First Signs of Lake Life Having Sex on the Beach

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A vacation lake trip can involve plenty of party time, taking in the sun’s rays, as well as a lot of shore-side romance if the weather is nice.

Early life was taking in the sun and looking for love in lakes too. One billion year old fossilized microorganisms from Scotland’s Loch Torridon had complex structures that made photosynthesis and sexual reproduction possible.

What makes these early eukaryotic fossils important is that they came from what was once a lakebed. Evolution of specialized structures in the cell, like the nucleus, mitochondria, and chloroplasts, had originally been thought to occur only in the oceans.

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“It may even be that the sort of conditions found in the ancient lakes around Loch Torridon favored a key step in this transformation, which involved the incorporation of symbiotic bacteria into the cell to form chloroplasts, rather than this occurring in the sea as usually envisaged,” said Martin Brasier of the University of Oxford in a press release from the University of Sheffield.

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Brasier was one of the authors of a paper published in Nature detailing the ancient Scottish lake-dwellers. He worked with a team of scientists from Boston College, University of Sheffield, and the University of Oxford, to uncover the fossils from rocks near Loch Torridon on the west coast of Scotland.

“During this time the continents are often considered to have been essentially barren of life – or at the most with an insignificant microbial biota dominated by cyanobacteria. We have discovered evidence for complex life on land from 1 billion year old deposits from Scotland,” said Charles Wellman of the University of Sheffield in a press release by that school.

Some of the fossils found were from organisms living in the lake, but others were from organisms living on land that were washed into the lake and fossilized.

“This suggests that life on land at this time was more abundant and complex than anticipated. It also opens the intriguing possibility that some of the major events in the early history of life may have taken place on land and not entirely within the marine realm,” said Wellman.

The fossils from the Scottish lake lived during an important time when simple celled organisms called prokaryotes, such as cyanobacteria, were evolving into more complex organisms called eukaryotes. Prokaryotes lack many of the structures that allow more advanced life to use resources from their environment, like sunlight.

Prokaryotes also lack the ability to exchange genes and create offspring with a different genetic code. Without this process, which is the basic form of sex, evolution proceeds much slower, and less efficiently.

With their sexual reproduction, the ancient Scottish lake-dwellers may have had a profound influence on life on Earth. “It was arguably these organisms that helped to turn our landscape from a harsh and rocky desert into a green and pleasant place,” said Brasier.

IMAGE 1: Loch Torridon, Scotland (Wikimedia Commons).

IMAGE 2: A cluster of cells, one of the fossils from Scotland. (Credit: Oxford University/Martin Brasier).

IMAGE 3: Cell pairs, another example of fossils from Scotland. (Credit: Oxford University/Martin Brasier).

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