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Ancient Lake Challenges the View that Eukaryotic Life Developed in the Oceans

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Posted May 29, 2015

New research suggests that the ancient Bay of Stoer, located in Northwest Scotland, may be of utmost importance to our understanding of the evolution of complex terrestrial life.

This ancient region of Scotland may hold the key to our understanding of how complex eukaryotic and nitrogen-fixing bacterial life first appeared and then spread across the Earth. Image credit: Gordon Hatton via geograph.org.uk, CC BY-SA 2.0.

This ancient region of Scotland may hold the key to our understanding of how complex eukaryotic and nitrogen-fixing bacterial life first appeared and then spread across the Earth. Image credit: Gordon Hatton via geograph.org.uk, CC BY-SA 2.0.

Previous scientific enquiries have shown that molybdenum – a metal that played an essential role in the emergence of eukaryotic and nitrogen-fixing bacterial life – was not an abundant element of the marine environment around the time when complex organisms were expanding their domain about 1.5 billion years ago.

Now, a new study from the University of Aberdeen suggests this core shift in the Earth’s evolution may have happened in lakes and on land, rather in the cold depths of pre-historic oceans.

The discovery was made by a group of researchers, led by Professor John Parnell from the University’s School of Geosciences, who examined a number of ancient 1.5 billion year old Torridonian lake sediments. The average yearly flow of molybdenum into the lake was determined by studying the records of annual layering contained in the samples.

“Here we show that the flux of molybdenum to a Mesoproterozoic lake was 1 to 2 orders of magnitude greater than typical fluxes in the modern and ancient marine environment. Thus, there was no barrier to availability to prevent evolution in the terrestrial environment, in contrast to the nutrient-limited Mesoproterozoic oceans,” wrote the researchers in the abstract of their paper.

The site of this new discovery is already considered a highly-prized scientific resource, having provided evidence of how a critical point in evolution took place several hundred years earlier than scientists had previously understood.

One of the bay’s key distinguishing features is its geographic location, which makes it ideal for research purposes. “When carrying out this kind of research there are very few rocks that you can study that have been deposited in a terrestrial setting, which is what makes this site in Northwest Scotland special,” explained Parnell.

Even though there is a number of other worthwhile locations around the world, many of them are hard to reach – a serious impediment to recurrent field work. “The difference with this site is that it’s so well-preserved and easily accessible, which makes it an excellent place to look for the kind of evidence that we have uncovered.”

According to Parnell, this research is just one part of a bigger body of ongoing work on these rocks. “It is clear that the site is a very important archive to help us understand the Earth’s early history, so we will continue to develop that work at Aberdeen.”

Sources: study abstract, natureasia.com, abdn.ac.uk, phys.org.

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