Tag Archives: fish

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.

Devonian days

401-380 million years ago

Lots going on in the Devonian

Forests are spreading. The first tree, Wattieza, is kin to ferns and horsetails. It stands 10 meters tall. No leaves yet, just fronds. The first forests will absorb carbon dioxide, and cool the planet.

wattieza

Life is moving onto land. Tiktaaklik roseae, the “fishapod” discovered in 2006, is as nice a link between fish and amphibians as one could hope for, with both lungs and gills. Here’s a book by Neil Shubin, the co-discoverer.

titaalik

You can see a lot further in the air than underwater. This may be one of the early selective pressures for evolving a proper neck and sticking one’s head out of water. Eventually, for some, the rest of the body would follow.

eyes out of water

And evolution seems to be generally speeded up on land. It’s not just that animals and plants develop adaptations for life on land (obviously). But there is also a more general acceleration in the pace of evolution. Major innovations come at a faster pace among terrestrial organisms.

We are upside-down bugs

475-450 Mya

“We are upside-down bugs” is not as catchy a song lyric as “We are stardust.” But the story may be just as interesting.

The proto-evolutionist anatomist Etienne Geoffroy Saint-Hilaire (1772-1844) proposed long ago that all animals – insects to vertebrates — share a “unity of composition.” He was opposed by his sometime friend and sometime rival, anti-evolutionist anatomist Georges Cuvier (1769-1832), who argued that the animal world is organized in four great “embranchements,” with nothing in common in their body plans. Geoffroy Saint-Hilaire noted that insects have their nervous systems running ventrally (through their bellies) and their digestive systems dorsally (through their backs), the opposite of vertebrates. So he proposed the daring hypothesis that, from head to tail, vertebrates and insects have the same body plan, but belly to back they are flipped around.

Remarkably enough, a modernized version of this hypothesis has been vindicated by developmental genetics. Vertebrates have a series of genes, the Hox genes, that control development. They are laid out in order, with the genes switching on the development of the head followed by genes for the upper body, etc. It turns out that much the same genes in the same order control development in insects (not exactly the same, but clearly related), even though the actual structure of insect bodies is very different. On the other hand, the gene that turns on ventral development in the fruit fly Drosophila is related to the gene that turns on dorsal development in the toad Xenopus, while the gene that turns on dorsal development in Drosophila is related to the gene that controls ventral development in Xenopus.

The hypothesis that seems to account for this is that back in the day –- before the Cambrian explosion – there was a small wormy bilaterally symmetrical organism, ancestor to almost all animals (except sponges and jellyfish and the Ediacaran Petalonamae). Some of the descendants of that primordial animal gave rise to protostomes (where the first opening in the embryo becomes a mouth) including arthropods (spiders, insects, etc.), molluscs (including clams, crustaceans, octopuses), and annelids (earthworms).

But somewhere along the pathway leading to the deuterostomes (where the first opening in the embryo becomes the anus, the second becomes the mouth), including the chordates, the vertebrates, and us, another set of descendants started swimming upside down. And the rest is (pre)history: this initial minor quirk of evolutionary history was well-entrenched by the Ordovician 488 Million years ago.

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.

Devonian days

579-360 Mya

Lots going on in the Devonian

Forests are spreading. The first tree, Wattieza, is kin to ferns and horsetails. It stands 10 meters tall. No leaves yet, just fronds. The first forests will absorb carbon dioxide, and cool the planet.

wattieza

Life is moving onto land. Tiktaaklik roseae, the “fishapod” discovered in 2006, is as nice a link between fish and amphibians as one could hope for, with both lungs and gills. Here’s a book by Neil Shubin, the co-discoverer.

titaalik

You can see a lot further in the air than underwater. This may be one of the early selective pressures for evolving a proper neck and sticking one’s head out of water. Eventually, for some, the rest of the body would follow.

eyes out of water

And evolution seems to be generally speeded up on land. It’s not just that animals and plants develop adaptations for life on land (obviously). But there is also a more general acceleration in the pace of evolution. Major innovations come at a faster pace among terrestrial organisms.

We are upside-down bugs

502-475 Mya

“We are upside-down bugs” is not as catchy a song lyric as “We are stardust.” But the story may be just as interesting.

The proto-evolutionist anatomist Etienne Geoffroy Saint-Hilaire (1772-1844) proposed long ago that all animals – insects to vertebrates — share a “unity of composition.” He was opposed by his sometime friend and sometime rival, anti-evolutionist anatomist Georges Cuvier (1769-1832), who argued that the animal world is organized in four great “embranchements,” with nothing in common in their body plans. Geoffroy Saint-Hilaire noted that insects have their nervous systems running ventrally (through their bellies) and their digestive systems dorsally (through their backs), the opposite of vertebrates. So he proposed the daring hypothesis that, from head to tail, vertebrates and insects have the same body plan, but belly to back they are flipped around.

Remarkably enough, a modernized version of this hypothesis has been vindicated by developmental genetics. Vertebrates have a series of genes, the Hox genes, that control development. They are laid out in order, with the genes switching on the development of the head followed by genes for the upper body, etc. It turns out that much the same genes in the same order control development in insects (not exactly the same, but clearly related), even though the actual structure of insect bodies is very different. On the other hand, the gene that turns on ventral development in the fruit fly Drosophila is related to the gene that turns on dorsal development in the toad Xenopus, while the gene that turns on dorsal development in Drosophila is related to the gene that controls ventral development in Xenopus.

The hypothesis that seems to account for this is that back in the day –- before the Cambrian explosion – there was a small wormy bilaterally symmetrical organism, ancestor to almost all animals (except sponges and jellyfish). Some of the descendants of that primordial animal gave rise to protostomes (where the first opening in the embryo becomes a mouth) including arthropods (spiders, insects, etc.), molluscs (including clams, crustaceans, octopuses), and annelids (earthworms).

But somewhere along the pathway leading to the deuterostomes (where the first opening in the embryo becomes the anus, the second becomes the mouth), including the chordates, the vertebrates, and us, another set of descendants started swimming upside down. And the rest is (pre)history: this initial minor quirk of evolutionary history was well-entrenched by the Ordovician 488 Million years ago.

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.

Yet 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 getting out from under 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.