Tag Archives: arms races

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.)

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.


Planet of the apes

22.9-21.6 million years ago

The Miocene (23 – 5 million years ago) is a period of extraordinary success for our closest relatives, the apes. Overall there may have been as many as a hundred ape species during the epoch. Proconsul (actually several species) is one of the earliest. We will meet just a few of the others over the course of the Miocene, as some leave Africa for Asia, and some (we think) migrate back.

Sometimes evolution is a story of progress – not necessarily moral progress, but at least progress in the sense of more effective animals replacing less effective. For example, monkeys and apes largely replace other primates (prosimians, relatives of lemurs and lorises) over most of the world after the Eocene, with lemurs flourishing only on isolated Madagascar. This replacement is probably a story of more effective forms outcompeting less effective. And the expansion of brain size that we see among many mammalian lineages throughout the Cenozoic is probably another example of progress resulting from evolutionary arms races.

But measured by the yardstick of evolutionary success, (non-human) apes — some of the brainiest animals on the planet — will turn out not to be all that effective after the Miocene. In our day, we’re down to just about four species of great ape (chimpanzees, bonobos, gorillas, and orangutans), none of them very successful. Monkeys, with smaller body sizes and more rapid reproductive rates, are doing better. For that matter, the closest living relatives of primates (apart from colugos and tree shrews) are rodents, who are doing better still, mostly by reproducing faster than predators can eat them.

So big brains aren’t quite the ticket to evolutionary success that, say, flight has been for birds. One issue for apes may be that with primate rules for brain growth – double the brain size means double the neurons means double the energy cost – a large-bodied, large brained primate (i.e. an ape) is going to face a serious challenge finding enough food to keep its brain running. It’s not until a later evolutionary period that one lineage of apes really overcomes this problem, with a combination of better physical technology (stone tools, fire) and better social technology (enlisting others to provision mothers and their dependent offspring).

Strange relations and island continents

56.2-53.2 Mya

We’re now in the Cenozoic era – our era. The transition from Paleocene to Eocene epochs in the early Cenozoic (55.9 million years ago) saw a spike in CO2 levels and a sharp rise in temperatures that lasted for several hundred thousand years – perhaps an analog for even more rapid human-caused global warming in our own time. (A recent review is here.)

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.

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

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, Saturday 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 more like sheepdogs and less like wolves.

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.

5.62-5.32 Mya

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?)



Both simple and complex types of language of an indefinite number of varieties may be found spoken at any desired level of cultural advance. When it comes to linguistic form, Plato walks with the Macedonian swineherd, Confucius with the head-hunting savage of Assam.

Edward Sapir. Language: An Introduction to the Study of Speech

The institutions of men are as distinctly stratified as the earth on which he lives. They succeed each other in series substantially uniform over the globe, independent of what seem the comparatively superficial differences of race and language, but shaped by similar human nature acting through successively changed conditions in savage, barbaric, and civilized life. … Few would dispute that the following … are arranged rightly in order of culture: Australian, Tahitian, Aztec, Chinese, Italian.

Edward Burnett Tylor, Primitive Culture

These quotations capture two aspects of cultural evolution. Cultures (including languages) diverge and diversify over time. But cultures can also be ranked from simple to complex, from small scale to large scale, and complexity tends to increase over time. A recent publication provides quantitative evidence for this second, unilinear aspect of cultural evolution. The publication is the product of project Seshat (named after the Egyptian goddess of wisdom, alleged inventor of writing), which has been building up a massive databank of global history. (You can follow them on Twitter here.) The authors of the study (54 of them!) find that a single dimension of social scale/complexity accounts for a large fraction of cultural variation over space and time, and that the correlates of social scale are much the same in different world regions – Tylor vindicated.*

Turning from cultural to biological evolution we find the same two phenomena, both diversification over time, and increasing complexity and improved design. But in the biological case, it is diversification that is relatively more conspicuous. Presumably this reflects that fact that in biology, adaptive organization is found mostly at the level of organisms (or, less often, at the level of superorganisms, like insect colonies, or mutualistic associations). A great diversity of organisms can be found in any ecosystem, adapted to a diversity of niches. They are mostly not in direct competition and may be hard to rank along a single scala naturae. In cultural evolution, by contrast, adaptive organization is commonly found not just at the individual level, but at the level of political communities – tribes, chiefdoms, states – which typically claim possession of a piece of territory. Success or failure at holding territory provides a metric for comparing societies, which usually (not always) favors the more complex.

So both the history of humanity, and the evolution of life on earth, and are, in some degree, stories of progress and improvement. But this progress comes at a cost; the success of some is bought at the expense of others’ failures. We could end the year on a pessimistic note, with Edward Gibbon –  “History is little more than the register of the crimes, follies, and misfortunes of mankind” or Charles Darwin – “What a book a devil’s chaplain might write on the clumsy, wasteful, blundering low and horridly cruel works of nature!” Instead, for a final thought, I’ll finish by quoting myself from two years back, on New Year’s Eve 2015:

Darwin’s theory implies that some organisms are adapted, as a result of cumulative natural selection, to survive and reproduce, often at the expense of others. We’ve seen on Logarithmic History how much of evolution has been driven by evolutionary “arms races,” especially between predators and prey. And we’ve seen that group-against-group competition is arguably a major motor of human social evolution. It’s possible to draw a grim lesson from this: that we must embrace violent struggle and population replacement as our destiny. But there are more palatable options.

So here’s a different take: At the beginning of The Godfather, movie and book, Michael Corleone, the scion of a mafia family, is set on getting out of the bloody family business, and going straight. In the story, he fails, and is drawn back into a life of violence. The tragic arc makes for a great story, but there’s nothing inevitable about it. By analogy, every one of us is the product of a long evolutionary and cultural history which includes generous helpings of violence. But history is not destiny: there’s no reason we can’t get out of the old bloody business of our species, and go straight.

* although his Chinese < Italian ranking maybe reflects more the prejudices of his time.

Uneven development


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 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.

 Stalin’s policies were not just a response to perceived external threats, but helped to generate those threats: if the German Communist Party (which took direction from Moscow) had cooperated with the Social Democrats and other supporters of the Weimar government, they could have kept Hitler out of power.