Category: 7. Science

Input and preservation conditions of organic matter

Paleo-productivity

Paleo-productivity refers to the amount of organic carbon fixed by ancient marine or lacustrine ecosystems per unit of time and area⁵typically associated with the photosynthetic activity of planktonic organisms. During photosynthesis, phytoplankton can convert atmospheric CO₂ into organic matter²⁰and eventually settles and forms organic-rich sediments. High paleo-productivity often implies significant input of organic matter into the depositional environment. Previously, different proxies have been developed to indicate the paleo-productivity in ancient environments^21,22,23. P is an important limiting nutrient for primary producers in aquatic ecosystems and it acts as an essential element for the skeletal system of organisms²⁴. In general, the proliferation of primary producers leads to increased consumption of P, which consequently enhances the deposition of P in the sediments. However, Ti is a common element in the Earth’s crust, typically unaffected by biological processes. Hence, P/Ti ratio increases when higher paleo-productivity of the ancient marine or lacustrine ecosystem²⁵. Cu and Ni can also been obviously influenced by organism activities and Cu/Al (ppm/%) and Ni/Al (ppm/%) ratios can serve as indicators of paleo-productivity^{22,24,26,27,28}. In addition, the Al/Ti ratio minimizes the influence of variations in absolute terrigenous flux and instead acts as an indicator of the relative enrichment of nutrient-rich, clay-sized aluminosilicates within the total detrital sediment fraction. A higher ratio signifies a greater potential supply of crucial micronutrients and macronutrients associated with these clays, pointing to conditions conducive to enhanced biological productivity in the overlying water column during deposition.

In general, Ordovician sediments commonly experienced repeated redox oscillations driven by multiple sea-level fluctuations, leading to far more intense phosphorus remobilization than often appreciated. A critical complication arises from the thermal evolution of Ordovician source rocks. Samples having reached overmature stages may have experienced substantial Cu and Ni leaching during late-stage hydrocarbon generation and expulsion processes. Hence, as a baseline indicator of terrigenous flux and nutrient efficiency, Al/Ti is broadly applicable and reliable in Ordovician successions. In this study, Al/Ti ratios in the Sandaokan, Zhuozishan, Kelimoli, Wulalike and Lashizhong formations are 11.38, 13.18, 17.58, 22.33, and 19.41, respectively. Data from sedimentary proxies may suggest the Wulalike Formation had the highest paleoproductivity among the Ordovician strata.​.

Redox condition

Redox condition acts as an important factor influencing the preservation of the organic matters in sediments²⁹. In general, oxygen is a primary factor driving the oxidation of organic matter, promoting its decomposition. In a reducing environment, the absence of oxygen limits oxidative processes, thereby slowing the breakdown of organic matter^30,31. Apart from this, most microorganisms responsible for organic matter decomposition rely on oxygen for aerobic respiration. In anaerobic conditions, the activity of these microbes is significantly reduced, or the microbial community shifts to anaerobic organisms, which decompose organic matter at a slower rate, thus favoring its preservation^32,33. Trace elements are commonly used as indicators of redox conditions in aquatic environments during sedimentary processes, owing to their sensitivity to changes in oxidation-reduction states²⁴. This sensitivity arises from the distinct chemical behavior of trace elements under different redox conditions, which significantly alters their oxidation states, speciation, and concentration profiles.

U/Th ratio is a useful geochemical proxy for assessing the redox conditions of sedimentary environments and it has been widely applied in previous studies^7,34,35. Generally, U is immobile and tends to precipitate out as uranium minerals such as uraninite (UO₂) at reducing conditions, while it is more mobile in its oxidized form at oxidizing conditions²⁴. Th always exists as highly insoluble state in both oxidizing and reducing conditions³⁶. Hence, U/Th ratio of < 0.75 and > 1.25 indicates oxic and anoxic environments, respectively ³⁶.U/Th ratios provide a ​quantitative, diagenetically robust, and widely applicable​ tool for paleoredox reconstructions. When combined with complementary proxies (e.g., Mo, V, Fe speciation), they offer one of the most reliable frameworks for discriminating marine oxygenation states in ancient sedimentary systems. However, lithological differences across formations can also exert a significant influence on Al/Ti ratios. Carbonate-dominated intervals (e.g., Sandaokan and Zhuozishan formations) generally contain lower detrital clay fractions, which may dilute aluminosilicate-associated Al, resulting in lower Al/Ti values. In contrast, shale- or marl-rich intervals (e.g., Wulalike Formation) typically have higher proportions of fine-grained aluminosilicates, increasing the Al content relative to Ti and thereby elevating the Al/Ti ratio. Therefore, part of the observed stratigraphic variation in Al/Ti may reflect primary lithological shifts rather than solely changes in nutrient availability or productivity. Accounting for this lithological control is essential for a more robust interpretation of paleo-productivity trends. In this study, the average U/Th ratios in the Sandaokan, Zhuozishan, Kelimoli, Wulalike and Lashizhong formations are 1.02, 0.92, 0.71, 0.92, and 0.73, respectively. Data from sedimentary proxies suggest the Ordovician strata is generally characterized by a dysoxic condition.

Paleo-climate

Paleo-climate can influence temperature, precipitation, sea-level fluctuations, ocean circulation, and nutrient supply, thereby impacting the accumulation and preservation of organic matter. Sr/Cu ratio is always used as an effective proxy to reflect paleo-climate^37,38. It is generally believed that Sr/Cu > 10 indicates a dry climate, 5 < Sr/Cu < 10 suggests a semi-humid to semi-arid climate, and 1 < Sr/Cu < 5 indicates a warm and humid climate³⁹. In this study, Sr/Cu ratios in the Sandaokan, Zhuozishan, Kelimoli, Wulalike and Lashizhong formations are 15.95, 18.49, 32.22, 13.50, and 17.83, respectively.

Rb/Sr ratio also serves as an indicator of paleo-climate^40,41. Rb is relatively stable, while Sr is more susceptible to leaching and loss in humid environments⁴². Hence, the Rb/Sr ratio is generally higher in humid environments, and arid climate conditions are typically associated with a lower Rb/Sr ratio. In this study, Rb/Sr ratios in the Sandaokan, Zhuozishan, Kelimoli, Wulalike and Lashizhong formations are 0.87, 0.82, 0.54, 0.71, and 0.50, respectively.

The classification of paleo-climate by Sr/Cu and Rb/Sr ratios is shown in Fig. 6. The results generally reveal a dry climate of the Ordovician strata. Meanwhile, among the different formations in the Ordovician, the Kelimoli Formation is generally characterized by the driest condition. Paleomagnetic constraints indicate that the western margin of the Ordovician Ordos Basin resided in a low-latitude position proximal to the paleoequator. This latitudinal setting aligns precisely with the basin’s diagnostic paleoclimatic signatures—specifically, the dominance of evaporitic facies and climatically sensitive geochemical proxies—consistent with the persistent influence of tropical atmospheric circulation patterns that govern global climate through latitudinal and altitudinal controls.

Paleo-salinity

Optimal conditions for organic matter accumulation and preservation include anoxia, reducing sedimentary environments, rapid burial, and the presence of silica-rich lithologies that limit microbial degradation. Among these conditions, paleo-salinity could influence the input and preservation of organic matter by controlling the growth of organisms⁴³. In general, Sr/Ba is a reliable proxy in revealing characteristics of aqueous medium and the ratio increases from freshwater to saline water⁴⁴. Sr/Ba ratios of < 0.5, 0.5-1, and > 1 reveal fresh water, brackish water and salt water, respectively^6,42. In this study, ratios in the Sandaokan, Zhuozishan, Kelimoli, Wulalike and Lashizhong formations are 3.02, 3.21, 6.46, 0.77, and 0.85, respectively. The results indicate a salt water environment during the deposition of the Sandaokan, Zhuozishan, Kelimoli formaitons, and a brackish water environment during the deposition of Wulalike and Lashizhong formations.

Paleo-water depth

Paleo-water depth acts as an important factor influencing the organic matter enrichment and decomposition. Different elemental proxies were developed to reveal the paleo-water depth due to their different behavior in accumulation and dispersion at varying water depths during deposition⁴⁵. As a stable element in sediments, K primarily resides in coarse detrital minerals (e.g.-feldspar, muscovite). In high-energy hydrodynamical settings (shallow water), coarse-grained minerals (sand fraction) are preferentially enriched, elevating bulk sediment K content. However, Rb is more reactive and prone to being adsorbed and its content tends to increase in deep lake sediments⁴⁶. Therefore, Rb/K ratio was widely applied in determining paleo-water depth and the ratio increases with increasing water depth. In this study, Rb/K ratios of the Sandaokan, Zhuozishan, Kelimoli, Wulalike and Lashizhong formations are 0.005, 0.006, 0.009, 0.004, and 0.004, respectively. Previous studies demonstrate distinct Rb/K ratio trends across bathymetric gradients in both modern and ancient sedimentary systems. Analysis of shelf-to-basin transects in the Atlantic Ocean reveals Rb/K values of 0.004–0.006 in shallow-marine sandy sediments, increasing to 0.008–0.015 in deep-marine muddy deposits (Tribovillard et al., 2006). In addition, in Ordovician strata of the Appalachian Basin, deep-water graptolitic shale facies exhibit elevated Rb/K ratios (0.012–0.018), contrasting with lower values (0.003–0.005) in coeval shallow-water shelly limestone facies (Rimmer et al., 2004). Collectively, paleobathymetric proxies record significant shifts in water depth during Ordovician deposition in the Ordos Basin. Analysis of sedimentary facies and geochemical indices demonstrates a shallowing-upward mega sequence across key formations: Deposition of the Sandaokan​and Zhuozishan formations​occurred under relatively shallow-water conditions. A pronounced deepening event is registered during sedimentation of the Kelimoli Formation. Subsequent shallowing is documented through the Wulalike Formation to the Lashizhong Formation, reflected by transitional facies associations culminating in peritidal carbonates and evaporites characteristic of very shallow subtidal to supratidal environments.

Variation of paleo-environments across the ordovician

The variation of different paleo-environmental proxies across the Ordovician was presented in Fig. 5. Paleosalinity reconstructions based on Sr/Ba ratios reveal a progressive increase from the Sandaokan to Kelimoli Age, followed by a decline through the Kelimoli to Wulalike Age, indicating an initial salinity rise and subsequent freshening of paleoseawater. Concurrently, Sr/Cu and Rb/Sr ratios remained stable from the Sandaokan to Zhuozishan Age, reflecting persistently arid and hot climatic conditions, but showed a gradual decrease from the Kelimoli to Wulalike Age, signaling a transition toward warmer and more humid conditions. Synchronous trends are observed in redox-sensitive, bathymetric, and productivity proxies: U/Th ratios, Rb/K ratios, and Al/Ti ratios collectively indicate dominantly suboxic conditions, slow water deepening, and progressively enhanced paleoproductivity during the Sandaokan-Zhuozishan interval. This shifted markedly to anoxic/euxinic conditions, rapid deepening, and intensified productivity from the Kelimoli to Wulalike Age. These integrated paleoenvironmental trends align with global Ordovician eustatic records, demonstrating an oscillatory transgressive phase (overall sea-level rise) spanning the Sandaokan through Wulalike stratigraphic succession.

Under the constraints of the reconstructed paleoenvironmental evolution and integrating previous sedimentological and petrological investigations, the Ordovician sedimentary facies in the western Ordos Basin have been classified⁴⁷. The stratigraphic succession from the complete transgressive-regressive cycle dominated by an overall sea-level rise. This trend was punctuated by high-frequency sea-level oscillations, particularly pronounced during Zhuozishan Formation deposition. Seven principal sedimentary facies types have been identified as platform margin shoal facies, platform margin reefal facies, fore-slope facies, basin slope (or basin margin) facies, open marine shelf facies, and basin facies.

The depositional systems within key Ordovician successions of the western Ordos Basin—spanning the Sandaokan, Zhuozishan, Kelimoli, and Wulalike formations—exhibit complex lateral transitions between multiple facies belts. Despite these variations, the overall stratigraphic trend registers progressive water deepening, punctuated by numerous relative sea-level fluctuations. Spatially, the Sandaokan Formation demonstrates a westward-to-eastward progression from limestone-dominated basin margin facies through dolomitic limestone fore-slope deposits to platform interior and marginal facies (including shoal complexes and bioconstructed reefal banks). The overlying Zhuozishan Formation transitions similarly from basin margin limestones and dolomitic fore-slope sequences to dolomitized ridge-like paleohighs (interpreted as dolomitized platform margin buildups). In the Kelimoli Formation, facies evolve westward-to-eastward from thin-bedded open-marine shelf limestones to basin margin limestones, dolomitic fore-slope deposits, and peritidal dolomitic flats with circum-continental affinities. Finally, the Wulalike Formation is dominated by carbonaceous shale basin facies, with subordinate argillaceous dolomitic limestones of the open marine shelf and localized marl-rich shelf sequences.​.

The paleogeographic evolution of the Ordos Basin can be reconstructed. In general, the basin commences with the well-consolidated North China Platform (NCP) in the Precambrian, which formed the unified Paleo-North China Continent. Through the Early-Middle Cambrian, the Yimeng Paleocontinent (north) and Qingyang Paleocontinent (south) experienced successive uplift, establishing the tectonic framework of the Central Paleo-High that persisted into the Late Cambrian-Ordovician. During the Sandaokan Age (Early Ordovician), marine waters gradually transgressed the Ordos Basin, initiating the first Ordovician-wide transgression characterized by shallow depths. The western basin margin developed predominantly platform margin facies. By the Zhuozishan-Kelimoli Ages (Middle Ordovician), progressive deepening facilitated a depositional transition along the western margin to​fore-slope, basin margin, and open marine shelf facies. This evolution culminated in the Wulalike Age with accelerated deepening, establishing a carbonaceous shale-dominated basin fill facies as the principal paleogeographic environment.

Tasmanian tigers, or Thylacines (Thylacinus cynocephalus), sometimes known as the Tasmanian wolf, were closely related to the Tasmanian devil (Sarcophilus harrisii). They were carnivores that sported a sandy cultured fur with distinct dark stripes running down their backs to their tails. For millions of years, the marsupial was native to the Australian mainland, Tasmania and New Guinea, but gradually they started to disappear, especially from the mainland. By the early 1800s, their numbers had already declined in Tasmania to around 5,000 as European settlers introduced new stressors to their environment.

The last known specimen died in Tasmania in 1936, and it is now believed that they are completely extinct. But the exact cause for this extinction has never been clear. Was it competition with dogs or was it human hunters who saw them as pests? Or could it have been something different? According to new genomic research, the Tasmanian tiger’s own genetics may have significantly contributed to their decline.

The researchers tested their hypothesis by leveraging palaeogenomic data related to the Tasmanian tiger and compared it to genomic data of other marsupials, including Tasmanian devils. They did so by using machine learning-based comparative genomic tools to search for lost genes while also attempting to reconstruct when the animals lost genes using molecular evolutionary methods. 

They found that Tasmanian tigers lost four genes – SAMD9L, HSD17B13, CUZD1, and VWA7 – sometime between 13 million and 1 million years ago. This was long before humans and dingoes arrived and began to interfere with their habitats.

“The thylacine genome exhibits the loss of four genes—SAMD9L, HSD17B13, CUZD1 and VWA7—each with important biological functions and implications for species fitness. Our investigation into the timing of gene loss events revealed a staggered pattern, occurring over a span of approximately 13−1 [million years ago],” the team explains in their paper.

“This temporal distribution,” they argue, “indicates that the gene losses were not confined to a single evolutionary event but occurred progressively after the Middle Miocene Climate Transition.”

The Middle Miocene Climate Transition occurred around 15 to 13 million years ago and was marked by significant ecological and climatic change. At the time, the Tasmanian tiger was smaller than it would later become and was unspecialized in terms of its diet. It is possible that the gene loss occurred as the animals began to undergo adaptive changes.

The four genes that they lost played crucial roles in the thylacine’s immune function, especially for their antiviral factors and tumor suppression. The researchers believe that a shift towards carnivory may have favored the loss of these genes, while also facilitating a larger body size. Taken together, the authors argue, the loss of these genes may have reduced the Tasmanian tiger’s fitness to thrive in their environment.

The team also found that the animals experienced a decrease in olfactory lobe size and a loss of olfactory receptor genes, which could mean they shifted away from using smell as a primary means for hunting. This could have been the result of their larger size and changes in their visual ability. Basically, as Tasmanian tigers got bigger, they could see their prey over obstacles that had previously obstructed their vision.

“Unlike the Tasmanian Devil, a scavenger, the taller thylacine likely depended on vision and sound for hunting, aided by its ability to see over vegetation,” the team explains.

Although these genetic changes may have helped the Tasmanian tiger in the (relative) short term, they may have ultimately led to their downfall.

“Whatever the cause for gene loss, the loss of SAMD9L, HSD17B13, CUZD1, and VWA7 genes in the thylacine possibly had negative pleiotropic effects, potentially compromising its health by affecting antiviral defence, metabolic processes, lactation, pancreatitis, and tumour susceptibility. Although model-based population viability analyses suggest that the disease played only a minor role in thylacine extinction, other studies suggest that a ‘canine-distemper-like’ disease played a role in exacerbating its extinction,” the team concludes.

The team believes their work offers a new framework for approaches to comparative genomics and ancestral gene loss. This, they argue, “could provide valuable insights into the causes of species extinction and offer clues about evolutionary processes, such as trait evolvability.”

It is possible that similar investigations into both existing and extinct species could offer a more comprehensive view of their past ecologies and trait evolution.

The paper is published in the Proceedings of the Royal Society.

“We just couldn’t believe how weird it was and how unlike any other dinosaur, or indeed any other animal we know of, alive or extinct,” said Richard Butler, project co-lead and a paleontologist at the University of Birmingham in England.

The chance to see and study the Spicomellus fossils was “spine-tingling,” said Butler.

It wasn’t just those involved in the project who were enthused.

“This is truly one of the weirdest, wackiest dinosaurs I’ve ever seen,” said Steve Brusatte, a vertebrate paleontologist at the University of Edinburgh who was not involved in the research.

“It has bony spikes protruding from all over its body, like it’s some kind of reptilian porcupine,” he said Thursday. “If you were a meat-eating dinosaur living back in the Jurassic period, you would stay well away from this animal.”

Brusatte added: “It’s a great example of how there are still so many new things to discover. Until these fossils were found, we had no inclination that an animal this fantastic had ever lived.”

Maidment, the study co-lead, said the discovery showed that a lot more research needs to be done in Africa, with countries like Morocco an untapped gold mine for dinosaur research.

“It is wildly undersampled compared to the other continents,” said Maidment, from London’s National History Museum.

Maidment said that the Spicomellus project, which actually began in 2018, faced several hurdles along the way, including the Covid-19 pandemic.

The U.K. team was set to fly out to meet its Moroccan counterparts for the project when British Prime Minister Boris Johnson announced a lockdown, ultimately delaying their plans until 2022.

Despite those challenges, the research project has proved to be a major step forward for science in Morocco.

“This study is helping to drive forward Moroccan science. We’ve never seen dinosaurs like this before, and there’s still a lot more this region has to offer,” said Driss Ouarhache, who led the Moroccan team.

Genomes contain the complete library of information required to build and maintain a living organism — the figurative blueprints of life. In eukaryotes, genomes are stored in the nuclei, where they are organized into chromosomes. A eukaryote is an organism whose cells have a nucleus surrounded by a membrane: plants, animals, fungi and many microbes are eukaryotes.

The human genome, for example, is organized in 23 chromosomes, each containing a portion of the complete genetic code. Until recently, it has always been assumed that each nucleus contains at least a complete set of chromosomes, and thus the “one nucleus, one full genome” rule.

However, our research has revealed that in two species of fungi, their genomes can be split across multiple nuclei, with each nucleus receiving only part of the total chromosomes.

A surprising discovery

Our laboratory at the University of British Columbia studies the fungus Sclerotinia sclerotiorum, which is a soil-borne pathogen causing stem rot or white mold in various crop plants, including canola, soybean and sunflower.

Despite its impact on cash crops, S. sclerotiorum‘s genetics and cell biology are not well understood.

While trying to better understand the biology of this fungus, our laboratory made a startling discovery about the organization of S. sclerotiorum’s 16 chromosomes during cell division and reproduction.

Most eukaryotic cells are diploid, meaning the nucleus contains two copies of each different chromosome. In many fungi, such as baker’s yeast, reproduction begins with a parent diploid cell dividing to form haploid spore cells with one nucleus housing one copy of each chromosome.

However, S. sclerotiorum spores, known as ascospores, each contain two separate nuclei. Previously, it was assumed that each nucleus was haploid, containing the full suite of 16 chromosomes. This would mean that each ascospore contains a total of 32 chromosomes, similar to a diploid cell.

Using fluorescent microscopy, we were able to directly count the number of chromosomes present in a single ascospore. Remarkably, we consistently observed only 16 chromosomes per ascospore, in conflict with the 32 predicted by the current “one nucleus, one full genome” theory.

Additionally, we used fluorescent probes to label specific chromosomes, and found that the two nuclei in an ascospore contain distinct chromosomes. Ascospores contain one set of 16 chromosomes divided across two nuclei, rather than each nucleus containing a complete set of chromosomes.

An irregular manner

The next question we asked was whether the 16 chromosomes are randomly assorted between the two nuclei, or whether this genomic division follows a regular pattern.

To answer this, we separated individual nuclei and determined which chromosomes were present through polymerase chain reaction (PCR) analysis. We found that chromosome composition varies among nuclei, suggesting the division of chromosomes between nuclei is in an irregular manner.

Intrigued, we sought to investigate whether similar phenomenon occurs in other fungi. Botrytis cinerea is another species of plant pathogenic fungi in the same family as S. sclerotiorum.

B. cinerea produces conidial spores typically with four to six nuclei, rather than the two regularly observed in ascospores of S. sclerotiorum. Using similar methods, we found that the 18 chromosomes in the B. cinerea genome are similarly split across nuclei, with each nucleus generally carrying three to eight chromosomes.

This observation showed that haploid genome “splitting” across nuclei occurs in multiple plant pathogenic fungi. However, whether this phenomenon is wider spread across fungal families, or even other eukaryotes, requires further study.

An unknown mechanism

The observation that the S. sclerotiorum and B. cinerea haploid genomes are divided across nuclei raises questions about how this separation plays a role in the rest of the fungal life cycle.

In order to produce the next generation, these fungi need to reform a diploid cell with the full suite of chromosomes, from which new ascospores can be produced. Presumably, this requires the fusion of nuclei with complementary chromosomes to reunite the genome. So how do these fungi ensure that the correct nuclei fuse?

Perhaps the simplest explanation would be one of viability selection: nuclei may fuse randomly, but only those with a complete genome would produce viable ascospores. This seems inefficient, and a more attractive scenario would involve some structure or mechanism to keep complementary nuclei together after the initial division, allowing them to easily reassemble later in the fungal life cycle.

We hope our future work will provide answers to these fascinating questions, and help broaden our understanding of the fundamental dynamics of nuclei and their genomes. This improved understanding will enable dramatic revolutions in gene editing, allowing researchers to manipulate chromosomes and nuclei at will.

In a rocky outcrop on Mount Carmel, in what is now Israel, a group of ancient humans buried their dead about 140,000 years ago. Scientists uncovered the site, called Skhul Cave, in 1928, and about three years later they found the remains of more than a dozen individuals.

The site is one of the oldest examples of burial practices among ancient humans, but researchers were puzzled by the excavated hominins’ anatomy. Some of their skeletal features resembled those of Homo sapiens, while others were more Neanderthal-like, making the species difficult to classify.

The first skeleton discovered at the Skhul burial site belonged to a child between 3 and 5 years old, most likely a girl. Using high-resolution scans of the child’s cranium and jaw, scientists now propose that the individual possessed anatomical traits of both Homo neanderthalensis and Homo sapiens. If that finding is the case, the skull — and other remains at Skhul Cave — represents the earliest known example of interbreeding between Neanderthals and our own species, researchers reported in the July-August issue of the journal L’Anthropologie.

Earlier analysis of DNA in the modern human and Neanderthal genomes suggested that the two species interbred between 50,500 and 43,500 years ago. The new findings could push back this genetic mingling by nearly 100,000 years, said senior study author Dr. Israel Hershkovitz, a professor in the Gray Faculty of Medical and Health Sciences at Tel Aviv University.

They also indicate an extended period of peaceful coexistence between modern humans and Neanderthals in the Levant, a region bordering the eastern Mediterranean Sea, Hershkovitz told CNN.

“What we bring to the story of human evolution is not a short overlap with our relatives, the Neanderthals, but a very long overlap in time and space,” Hershkovitz said. “You would think that those are two Homo groups that are considered to be competing populations. Suddenly, you see that they managed to live together side by side.”

This interpretation of Neanderthal-Homo sapiens hybridization requires caution, however, as anatomical features can be more ambiguous than genetic data, and factors such as an individual’s life history can affect the expression of anatomical traits, said William Harcourt-Smith, a resident research associate at the American Museum of Natural History in New York City and an adjunct professor at the museum’s Richard Gilder Graduate School.

The young age of the individual in the study must also be considered, as childhood growth can affect anatomical variations, added Harcourt-Smith, who was not involved in the new research.

“Most species comparison studies tend to focus on adult individuals only, to minimize this problem,” he said. Scientists therefore need to be careful when using only skeletal data as proof that a fossil represents a hybrid species.

Certain features can also be retained from ancestors and do not necessarily represent hybridization, said Dr. Zeresenay Alemseged, a Donald N. Pritzker Professor in the University of Chicago’s department of organismal biology and anatomy who was also not involved in the new study. Still, this hypothesis that the child’s ancestry included interbreeding “is not farfetched,” Alemseged, who was not involved in the new research, told CNN in an email.

“Previous DNA studies show that the two (species) interbred, and fossil evidence shows that they geographically overlapped in the Levant before 100,000 years ago, when H. sapiens first attempted to leave Africa,” he added. “But the ultimate arbiter is DNA or another biochemical marker.”

Mingling and interbreeding

Modern humans and Neanderthals share an ancestor that originated in Africa, but the two lineages diverged at least 500,000 years ago. The first Neanderthals appeared in Asia and Europe about 400,000 years ago, while H. sapiens evolved in Africa about 300,000 years ago and later migrated to the Asian and European continents.

Outside Africa, populations of Neanderthals and H. sapiens mingled and interbred until Neanderthals went extinct about 40,000 years ago. Today, the genomes of most modern humans whose ancestors migrated to Europe and Asia contain about 1% to 4% of Neanderthal DNA.

When scientists discovered the Skhul fossils nearly a century ago, they suggested that hybridization between the two species could explain the hominins’ unusual anatomy. Tools available at the time were unable to investigate the bones at high resolution, of course.

In the new study, however, researchers from France and Israel used micro-CT scans to capture images of structures of the Skhul child’s skull and jaw in unprecedented detail and then digitally modeled the bones in 3D.

In its overall shape, especially in the curve of the skull vault around the brain, the cranium looked like a H. sapiens skull. But the structure of the bony labyrinth — a rigid area surrounding the inner ear, too small to see except with micro-CT — was a closer match to the anatomy of Neanderthals. The shape of the lower jaw, the inner structure of the teeth and the underdeveloped blood vessel network inside the skull were also more Neanderthal-like.

Skeletons of seven adults and three children who were intentionally buried, as well as isolated bones from 16 other individuals, have been uncovered in the Skhul Cave. Of the 10 burials, each person possessed a different combination of H. sapiens and Neanderthal traits, Hershkovitz said. While the skull of the first child discovered was the only Skhul fossil examined for the study, “all of them manifest what we call ‘mosaic morphology,’ in the sense that they have both Neanderthal and Homo sapiens features.”

The burials at Skhul also call for a reevaluation of the development of culture in early humans, Hershkovitz said. By designating the rocky outcrop as a cemetery, the people who buried their dead there were demonstrating territoriality, a type of social behavior typically associated with the start of agriculture nearly 12,000 years ago.

“And here we see that 140,000 years ago, people were already some kind of territorial group,” Hershkovitz said. “We have to go back and redo our studies of human behavior, not just biology.”

Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American and How It Works magazine. She is the author of “Rise of the Zombie Bugs: The Surprising Science of Parasitic Mind-Control” (Hopkins Press).

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Aug. 28 (UPI) — Ecologists saw nocturnal spiders attracting prey with their web by using fireflies as bait, according to a new study.

Tunghai University researchers observed Psechrus Clavis a sheet web spider capturing fireflies using their bioluminescent light to catch prey. The spiders also went back from time to time to check on the captured fireflies.

Researchers set up a test using LED lights resembling fireflies to see if the newly found strategy increased spider hunting success.

The findings published in the Journal of Animal Ecology have found that three times the amount of prey was attracted to webs with LED webs and the LED webs grabbed 10 times more fireflies than the non-LED webs.

“Our findings highlight a previously undocumented interaction where firefly signals, intended for sexual communication, are also beneficial to spiders. This study sheds new light on the ways that nocturnal sit-and-wait predators can rise to the challenges of attracting prey and provides a unique perspective on the complexity of predator-prey interactions,” said Dr. I-Min Tso, the lead author of the study.

The researchers think the spiders have developed their own bioluminescence as sheet web spiders normally wait for prey in the dark.

“Handling prey in different ways suggests that the spider can use some kind of cue to distinguish between the prey species they capture and determine an appropriate response,” Tso said. “We speculate that it is probably the bioluminescent signals of the fireflies that are used to identify fireflies enabling spiders to adjust their prey handling behavior accordingly.”

As SpaceX’s Starship vehicle gathered all of the attention this week, the company’s workhorse Falcon 9 rocket continued to hit some impressive milestones.

Both occurred during relatively anonymous launches of the company’s Starlink satellites but are nonetheless notable because they underscore the value of first-stage reuse, which SpaceX has pioneered over the last decade.

The first milestone occurred on Wednesday morning with the launch of the Starlink 10-56 mission from Cape Canaveral, Florida. The first stage that launched these satellites, Booster 1096, was making its second launch and successfully landed on the Just Read the Instructions drone ship. Strikingly, this was the 400th time SpaceX has executed a drone ship landing.

Then, less than 24 hours later, another Falcon 9 rocket launched the Starlink 10-11 mission from a nearby launch pad at Kennedy Space Center. This first stage, Booster 1067, subsequently returned and landed on another drone ship, A Shortfall of Gravitas.

This is a special booster, having made its debut in June 2021 and launching a wide variety of missions, including two Crew Dragon vehicles to the International Space Station and some Galileo satellites for the European Union. On Thursday, the rocket made its 30th flight, the first time a Falcon 9 booster has hit that level of experience.

A decade in the making

These milestones came about one decade after SpaceX began to have some success with first-stage reuse.

The company first made a controlled entry of the Falcon 9 rocket’s first stage in September 2013, during the first flight of version 1.1 of the vehicle. This proved the viability of the concept of supersonic retropropulsion, which was, until that time, just theoretical.

This involves igniting the rocket’s nine Merlin engines while the vehicle is traveling faster than the speed of sound through the upper atmosphere, with external temperatures exceeding 1,000 degrees Fahrenheit. Due to the blunt force of this reentry, the engines in the outer ring of the rocket wanted to get splayed out, the company’s chief of propulsion at the time, Tom Mueller, told me for the book Reentry. Success on the first try seemed improbable.

He recalled watching this launch from Vandenberg Space Force Base in California and observing reentry as a camera aboard SpaceX founder Elon Musk’s private jet tracked the rocket. The first stage made it all the way down, intact.

Scientists discovered that communities of microbes living beneath the seafloor are able to survive in rock sediments for over 100 million years with desperately little nutrients. After being coaxed under the right conditions in a lab, the ancient microbes are even able to snap out of their “hibernation” to metabolize and multiply once again.

Reported in the journal Nature Communications back in July 2020, researchers from Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and the University of Rhode Island got their hands on these microbes by gathering sediment samples from 75 meters (246 feet) below the seafloor in the South Pacific Ocean, nearly 5,700 meters (18,700 feet) below sea level. 

The microbial life was capable of being revived through finely tuned techniques in a laboratory. Incubated with isotope-labeled carbon and nitrogen-laced nutrients, within 10 weeks the isotopes showed up in the microbes, demonstrating they were in a metabolically active state, even capable of feeding and dividing.

“These are the oldest microbes revived from a marine environment,” Steven D’Hondt, study author and Professor of Oceanography at the University of Rhode Island, told IFLScience in 2020.

“Even after 100 million years of starvation, some microbes can grow, reproduce, and engage in a wide variety of metabolic activities when they’re returned to the surface world,” he added.

The microbe communities became trapped beneath the seafloor long ago after being buried by layers of sediment made up of “marine snow,” debris, dust, and other particles. This layer of sediment from the study was deposited over a period from 13 to 101.5 million years ago. 

If the sediment is formed under the right circumstances, oxygen is still just about able to penetrate to these depths, but little else can migrate, suggesting the microbial communities have stayed put for all these years. While the layer does contain oxygen, it has very limited amounts of organic material, such as carbon, and is an unbelievably harsh environment for life. 

In the incubated lab conditions, some of the microbes responded rapidly, increasing in number by more than four orders of magnitude over the 68 days of incubation. Even in the oldest 101.5-million-year-old sediment, they observed the microbes uptaking the isotopes and increasing in cell numbers.

Most of the microbes appear to be aerobic bacteria, meaning they are microbes that need oxygen to survive and grow. Given the scarcity of nutrients that far down, it’s likely these microbes have slowed down their “body clocks” to live an extremely sluggish life, complete with a slow metabolism and very slow evolutionary speed. 

“We believe the community has remained there for 100 million years, with an unknown number of generations. Since the calculated energy flux for subseafloor sedimentary microbes is barely sufficient for molecular repair, the number of generations could be inconceivably low,” Professor D’Hondt explained to IFLScience.

It was once assumed that life could only survive just a few meters beneath the seabed, namely near continental edges where lots of organic matter can be found. However, as this study affirms, researchers are now showing that life beneath the seafloor is much more diverse and fascinating than previously realized. In a separate study published in March 2020, scientists even discovered microbial communities living some 750 meters (2,500 feet) beneath the seabed.

An earlier version of this article was published in July 2020.