Sometimes we yearn for days gone by. A time when life was simple. Before taxes, before traffic jams, before money. Before pollution and global warming. Life was so simple back then ...
So, let's go back to when life was simpler, way simpler. But to do that, we'll have to go back quite a bit: Over two billion years to be precise! To a time called the Proterozoic Era. And although life was less complex, and there were no traffic jams or taxes, pollution was so pervasive it killed organisms where they lay, brought down acid rain, and ultimately a nuclear winter the likes of which hasn't been seen in almost a billion years. And there is war which will last eons: The Gas Wars.
Large Graphics Below!
The earth and oceans, as they may have appeared two and a half billion years ago
For the first couple of billions years on earth, our familiar blue-green planet didn't exist. The skies were brown, yellow, and red, full of dark clouds stained with hydrocarbon tars condensed out of a methane rich nitrogen/carbon dioxide atmosphere. A moon appearing six times larger than our present day lunar companion haunted the heavens, over a sea tinted scarlet-yellow with algal blooms and the multicolored, burning sky's reflection. There were no animals, no plants, no creature larger than a single cell, and most were much, much, smaller. But deep beneath the ancient ocean waves, bubbling with escaping CO2 like a frosty glass of soda, an epic struggle for global dominance was taking place between armies of microbes.
The Reds and the Greens: Micrographs of red and green bacteria
On one side were the old guard. These primeval microbes could thrive in the most inhospitable conditions. They lived in scalding water, literally 'eating' poisonous substances like sulfides, extracting their energy from the vibrating bonds of resonating electrons binding hydrogen to various elements. They gave off simple methane, and they had one hell of a track record stretching back a whopping two-billion years to the beginning of the earth! The methanogens were so successful, so numerous, they had painted the skies and oceans blood-red and soft yellow-brown with their breath. Let's call them the Reds. These were the original Archaea neither animal or plant, led by the corp of methanogens. But a challenger had arisen.
Their enemies were the new Archaea, The Greens. Led by the cyanos (si-A-nos); the latest, high-tech model of chemosynthetic bacteria. These green soldiers had a toxic trick up their sleeve. They emitted oxygen, a killer chemical weapon which burnt the methanogens to a crisp. And they had an unlimited energy source, for these organisms were solar powered!
Although there were other critters in the ancient seas, scraps of RNA, the forerunners of modern viri, and amoeba-like predators which engulfed Green or Red alike and treated them to a homemade acid bath, it was the Greens and the Reds who were fighting it out for world dominance. There was no mercy between the two armies, no POWs, no quarter given; these creatures were competing for the very right to exist. This war would last for eons, encompass the entire world, echo even into our present epoch, and the wreckage was so immense it formed thick layers of strata visible in the geological column to this day.
The first salvo in the Gas Wars was fired by the Green cyanos. They had evolved to take carbon-dioxide out of the air, break it and take the carbon, and then using sunlight produce a simple sugar which was the backbone of all ribonucleic acids like RNA or DNA. The left over oxygen, a deadly poison to early life, was then released into the ocean.
Banded iron formation from 2 billion years ago
The Reds had help, at first, from iron and other elements also dissolved in the ocean which would bind with the free oxygen to form solid matter, and safely settle to the bottom of the sea. Being solar powered had its pros and cons. One con was the Greens were only active during the daylight. And they waxed and waned with the seasons and the amount of incident sunlight they could harvest for their solar powered metabolism. Today we can see these ancient growing seasons as bands of iron rust preserved in rocks billions of years old (Above). (The iron in your car engine and home is probably mined from iron ore, produced by photosynthetic waste gas, oxygen, which combined with iron solute billions of years ago and was laid down in this manner)
But the Green's poison gas was a doubled edged sword which acted as a sort of doomsday weapon, killing both themselves and the Reds indiscriminately. Not only did it corrode everything it touched, once released into the atmosphere it would be married by heat and lightning to molecules containing nitrogen and sulfur, forming deadly acids which rained out, disintegrating living organisms on contact. Both populations crashed and quickened in cycles lasting millions of years. What the Greens needed was a sort of container, replete with the equivalent of a moat surrounding the cyanos to act as a barrier to the oxygen and pesky microbial predators. And that's exactly the next tactic they employed.
We don't know exactly when, we don't know exactly how, but at some point, perhaps two and a half billion years ago, a primitive amoebae like creature ingested some green cyanos. These latest models were resistant to digestion and survived inside the tiny predator. The cyanos could still obtain sunlight, the amoebae's membrane was transparent, and they could still find carbon dioxide; it was present through out the sea water and therefore present inside the amoebae. So the cyanos happily continued producing their simple sugars and replicating under the protection of their new host. Some of that sugar leaked out which was just dandy for the amoebae. It was like the tiny blob had opened up a little farm inside its body which supplied it with the ribose sugar the amoebae would otherwise have to steal via predation. The lucky amoebae no longer had to do a lick of work, it was in blob heaven.
When the amoebas reproduced by simple fission, some of the cyanos would be present in each daughter, and the cyanos themselves reproduced independently of their host true to their bacterial heritage. After a few hundred million years the symbiotic living conditions between the two organisms had merged into a brand new kind of creature. The cyanos had evolved into what are now called chloroplasts, and the amoebae had become the first green plant cell. Every tree, flower, weed, liverwort, and moss you've ever seen descends directly from this simple partnership struck long ago under seltzer seas.
The new arrangement was wildly successful. The green plant cells proliferated, spewing out oxygen to the point that all of the free iron was taken out of the water and the poisonous gas began to accumulate in the atmosphere in significant quantities. The free oxygen in the air and ocean was catastrophic to pretty much every living thing. Hordes of microbes withered and died by the trillions as the corrosive gas ate them alive. Over 90% of all bacteria bit the dust, the biological carnage was so immense it is known as the Oxygen Holocaust.
But the Reds weren't giving up, they could make symbiotic arrangements with amoebae like predators also, they just needed a new type of bacteria which could deal with oxygen, and the population of red algae, under selective pressure of the new oxygen rich world-which boiled down to adapt or die-came up with one from within the ranks of the Purple Bacterial Brigade of the methanogens.
And, like the cyanos who took up residence in a primitive cell, the new purple bacteria which were acclimated to oxygen were also engulfed and put to work. Over time they also become exquisitely adapted to their new cellular benefactors and pitched in by combining the oxygen with hydrated carbons stolen by the predatory amoeba-like hunters from their bacterial prey, and produced an energy kick that blew anything the plant cells could produce out of the park. If the plant cells were like a glowing ember, this new coop was a nuclear reactor.
The cells infested with the progeny of the purple Reds (below) now literally had a controlled fire burning inside them. As long as the fire was primed with prey and fueled with oxygen, the purple bacteria would burn it safely and offer the enormous energy to the their cellular hosts. By a little over one billion years ago, these purple bacteria evolved into what are now called mitochondria. And the cellular overlords of the purple bacteria became a special type of eukaryote, the first animal cells. The animal eukaryotes were huge, a thousand times larger than the plant cells. And their waste product, carbon dioxide, was a powerful greenhouse which warmed the planet, producing global clouds of water vapor, and dimmed the life giving sunlight the Greens depended on. The Reds had fired back with their own salvo in the Gas War. And on top of that, they ate the plants!
Both types of cells bloomed across the ancient seas, filled the atmosphere with their deadly gas to which they were each now immune, and the population of primitive bacterial methanogens crashed for the last time. They would eek out a living only in the lightless environments of the deep ocean and anaerobic swamp-mud. The war continued, but was now taken up by the animal eukaryotes and the plant cells.
The Green victory over the simple methanogens had unintended consequences. As the methane waste was taken out of the atmosphere by the new reactive oxygen, and as the simple old-style methanogens dwindled in number and were unable to replenish the methane compounds in the air, the greenhouse effects that methane had provided declined rapidly. The earth was plunged into a deep freeze starting 850 million years ago. This Period is known fittingly as the Cyrogenian. But we call it the Snowball Earth.
Simple polyp animal
Here and there in icy cracks and hot springs liquid water could still sustain the plant and animal cells. The war could continue. And the oxygen made possible a substance called Collagen which acted as a framework in which the animal cells could group and organize. the first metazoa (multicelled) animals. These tiny, millimeter long tubes, called polyps, were basically a 'sack'. The open end was the mouth and the inside was the gut (And like so many politicians, the mouth also served as the anus). The sacks huddled around islands of evolution scattered over the earth in pockets of ice free water. And from time to time during brief respites from the glaciers, these polyps would be able to meet up with each other, join as colonies, specialize into diverse functions in the same colony, and the first true creatures we would recognize as animals, corals, simple jellyfish, would come to be. From those simple beginnings would spring the first worms, the first clams, the first arthropods, and the first vertebrates.
A collection of different kinds of polyps, called a Siphonophore, was probably the first animal easily seen by the unaided eye. These colonial organisms likely arose in Cryogenian, ~750 MYA
Likewise the Green plant cells would also be able to group together as more than just a disorganized clump. Plant tissue evolved using an analogue of the animal collagen. During respites in the frigid Cryogenian, these new multi-cellular plants evolved into the first mosses and liverworts.
The war between the Greens and the Reds had entered a new, high-tech epoch of titanic multi-cellular armored juggernauts battling furiously first in the sea, then on land.
We animals, descendants of those early red bacterial cooperatives called eukaryotes, consume the descendants of the Greens, the green plants. We steal their carbohydrates manufactured slowly in those plants to obtain huge spikes of energy which allows us to move, and think, and digest-or we steal them from our fellow animals who in turn stole them from plants. We take in the poisonous oxygen, isolate it in microbial factories overseen by the purple bacteria, our own mitochondria, stoke the chemical fires, and emit safe carbon dioxide. But ultimately we are fertilizer for the plants. While we live fast and burn out quick, they wait with ancient vegetable patience for our decayed bodies to feed them. And in the meantime, we each inhale each other's waste gases. The Gas Wars have turned into a global symbiotic partnership between what were once bitter enemies. Now one veteran combatant is rarely found without the other, and they are interwoven into a tapestry of life which can only be described as stunningly beautiful.
So, the Gas War between the Greens and the Reds started 2.5 billion years ago still echoes, deep within our very tissues and inside each of our cells. The stalemate led to cooperation, the cooperation led to interdependence. Today we all get along swimmingly.
The irony is manifold. At present we complicated animals called humans sport the most prodigious intellects on the planet, easily dwarfing our Red and Green antecedents in every metric imaginable. We think of our ancient bacterial progenitors with biased contempt, as brainless slime, not even fit to eat. Yet we cannot solve our petty internal problems with one another with anything approaching the symbiotic grace those ancient algal warriors finally settled on, to our great benefit I might add. Perhaps we complex creatures could take a lesson in peacemaking from our distant microbial ancestors; we are all one planet and we live, or die, as one community.
It's understandable that it took so long for the Greens and the Reds to settle their differences and become partners in the community of life. After all they had no mind, no organs, no hands, no eyes, no ears. They were limited only to simple chemical stimuli, blind biochemical reactions, and the relentless forces of natural selection.
But if they can do it in a few billion years, can't we allegedly superior metazoic geniuses come to terms with our own internal disputes by conscious decision in a few thousand? Maybe if we could emulate some modern day version of the detente reached by brainless microbes ages ago, we cerebral critters could get on with living instead of killing; and life really could be simple for everything again.