ONTO SHAKY GROUND
‘So it is necessary, at least intermittently. . . this thing called sex.
As of course you and I knew it must be.
Otherwise surely, by now, we mammals and dragonflies
would have come up with something more dignified.’
David Quammen
As of course you and I knew it must be.
Otherwise surely, by now, we mammals and dragonflies
would have come up with something more dignified.’
David Quammen
Around 360 million years ago, at a time that marks the beginning of what scientists call the Carboniferous Period, Earth’s Second Major Mass Extinction occurred. The apparent tipping point was extensive rifting and volcanic activity.
About 50% of the existing species were made extinct, including more trilobites and many kinds of early fish. And the transition period of intense experimentation and competition among plants and animals lasted 10-30 million years.
As Earth recovered and warmed, longer-living woody shrubs and trees began to form communities of compatible species. Most, such as giant horsetails and tree-ferns, reproduced themselves asexually by spores from under their fronds or by offshoots from their roots. (Australia’s tree-ferns still do this, clumping around a parent.)
But a few (like Glossopteris in what is now Australia) had much stronger trunks with true branches and also reproduced sexually. Small spore-like male cells drifted onto larger female cells where fertilized seeds then developed. Large forests evolved as trees over-reached each other in search of sunlight and they sent taproots deep into the soil.
It was some time before fungi able to dissolve these ‘woody’ plants evolved. So as the first trees died and fell their energy was stored in their remains, which piled up and compressed into vast peat deposits.
Over millions of years of external pressure and internal heat some was progressively transformed into the various stages of coal: soft brown coal; bituminous coal; and finally shiny black anthracite. At each stage there was a higher percentage of carbon, and therefore more stored energy. Trees are about 50% carbon (dry weight); peat is about 60% carbon; and anthracite is about 95% carbon.
Eventually, in places under extreme heat and pressure from rocks above, some would even harden and crystallize into layers of lustreless, translucent diamonds. Their stored energy makes them Earth’s hardest natural substance, excellent for cutting other substances, and for being cut into sparkling jewels.
Back in our story, photosynthesis in the large forests was releasing more and more oxygen into the atmosphere. And it wasn’t long before several insect species took flight.
They metamorphosed from eggs laid and fertilized in water through water-living nymphs into winged adults, and helped by their short life cycle, they soon developed new ways to find food or a mate, or escape predators: light bodies, detailed vision and swift expert movement through the air.
Most amazing were the huge dragonflies, with nearly weightless bodies and wingspans up to that of modern seagulls. Since their wings didn’t fold away none of these insect species could hide from predators, but flight opened up a whole new world for them – and for our Universe.
Meanwhile spiders, and some insects, were also experimenting with direct sexual engagement rather than fertilization of ejected eggs. Coupled with eggs able to live out of the water this enabled them to reproduce on land, but their mating was more of an attack than an embrace.
The female was larger than the male and often completed the process by eating him. His job was now done, and, unless he escaped to live just a bit longer, she recycled him into nutrients for her developing offspring. Both sexes took a few years to reach maturity, but she lived for several more years, breeding with a younger male each time.
Today most female spiders and several female insects, such as the praying mantis, still practise partner assassination. But of course several other mating solutions have also evolved, particularly among insects.
Now some amphibians were evolving into thicker-skinned reptiles, with strong legs that raised their bodies slightly off the ground, making them more agile.
Two of the earliest confirmed reptiles were the lizard-like Hylonomus lyelli (forest mouse), which was 20 cm long; and the Proganochelys, ancestor of today’s turtles, 1 metre long and unable to retract its head.
Like insects reptiles practised sexual intercourse, with their own versions of land-eggs and the innovative probing organ invented by male insects (the penis).
Since fertilization within the female's body was less haphazard, reptile females didn’t have to produce so many eggs as fish and amphibians did, and so the eggs could develop in special salty fluids inside the female’s body.
Like all female animals at that time she had a single evacuation and reproduction cavity (a cloaca) through which he ejaculated his sperm. She enclosed her eggs in soft leathery shells so that each offspring could develop inside its own bubble of fluid, and then laid them together on the ground. And as in other egg-laying animals the egg contained enough food to last until they were ready to hatch as miniature versions of their parents, prepared to struggle for survival and maturity on their own.
Since partner assassination was not really an option for reptiles, sexual intercourse for them entailed a whole new set of behaviours.
And there was another complication. As the numbers in a species grew, males often had to compete for access to females. In order to mate successfully he must be intimidating - first to deter any rivals and then to persuade the female to submit.
So in a reversal of insect sexual specialization, reptile males usually became the larger gender, a pattern that would be passed on to most mammals.
But although their mating was essentially coercive rather than seductive, reptiles had inherited dominance and submission postures from amphibians as a way of avoiding conflict, and a successful male wanted as little danger to himself as possible.
So as their brains developed to handle intimate sexual contact, reptiles adopted a clear, intimidating body language among all adults. This is how self-protection by an instinctive choice between dominance and submission evolved, within a species as well as between members of different species.
The sexual behaviours of early reptiles may seem rather crude to us, but they were actually paving the way for mammals’ more emotional interactions – including ours.
Today the pre-programmed inner layer of our brain, loosely called the reptilian brain, still manages not only our involuntary functions such as breathing, digestion and blood-circulation, but also, through a special organ (the amygdala), the instinctive self-protective reactions commonly known as Fight (an evolutionary variant of submission) or Flight (an evolutionary variant of submission).
Back in our story, even though the cells, tissues and organs were co-operating within their bodies, these reptiles themselves generally functioned in their environment as fiercely competing individuals. Just as insects, spiders and amphibians did, reptile males and females had solitary lives outside mating times, much of it devoted to finding food safely.
And as insects, spiders and amphibians were very tasty foods to reptiles, some adapted to this new danger by becoming smaller and hiding in burrows, while others moved higher into the foliage. But upwardly mobile spiders came much later – for now they stayed underground.
Meanwhile, with a lot of violent upheaval and the usual volcanic eruptions and earthquakes, tectonic plate movement had clumped the various landmasses together into one vast landmass extending over the South Pole. Paleontologists call this supercontinent Pangaea (see Title page image for Our Second Age), and the ocean around it the Panthalassa Ocean.
Across Earth coastlines, continental shelves and ocean currents were changed, and all life was disrupted. Because reptiles no longer needed ready access to bodies of water for breeding, some left the dwindling coastlines for river valleys and other inland areas.
Three mountain ranges that had been on separate landmasses, now became one extended range for millions of years. Today they are on separate continents again, as the Appalachian, Caledonian and Scandinavian Mountains.
(Also in the area that is desert in today’s Central Australia, a mighty river was flowing from a towering mountain range. Today this river (the Finke) is little more than a series of billabongs and underground streams; and the mountains (the Macdonnell Ranges) are just an eroded remnant.)
By this time some reptiles, no longer in need of ready access to bodies of water for breeding, had left the dwindling coastlines for river valleys and other inland areas. But now, as gigantic deserts and salt-beds formed away from the rivers and new coasts, the climate there became colder and colder, and drier and drier.
Reptiles in these areas had to cope with very little water as well as widely fluctuating day and night temperatures. Most of them adapted by digging burrows and by slowing down their metabolism.
For millions of years glaciers covered 1/3 of the land in the Southern Hemisphere (including 1/3 of what would be Australia) and all sea levels dropped. Giant horsetails and other early trees started dying out, and there were frequent wildfires.
These were usually sparked by lightning, and then fuelled by the dryness, and also by the many flammable woody plants - alive and dead.
Suddenly in today’s Siberia a volcanic plume from deep in the mantle began to send out huge rivers of black lava, and the eruptions seem to have continued off and on for around 600,000 years. Lava flowed across Pangaea and massive amounts of sulphur dioxide and carbon dioxide gases were released into the atmosphere.
This apparently tipped Earth into its Third Major Mass Extinction, today seen as the most devastating our planet has ever endured. 90% of species disappeared, and it took 50-100 million years for a relatively stable level of biodiversity to emerge.
What’s more most of the survivors only just made it. Even insects were reduced to very few species, whereas today they are our planet’s most prolific and diverse multi-celled animals. There are estimated to be 30-100 million insect species compared with 12,000 species of birds and mammals. How’s that as an example of recovery from a near-death experience?
(The Sydney Basin sandstones that make up the mass of today’s Blue Mountains were laid down around this time. The area that would later be uplifted into a high plateau was part of a vast coastal flood plain extending east beyond today’s Sydney.
(Its rivers rose in colder areas far to the south, and sand was washed down continually with snow-melt from these rivers. As it was deposited on the plain, it slowly built up into layers of sandstone.
(Below the sandstones were layers of coal from forests, formed long before from trees in ancient river deltas. And below the coal were marine shales deposited when the area was covered by an ancient sea.
(Because of later uplifting and erosion the various layers are seen clearly today in Katoomba’s Mount Solitary, which the local Gundungurra people call Korowal.)
About 50% of the existing species were made extinct, including more trilobites and many kinds of early fish. And the transition period of intense experimentation and competition among plants and animals lasted 10-30 million years.
As Earth recovered and warmed, longer-living woody shrubs and trees began to form communities of compatible species. Most, such as giant horsetails and tree-ferns, reproduced themselves asexually by spores from under their fronds or by offshoots from their roots. (Australia’s tree-ferns still do this, clumping around a parent.)
But a few (like Glossopteris in what is now Australia) had much stronger trunks with true branches and also reproduced sexually. Small spore-like male cells drifted onto larger female cells where fertilized seeds then developed. Large forests evolved as trees over-reached each other in search of sunlight and they sent taproots deep into the soil.
It was some time before fungi able to dissolve these ‘woody’ plants evolved. So as the first trees died and fell their energy was stored in their remains, which piled up and compressed into vast peat deposits.
Over millions of years of external pressure and internal heat some was progressively transformed into the various stages of coal: soft brown coal; bituminous coal; and finally shiny black anthracite. At each stage there was a higher percentage of carbon, and therefore more stored energy. Trees are about 50% carbon (dry weight); peat is about 60% carbon; and anthracite is about 95% carbon.
Eventually, in places under extreme heat and pressure from rocks above, some would even harden and crystallize into layers of lustreless, translucent diamonds. Their stored energy makes them Earth’s hardest natural substance, excellent for cutting other substances, and for being cut into sparkling jewels.
Back in our story, photosynthesis in the large forests was releasing more and more oxygen into the atmosphere. And it wasn’t long before several insect species took flight.
They metamorphosed from eggs laid and fertilized in water through water-living nymphs into winged adults, and helped by their short life cycle, they soon developed new ways to find food or a mate, or escape predators: light bodies, detailed vision and swift expert movement through the air.
Most amazing were the huge dragonflies, with nearly weightless bodies and wingspans up to that of modern seagulls. Since their wings didn’t fold away none of these insect species could hide from predators, but flight opened up a whole new world for them – and for our Universe.
Meanwhile spiders, and some insects, were also experimenting with direct sexual engagement rather than fertilization of ejected eggs. Coupled with eggs able to live out of the water this enabled them to reproduce on land, but their mating was more of an attack than an embrace.
The female was larger than the male and often completed the process by eating him. His job was now done, and, unless he escaped to live just a bit longer, she recycled him into nutrients for her developing offspring. Both sexes took a few years to reach maturity, but she lived for several more years, breeding with a younger male each time.
Today most female spiders and several female insects, such as the praying mantis, still practise partner assassination. But of course several other mating solutions have also evolved, particularly among insects.
Now some amphibians were evolving into thicker-skinned reptiles, with strong legs that raised their bodies slightly off the ground, making them more agile.
Two of the earliest confirmed reptiles were the lizard-like Hylonomus lyelli (forest mouse), which was 20 cm long; and the Proganochelys, ancestor of today’s turtles, 1 metre long and unable to retract its head.
Like insects reptiles practised sexual intercourse, with their own versions of land-eggs and the innovative probing organ invented by male insects (the penis).
Since fertilization within the female's body was less haphazard, reptile females didn’t have to produce so many eggs as fish and amphibians did, and so the eggs could develop in special salty fluids inside the female’s body.
Like all female animals at that time she had a single evacuation and reproduction cavity (a cloaca) through which he ejaculated his sperm. She enclosed her eggs in soft leathery shells so that each offspring could develop inside its own bubble of fluid, and then laid them together on the ground. And as in other egg-laying animals the egg contained enough food to last until they were ready to hatch as miniature versions of their parents, prepared to struggle for survival and maturity on their own.
Since partner assassination was not really an option for reptiles, sexual intercourse for them entailed a whole new set of behaviours.
And there was another complication. As the numbers in a species grew, males often had to compete for access to females. In order to mate successfully he must be intimidating - first to deter any rivals and then to persuade the female to submit.
So in a reversal of insect sexual specialization, reptile males usually became the larger gender, a pattern that would be passed on to most mammals.
But although their mating was essentially coercive rather than seductive, reptiles had inherited dominance and submission postures from amphibians as a way of avoiding conflict, and a successful male wanted as little danger to himself as possible.
So as their brains developed to handle intimate sexual contact, reptiles adopted a clear, intimidating body language among all adults. This is how self-protection by an instinctive choice between dominance and submission evolved, within a species as well as between members of different species.
The sexual behaviours of early reptiles may seem rather crude to us, but they were actually paving the way for mammals’ more emotional interactions – including ours.
Today the pre-programmed inner layer of our brain, loosely called the reptilian brain, still manages not only our involuntary functions such as breathing, digestion and blood-circulation, but also, through a special organ (the amygdala), the instinctive self-protective reactions commonly known as Fight (an evolutionary variant of submission) or Flight (an evolutionary variant of submission).
Back in our story, even though the cells, tissues and organs were co-operating within their bodies, these reptiles themselves generally functioned in their environment as fiercely competing individuals. Just as insects, spiders and amphibians did, reptile males and females had solitary lives outside mating times, much of it devoted to finding food safely.
And as insects, spiders and amphibians were very tasty foods to reptiles, some adapted to this new danger by becoming smaller and hiding in burrows, while others moved higher into the foliage. But upwardly mobile spiders came much later – for now they stayed underground.
Meanwhile, with a lot of violent upheaval and the usual volcanic eruptions and earthquakes, tectonic plate movement had clumped the various landmasses together into one vast landmass extending over the South Pole. Paleontologists call this supercontinent Pangaea (see Title page image for Our Second Age), and the ocean around it the Panthalassa Ocean.
Across Earth coastlines, continental shelves and ocean currents were changed, and all life was disrupted. Because reptiles no longer needed ready access to bodies of water for breeding, some left the dwindling coastlines for river valleys and other inland areas.
Three mountain ranges that had been on separate landmasses, now became one extended range for millions of years. Today they are on separate continents again, as the Appalachian, Caledonian and Scandinavian Mountains.
(Also in the area that is desert in today’s Central Australia, a mighty river was flowing from a towering mountain range. Today this river (the Finke) is little more than a series of billabongs and underground streams; and the mountains (the Macdonnell Ranges) are just an eroded remnant.)
By this time some reptiles, no longer in need of ready access to bodies of water for breeding, had left the dwindling coastlines for river valleys and other inland areas. But now, as gigantic deserts and salt-beds formed away from the rivers and new coasts, the climate there became colder and colder, and drier and drier.
Reptiles in these areas had to cope with very little water as well as widely fluctuating day and night temperatures. Most of them adapted by digging burrows and by slowing down their metabolism.
For millions of years glaciers covered 1/3 of the land in the Southern Hemisphere (including 1/3 of what would be Australia) and all sea levels dropped. Giant horsetails and other early trees started dying out, and there were frequent wildfires.
These were usually sparked by lightning, and then fuelled by the dryness, and also by the many flammable woody plants - alive and dead.
Suddenly in today’s Siberia a volcanic plume from deep in the mantle began to send out huge rivers of black lava, and the eruptions seem to have continued off and on for around 600,000 years. Lava flowed across Pangaea and massive amounts of sulphur dioxide and carbon dioxide gases were released into the atmosphere.
This apparently tipped Earth into its Third Major Mass Extinction, today seen as the most devastating our planet has ever endured. 90% of species disappeared, and it took 50-100 million years for a relatively stable level of biodiversity to emerge.
What’s more most of the survivors only just made it. Even insects were reduced to very few species, whereas today they are our planet’s most prolific and diverse multi-celled animals. There are estimated to be 30-100 million insect species compared with 12,000 species of birds and mammals. How’s that as an example of recovery from a near-death experience?
(The Sydney Basin sandstones that make up the mass of today’s Blue Mountains were laid down around this time. The area that would later be uplifted into a high plateau was part of a vast coastal flood plain extending east beyond today’s Sydney.
(Its rivers rose in colder areas far to the south, and sand was washed down continually with snow-melt from these rivers. As it was deposited on the plain, it slowly built up into layers of sandstone.
(Below the sandstones were layers of coal from forests, formed long before from trees in ancient river deltas. And below the coal were marine shales deposited when the area was covered by an ancient sea.
(Because of later uplifting and erosion the various layers are seen clearly today in Katoomba’s Mount Solitary, which the local Gundungurra people call Korowal.)
* * * * * *
With around 450,000 species,
beetles constitute by far the largest group of insects on Earth.
This collection gives us a glimpse
of the remarkable (and beautiful) diversity of just a few of them.
(another Google image)
With around 450,000 species,beetles constitute by far the largest group of insects on Earth.
This collection gives us a glimpse
of the remarkable (and beautiful) diversity of just a few of them.
(another Google image)
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