Life exploded on Earth after slow rise of oxygen

December 18, 2015
A composite image of the Western hemisphere of the Earth. Credit: NASA

It took 100 million years for oxygen levels in the oceans and atmosphere to increase to the level that allowed the explosion of animal life on Earth about 600 million years ago, according to a UCL-led study funded by the Natural Environment Research Council.

Before now it was not known how quickly Earth's oceans and atmosphere became oxygenated and if animal life expanded before or after rose. The new study, published today in Nature Communications, shows the increase began significantly earlier than previously thought and occurred in fits and starts spread over a vast period. It is therefore likely that early animal evolution was kick-started by increased amounts of oxygen, rather than a change in animal behaviour leading to oxygenation.

Lead researcher, Dr Philip Pogge von Strandmann (UCL Earth Sciences), said: "We want to find out how the evolution of life links to the evolution of our climate. The question on how strongly life has actively modified Earth's climate, and why the Earth has been habitable for so long is extremely important for understanding both the climate system, and why life is on Earth in the first place."

Researchers from UCL, Birkbeck, Bristol University, University of Washington, University of Leeds, Utah State University and University of Southern Denmark tracked what was happening with oxygen levels globally 770 - 520 million years ago (Ma) using new tracers in rocks across the US, Canada and China.

Samples of rocks that were laid down under the sea at different times were taken from different locations to piece together the global picture of the oxygen levels of Earth's oceans and atmosphere. By measuring selenium isotopes in the rocks, the team revealed that it took 100 million years for the amount of oxygen in the atmosphere to climb from less than 1% to over 10% of today's current level. This was arguably the most significant oxygenation event in Earth history because it ushered in an age of animal life that continues to this day.

Dr Pogge von Strandmann, said: "We took a new approach by using selenium isotope tracers to analyse marine shales which gave us more information about the gradual changes in oxygen levels than is possible using the more conventional techniques used previously. We were surprised to see how long it took Earth to produce oxygen and our findings dispel theories that it was a quick process caused by a change in ."

During the period studied, three big 'snowball Earth' glaciations - Sturtian (~716Ma), Marinoan (~635Ma) and Gaskiers (~580Ma) - occurred whereby the Earth's land was covered in ice and most of the oceans were frozen from the poles to the tropics. During these periods, temperatures plummeted and rose again, causing glacial melting and an influx of nutrients into the ocean, which researchers think caused oxygen levels to rise deep in the oceans.

Increased nutrients means more ocean plankton, which will bury organic carbon in seafloor sediments when they die. Burying carbon results in oxygen increasing, dramatically changing conditions on Earth. Until now, oxygenation was thought to have occurred after the relatively small Gaskiers glaciation melted. The findings from this study pushes it much earlier, to the Marinoan glaciation, after which animals began to flourish in the improved conditions, leading to the first big expansion of animal life.

Co-author Prof. David Catling (University of Washington Earth and Space Sciences), added: "Oxygen was like a slow fuse to the explosion of . Around 635 Ma, enough oxygen probably existed to support tiny sponges. Then, after 580 Ma, strange creatures shaped like pizzas lived on a lightly oxygenated seafloor. Fifty million years later, vertebrate ancestors were gliding through oxygen-rich seawater. Tracking how oxygen increased is the first step towards understanding why it took so long. Ultimately, a grasp of geologic controls on oxygen levels can help us understand whether animal-like life might exist or not on Earth-like planets elsewhere."

Explore further: Ocean toxicity hampered the rapid evolution of complex life

More information: Nature Communications, dx.doi.org/10.1038/NCOMMS10157

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8 comments

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Torbjorn_Larsson_OM
5 / 5 (4) Dec 18, 2015
Of course, the glaciations were a result of increased atmospheric oxygen (decreased methane greenhouse effect)...

Maybe we can see these global slushballs elsewhere, and tie it to increased complexity of life.
antigoresockpuppet
3 / 5 (2) Jan 06, 2016
"We want to find out how the evolution of life links to the evolution of our climate. The question on how strongly life has actively modified Earth's climate, and why the Earth has been habitable for so long is extremely important for understanding both the climate system, and why life is on Earth in the first place."


That's all wrong. Life can not affect climate. Sugar Daddy said it, history proves it and I believe it.
gkam
1 / 5 (5) Jan 07, 2016
Believe any silly thing you want: The rest of us are going to ignore you and save the Earth.

You're welcome.
Uncle Ira
4 / 5 (4) Jan 07, 2016
Believe any silly thing you want: The rest of us are going to ignore you and save the Earth.

You're welcome.


Do you ever pass up the chance to prove you are the moron? Read what he wrote again, and see if you get a feeling for what he believes.

This is kind of like you calling Jenkins-Skippy the NAZI the other for pointing out that there were posters here who are also making postums on a NAZI interweb place.

Or the time you "Heil Hitlered" Captain-Skippy because he wrote the very common German saying that you could not understand or be bothered to look up.

glam-Skippy, you are old and tired and seem really dissatisfied with your life. You make your self the target for ridicule and fun and think you are doing something really important and noticing worthy here. Do you have a drinking or marijuana problems? Or something? It ain't natural what you do Cher. It is unhealthy what you subject your self to.
gkam
1 / 5 (5) Jan 07, 2016
Ira, got ANY technical knowledge at ALL?

All you can do is make your adolescent personal comments. Folk can get that at the bus station, thanks.

BTW, who are you, and why are you hiding like otto behind a phony name?
Uncle Ira
4 / 5 (4) Jan 07, 2016
All you can do is make your adolescent personal comments. Folk can get that at the bus station, thanks.


Well if you do it why I can not do it too?

BTW, who are you, and why are you hiding like otto behind a phony name?


Ira is my real name Cher. Borned with it. If you don't like it that is fine. But I have had 38 years to get used to it and like it just fine. So saying it is the phony name is just more of you saying things that only so because you thought it and you thought it wrong.
DavidTheShepherd
1 / 5 (2) Jan 09, 2016
The obvious unspoken assumption here is that life arose spontaneously all by itself ffrom random physical and chemical processes in the early earth history.
The problem with that assumption is that there is no way to demonstrate that life can arise from dead materials all by itself. There is no observed and recorded history, nor can we have any repeated observations of this unstated assumption.
Quite to the contrary we repeatedly observe that things die and NEVER come back to life again all by themselves. We have almost 6000 years of confirmed, repeated observations that life does not arise from the dead all by itself. So the unstated assumption can be ruled out if one applies true and strict scientific methodology to this question of abiogenesis.
To take it further, one can use strict reasoning based on well-established and proven chemical and physical laws to discount the possibility of this occurring, EVER.
So this whole model is based on speculation.
gkam
2 / 5 (4) Jan 09, 2016
It is better than relying on old stories from the Age of Ignorance. Is it any more ridiculous than taking "days" to crate the Universe, when we know "days" are due to the rotation of the Earth? Any more ridiculous than raising folk from the dead? You brought it up.

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