Evolution: rate depends on tectonics and environment (Evolution)

by David Turell , Monday, March 29, 2021, 23:35 (1117 days ago) @ David Turell

A new geologic approach to understanding evolution:

https://cosmosmagazine.com/earth/earth-sciences/explainer-myth-busting-the-boring-billi...

"Geologists are fond of giving dramatic names to past events, such as “The Great Dying” or “Snowball Earth” or “The Cambrian Explosion”. But perhaps the most inaccurate is the “Boring Billion”, also charmingly known as “The Dullest Time in Earth’s History”.

"...a quarter of the planet’s entire history, spanning from 1.8–0.8 billion years ago. It’s thought to have been nowhere near as dynamic and changeable as the planet today, but instead rather slimy and static. Volcanoes lay dormant, the atmosphere had much less oxygen than today, the oceans swilled about stagnant, and ice ages were absent.

"Tectonic plates ground to a standstill, too – the supercontinent Rodinia remained surprisingly stable from 1.8 billion to 750 million years ago.

“'The climate appears to be very stable, and life evolution was sluggish,” adds geologist Ming Tang from Peking University in Beijing. “For example, eukaryotes appeared on Earth about 1.7 billion years ago but only rose to dominance some 0.8 billion years ago. How Earth got stuck in this one-billion-year stasis is unclear.”

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“'Erosion and weathering of mountain rocks provide life-essential nutrients such as phosphorus and many trace metals,” he explains. “These nutrients are critical to sustaining a productive primary biomass, which produces food and oxygen to be used by more complex life.”

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"But further research has suggested that these isotopes were more variable than thought. Moreover, as Collins points out, this period is “actually where the most fundamental biological innovation happened – that’s endosymbiosis, which is the formation of eukaryote fossils”.

"The first eukaryote cells – which today make up every plant, animal and fungi today – evolved at the very beginning of the Boring Billion. Then, around 1.6 billion years ago, plants diverged from animals and fungi and 1.5 billion years ago animals and fungi split.

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"A 2018 study from of the University of Tasmania, for example, suggests that the stress of limited nutrients during the Boring Billion may have actually promoted endosymbiosis, where single cells are ingested by another.

“'There’s always been a lot of focus on macro evolution and the Cambrian explosion 541 million years ago,” says lead author of the study, Indrani Mukherjee. “Yet, evolution really starts with the transformation of simple cells into complex ones, and it is in the Boring Billion that scientists have previously found the first fossilised evidence of a complex cell.”

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"This point – ending the Boring Billion once and for all – was likely triggered by a combination of plate tectonics and climactic changes: glaciers grinding up rocks and moving elements into oceans, as well as mountains becoming eroded, providing the nutrients for life.

“But we don’t we don’t really understand all those things yet,” Collins says.

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"Paleontologists are beginning to uncover increasingly rich evidence of life from across that period, such as fossilised algae from 1.56 billion years ago, and lichen fungi that grazed on microbial mats around 1.3 billion years ago.

"It’s really what has happened since that time that has made our Earth so different to other terrestrial worlds, and so understanding where we have come – that is, the pathway of life through the Boring Billion – is fundamental to understanding our unique place in the Solar System."

Comment: this study begins to reveal how mixed up an interplay of factors was involved in helping to speed or slow evolution. We finally ended up as a fully 'privileged planet', possibly different from all the other planets in the universe