by the British and the French capitalists. She was beaten by the Japanese barons. All beat her – because of her backwardness, because of her military backwardness, cultural backwardness, political backwardness, industrial backwardness, agricultural backwardness. They beat her because to do so was profitable and could be done with impunity. You remember the words of the pre-revolutionary poet : ‘You are poor and abundant, mighty and impotent, Mother Russia.’ Those gentlemen were quite familiar with the verses of the old poet. They beat her, saying : ‘You are abundant’, so one can enrich oneself at your expense. They beat her, saying : ‘ You are poor and impotent,’ so you can be beaten and plundered with impunity. Such is the law of the exploiters – to beat the backward and the weak. It is the jungle law of capitalism. You are backward, you are weak – therefore you are wrong; hence you can be beaten and enslaved. You are mighty – therefore you are right; hence we must be wary of you.

That is why we must no longer lag behind.

In the past we had no fatherland, nor could we have had one. But now that we have overthrown capitalism and power is in our hands, in the hands of the people, we have a fatherland, and we will uphold its independence. Do you want our socialist fatherland to be beaten and to lose its independence ? If you do not want this, you must put an end to its backwardness in the shortest possible time and develop a genuine Bolshevik temperament in building up its socialist economy. There is no other way…

We are fifty or a hundred years behind the advanced countries. We must make good this distance in ten years. Either we do it, or they crush us.