Dancing galaxies make a monster at the cosmic dawn

Astronomers have spotted a pair of galaxies in the act of merging 12.8 billion years ago. The characteristics of these galaxies indicate that the merger will form a monster galaxy, one of the brightest types of objects in the Universe. These results are important for understanding the early evolution of galaxies and black holes in the early Universe.

Quasars are bright objects powered by matter falling into a supermassive black hole at the center of a galaxy in the early Universe.

The most accepted theory is that when two gas-rich galaxies merge to form a single larger galaxy, the gravitational interaction of the two galaxies causes gas to fall towards the supermassive black hole in one or both of the galaxies, causing quasar activity.

To test this theory, an international team of researchers led by Takuma Izumi used the ALMA (Atacama Large Millimeter/submillimeter Array) radio telescope to study the earliest known pair of close quasars.

This pair was discovered by Yoshiki Matsuoka, at Ehime University in Japan, in images taken by the Subaru Telescope.

Located in the direction of the constellation Virgo, this pair of quasars existed during the first 900 million years of the Universe.

The pair is dim, indicating that the quasars are still in the early stages of their evolution.

The ALMA observations mapped the host galaxies of the quasars and showed that the galaxies are linked by a "bridge" of gas and dust.

This indicates that the two galaxies are in fact merging.

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Early evolution of sea urchins

New insight on the origins and early evolution of echinoids, a group that includes the sea urchins, the sand dollars, and their relatives, has been published today in the journal eLife.

The study suggests that modern echinoids emerged approximately 300 million years ago, survived the Permo-Triassic mass extinction event -- the most severe biodiversity crisis in Earth's history -- and rapidly diversified in its aftermath. These findings help address a gap in knowledge caused by the relative lack of fossil evidence for this early diversification.

There are more than 1,000 living species of echinoids, including sea urchins, heart urchins, sand dollars and sea biscuits, which live across different ocean environments ranging from shallow waters to abysses. Throughout history, the hard spine-covered skeletons of these creatures have left an impressive number of fossils. However, despite this remarkable fossil record, their emergence is documented by few fossil specimens with unclear affinities to living groups, making their early history uncertain.

"There are still debates among scientists about when the ancestors of echinoids emerged and what role the mass extinction event that occurred between the Permian and Triassic periods may have played in their evolution," says first author Nicolás Mongiardino Koch, who completed the work while he was at Yale University, New Haven, Connecticut, US, and is now a postdoctoral fellow at Scripps Institution of Oceanography at UC San Diego, US.

"We set out to help resolve these debates by combining genomic and paleontological data to disentangle their evolutionary relationships. The extraordinary fossil record of echinoids and the ease with which these fossils can be incorporated in phylogenetic analyses make them an ideal system to explore their early evolution using this approach."

Mongiardino Koch and the team built upon available molecular resources with 18 novel genomic datasets, creating the largest existing molecular matrix for echinoids. Using this dataset, they were able to reconstruct the phylogenetic relationships and divergence times of the major lineages of living echinoids and place their diversification within broader evolutionary history. They did so by applying a 'molecular clock' technique to their dataset, whereby the rate at which mutations accumulated in the echinoid genomes is translated into geological time with the use of fossil evidence, allowing researchers to determine when different lineages first diversified.

Their analyses suggest that the ancestors of modern echinoids likely emerged during the Early Permian, and rapidly diversified during the Triassic period in the aftermath of a mass extinction event, even though this evolutionary radiation does not seem to have been captured by the fossil record.

Additionally, the results suggest that sand dollars and sea biscuits likely emerged much earlier than thought, during the Cretaceous period about 40 to 50 million years before the first documented fossils of these creatures. The authors say this result is remarkable, as the tough skeleton of the sand dollars, their buried lifestyles, and their extremely distinct morphologies imply that their fossil record should faithfully reflect their true evolutionary history.

The team also developed a multivariate statistical approach called a 'chronospace' to help them visualise and assess the robustness of their evolutionary timeline to different choices in their analyses. They found that different implementations of the molecular clock model had the strongest impact on divergence times, while other decisions showed minimal effects.

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New fossil species represents ancient forerunner of most modern reptiles

Lizards and snakes are a key component of most terrestrial ecosystems on earth today. Along with the charismatic tuatara of New Zealand (a "living fossil" represented by a single living species), squamates (all lizards and snakes) make up the Lepidosauria -- the largest group of terrestrial vertebrates in the planet today with approximately 11,000 species, and by far the largest modern group of reptiles. Both squamates and tuataras have an extremely long evolutionary history. Their lineages are older than dinosaurs having originated and diverged from each other at some point around 260 million years ago. However, the early phase of lepidosaur evolution 260-150 million years ago, is marked by very fragmented fossils that do not provide much useful data to understand their early evolution, leaving the origins of this vastly diverse group of animals embedded in mystery for decades.

In a study published August 25 in Nature an international team of researchers describe a new species that represents the most primitive member of lepidosaurs, Taytalura alcoberi, found in the Late Triassic deposits of Argentina. Discovered by lead author Dr. Ricardo N. Martínez, Universidad Nacional de San Juan, Argentina, and curator at the Instituto y Museo de Ciencias Naturales, Taytalura is the first three-dimensionally preserved early lepidosaur fossil. It allowed scientists to infer with great confidence it's placement in the evolutionary tree of reptiles and aids in closing the gap of our knowledge of the origin and early evolution of lepidosaurs.

Martínez and co-author Dr. Sebastián Apesteguía, Universidad Maimónides, Buenos Aires, Argentina,conducted high-resolution CT scans of Taytalura which provided confirmation that it was something related to ancient lizards. They then contacted co-author Dr. Tiago R. Simões, postdoctoral fellow in The Department of Organismic and Evolutionary Biology, Harvard University, to help identify and analyze the fossil. Simões specializes in studying these creatures and in 2018 published the largest existing dataset to understand the evolution of the major groups of reptiles (living and extinct) in Nature.

"I knew the age and locality of the fossil and could tell by examining some of its external features that it was closely related to lizards, but it looked more primitive than a true lizard and that is something quite special," said Simões.

The researchers then contacted co-author Dr. Gabriela Sobral, Department of Palaeontology, Staatliches Museum für Naturkunde Stuttgart, Germany, to process the CT scan data. Sobral, a specialist in processing CT data, created a mosaic of colors for each bone of the skull allowing the team to understand the fossil's anatomy in high-detail resolution on a scale of only a few micrometers -- about the same thickness as a human hair.

With Sobral's data, Simões was able to apply a Bayesian evolutionary analysis to determine the proper placement of the fossil in the reptile dataset. Simões had recently applied the Bayesian method -- which was adapted from methods originally developed in epidemiology to study how viruses like COVID-19 evolve -- to precisely estimate the time and rates of anatomical evolution during the rise of tetrapods. The statistical analysis confirmed their suspicions that Taytalura was in fact the most primitive member of the lineage that eventually originated all lizards and snakes. "It's not even a lizard in the evolutionary tree," said Simões, "but it's the very next thing there, between true liizards and tuataras, and all other reptiles."

"This beautifully 3D preserved fossil is really an important finding. It is the most complete fossil representing the early stages of lepidosaur evolution that we have so far. All other known fossils are too incomplete, which makes it difficult to classify them for sure, but the complete and articulated nature of Taytalura makes its relationships much more certain," said Sobral.

Simões agreed, "Taytalura is a major point in the reptile tree of life that was previously missing. Because these fossils are so small they are very difficult to preserve in the fossil record. And what candidate fossils we do have are very fragmented and poorly preserved, so they don't provide as much useful data for analysis."

Taytalura's skull reveals that the first lepidosaurs looked substantially more like the tuataras than squamates, and therefore, that squamates represent a major deviation from this ancestral pattern. Further, it has a unique dentition, differing from the teeth found in any living or extinct group of lepidosaurs. "What our analyses tells us, besides some other anatomical traits that we could see on it, in the skull specifically, is that this sphenodontian body type, at least for the skull, is the ancestral pattern for lepidosaurs. The ancestral pattern seems to be more similar to tuataras," said Simões.

"Taytalura preserves a composition of features that we were not expecting to find in such an early fossil. For instance, it shows some features that we thought were exclusive for the tuatara group. On the other hand, it made us question how truly "primitive" certain lizard features are, and it will make scientists reconsider several points in the evolution of this group," said Sobral.

"The almost perfectly preserved Taytalura skull shows us details of how a very successful group of animals, including more than 10,000 species of snakes, lizards, and tuataras, originated," said Martínez. "But it also highlights the paleontological importance of the paleontological site of Ischigualasto Formation, known for preserving some of the most primitive dinosaurs known in the world. The extraordinary quality of preservation of the fossils at this site allowed something as fragile and tiny as this specimen to be preserved for 231 million years."

"Contrary to almost all fossils of Triassic lepidosaurs found in Europe, this is the first early lepidosaur found in South America, suggesting lepidosaurs were able to migrate across vastly distant geographic regions early in their evolutionary history," agreed Simões.

"We are accustomed to accept that the Mesozoic Era was an age of gigantic reptiles, enormous proto-mammals, and huge trees, and thus we commonly look for fossils that are visible at human height, just walking," said Apesteguía. "However, the largest part of the ancient ecosystem components was small, as today. There was a universe of fauna sneaking among bigger, clawed or hoofy paws. Taytalura teaches us that we were missing important information by looking not only for bigger animals, but for also thinking that the origin of lizards occurred only in the Northern Hemisphere as evidence seemed to support until now."

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Research shows we're surprisingly similar to Earth's first animals

 The earliest multicellular organisms may have lacked heads, legs, or arms, but pieces of them remain inside of us today, new research shows.

According to a UC Riverside study, 555-million-year-old oceanic creatures from the Ediacaran period share genes with today's animals, including humans.

"None of them had heads or skeletons. Many of them probably looked like three-dimensional bathmats on the sea floor, round discs that stuck up," said Mary Droser, a geology professor at UCR. "These animals are so weird and so different, it's difficult to assign them to modern categories of living organisms just by looking at them, and it's not like we can extract their DNA -- we can't."

However, well-preserved fossil records have allowed Droser and the study's first author, recent UCR doctoral graduate Scott Evans, to link the animals' appearance and likely behaviors to genetic analysis of currently living things. Their research on these links has been recently published in the journal Proceedings of the Royal Society B.

For their analysis, the researchers considered four animals representative of the more than 40 recognized species that have been identified from the Ediacaran era. These creatures ranged in size from a few millimeters to nearly a meter in length.

Kimberella were teardrop-shaped creatures with one broad, rounded end and one narrow end that likely scraped the sea floor for food with a proboscis. Further, they could move around using a "muscular foot" like snails today. The study included flat, oval-shaped Dickinsonia with a series of raised bands on their surface, and Tribrachidium, who spent their lives immobilized at the bottom of the sea.

Also analyzed were Ikaria, animals recently discovered by a team including Evans and Droser. They were about the size and shape of a grain of rice, and represent the first bilaterians -- organisms with a front, back, and openings at either end connected by a gut. Evans said it's likely Ikaria had mouths, though those weren't preserved in the fossil records, and they crawled through organic matter "eating as they went."

All four of the animals were multicellular, with cells of different types. Most had symmetry on their left and right sides, as well as noncentralized nervous systems and musculature.

Additionally, they seem to have been able to repair damaged body parts through a process known as apoptosis. The same genes involved are key elements of human immune systems, which helps to eliminate virus-infected and pre-cancerous cells.

These animals likely had the genetic parts responsible for heads and the sensory organs usually found there. However, the complexity of interaction between these genes that would give rise to such features hadn't yet been achieved.

"The fact that we can say these genes were operating in something that's been extinct for half a billion years is fascinating to me," Evans said.

The work was supported by a NASA Exobiology grant, and a Peter Buck postdoctoral fellowship.

Going forward, the team is planning to investigate muscle development and functional studies to further understand early animal evolution.

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Apollo rock samples capture key moments in the Moon's early history

 Volcanic rock samples collected during NASA's Apollo missions bear the isotopic signature of key events in the early evolution of the Moon, a new analysis found. Those events include the formation of the Moon's iron core, as well as the crystallization of the lunar magma ocean -- the sea of molten rock thought to have covered the Moon for around 100 million years after the it formed.

The analysis, published in the journal Science Advances, used a technique called secondary ion mass spectrometry (SIMS) to study volcanic glasses returned from the Apollo 15 and 17 missions, which are thought to represent some of the most primitive volcanic material on the Moon. The study looked specifically at sulfur isotope composition, which can reveal details about the chemical evolution of lavas from generation, transport and eruption.

"For many years it appeared as though the lunar basaltic rock samples analyzed had a very limited variation in sulfur isotope ratios," said Alberto Saal, a geology professor at Brown University and study co-author. "That would suggest that the interior of the Moon has a basically homogeneous sulfur isotopic composition. But using modern in situ analytical techniques, we show that the isotope ratios of the volcanic glasses actually have a fairly wide range, and those variations can be explained by events early in lunar history."

The sulfur signature of interest is the ratio of the "heavy" sulfur-34 isotope to the lighter sulfur-32. Initial studies of lunar volcanic samples found that they uniformly leaned toward the heavier sulfur-34. The nearly homogeneous sulfur isotope ratio was in contrast with large variations in other elements and isotopes detected in the lunar samples.

This new study looked at 67 individual volcanic glass samples and their melt inclusions -- tiny blobs of molten lava trapped within crystals inside the glass. Melt inclusions capture the lava before sulfur and other volatile elements are released as gas during eruption -- a process called degassing. As such, they offer a pristine picture of what the original source lava was like. Using the SIMS at the Carnegie Institution for Science, Saal with his colleague, the late Carnegie scientist Eric Hauri, were able to measure the sulfur isotopes in these pristine melt inclusions and glasses, and use those results to calibrate a model of the degassing process for all the samples.

"Once we know the degassing, then we can estimate back the original sulfur isotope composition of the sources that produced these lavas," Saal said.

Those calculations revealed that the lavas had been derived from different reservoirs within the interior of the Moon with a wide range of sulfur isotope ratios. The researchers then showed that the range of values detected in the samples could be explained by events in the Moon's early history.

The lighter isotope ratio in some of the volcanic glasses, for example, is consistent with the segregation of the iron core from the early molten Moon. When an iron core separates from other material in a planetary body, it takes a bit of sulfur with it. The sulfur that's taken tends to be the heavier sulfur-34 isotope, leaving the remaining magma enriched in the lighter sulfur-32.

"The values we see in some of the volcanic glasses are fully consistent with models of the core segregation process," Saal said.

The heavier isotope values can be explained by the further cooling and crystallization of the early molten Moon. The crystallization process removes sulfur from the magma pool, producing solid reservoirs with heavier sulfur-34. That process is the likely source of the heavier isotope values found in some of the volcanic glasses and basaltic rocks returned from the Moon.

"Our results suggest that these samples record these critical events in lunar history," Saal said. "As we keep looking at these samples with newer and better techniques, we keep learning new things."

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Discovery of microbes with mixed membranes sheds new light on early evolution of life

 Current research suggests that more complex life-forms, including humans, evolved from a symbiosis event between bacteria and another single-celled organism known as archaea. However, evidence of a transition period in which the two organisms mixed where nowhere to be found. That is, until now. In the deep waters of the Black Sea, a team of scientists found microbes that can make membrane lipids of unexpected origin.

Cells are surrounded by a layer of membrane lipids that protect them from changes in their environment such as temperature, much in the same way that our skin changes when we are cold or exposed to the sun. Lead author and NIOZ senior scientist Laura Villanueva explains why they make such interesting biomarkers. 'When a cell dies, these lipids preserve like fossils and hold ancient-old information on Earths' early environmental conditions.' Our tree of life includes small and simple cells (Bacteria and Archaea) and more complex cells (Eukaryotes), including animals and humans. Bacteria and Eukaryotes share a similar lipid membrane. Looking at Archaea, their 'skin' or membrane looks very different and is primarily designed to help these microorganisms to survive in extreme environments. Villanueva: 'This "lipid divide," or difference in membranes between Bacteria and Eukaryotes on the one hand and Archaea on the other, is believed to have happened after the emergence of Bacteria and Archaea from the last universal cellular ancestor (LUCA).'

Missing piece hidden in the deep Black Sea

The leading theory is that Eukaryotes evolved from a symbiosis event between archaeal and bacterial cells in which the archaeal cell was the host. But how does this work when their 'skins' are so different and share no sign of common ancestry? Villanueva: 'To explain the creation of more complex life-forms, the archaeal membrane must have made a switch to a bacterial type membrane. Such a switch likely needed a transition period in which the two membrane types were mixed.' However, mixed lipid membranes had never been found in microbes until the team of Villanueva made an unexpected discovery in de deep waters of the Black Sea.

Villanueva: 'We found a possible missing piece of this puzzle in the Black Sea. Here, an abundant group of bacteria thrive in the deep-sea, absent of oxygen and with high sulfide concentration. We discovered that the genetic material of this group did not only carry pathway genes for bacterial lipids but archaeal ones as well.' The peculiarity was also found in the genetic material of other, closely related Bacteria and supports the idea that this ability to create 'mixed' membranes is more widespread than previously thought. This discovery sheds new light on the evolution of all cellular life forms and may have important consequences for the interpretation of archaeal lipid fossils in the geological record and paleoclimate reconstructions.

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