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Ancient oceans offer new insight into the origins of animal life
September 10, 2009Analysis of a rock type found only in the world's oldest oceans has shed new light on how large animals first got a foothold on the Earth.
A scientific team led by Professor Robert Frei at the University of Copenhagen in Denmark, and including scientists from Newcastle University, UK, and universities in Uruguay and Southern Denmark, have for the first time managed to plot the rise and fall of oxygen levels in the Earth's atmosphere over the last 3.8 billion years.
By analysing the isotopes of chromium in iron-rich sediments formed in the ancient oceans, the team has found that a rise in atmospheric oxygen levels 580 million years ago was closely followed by the evolution of animal life.
Published today in the academic journal Nature, the data offers new insight into how animal life - and ultimately humans - first came to roam the planet.
"Because animals evolved in the sea, most previous research has focussed on oceanic oxygen levels," explains Newcastle University's Dr Simon Poulton, one of the authors of the paper.
"Our research confirms for the first time that a rise in atmospheric oxygen was the driving force for oxygenation of the oceans 580 million years ago, and that this was the catalyst for the evolution of large complex animals."
The study
Distinctive chromium isotope signals occur when continental rocks are altered and weathered as a result of oxygen levels rising in the atmosphere.
The chromium released by this weathering is then washed into the seas and deposited in the deepest oceans - trapped in iron-rich rocks on the sea bed.
Using this new data, the research team has not only been able to establish the trigger for the evolution of animals, but have also demonstrated that oxygen began to pulse into the atmosphere earlier than previously thought.
"Oxygen levels actually began to rise 2.8 billion years ago" explains Dr Poulton.
"But instead of this rise being steady and gradual over time, what we saw in our data was a very unstable situation with short-lived episodes of free oxygen in the atmosphere early in Earth's history, followed by plummeting levels around 2 billion years ago.
"It was not until a second rise in atmospheric oxygen 580 million years ago that larger complex animals were able to get a foothold on the Earth."
Newcastle University
Published today in the academic journal Nature, the data offers new insight into how animal life - and ultimately humans - first came to roam the planet.
"Because animals evolved in the sea, most previous research has focussed on oceanic oxygen levels," explains Newcastle University's Dr Simon Poulton, one of the authors of the paper.
"Our research confirms for the first time that a rise in atmospheric oxygen was the driving force for oxygenation of the oceans 580 million years ago, and that this was the catalyst for the evolution of large complex animals."
The study
Distinctive chromium isotope signals occur when continental rocks are altered and weathered as a result of oxygen levels rising in the atmosphere.
The chromium released by this weathering is then washed into the seas and deposited in the deepest oceans - trapped in iron-rich rocks on the sea bed.
Using this new data, the research team has not only been able to establish the trigger for the evolution of animals, but have also demonstrated that oxygen began to pulse into the atmosphere earlier than previously thought.
"Oxygen levels actually began to rise 2.8 billion years ago" explains Dr Poulton.
"But instead of this rise being steady and gradual over time, what we saw in our data was a very unstable situation with short-lived episodes of free oxygen in the atmosphere early in Earth's history, followed by plummeting levels around 2 billion years ago.
"It was not until a second rise in atmospheric oxygen 580 million years ago that larger complex animals were able to get a foothold on the Earth."
Newcastle University
Atmospheric Oxygen Current Events and Atmospheric Oxygen News RSSBanded rocks reveal early Earth conditions, changes
The strikingly banded rocks scattered across the upper Midwest and elsewhere throughout the world are actually ambassadors from the past, offering clues to the environment of the early Earth more than 2 billion years ago.
Reprogramming Human Cells Without Inserting Genes
A research team comprised of faculty at Worcester Polytechnic Institute's (WPI) Life Sciences and Bioengineering Center (LSBC) and investigators at CellThera, a private company also located at the LSBC, has discovered a novel way to turn on stem cell genes in human fibroblasts (skin cells) without the risks associated with inserting extra genes or using viruses.
University of Leicester geologists demonstrate extent of ancient ice age
Geologists at the University of Leicester have shown that an ancient Ice Age, once regarded as a brief 'blip', in fact lasted for 30 million years.
The Rise of Oxygen Caused Earth's Earliest Ice Age
Geologists may have uncovered the answer to an age-old question - an ice-age-old question, that is.
Fire is important part of global climate change, report scientists
Fire must be accounted for as an integral part of climate change, according to 22 authors of an article published in the April 24 issue of the journal Science. The authors determined that intentional deforestation fires alone contribute up to one-fifth of the human-caused increase in emissions of carbon dioxide, a heat-trapping gas that raises global temperature.
A new link between nickel, methane gas and the evolution of complex life forms on Earth
A University of Alberta researcher is lead author on a paper that reaches back billions of years to establish a new link between nickel, methane gas and the evolution of complex life forms on Earth.
Research team reports how, when life on Earth became so big
In 3.5 billion years, life on earth went from single microscopic cells to giant sequoias and blue whales. Scientists have now documented quantitatively that the increase in maximum size of organisms was not gradual, but happened in two distinct bursts "tied to the geological evolution of the planet," said Michal Kowalewski, professor of geosciences at Virginia Tech.
Toxic to aliens -- but key to health of planet
Scientists at the University of Leicester are using an ingredient found in common shampoos to investigate how the oxygen content of the oceans has changed over geologically recent time.
Low oxygen and molybdenum in ancient oceans delayed evolution of life by 2 billion years
A deficiency of oxygen and the heavy metal molybdenum in the ancient deep ocean may have delayed the evolution of animal life on Earth by nearly two billion years, a study led by UC Riverside biogeochemists has found.
Scientists uncover the source of an almost 2 billion year delay in animal evolution
A deficiency of oxygen and the heavy metal molybdenum in the ancient deep ocean may have delayed the evolution of animal life on Earth for nearly two billion years.
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