460 million years ago, ocean plant life on the margins begin to colonize the land edges. Mosses, ferns evolve on dry land adapting to take moisture from rain.
The presence of plant life and oxygen create the required conditions for the first fire in our solar system. Eyes continue to evolve but only work in water.
Plants aren’t the only things that started out in the photosynthesis business. While the first molecule and the first stirrings of life were a long time ago, early on, the cyano bacteria was on this gig, turning sunlight into energy and pooping out the excess oxygen. This is bad news indeed for the other bacteria that were swimming around in the oceanic soup, because oxygen is poisonous if you are anaerobic, which was everyone really.
All this oxygen also dissolved the iron in the water, which naturally sank to the bottom, forming the foundations for the iron ore business making a few Australians very rich indeed.
Dating this iron and the rock in which it lies, gives a pretty good indication of when the first organisms started photosynthesizing, as there was no oxygen to dissolve the iron before that. The answer is about 580 million years ago.
It also puts a date on something was going to come in handy for future humans, the ultraviolet light reacting with the oxygen making ozone in the stratosphere, a sort of souped up oxygen creating our own sunblock.
A lot of these cyano bacteria lived together happily pumping out oxygen in Western Australia and haven’t left home. (Western Australia is the largest state in Australia at a handy 2.6 million square kilometres or about one million square miles) They reside in a very unglamorous grey lump called a Stromatolite, a sort of low rise apartment block about the size of a small car, in the salty waters of Shark Bay in WA.
Evolution worked its magic and some cyano formed partnerships with other organisms which eventually led to more sophisticated life in the form of green algae.
Obviously being soft, they did not produce much by way of fossils but there is plenty of sturdier stuff further down the tree to be able to work backwards to the first plants, that were rather delicate.
By the time we get to the half billion mark, 500 million years ago, complex life had evolved into millions of different shapes and sizes according to their environment. The first creature with a spine evolved and fish were taking advantage of all the new oxygen that was dissolved in the oceans.
Ten millions years later, while all this evolving was going on, Canada was hit by large asteroid leaving behind a 24 kilometre wide crater, quite a modest impact on the scale of asteroids. No doubt this was not a good day for those creatures living in the immediate area but that didn’t stop groups of photo reactor cells becoming primitive ‘eyes’ in many species.
(The first ‘eyes’ were just cells that react to light. When several or lots happened to be in the same area, they served as a signal that something large was blocking the light. ‘Something large’ often meant ‘something hungry’ and those that took the hint to make a hasty retreat, were the ones that survived to pass on this trait.)
In fact, lots of interesting things were happening. Reef-builders were abundant, as were worms, sponges and numerous other animals. The invertebrates diversified into many new types, including trilobites, starfish, long straight-shelled cephalopods bivalves, nautiloids, and many other types.
Fungi and algae did so well they continue to the present day and while oxygen was in full production, carbon dioxide was hugely more than it is now, something like 25 times as much, but then the earth didn’t have to worry about sea levels and mega storms.
All this synthesizing came on the back of the evolution of complex life, some 180 million years before green algae was the main act. Even so, there were no land plants until 475 million years ago. Bear in mind the earth had been around for most of its life to date. If you imagine the earth time line as a single year, at this point when land plants first got going, it was late November. Put another way, if the earth was like the life of a person, it was already 90 years old before the first plant sprung up. And you thought 460 million years was a long time. It’s just the last 10 years.
We are pretty safe in assuming that the first land plants, which were mostly ferns and mosses had 15 million years to spread out and we know the atmosphere also had oxygen. Now it’s true that matches had not been invented yet, but it’s a fair guess that lightning was pretty common.
Lightening, oxygen and dead plants equals fire. These were probably pretty tame affairs as trees were still another 40 million years in the future.
While the first smoke was wafting across the planet, back in the oceans the first eyes had evolved from the light sensitive cells that were part of the makeup of many creatures.
While the first fires were burning up the dead bacterial and algal mats, these primitive plants were industriously creating the first recognizable soils. They also harboured some arthropods like mites and scorpions but they didn’t have roots or leaves and probably didn’t grow very tall, however, they grew, they survived, they thrived in fact.
By the time a few more million years had passed, the pioneers had developed true roots and leaves and some were getting quite tall, some of the giant versions had developed wood and are the first, the oldest known trees that formed the first forests. One of them was an enormous mushroom something like 8 metres or 25 foot tall.
It was not long before fire was a part of the natural environment and plants and trees moved to adapt.