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Oldest Life On Earth (Earliest Organisms; Early Evolution)

A billion year old micro fossil, found in the Scottish highlands, is the earliest evidence of a multicellular animal found so far.

"The microscopic fossil was discovered at Loch Torridon in Wester Ross by researchers led by the University of Sheffield and the US's Boston College.

Scientists said it could prove a new link in the evolution of animals.

Researchers could identify it contained two distinct cell types thanks to the fossil's "exceptional preservation"."

https://www.bbc.com/news/uk-scotland-highlands-islands-56917272
 
More Archaea fossils (maybe).

Threadlike filaments pressed in rock may be the remnants of archaea that burped methane near hydrothermal vents 3.42 billion years ago.

If so, these strands in rock excavated in South Africa around a decade ago, would provide the earliest direct evidence of a methane-based metabolism, researchers report July 14 in Science Advances.

Such ancient fossil filaments may contain clues about Earth’s early inhabitants and hint at where to look for extraterrestrial life. Scientists suspect that life on our planet could have arisen in such an environment (SN: 9/24/20).

Biologists have deduced that metabolisms based on munching or belching methane evolved early on, but don’t know exactly when, says Barbara Cavalazzi, a geobiologist at University of Bologna in Italy. Previous research has found indirect evidence for methane-cycling microbes in the chemistry of fluid-filled pockets of ancient rocks from around 3.5 billion years ago. But that work didn’t find the actual microbes. With this fossil analysis, “what we find, basically, is evidence of about the same age. But this is a cellular remain — it’s the organism,” Cavalazzi says.

The newly identified fossil threads have a carbon-based shell. That shell is different structurally from the preserved interior, suggesting a cell envelope enclosing the cells’ insides, the authors write. And the team found relatively high nickel concentrations in the filaments. The concentrations were similar to levels found in modern methane-makers, suggesting the fossils’ metal may come from nickel-containing enzymes in the microbes.

https://www.sciencenews.org/article/oldest-archaea-microbe-fossil-fillaments-life-evolution
 
Did volcanic glasses spark earliest life or are these researchers making spectacles of themselves?

When life emerged, it did so quickly.

Fossils suggest microbes were present 3.7 billion years ago, just a few hundred million years after the 4.5-billion-year-old planet had cooled enough to support biochemistry, and many researchers think the hereditary material for these first organisms was RNA. Although not as complex as DNA, RNA would still be difficult to forge into the long strands needed to convey genetic information, raising the question of how it could have spontaneously formed.

Now, researchers may have an answer. In lab experiments, they show how rocks called basaltic glasses help individual RNA letters, known as nucleoside triphosphates, link into strands up to 200 letters long. The glasses would have been abundant in the fire and brimstone of early Earth; they are created when lava is quenched in air or water or when the melted rock created in asteroid strikes cools off rapidly.

The result has divided top origin-of-life researchers. “This seems to be a wonderful story that finally explains how the nucleoside triphosphates react with each other to give RNA strands,” says Thomas Carell, a chemist at Ludwig Maximilians University of Munich. But Jack Szostak, an RNA expert at Harvard University, says he won’t believe the result until the research team better characterizes the RNA strands.

Origin-of-life researchers are fond of a primordial “RNA world” because the molecule can carry out two distinct processes vital for life. Like DNA, it’s made up of four chemical letters that can carry genetic information. And like proteins, RNA can also catalyze chemical reactions needed for life.

https://www.science.org/content/article/did-volcanic-glasses-help-spark-early-life
 
Newly published research confirms western Australian rocks suspected of representing 3.48-billion-year-old microbial mats are indeed evidence of living organisms.
3.5 billion-year-old rock structures are one of the oldest signs of life on Earth

Layered rocks in Western Australia are some of Earth's earliest known life, according to a new study.

The fossils in question are stromatolites, layered rocks that are formed by the excretions of photosynthetic microbes. The oldest stromatolites that scientists agree were made by living organisms date back 3.43 billion years, but there are older specimens, too. In the Dresser Formation of Western Australia, stromatolites dating back 3.48 billion years have been found.

However, billions of years have wiped away traces of organic matter in these older stromatolites, raising questions about whether they were really formed by microbes or whether they might have been made by other geological processes.

The new study's verdict: It was ancient life. ...

"We were able to find certain specific microstructures within particular layers of these rocks that are strongly indicative of biological processes" ...

The evidence that the Dresser Formation stromatolites are signs of ancient life doesn't make them the oldest life on the planet. That (possible) honor may go to stromatolites found in 3.7 billion-year-old rock in Greenland, or possibly to microfossils from Canada that might be as old as 4.29 billion years. It's very difficult to distinguish biological life from non-organic processes in these very old rocks, however, so these finds and others from a similar timeframe are controversial. ...
Click to expand...
FULL STORY: https://www.livescience.com/oldest-stromatolites-australia

PUBLISHED RESEARCH REPORT: https://pubs.geoscienceworld.org/gs...anced-two-and-three-dimensional-insights-into

(A PDF file of the entire publication can be accessed from the webpage linked above.)
 
SummerLightning said:
Stromatolites are still with us - and Western Australia is home to one of the few significant surviving colonies:

https://www.bushheritage.org.au/species/stromatolites
Click to expand...
"Stromatolites are the reason why we’re alive today! Before cyanobacteria the air was only 1% oxygen."
I know I keep banging on about this but we (humans) did not evolve from photosynthesing cyanobacter, else we'd still be green or blue or red. Our ancestors were most likely anaerobic Archea organisms living near the marine hot vents utilising sulphur as a source of energy via reduction/oxidation (redox) reactions. Free oxygen was a poison interfering with that process and very nearly wiped them out. The reason why we're alive today was due to a symbiotic relationship with a proto-mitochondria who could make effective use of the new fangled pollutant. Mitochondrial DNA still remains separate from our genome ie we don't have genes for it.
 
Surviving Snowball Earth.

More than 600 million years ago, the planet was frozen from pole to pole, covered in half-kilometer-thick ice sheets that darkened every ocean. How sea life clung on during Snowball Earth, as this inhospitable period is known, has long been a mystery.

A new study bolsters the idea that the global glaciation wasn’t all encompassing. Geochemical evidence from ancient rocks suggests zones of open ocean may have been present north of the Tropic of Cancer, a region that was previously considered too cold to host life during this period. “There’s a habitable zone,” says Shuhai Xiao, a geobiologist at the Virginia Polytechnic Institute and State Universityand co-author of the new work. And it’s “perhaps wider than previously thought.”

Other scientists aren’t yet convinced, however. Climate simulations have trouble creating even an ice-free equator during Snowball Earth periods. The possibility that there was uncovered ocean outside the tropics “makes this thing really difficult to swallow,” says Paul Hoffman, a geologist at Harvard University who pioneered the Snowball Earth hypothesis.

Climate models since the 1960s have shown how planetary deep freezes can arise from a simple feedback loop. When temperatures drop, Earth’s ice caps expand, reflecting sunlight and creating further cooling. If the ice manages to creep to roughly 30° to 40° latitude—about where North Africa and the continental United States are today—the global climate enters a runaway freezing cycle and glaciers end up covering the entire planet within a few hundred years.

The geological record indicates Earth has experienced at least two such periods. The most recent one is known as the Marinoan Ice Age, between 654 million and 635 million years ago. Life was limited to the oceans and large creatures had yet to evolve, but fossils show that microscopic eukaryotes such as algae lived before and after the episode. Such organisms require sunlight and open water, Xiao says. “You have to envision some sort of refuge where these algae can survive.” ...

https://www.science.org/content/art...vived-far-north-equator-during-snowball-earth
 
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