Tag Archives: major transitions in evolution

Life goes nuclear

2.06-1.95 Gya

Eukaryotic cells (Domain Eucaryota, which includes multicellular life, like plants, animals, and fungi) are, on average, much larger and more complex than the earlier evolved prokaryote cells (Domains Bacteria and Archaea*). They have organelles, including mitochondria that power them and chloroplasts (at least among plants) that carry out photosynthesis. Their DNA is stored in a nucleus, and consists not just of genes (as in prokaryotes), but of large stretches of non-coding DNA (most of their genome), separating pieces of genes. The ancestor of present-day eukaryotes reproduced sexually, although some eukaryotes have since given up sex.

There are different ways that life increases in complexity. The origin of the Eucarya has something in common with a much later event, the origin of agriculture (check out September 10 on logarithmichistory). Starting 10,000 years ago, we Homo sapiens brought other animals and plants under our control, managing their reproduction, and selecting them (first unintentionally, then intentionally) to suit our purposes, until now most domesticated creatures couldn’t survive in the wild. Our own numbers and social scale increased enormously with the rise of agriculture.

At least 2 billion years ago, an archaeon cell gobbled up one or more bacterial cells (or was parasitized by them). The bacteria ended up surviving inside it, and after many generations became a kind of domesticate inside their host. Eukaryotes do domestication one better than humans: they carry their livestock inside their bodies. Eventually this domesticate evolved into mitochondria, the little power packs that pump out ATP for the rest of the cell to use as as an energy source. Over the course of time all but a small fraction of the original bacterial genome was moved into the nucleus.

In the last few years we have come closer to understanding how this momentous step occurred: we have discovered a new branch of the Archaean tree, the Asgard archaea. The Asgard archaeans carry some genes otherwise found only in eukaryotes, and it looks likely the first eukaryote to start hosting the bacterial ancestors of mitochondria was an Asgarder, or close relative. Just this year we finally succeeded in cultivating these creatures in the lab. (It was hard to do.) They are tiny little spheres with long filaments protruding from them. The partnership between Archaeans and bacteria may have begun with bacteria nestling in these protrusions.

Humans developed agriculture multiple times independently around the world. As far as we know, eukaryotes evolved only once, long after the origin of simpler forms. The evolution of eukaryotes might be a very unlikely chance event. The universe may be full of bacteria, but harbor more complex cells only sparsely.

* Domain Archaea, a billions-of-years-old group of single-celled organisms looking like bacteria but biochemically different, should not be confused with the Archaean Eon, a billions-of-years-long stretch of Earth history.

Uneven development

1932-1938

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.

Learn This One Weird Trick … (Part One)

… that humans use, and now you can too!

There are people who think that human beings are nothing special. Sure (the argument goes) people have uniquely large brains. But all sorts of creatures have unique features. Elephants are the only animals with trunks. Tamarins and marmosets are the only primates that give birth to twins. Platypuses are the only venomous mammals. Spotted hyenas are the only mammals whose females sport pseudo-penises (through which they give birth!). And so on. If we could ask members of these species they’d claim that they’re the special ones.

But of course we can’t ask them, and in any case, this isn’t a very convincing argument. Human beings have an absolutely outsize impact on the Earth, and the advent of human beings looks like one of the major evolutionary transitions, comparable in importance to the origin of the eukaryotic cell or multicellular life. But even if we buy this, it still leaves open the question of whether there’s a key adaptation – a One Weird Trick – that accounts for the exceptional course of human evolution. Here are some candidates that being are being batted around these days:

1) The cognitive niche. The basic idea is at least as old as Aristotle, that human brings are defined by their capacity for Reason. A modern version of this is advocated by evolutionary psychologist John Tooby and cognitive scientist Steven Pinker. Pinker in particular has elaborated the argument that humans are uniquely adapted to acquire and share knowledge, by virtue of a suite of cognitive, social, and linguistic adaptations. We’ve already touched on several aspects of this: Human beings seem to have taken the capacity for thinking about physical space and retooled it for thinking about the abstract cognitive space of possession – a social relationship. (Other abstract cognitive spaces include kinship, time, and change-of-state.) And humans seem to harness the machinery for processing the sounds of interacting solid objects in creating major categories of phonemes. For a more complete exposition, here’s an academic article by Pinker, and a talk on youtube.

2) Culture. Rob Boyd and Pete Richerson, who’ve done a lot of mathematical modeling of cultural evolution, are skeptical about the “cognitive niche” argument. Too much culture, they argue, is things that have been learned by trial-and-error, and are passed on from one generation to the next without people understanding why they work. Boyd and Richerson appeal, as anthropologists have for generations, to the importance of culture. We mentioned earlier their argument that the frequency of climate change in the Ice Age was nicely calibrated to favor social learning rather than individual learning or instinct. Joseph Henrich provides a recent defense of the importance of culture. Contra Pinker, he thinks humans often don’t have a good cause-and-effect understanding of the things they do, but depend heavily on imitation and the accumulated wisdom of the elders. And see this post, for the importance of High Fidelity cultural transmission in the evolution of animal and human intelligence.

Coming up: Part Two. Recursion and Shared Intentionality

Consider her ways

104-99 million years ago.

There are some pieces of paleontology that really stand out in the popular imagination. Dinosaurs are so cool that even if they hadn’t existed we would have invented them. (Maybe we did, in the form of dragons. And look ahead (or back) to early April for the dinosaur-griffin connection.) Also, as I suggested in a previous post, transitions from one form of locomotion to another – flightless dinosaurs to birds, fish to tetrapods, land mammals to whales – really grab the imagination (and annoy creationists) because the largest and most distinctive named folk categories of animals (snakes, fish, birds) are built around modes of locomotion.

Evolutionary biologists tend to see things differently. Turning fins into legs, legs into wings, and legs back into flippers is pretty impressive. But the really major evolutionary transitions involve the evolution of whole new levels of organization: the origin of the eukaryotic cell, for example, and the origin of multicellular life. From this perspective, the really huge change in the Mesozoic – sometimes called the Age of Dinosaurs – is the origin of eusociality among insects like ants and bees. An ant nest or a bee hive is something like a single superorganism, with most of its members sterile workers striving – even committing suicide — for the colony’s reproduction, not their own. (100 million years ago – corresponding to March 29 in Logarithmic History — is when we find the first bee and ant fossils, but the transition must have been underway before that time.)

Certainly the statistics on social insects today are impressive.

The twenty thousand known species of eusocial insects, mostly ants, bees, wasps and termites, account for only 2 percent of the approximately one million known species of insects. Yet this tiny minority of species dominate the rest of the insects in their numbers, their weight, and their impact on the environment. As humans are to vertebrate animals, the eusocial insects are to the far vaster world of invertebrate animals. … In one Amazon site, two German researchers … found that ants and termites together compose almost two-thirds of the weight of all the insects. Eusocial bees and wasps added another tenth. Ants alone weighed four times more than all the terrestrial vertebrates – that is, mammals, birds, reptiles, and amphibians combined. E. O. Wilson pp 110-113

E. O. Wilson, world’s foremost authority on ants, and one of the founders of sociobiology, thinks that the origin of insect eusociality might have lessons for another major evolutionary transition, the origin of humans (and of human language, technology, culture, and complex social organization). In his book The Social Conquest of Earth he argues that a key step in both sets of transitions was the development of a valuable and defensible home – in the case of humans, a hearth site. Wilson returns to this argument in his book Genesis: The Deep Origin of Human Societies, just published, which I’ll get around to saying more about here eventually. On the same topic, I’m also looking forward to Mark Moffett’s forthcoming book The Human Swarm: How Human Societies Arise, Thrive, and Fall, which asks how it is that we somehow rival the social insects in our scale of organization.

One trait found in both ants and humans is large-scale warfare. Wilson gives an idea of the nature of ant warfare in fictional form in his novel Anthill. It’s an interesting experiment, but also disorienting. Because individual recognition is not important for ants, his story of the destruction of an ant colony reads like the Iliad with all the personal names taken out. But Homer’s heroes fought for “aphthiton kleos,” undying fame (and got some measure of it in Homer’s poem). The moral economy of reputation puts human cooperation in war and peace on a very different footing from insect eusociality. (Here’s my take on “ethnic group selection,” which depends on social enforcement, perhaps via reputation.)

Consider her ways” is the title of a short story by John Wyndham, about a woman from the present trapped in a future ant-like all-female dystopia. It was made into an episode of Alfred Hitchcock Presents. The title is from Proverbs 6:6, “Go to the ant, thou sluggard, consider her ways and be wise.”

Life goes nuclear

2.04-1.93 Bya

Eukaryotic cells (Domain Eucaryota, which includes multicellular life, like plants, animals, and fungi) are, on average, much larger and more complex than the earlier evolved prokaryote cells (Domains Bacteria and Archaea*). They have organelles, including mitochondria that power them and chloroplasts (at least among plants) that carry out photosynthesis. Their DNA is stored in a nucleus, and consists not just of genes (as in prokaryotes), but of large stretches of non-coding DNA (most of their genome), separating pieces of genes. The ancestor of present-day eukaryotes reproduced sexually, although some eukaryotes have since given up sex.

There are different ways that life increases in complexity. The origin of the Eucarya has something in common with a much later event, the origin of agriculture (check out September 10 on logarithmichistory). Starting 10,000 years ago, we Homo sapiens brought other animals and plants under our control, managing their reproduction, and selecting them (first unintentionally, then intentionally) to suit our purposes, until now most domesticated creatures couldn’t survive in the wild. Our own numbers and social scale increased enormously with the rise of agriculture.

At least 2 billion years ago, an archaeon cell gobbled up one or more bacterial cells (or was parasitized by them). The bacteria ended up surviving inside it, and after many generations became a kind of domesticate inside their host. Eukaryotes do domestication one better than humans: they carry their livestock inside their bodies. Eventually this domesticate evolved into mitochondria, the little power packs that pump out ATP for the rest of the cell to use as as an energy source. Over the course of time all but a small fraction of the original bacterial genome was moved into the nucleus. Archaean and bacterial genomes are so intertwined, that the evolution of eucaryotes is better represented as a ring than a tree.

ringoflife

Humans developed agriculture multiple times independently around the world. As far as we know, eukaryotes evolved only once, long after the origin of simpler forms. The evolution of eukaryotes might be a very unlikely chance event. The universe may be full of bacteria, but harbor more complex cells only sparsely.

* Domain Archaea, a billions-of-years-old phylum of single-celled organisms looking like bacteria but biochemically different, should not be confused with the Archaean Eon, a billions-of-years-long stretch of Earth history.

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.

Consider her ways

104-99 million years ago.

There are some pieces of paleontology that really stand out in the popular imagination. Dinosaurs are so cool that even if they hadn’t existed we would have invented them. (Maybe we did, in the form of dragons. And look ahead (or back) to early April for the dinosaur-griffin connection.) Also, as I suggested in a previous post, transitions from one form of locomotion to another – flightless dinosaurs to birds, fish to tetrapods, land mammals to whales – really grab the imagination (and annoy creationists) because the largest and most distinctive named folk categories of animals (snakes, fish, birds) are built around modes of locomotion.

Evolutionary biologists tend to see things differently. Turning fins into legs, legs into wings, and legs back into flippers is pretty impressive. But the really major evolutionary transitions involve the evolution of whole new levels of organization: the origin of the eukaryotic cell, for example, and the origin of multicellular life. From this perspective, the really huge change in the Mesozoic – sometimes called the Age of Dinosaurs – is the origin of eusociality among insects like ants and bees. An ant nest or a bee hive is something like a single superorganism. with most of its members sterile workers striving – even committing suicide — for the colony’s reproduction, not their own. (100 million years ago – corresponding to March 29 in Logarithmic History — is when we find the first bee and ant fossils, but the transition must have been underway before that time.)

Certainly the statistics on social insects today are impressive.

The twenty thousand known species of eusocial insects, mostly ants, bees, wasps and termites, account for only 2 percent of the approximately one million known species of insects. Yet this tiny minority of species dominate the rest of the insects in their numbers, their weight, and their impact on the environment. As humans are to vertebrate animals, the eusocial insects are to the far vaster world of invertebrate animals. … In one Amazon site, two German researchers … found that ants and termites together compose almost two-thirds of the weight of all the insects. Eusocial bees and wasps added another tenth. Ants alone weighed four times more than all the terrestrial vertebrates – that is, mammals, birds, reptiles, and amphibians combined. E. O. Wilson pp 110-113

E. O. Wilson, world’s foremost authority on ants, and one of the founders of sociobiology, thinks that the origin of insect eusociality might have lessons for another major evolutionary transition, the origin of humans (and of human language, technology, culture, and complex social organization). In his book The Social Conquest of Earth he argues that a key step in both sets of transitions was the development of a valuable and defensible home – in the case of humans, a hearth site.

One trait found in both ants and humans is large-scale warfare. Wilson gives an idea of the nature of ant warfare in fictional form in his novel Anthill. It’s an interesting experiment, but also disorienting. Because individual recognition is not important for ants, his story of the destruction of an ant colony reads like the Iliad with all the personal names taken out. But Homer’s heroes fought for “aphthiton kleos,” undying fame (and got some measure of it in Homer’s poem). The moral economy of reputation puts human cooperation in war and peace on a very different footing from insect eusociality. (Here’s my take on “ethnic group selection,” which depends on social enforcement, perhaps via reputation.)

Consider her ways” is the title of a short story by John Wyndham, about a woman from the present trapped in a future ant-like all-female dystopia. It was made into an episode of Alfred Hitchcock Presents. The title is from Proverbs 6:6, “Go to the ant, thou sluggard, consider her ways and be wise.”