Life May Have Started as Sticky Goo, Long Before Cells Even Existed

Extraits de l'article:

Scientists have many theories about how Earth's raw materials turned into living cells, but a new proposal is particularly slimy.

In a recent paper, an international team argues that life may have first emerged within a blob of sticky goo clinging to a rock, long before true cells existed.

Similar to the bacterial biofilms we see today on rocks, pond surfaces, and even your unbrushed teeth, a semi-solid gel matrix would provide the perfect place for life to set up shop, the authors propose, both on Earth and, potentially, on other planets.

This jelly-life notion is a bit niche: Most origin-of-life theories set the scene for the first organic chemistry in water, not goo.

But those theories also struggle to explain how simple molecules of the kind that were probably floating around in Earth's waters could have transformed into something as complex as RNA (ribonucleic acid) or DNA (deoxyribonucleic acid) without some extra support.

A gel-like environment could solve several of those issues at once.

"While many theories focus on the function of biomolecules and biopolymers, our theory instead incorporates the role of gels at the origins of life," says Hiroshima University astrobiologist Tony Jia.

A gel medium, Jia and co-authors propose, would be able to trap and organize molecules into formations stable enough to overcome some key barriers in pre-life chemistry.

Early Earth was not the relatively mild, ozone-blanketed place we know today. Intense ultraviolet radiation could hit the surface unimpeded, and temperatures were extreme.

Prebiotic gels, the team suggests, could have offered much-needed protection to life's fragile chemistry, long before actual membrane-bound cells had a chance to develop.

In this theory, which was first proposed in 2005 and expanded on here, protocells were not the first step in the origin of life, but rather the outcome of the chemical organization established by the primordial goo.

"Here, we outline the prebiotic gel-first framework, which considers that early life may have emerged within surface-attached gel matrices," the researchers write.

"Such prebiotic gels may have allowed primitive chemical systems to overcome key barriers in prebiotic chemistry by enabling molecular concentration, selective retention, reaction efficiency, and environmental buffering."

In these early gels, they propose, the first murmurs of a metabolism could have arisen as chemicals traded electrons. Along with visible and infrared light, ultraviolet light penetrating the gel could have provided additional energy for chemical reactions within, much as photosynthesis does in plants today.

Gels can concentrate monomers, such as activated nucleotides and amino acids, the team adds, and are composed in a way that selectively retains and interacts with certain chemicals, not others.

The moist but not-quite-wet environment within a gel matrix favors reactions that can link monomers together to form polymers – complex molecules like those in our own bodies – as opposed to hydrolysis reactions, in which chemicals break down into smaller parts.

This broadens what we're looking for when it comes to life beyond Earth, too. Structures like gels, rather than specific chemicals, may be targets in future missions looking for life in space.

Who Was Cernunnos? (Mysteries of Mythology)

 

Le guerrier Franc (Max Histoire)

 

How Plants Evolved (People Are Fish)

 

Le druide gaulois

 

The Deadliest Place On Earth 250,000,000 Years Ago (ExtinctZoo)

 

Fossilized vomit reveals 290-million-year-old predator’s diet

Extrait de l'article:

Two hundred and ninety million years ago, in a mountain valley within the central region of the supercontinent Pangaea, an apex predator snapped up at least three other animals and sometime later puked up the bones.

That material hardened over the ages, and is now the oldest fossilized vomit ever discovered from a land-based ecosystem. The cluster of bones and digestive material provides rare information, published January 30 in Scientific Reports, about the behavior of some of the world’s earliest land predators.

“It’s kind of like a photograph of a moment in the past that is telling us about the animal that was living,” says Arnaud Rebillard, a paleontologist at Museum für Naturkunde in Berlin. “Any data that we can find about their behavior is very precious.”

Paleontologists discovered the lime-sized specimen in 2021 at a site called the Bromacker locality in central Germany. Researchers then scanned the bones to create 3-D models showing a cluster of parts from different animals, suggesting they had come from a predator’s gut. They also chemically analyzed the material surrounding the bones and found that it was low in phosphorus, suggesting it was not a fossilized dropping.

While the specific predator that regurgitated the bones is unknown, the researchers strongly suspect that it was one of two animals that resemble today’s monitor lizards like Komodo dragons: Dimetrodon teutonis, with a prominent sail on its back, and Tambacarnifex unguifalcatus. Though reptilian in appearance, both are from a group of animals called synapsids that includes mammals and their extinct relatives.

Among the 41 disgorged bones, the researchers were able to distinguish two small lizardlike reptiles and a limb bone from a larger reptilelike herbivore. This collection of remains, along with several unidentified bones, indicates that the predator ate whatever it could find rather than specializing in a specific type of prey.

Because the fossilized vomit, or regurgitalite, contains three different animals eaten by one predator, “we can literally say, for sure, that these three animals were living at exactly the same place and exactly the same time, maybe to the week or even to the day,” Rebillard says.

Several living predators habitually regurgitate bones and other body parts that are tough to digest after eating. Scientists don’t know if this is why the ancient animal spit up the bones, but it is one of the most plausible explanations, along with simply overeating, Rebillard says.

Fossils of partially digested material, including regurgitalites, as well as fossilized feces, are valuable clues for studying Earth’s past. “We need fossils like this to really tie together how the ecosystem functioned and how the food webs were structured,” says Martin Qvarnström, a paleontologist at Uppsala University in Sweden who was not involved in the new study.

The German regurgitalite is particularly exciting because the Bromacker site preserves a snapshot of an early terrestrial ecosystem. Older predators that could travel on land often lived in semiaquatic environments where they hunted crustaceans and fish. The Permian period represents a time when large herbivores became prominent in inland environments, followed by new predators. Fossil dung and vomit are much rarer in inland environs than in aquatic ones.

“We’re talking about almost 300-million-year-old ecosystems,” Rebillard says. “So to have such a temporal vision about this to the day they were living, in the same area and the same moment, is extremely fascinating.”