own name, with the jaw-breaking name“Lomagundi-Jatuli excursion,” and it is the biggest and longest such event yet found in the entire history of our planet. Most of the carbon being emitted from volcanoes was being sequestered as organic material, releasing oxygen to the air; today this ratio is only about 20 percent. This is the evidence of an Earth with oxygen but without organisms capable of breathing it: wild swings in the carbon cycle caused by cyanobacteria excreted lots of carbon compounds as waste, but with no organisms using these chemicals as food. In fact, the remnants of this sludge appear to exist in the Russian province of Karelia, as a weird rock type called shungite. Today, most of these oil-like compounds would have been quickly biodegraded by microorganisms that breathe oxygen, like the fate of most of the Deepwater Horizon spill. This is direct evidence that the environment choked on hydrocarbons, rather than recycling them directly. As a result oxygen kept rising in content until it was so abundant that it produced an atmosphere supersaturated in oxygen, existing at pressures much higher than today. Had there been any forests, the first spark from lightning would have caused a global forest fire of heat and scope beyond anything that has ever occurred on Earth in the time of forests.
This weird episode in the history of life ended abruptly when evolution produced the first organisms that could breathe oxygen efficiently. Special copper-based enzymes evolved to do this, but copper deposits themselves require oxygen-rich environments to form. An entirely new kind of intracellular body came into existence, and it exists still, the organelle called the mitochondria, the major source of energy for eukaryotic cells, which are cells that are larger than their prokaryotic (bacterial) ancestors, as well as being cells that contain walled-off interior “rooms” in the giant (compared to all that came before) cells. The mitochondria has its own little piece of DNA, left over from when it was once a free-living bacterium, a microbe that learned to breathe oxygen efficiently. As a result, it has been enslaved for the past 2 billion years.
It is intriguing to note that the best estimate for the age of the last common ancestor of all eukaryotes is about 1.9 billion years, and thatmay mark the time that eukaryotes finally evolved to restore balance to the global carbon cycle. It would seem that the biosphere required over 200 million years of evolution to come up with an adequate response to the presence of the intrinsically poisonous oxygen.
CHAPTER VI
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The Long Road to Animals: 2.0–1.0 GA
----
The time between the great oxygenation event (culminating at ~2.3 GA) and the first appearance of common multicellular life has been called the boring billion. The reason is that (supposedly) virtually nothing happened in terms of major biological change. It is as if the history of life took a snooze. A billion years is a long time for almost nothing to happen. But like so much else, the boring billion has recently been shown to be not so boring. New discoveries are showing us that life was not resting at all. But at the same time, in spite of repeated suggestions to the contrary, there are no animals a billion years in age. Instead, this long interval begins with the first significant oxygen in the atmosphere, and by 2 billion years ago a major revolution in life had occurred—the common occurrence of eukaryotic life, our kind of life, large cells with a nucleus. And while the greatest diversity of these new creatures during this period of time were protozoa, familiar to us as the still-living amoeba, paramecia, euglena, and their cohorts, there appeared some strange larger fossils as well, including one of the most bizarre fossils ever recovered.
The various experts agree that there was probably not enough oxygen between 2.2 and 1.0 billion years ago to support animal life. 1 (This is a good time to quickly
This weird episode in the history of life ended abruptly when evolution produced the first organisms that could breathe oxygen efficiently. Special copper-based enzymes evolved to do this, but copper deposits themselves require oxygen-rich environments to form. An entirely new kind of intracellular body came into existence, and it exists still, the organelle called the mitochondria, the major source of energy for eukaryotic cells, which are cells that are larger than their prokaryotic (bacterial) ancestors, as well as being cells that contain walled-off interior “rooms” in the giant (compared to all that came before) cells. The mitochondria has its own little piece of DNA, left over from when it was once a free-living bacterium, a microbe that learned to breathe oxygen efficiently. As a result, it has been enslaved for the past 2 billion years.
It is intriguing to note that the best estimate for the age of the last common ancestor of all eukaryotes is about 1.9 billion years, and thatmay mark the time that eukaryotes finally evolved to restore balance to the global carbon cycle. It would seem that the biosphere required over 200 million years of evolution to come up with an adequate response to the presence of the intrinsically poisonous oxygen.
CHAPTER VI
----
The Long Road to Animals: 2.0–1.0 GA
----
The time between the great oxygenation event (culminating at ~2.3 GA) and the first appearance of common multicellular life has been called the boring billion. The reason is that (supposedly) virtually nothing happened in terms of major biological change. It is as if the history of life took a snooze. A billion years is a long time for almost nothing to happen. But like so much else, the boring billion has recently been shown to be not so boring. New discoveries are showing us that life was not resting at all. But at the same time, in spite of repeated suggestions to the contrary, there are no animals a billion years in age. Instead, this long interval begins with the first significant oxygen in the atmosphere, and by 2 billion years ago a major revolution in life had occurred—the common occurrence of eukaryotic life, our kind of life, large cells with a nucleus. And while the greatest diversity of these new creatures during this period of time were protozoa, familiar to us as the still-living amoeba, paramecia, euglena, and their cohorts, there appeared some strange larger fossils as well, including one of the most bizarre fossils ever recovered.
The various experts agree that there was probably not enough oxygen between 2.2 and 1.0 billion years ago to support animal life. 1 (This is a good time to quickly
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