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A History Of Life On Earth: The Precambrian Era

Updated on July 28, 2014

The Blue Planet

Earth is the only planet we know of that harbours life. But incredibly, for most of its history it only harboured single celled organisms.
Earth is the only planet we know of that harbours life. But incredibly, for most of its history it only harboured single celled organisms. | Source

The Beginning

Earth’s story begins with its birth and the start of its first geological period, the Precambrian, which is also incidentally the longest geological time period in Earth’s history, lasting nearly 4 billion years. It was during this time that Earth transformed from a lifeless ball floating in the vastness of the solar system to a blue water world, home to many types of life. However, much of the life at this time was what we call primitive and their fossils were rather more small and delicate, meaning that they were comparatively rare when compared to fossils from later periods.

How Did the Solar System and Earth Form?

The Geological Clock

This is the entire history of Earth represented fittingly as a clock that never stops.
This is the entire history of Earth represented fittingly as a clock that never stops. | Source

The Moment Everything Changed

The moment when a giant planet called Theia smashed into Earth to create the Moon.
The moment when a giant planet called Theia smashed into Earth to create the Moon. | Source

The Cradle of Life

Deep sea vents such as these may have provided the energy required for life to begin in earnest.
Deep sea vents such as these may have provided the energy required for life to begin in earnest. | Source

Bacterial Pioneers

More than 3 billion years ago- cyanobacteria evolved a stunning new way of extracting energy from the sun called photosynthesis. They soon formed vast mats on the sea floor called stromatolites.
More than 3 billion years ago- cyanobacteria evolved a stunning new way of extracting energy from the sun called photosynthesis. They soon formed vast mats on the sea floor called stromatolites. | Source

Archaean Eon: 4600-2500 Million Years Ago

For centuries it was believed that our world and everything in it was at most only a few thousand years old and all life including man had been created within the space of just few days. Then, around 200 years ago, people practising the relatively new scientific discipline of geology began making sense of the strange fossilised plants and animals that were being brought to them quarries and rocky outcrops around the world. Thanks to these fossils, those pioneering scientists began to draw the conclusion that the world was in fact much older than mere millennia.

Detailed studies of rocks, fossils, meteorites and other objects tell us that the Earth was in fact formed around 4600 million years ago. Before the formation of Earth, there were no planets in our solar system; instead there was just a loose mass of rock and dust swirling about the relatively young sun. Eventually gravity drove the loose rock and dust together into large balls; these balls eventually formed the first planets, which included among them, Earth.

For the first few hundred million years of its existence the Earth was a hellish place, with a boiling hot surface, dominated by constantly erupting volcanoes. Moreover, Earth at this time was continuously being pelted by giant asteroids. The atmosphere would have been thick with poisonous gasses, leaving little chance for life of any kind to evolve.

But then something truly monumental happened, a turning point that occurred some 4 billion years ago. A planet roughly the size of Mars called Theia was hurtling wildly through the cosmos before smashing violently into our world. The collision was so violent that it almost smashed the planet completely in two. A part of Earth though, was thrown back into space where it gradually moulded itself into a natural satellite which we now call the Moon. The formation of the Moon had a profound effect on the development of life because it stabilised Earth’s orbit around the sun, and created the tides that we often take for granted today. The tides helped to aerate and cleanse the shallow seas where the first life forms evolved. Vast oceans of liquid water spread right around the world, transforming Earth into a blue planet. The oceans offered a constant and stable environment in which the slow process of life and evolution could begin.

The oldest sign of life on Earth is a chemical signature in rocks from Greenland that are around 3850 million years old. No one is entirely certain how life on Earth first evolved and there are a number of different theories that attempt to answer the question. One intriguing possibility is that the first organisms may have evolved in underwater hot springs, where there would’ve been an abundance of heat and the right sort of chemicals to permit life to evolve. For hundreds of millions of years life on Earth consisted of simple single celled bacteria that formed thin layers of slime across the ancient seabeds, hence where we get the term ‘primordial slime’ from. These first organisms lived by extracting energy from chemical reactions, but then one group known as the cyanobacteria evolved a way of extracting energy directly from sunlight, they were first organisms to use what we call photosynthesis. Bacteria soon formed vast mats on the ocean floor, sometimes creating layered mounds called stromatolites, the earliest fossils of which date from around 3500 million years ago. For hundreds of millions of years the slow pace of evolution meant that these comparatively simple organisms were the only life on Earth.

Showcasing Deep Sea Vents On BBC's Planet Earth

The Gas That Made Our Lives Possible

This is oxygen in molecular form. It first became common on Earth, as a result of the growth and development of bacterial slime.
This is oxygen in molecular form. It first became common on Earth, as a result of the growth and development of bacterial slime. | Source

When Earth Became An Ice World

Around 600 million years ago, much of the Earth's surface looked like this.
Around 600 million years ago, much of the Earth's surface looked like this. | Source

Volcanoes As A Force Of Good

It's thought that volcanoes played a crucial role in filling the Earth's atmosphere with carbon dioxide which probably ended the era of 'Snowball Earth'.
It's thought that volcanoes played a crucial role in filling the Earth's atmosphere with carbon dioxide which probably ended the era of 'Snowball Earth'. | Source

Proterozoic Eon: 2500-543 Million Years Ago

If the Archaean eon marked the evolution of life on Earth, then the Proterozoic eon, which literally means ‘ahead of animal life’ saw it develop from bacterial slime into complex plants and animals of the sort that we would recognise today.

At the start of the Proterozoic eon, around 2500 million years ago, the oceans still harboured all life on Earth. The atmosphere contained significant quantities of carbon dioxide and possibly methane, but very little oxygen, which made the land simply too hostile for life. But this was soon to change; life would soon conquer the land.

The bacterial slime in Earth’s seas produced oxygen as a by-product of their growth. This excess oxygen was released into the environment and over millions of years built up into the atmosphere, until around 2000 million years ago, when the Earth finally achieved a permanently high level of the gas.

Oxygen is a highly reactive chemical and is an excellent fuel for life. Thus, the arrival of an oxygen rich atmosphere sparked the evolution of new, more complex single celled or organisms known as eukaryotes. Unlike bacteria (which are prokaryotes), each eukaryotic cell had a separate nucleus that contained DNA, the building blocks of life at its centre, it was another major turning point in the development of life on Earth. The first eukaryote fossils called acritarchs, are microscopic and date from around 1500 million years ago. Slowly these nucleated cells adapted to live together in colonies, eventually producing creatures similar to modern sponges and jellyfish.

So towards the end of the Proterozoic eon, the world was full of drifting jellyfishes and static filter feeders. But then, according to some, Earth encountered its first great disaster since the first appearance of life. Between 750 and 600 million years ago, the Earth became engulfed in a severe ice age, which sent temperatures plummeting to around -40 F and caused all of the world’s oceans to freeze over completely. This theory, which is called the ‘Snowball Earth’ theory is still rather controversial and has yet to be fully vindicated. But interestingly it was only after the period in which the Earth is said to have been completely frozen over that the first signs of truly complex animal life start to appear in the fossil record.

Fossils from 600 million years ago are very rare indeed, and they are often little more than faint impressions in the rock. Scientists find these fossils difficult to interpret, but it is thought they are remains of simple animals. They are often termed as ‘Ediacaran animals’ on account of the fact they were first found near Ediacara in Australia. They lived in warm, shallow coastal waters right across the world. Among their number was an intriguing creature known as Spriggina, a worm like animal that must have pushed its way forward through the mud. Creatures like Spriggina with a distinct head and rear end, were to lay the foundations for a spectacular explosion of life that has never been matched. It is also may represent the common ancestor to everything from earthworms, crabs, dinosaurs, whales and humans.

More to follow...

A Possible Ancestor?

This tiny worm like creature called Spriggina is one of the first creatures with a recognisable head and rear. It may represent our earliest known ancestor.
This tiny worm like creature called Spriggina is one of the first creatures with a recognisable head and rear. It may represent our earliest known ancestor. | Source

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    • JKenny profile image
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      James Kenny 4 years ago from Birmingham, England

      Thanks very much SG, really appreciate your kind words, makes all the research worthwhile. Thanks for popping by.

    • sgbrown profile image

      Sheila Brown 4 years ago from Southern Oklahoma

      This is an excellent hub! Very well written and you had to do a lot of research. I agree with you that the story of live is the most entertaining. I applaud all the research and time you spent on this hub. I look forward to reading what follows! Voted up and more! :)

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Thanks Rahul, I think the story of life is far more entertaining than anything conjured up by mankind, and what's great about it, is that we are part of that story, and we have no idea how it will end. Thanks for popping by.

    • rahul0324 profile image

      Jessee R 4 years ago from Gurgaon, India

      A very detailed and descriptive take on the timeline of life on earth.. Its amazing isn't it.... all the science behind it

      I wonder whether this kind of stuff took place with any other planet in this universe

      Great hub my friend :)

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Thanks very much Curiad, glad you liked it!

    • Curiad profile image

      Mark G Weller 4 years ago from Lake Charles, LA.

      This is very well written and interesting JK!

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Thank you Matthew, glad you liked it. Thanks for stopping by.

    • Matthew Maktub profile image

      Matthew Foreman 4 years ago from Las Vegas

      Thanks for all the info. Definitely puts life in perspective.

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Thanks very much Alun, it did take a lot of work and research, so I appreciate your feedback . I agree that it can be very difficult to tackle a subject like this, but I'm glad that it seems to have turned out well. Thank you for visiting Alun.

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Thank you for the vote nanderson, much appreciated.

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Hi Nate, I know what you mean, I can't imagine Earth without plants, and yet it seems strange that for most of its history, they didn't exist. Its enough to make your head burst. Thanks for popping by.

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Hi mperrottet, really appreciate you stopping by and commenting. Just letting you know that the rest of the series is now up and published. Thanks for popping by.

    • JKenny profile image
      Author

      James Kenny 4 years ago from Birmingham, England

      Thanks asus ako, glad you liked it.

    • Greensleeves Hubs profile image

      Greensleeves Hubs 4 years ago from Essex, UK

      A useful, informative and comprehensive account of the early days of life on Earth. With good diagrams and videos too. Subjects like this are always difficult to present because so many factors are either unknown, or inter-related, so cause and effect becomes difficult to establish. But you've done a really good job here, which must have taken a lot of work. Voted up. Alun.

    • nanderson500 profile image

      nanderson500 4 years ago from Seattle, WA

      Very interesting. Voted up and awesome.

    • NateB11 profile image

      Nathan Bernardo 4 years ago from California, United States of America

      Very fascinating. It is interesting to think about what it was like so many millions of years ago and the events that took place.

    • mperrottet profile image

      Margaret Perrottet 4 years ago from Pennsauken, NJ

      This is a fascinating, wonderfully written account of the beginning of life on our planet. I look forward to the next installments. Voted up, useful, interesting awesome and beautiful.

    • asus ako profile image

      asus ako 4 years ago from australia

      Its really nice I like articles .