Life on earth, Precambrian origins

This video says about itself:

Origin of Life – How Life Started on Earth

2 June 2016

Four and a half billion years ago, the young Earth was a hellish place—a seething chaos of meteorite impacts, volcanoes belching noxious gases, and lightning flashing through a thin, torrid atmosphere. Then, in a process that has puzzled scientists for decades, life emerged. But how?

[Follow] mineralogist Robert Hazen as he journeys around the globe. From an ancient Moroccan market to the Australian Outback, he advances a startling and counterintuitive idea—that the rocks beneath our feet were not only essential to jump-starting life, but that microbial life helped give birth to hundreds of minerals we know and depend on today. It’s a theory of the co-evolution of Earth and life that is reshaping the grand-narrative of our planet’s story.

From the University of Bristol in England:

A timescale for the origin and evolution of all of life on Earth

August 20, 2018

A new study led by scientists from the University of Bristol has used a combination of genomic and fossil data to explain the history of life on Earth, from its origin to the present day.

Palaeontologists have long sought to understand ancient life and the shared evolutionary history of life as a whole.

However, the fossil record of early life is extremely fragmented, and its quality significantly deteriorates further back in time towards the Archaean period, more than 2.5 billion years ago, when the Earth’s crust had cooled enough to allow the formation of continents and the only life forms were microbes.

Holly Betts, lead author of the study, from the University of Bristol’s School of Earth Sciences, said: “There are few fossils from the Archaean and they generally cannot be unambiguously assigned to the lineages we are familiar with, like the blue-green algae or the salt-loving archaebacteria that colours salt-marshes pink all around the world.

“The problem with the early fossil record of life is that it is so limited and difficult to interpret — careful reanalysis of some of the very oldest fossils has shown them to be crystals, not fossils at all.”

Fossil evidence for the early history of life is so fragmented and difficult to evaluate that new discoveries and reinterpretations of known fossils have led to a proliferation of conflicting ideas about the timescale of the early history of life.

Co-author Professor Philip Donoghue, also from Bristol’s School of Earth Sciences, added: “Fossils do not represent the only line of evidence to understand the past. A second record of life exists, preserved in the genomes of all living creatures.”

Co-author Dr Tom Williams, from Bristol’s School of Biological Sciences, said: “Combining fossil and genomic information, we can use an approach called the ‘molecular clock’ which is loosely based on the idea that the number of differences in the genomes of two living species (say a human and a bacterium) are proportional to the time since they shared a common ancestor.”

By making use of this method the team at Bristol and Mark Puttick from the University of Bath were able to derive a timescale for the history of life on Earth that did not rely on the ever-changing age of the oldest accepted fossil evidence of life.

Co-author Professor Davide Pisani said: “Using this approach we were able to show that the Last Universal Common Ancestor all cellular life forms, ‘LUCA’, existed very early in Earth’s history, almost 4.5 Billion years ago — not long after Earth was impacted by the planet Theia, the event which sterilised Earth and led to the formation of the Moon.

“This is significantly earlier than the currently accepted oldest fossil evidence would suggest.

“Our results indicate that two “primary” lineages of life emerged from LUCA (the Eubacteria and the Archaebacteria), approximately one billion years after LUCA.

“This result is testament to the power of genomic information, as it is impossible, based on the available fossil information, to discriminate between the oldest eubacterial and archaebacterial fossil remains.”

The study confirms modern views that the eukaryotes, the lineage to which human life belongs (together with the plants and the fungi, for example), is not a primary lineage of life. Professor Pisani added: “It is rather humbling to think we belong to a lineage that is billions of years younger than life itself.”

In the beginning, life was small. For billions of years, all life on Earth was microscopic, consisting mostly of single cells. Then suddenly, about 570 million years ago, complex organisms including animals with soft, sponge-like bodies up to a meter long sprang to life. And for 15 million years, life at this size and complexity existed only in deep water. Scientists have long questioned why these organisms appeared when and where they did: in the deep ocean, where light and food are scarce, in a time when oxygen in Earth’s atmosphere was in particularly short supply. A new study from Stanford University, published Dec. 12 in the peer-reviewed Proceedings of the Royal Society B, suggests that the more stable temperatures of the ocean’s depths allowed the burgeoning life forms to make the best use of limited oxygen supplies: here.

An organic molecule detected in the material from which a star forms could shed light on how life emerged on Earth, according to new research led by Queen Mary University of London: here.

Most of Earth’s life-essential elements probably arrived with the planetary collision that produced the moon. Petrologists now conclude Earth most likely received the bulk of its carbon, nitrogen and other life-essential volatile elements from a collision with a Mars-sized planet more than 4.4 billion years ago: here.

3.5 billion years ago Earth hosted life, but was it barely surviving, or thriving? A new study carried out by a multi institutional team with leadership including the Earth-Life Science Institute (ELSI) of Tokyo Institute of Technology (Tokyo Tech) provides new answers to this question. Microbial metabolism is recorded in billions of years of sulfur isotope ratios that agree with this study’s predictions, suggesting life throve in the ancient oceans. Using this data, scientists can more deeply link the geochemical record with cellular states and ecology: here.

What did the very first proteins look like — those that appeared on Earth around 3.7 billion years ago? Prof. Dan Tawfik of the Weizmann Institute of Science and Prof. Norman Metanis of the Hebrew University of Jerusalem have reconstructed protein sequences that may well resemble those ancestors of modern proteins, and their research suggests a way that these primitive proteins could have progressed to forming living cells. Their findings were published in the Proceedings of the National Academy of Sciences (PNAS): here.

Clues from Canadian rocks formed billions of years ago reveal a previously unknown loss of life even greater than that of the mass extinction of the dinosaurs 65 million years ago, when Earth lost nearly three-quarters of its plant and animal species. Rather than prowling animals, this die-off involved miniscule microorganisms that shaped the Earth’s atmosphere and ultimately paved the way for those larger animals to thrive: here.

Until now, the Cambrian Explosion — which took place between 540 and 520 million years ago — was thought to have given rise to almost all the early ancestors of present-day animals. Scientists say, however, that it was probably just one in a series of similar events, the first of which took place at least 571 million years ago during the late Ediacaran Period: here.

Peptides, one of the fundamental building blocks of life, can be formed from the primitive precursors of amino acids under conditions similar to those expected on the primordial Earth, finds a new UCL study. The findings, published in Nature, could be a missing piece of the puzzle of how life first formed: here.

Were hot, humid summers the key to life’s origins? Here.