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Homo who? A new mystery human species has been discovered in Israel

June 24, 2021 

An international group of archaeologists have discovered a missing piece in the story of human evolution.

Excavations at the Israeli site of Nesher Ramla have recovered a skull that may represent a late-surviving example of a distinct Homo population, which lived in and around modern-day Israel from about 420,000 to 120,000 years ago

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Aerial view of the Nesher Ramla sinkhole. The site of Nesher Ramla during excavation. Yossi Zaidner

As researchers Israel Hershkovitz, Yossi Zaidner and colleagues detail in two companion studies published today in Science, this archaic human community traded both their culture and genes with nearby Homo sapiens groups for many thousands of years.
The new fossils

Pieces of a skull, including a right parietal (towards the back/side of the skull) and an almost complete mandible (jaw) were dated to 140,000–120,000 years old, with analysis finding the person it belonged to wasn’t fully H. sapiens.

The Nesher Ramla mandible and skull. Avi Levin and Ilan Theiler, Sackler / Tel Aviv University

Nor were they Neanderthal, however, which was the only other type of human thought to have been living in the region at the time.

Instead, this individual falls right smack in the middle: a unique population of Homo never before recognised by science

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Imaging of the Nesher Ramla mandible and teeth. Ariel Pokhojaev/Tel Aviv University

Through detailed comparison with many other fossil human skulls, the researchers found the parietal bone featured “archaic” traits that are substantially different from both early and recent H. sapiens. In addition, the bone is considerably thicker than those found in both Neanderthals and most early H. sapiens.

The jaw too displays archaic features, but also includes forms commonly seen in Neanderthals.

The bones together reveal a unique combination of archaic and Neanderthal features, distinct from both early H. sapiens and later Neanderthals.

Are there are more of these people?

The authors suggest fossils found at other Israeli sites, including the famous Lady of Tabun, might also be part of this new human population, in contrast to their previous Neanderthal or H. sapiens identification.

The “Lady of Tabun” (known to archaeologists as Tabun C1) was discovered in 1932 by pioneering archaeologist Yusra and her field director, Dorothy Garrod.

Extensively studied, this important specimen taught us much about Neanderthal anatomy and behaviour in a time when very little was known about our enigmatic evolutionary cousins.

Read more: Ancient teenager the first known person with parents of two different species

If Tabun C1 and others from the Qesem and Zuttiyeh Caves were indeed members of the Nasher Ramel Homo group, this reanalysis would explain some inconsistencies in their anatomy previously noted by researchers.

The mysterious Nesher Ramla Homo may even represent our most recent common ancestor with Neanderthals. Its mix of traits supports genetic evidence that early gene flow between H. sapiens and Neanderthals occurred between 400,000 and 200,000 years ago. In other words, that interbreeding between the different Homo populations was more common than previously thought.

Even more puzzling, the team also found a collection of some 6,000 stone tools at the Nesher Ramla site.
A flint scraper — one of the stone tools of Nesher Ramla Homo. Tal Rogovski

These tools were made the same way contemporaneous H. sapiens groups made their technology, with the similarity so strong it appears the two populations — Nesher Ramla Homo and H. sapiens — were hanging out on a regular basis. It seems they weren’t just exchanging genes, but also tips on tool-making.
And there was fire!

The site also produced bones of animals caught, butchered, and eaten on-site. These findings indicate Nesher Ramla Homo hunted a range of species, including tortoise, gazelle, aurochs, boar and ostrich.

Furthermore, they were using fire to cook their meals, evident through the uncovering of a campfire feature the same age as the fossils. Indeed, the Nesher Ramla Homo were not only collecting wood to make campfires and cook, but were also actively managing their fires as people do today.

Exposure of animal bones and lithic artifacts in the layer with the Nesher Ramla Homo fossils. Yossi Zaidner

While the earliest indications of controlled use of fire is much older — perhaps one million years ago - the interesting thing about this particular campfire is the evidence that Nesher Ramla people tended to it as carefully as contemporary H. sapiens and Neanderthals did their own fires.

Most impressive is that the campfire feature survived, intact, outside of a protected cave environment for so long. It is now the oldest intact campfire ever found in the open air.

In sum, if we think of the story of human evolution like an Ikea bookcase that isn’t quite coming together, this discovery is effectively like finding the missing shelf buried at the bottom of the box. The new Nesher Ramla Homo allows for a better-fitting structure, although a few mysterious “extra” pieces remain to be pondered over.

For example, exactly how did the different Homo groups interact with each other? And what does it mean for the cultural and biological changes that were occurring for Homo populations in this period?

Continuing to work with these questions (the “extra pieces”) will help us build a better understanding of our human past.


View of the deep section during excavation at Nesher Ramla, showing the deep. archaeological sequence. Yossi Zaidner

Author

Michelle Langley

Senior Research Fellow, Griffith University
Disclosure statement
Dr Michelle Langley is a Senior Research Fellow in the Australian Research Centre for Human Evolution and Lecturer in Archaeology in the School of Environment and Science at Griffith University. She receives funding from the Australian Research Council.

New fossils reveal previously unknown population of archaic hominin from the Levant

AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE

Research News

 

In two companion studies, researchers reveal a previously unknown population of archaic hominin- the "Nesher Ramla Homo" - from a recently excavated site in Israel dated to roughly 140,000 to 120,000 years ago. Analysis of both the fossils and associated artifacts from the site suggests that the group represents a last surviving population of Middle Pleistocene Homo, characterized by a distinctive combination of Neanderthal and archaic human features and technology that until only recently was linked to more modern Homo lineages. It's been assumed that Neanderthals originated and thrived on the European continent well before the arrival of modern humans. However, recent evidence suggests a genetic contribution from a yet unknown non-European group, indicating a long and dynamic history of interaction between Eurasian and African hominin populations. Here, Israel Hershkovitz, Yossi Zaidner and colleagues present fossil, artifact, and radiometric evidence from the Levant region of the Middle East that illustrates this complexity. According to Hershkovitz et al., the newly discovered Nesher Ramla Homo exhibits anatomical features that are more archaic than contemporaneous Eurasian Neanderthals and the modern humans who also lived in the Levant. The findings indicate that this archaic lineage may represent one of the last surviving populations of Middle Pleistocene Homo in southwest Asia, Africa and Europe. In the companion study, Zaidner et al. provide the archaeological context of the new fossils, reporting on the associated radiometric ages, artifact assemblages and the behavioral and environmental insights they offer. Zaidner et al. show that the Nesher Ramla Homo were well versed in technologies that were previously only known among H. sapiens and Neanderthals. Together, the findings provide archaeological support for close cultural interactions and genetic admixture between different human lineages before 120,000 years ago. This may help explain the variable expression of the dental and skeletal features of later Levantine fossils. "The interpretation of the Nesher Ramla fossils and stone tools will meet with different reactions among paleoanthropologists. Notwithstanding, the age of the Nesher Ramla material, the mismatched morphological and archaeological affinities, and the location of the site at the crossroads of Africa and Eurasia make this a major discovery," writes Marta Lahr in an accompanying Perspective.

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A new type of Homo unknown to science

Dramatic discovery in Israeli excavation

TEL-AVIV UNIVERSITY

Research News

 

IMAGE: .STATIC SKULL & MANDIBLE & PARIETAL ORTHOGRAPHIC. view more 

CREDIT: TEL AVIV UNIVERSITY

• The discovery of a new Homo group in this region, which resembles Pre-Neanderthal populations in Europe, challenges the prevailing hypothesis that Neanderthals originated from Europe, suggesting that at least some of the Neanderthals' ancestors actually came from the Levant.
• The new finding suggests that two types of Homo groups lived side by side in the Levant for more than 100,000 years (200-100,000 years ago), sharing knowledge and tool technologies: the Nesher Ramla people who lived in the region from around 400,000 years ago, and the Homo sapiens who arrived later, some 200,000 years ago.
• The new discovery also gives clues about a mystery in human evolution: How did genes of Homo sapiens penetrate the Neanderthal population that had presumably lived in Europe long before the arrival of Homo sapiens?
• The researchers claim that at least some of the later Homo fossils found previously in Israel, like those unearthed in the Skhul and Qafzeh caves, do not belong to archaic (early) Homo sapiens, but rather to groups of mixed Homo sapiens and Nesher Ramla lineage.

Nesher Ramla Homo type - a prehistoric human previously unknown to science: Researchers from Tel Aviv University and the Hebrew University of Jerusalem have identified a new type of early human at the Nesher Ramla site, dated to 140,000 to 120,000 years ago. According to the researchers, the morphology of the Nesher Ramla humans shares features with both Neanderthals (especially the teeth and jaws) and archaic Homo (specifically the skull). At the same time, this type of Homo is very unlike modern humans - displaying a completely different skull structure, no chin, and very large teeth. Following the study's findings, researchers believe that the Nesher Ramla Homo type is the 'source' population from which most humans of the Middle Pleistocene developed. In addition, they suggest that this group is the so-called 'missing' population that mated with Homo sapiens who arrived in the region around 200,000 years ago - about whom we know from a recent study on fossils found in the Misliya cave.

Two teams of researchers took part in the dramatic discovery, published in the prestigious Science journal: an anthropology team from Tel Aviv University headed by Prof. Israel Hershkovitz, Dr. Hila May and Dr. Rachel Sarig from the Sackler Faculty of Medicine and the Dan David Center for Human Evolution and Biohistory Research and the Shmunis Family Anthropology Institute, situated in the Steinhardt Museum at Tel Aviv University; and an archaeological team headed by Dr. Yossi Zaidner from the Institute of Archaeology at the Hebrew University of Jerusalem.

Timeline: The Nesher Ramla Homo type was an ancestor of both the Neanderthals in Europe and the archaic Homo populations of Asia.

Prof.Israel Hershkovitz: "The discovery of a new type of Homo" is of great scientific importance. It enables us to make new sense of previously found human fossils, add another piece to the puzzle of human evolution, and understand the migrations of humans in the old world. Even though they lived so long ago, in the late middle Pleistocene (474,000-130,000 years ago), the Nesher Ramla people can tell us a fascinating tale, revealing a great deal about their descendants' evolution and way of life."

The important human fossil was found by Dr. Zaidner of the Hebrew University during salvage excavations at the Nesher Ramla prehistoric site, in the mining area of the Nesher cement plant (owned by Len Blavatnik) near the city of Ramla. Digging down about 8 meters, the excavators found large quantities of animal bones, including horses, fallow deer and aurochs, as well as stone tools and human bones. An international team led by the researchers from Tel Aviv and Jerusalem identified the morphology of the bones as belonging to a new type of Homo, previously unknown to science. This is the first type of Homo to be defined in Israel, and according to common practice, it was named after the site where it was discovered - the Nesher Ramla Homo type.

CAPTION

Fossil remains of skull and jaw.

CREDIT

Tel Aviv University

Dr. Yossi Zaidner: "This is an extraordinary discovery. We had never imagined that alongside Homo sapiens, archaic Homo roamed the area so late in human history. The archaeological finds associated with human fossils show that "Nesher Ramla Homo" possessed advanced stone-tool production technologies and most likely interacted with the local Homo sapiens". The culture, way of life, and behavior of the Nesher Ramla Homo are discussed in a companion paper also published in Science journal today.

Prof. Hershkovitz adds that the discovery of the Nesher Ramla Homo type challenges the prevailing hypothesis that the Neanderthals originated in Europe. "Before these new findings," he says, "most researchers believed the Neanderthals to be a 'European story', in which small groups of Neanderthals were forced to migrate southwards to escape the spreading glaciers, with some arriving in the Land of Israel about 70,000 years ago. The Nesher Ramla fossils make us question this theory, suggesting that the ancestors of European Neanderthals lived in the Levant as early as 400,000 years ago, repeatedly migrating westward to Europe and eastward to Asia. In fact, our findings imply that the famous Neanderthals of Western Europe are only the remnants of a much larger population that lived here in the Levant - and not the other way around."

According to Dr. Hila May, despite the absence of DNA in these fossils, the findings from Nesher Ramla offer a solution to a great mystery in the evolution of Homo: How did genes of Homo sapiens penetrate the Neanderthal population that presumably lived in Europe long before the arrival of Homo sapiens? Geneticists who studied the DNA of European Neanderthals have previously suggested the existence of a Neanderthal-like population which they called the 'missing population' or the 'X population' that had mated with Homo sapiens more than 200,000 years ago. In the anthropological paper now published in Science, the researchers suggest that the Nesher Ramla Homo type might represent this population, heretofore missing from the record of human fossils. Moreover, the researchers propose that the humans from Nesher Ramla are not the only ones of their kind discovered in the region, and that some human fossils found previously in Israel, which have baffled anthropologists for years - like the fossils from the Tabun cave (160,000 years ago), Zuttiyeh cave (250,000), and Qesem cave (400,000) - belong to the same new human group now called the Nesher Ramla Homo type.

"People think in paradigms," says Dr. Rachel Sarig. "That's why efforts have been made to ascribe these fossils to known human groups like Homo sapiens, Homo erectus, Homo heidelbergensis or the Neanderthals. But now we say: No. This is a group in itself, with distinct features and characteristics. At a later stage small groups of the Nesher Ramla Homo type migrated to Europe - where they evolved into the 'classic' Neanderthals that we are familiar with, and also to Asia, where they became archaic populations with Neanderthal-like features. As a crossroads between Africa, Europe and Asia, the Land of Israel served as a melting pot where different human populations mixed with one another, to later spread throughout the Old World. The discovery from the Nesher Ramla site writes a new and fascinating chapter in the story of humankind."

Prof. Gerhard Weber, an associate from Vienna University, argues that the story of Neanderthal evolution will be told differently after this discovery: "Europe was not the exclusive refugium of Neanderthals from where they occasionally diffused into West Asia. We think that there was much more lateral exchange in Eurasia, and that the Levant is geographically a crucial starting point, or at a least bridgehead, for this process."

CAPTION

(Left to Right): Israel Hershkovitz, Marion Prevost, Hila May, Rachel Sarig and Yossi Zaidner

CREDIT

Tel Aviv University 

Link to the research video:

https://www.youtube.com/watch?v=OGPKRuyd-5M

Link to the research video:

https://www.youtube.com/watch?v=OGPKRuyd-5M

Static skull & mandible & parietal orthographic (also attached as a PNG file):

New fossil discovery from Israel points to complicated evolutionary process

BINGHAMTON UNIVERSITY

Research News

IMAGE: THE NESHER RAMLA HUMAN MANDIBLE (LEFT) AND PARIETAL BONE (RIGHT). view more 

CREDIT: AVI LEVIN AND ILAN THEILER, SACKLER FACULTY OF MEDICINE, TEL AVIV UNIVERSITY

BINGHAMTON, N.Y. -- Analysis of recently discovered fossils found in Israel suggest that interactions between different human species were more complex than previously believed, according to a team of researchers including Binghamton University anthropology professor Rolf Quam.

The research team, led by Israel Hershkovitz from Tel Aviv University, published their findings in Science, describing recently discovered fossils from the site of Nesher Ramla in Israel. The Nesher Ramla site dates to about 120,000-140,000 years ago, towards the very end of the Middle Pleistocene time period.

The human fossils were found by Dr. Zaidner of the Hebrew University during salvage excavations at the Nesher Ramla prehistoric site, near the city of Ramla. Digging down about 8 meters, the excavators found large quantities of animal bones, including horses, fallow deer and aurochs, as well as stone tools and human bones. The human fossils consist of a partial cranial vault and a mandible. Researchers made virtual reconstructions of the fossils to analyze them using sophisticated computer software programs and to compare them with other fossils from Europe, Africa and Asia. The results suggest that the Nesher Ramla fossils represent late survivors of a population of humans who lived in the Middle East during the Middle Pleistocene period.

"The oldest fossils that show Neandertal features are found in Wesern Europe, so researchers generally believe the Neandertals originated there," said Quam. "However, migrations of different species from the Middle East into Europe may have provided genetic contributions to the Neandertal gene pool during the course of their evolution."

The finds from Nesher Ramla are noteworthy because they sample a time period in the Middle East with few fossils, so they are important additions to the growing fossil record from the region. Other fossils from this approximate time period are difficult to classify taxonomically since they seem to show a combination of features seen in both Neandertals and modern humans. The Nesher Ramla fossils seem more Neandertal-like in the mandible and less Neandertal-like in the cranial vault, but are clearly distinct from modern humans. This pattern matches what has been suggested for both Neandertals and modern humans, where the diagnostic skeletal features of each species appear first in the facial region and later on the cranial vault.

Describing the significance of the find, Dr. Hershkovitz said: "It enables us to make new sense of previously found human fossils, add another piece to the puzzle of human evolution, and understand the migrations of humans in the old world. Even though they lived so long ago, in the late middle Pleistocene, the Nesher Ramla people can tell us a fascinating tale, revealing a great deal about their descendants' evolution and way of life."

CAPTION

Transparent view of the mandibular body and tooth roots in the Nesher Ramla mandible

CREDIT

Ariel Pokhojaev, Sackler Faculty of Medicine, Tel Aviv University

The researchers were careful not to attribute the Nesher Ramla fossils to a new species. Rather, they grouped them together with earlier fossils from several sites in the Middle East that have been difficult to classify and considered all of them to represent a local population of humans that occupied the region between about 420,000-120,000. Given the fact that the Middle East sits at the crossroads of three continents, it is likely that different human groups moved into and out of the region regularly, exchanging genes with the local inhabitants. This scenario might explain the variable anatomical features in these fossils, with the Nesher Ramla fossils representing the latest known survivors of this localized Middle Pleistocene population.

"This is a complicated story, but what we are learning is that the interactions between different human species in the past were much more convoluted than we had previously appreciated," said Quam.

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The study, "A Middle Pleistocene Homo from Nesher Ramla, Israel," was published in Science, along with a companion paper discussing the culture, way of life, and behavior of the Nesher Ramla Homo.

CAPTION

Virtual reconstruction of the Nesher Ramla mandible and molar.

CREDIT

: Ariel Pokhojaev, Sackler Faculty of Medicine, Tel Aviv University

Embryologists reveal a secret of a worm with regeneration super abilities

Biologists at St Petersburg University have studied mechanisms of regeneration of marine animals and found out what plays the key role in regeneration of tissues of Alitta virens

ST. PETERSBURG STATE UNIVERSITY

VIDEO: ALITTA VIRENS (FEMALE) SPAWNING view more 

CREDIT: SPBU

This worm that lives in the White Sea is able to restore lost body segments. However, it turned out that suppression of FGF protein activity disturbs this ability. Similar proteins are found in humans. This discovery may lead to developing methods of fast wound healing. The research findings are published in the journal Genes as part of the project supported by the Russian Science Foundation.

Fibroblast growth factors (FGF) are proteins that play an important role in wound healing and tissue growth. When the need for regeneration of damaged body parts occur, FGFs are produced by epidermis, nervous tissue, macrophages and fibroblasts, which are the main cells of connective tissue. As a result, the process of active cell division and the production of tropocollagen (the structural unit of a collagen fibre) is triggered; the intercellular matrix and the main substance of the connective tissue are synthesised; and the growth of nerves and blood vessels begins.

'Proteins of the FGF group are currently used in experimental methods of cell culture. They are added to the cocktail of nutritious medium in order to grow various cell cultures of animal origin. However, we can go beyond cell culture, for example, we can use them in fast wound treatment medicine', explains Vitaly Kozin, Head of the project, Assistant Professor at St Petersburg University.

CAPTION

Alitta virens

CREDIT

SPbU

Embryologists of St Petersburg University studied FGF of Alitta virens. This annelids live in the White Sea. They are the largest annelids (up to half a metre long) and thanks to their unusual colour they are look very impressive. They are extremely fecund, live long (three to seven years) and are able to grow lost body parts. Also, one can catch them with a scoop net: during spawning that happens at the end of June - beginning of July, when the animals swarm near the water surface. This is how the researchers gathered them. After that they fertilised them artificially in a laboratory and grew new individuals in controlled environment that were suitable for research.

First, the embryologists studied bioinformatics data base where they found the genes they were interested in. Then they described the structure and origins of the genes in order to compare them with the part of DNA which play the similar role in humans. Alitta virens has only two ligands (molecules that bind to cell surface thereby transmitting the signal) and two FGF receptors, which is much less than in humans. Then the scientists extracted these genes products from Alitta virens that were regenerating after damage, and cloned their fragments. They synthesised detectable probes that made it possible to see where exactly these genes work in worms. The method is called hybridisation in situ, which means RNA sticking inside the body.

When the time and the place of gene activity was identified, the scientists artificially blocked receptors and intermediates of FGF signalling pathway by adding inhibitors SU5402 and U0126 into sea water where the worms lived. The process was monitored using antibodies with a special colour, fluorescent dyes and impulse laballing of DNA precursors. It turned out that blocking of FGF affected not only the process of cell division in the damaged part of the body, but also the regeneration process in general. The control animals (those that did not receive inhibitors) started cell division in four hours after amputation and regeneration of muscles and nerves was observed for six days, whereas, inhibitors stopped regeneration completely.

CAPTION

Photographs of the White Sea during collecting of the material (Alexandra Shalaeva and Vitaly Kozin)

CREDIT

Vitaly Kozin

'We managed to study the mechanism of regeneration of the tissues in Alitta virens. This knowledge can be used for therapeutic approaches in regenerative medicine. The study showed that the principal role of FGF in vertebrates and invertebrates does not differ. The analysis showed that participation of FGF in regenerating processes must have existed in a common ancestor of animals with bilateral symmetry that lived 500 million years ago. We are still to find out what was the reason for slowing of regeneration in humans. This summer we will test synthesised fibroblast growth factor on Alitta virens. Perhaps, its increased level in comparison with a natural one will lead to speeding up regeneration. Also, we need to find out how damaging of tissues activates FGF and what other parts of genome comply with its signals', said Vitaly Kozin.

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Cosmic dawn, when stars formed for the first time, occurred 250 million to 350 million years after the beginning of the universe

 VIDEO: THE VIDEO SHOWS THE FORMATION AND EVOLUTION OF THE FIRST STARS AND GALAXIES IN A VIRTUAL UNIVERSE SIMILAR TO OUR OWN. THE SIMULATION BEGINS JUST BEFORE COSMIC DAWN, WHEN THE... view more 

CREDIT: CREDIT: DR HARLEY KATZ, BEECROFT FELLOW, DEPARTMENT OF PHYSICS, UNIVERSITY OF OXFORD

Cosmic dawn, when stars formed for the first time, occurred 250 million to 350 million years after the beginning of the universe, according to a new study led by researchers at University College London (UCL) and the University of Cambridge.

The study, published in the Monthly Notices of the Royal Astronomical Society, suggests that the NASA James Webb Space Telescope (JWST), scheduled to launch in November, will be sensitive enough to observe the birth of galaxies directly.

The UK-led research team examined six of the most distant galaxies currently known, whose light has taken most of the universe's lifetime to reach us. They found that the distance of these galaxies away from Earth corresponded to a "look back" time of more than 13 billion years ago, when the universe was only 550 million years old.

Analysing images from the Hubble and Spitzer Space Telescopes, the researchers calculated the age of these galaxies as ranging from 200 to 300 million years, allowing an estimate of when their stars first formed.

Lead author Dr Nicolas Laporte (University of Cambridge), who started the project while at UCL, said: "Theorists speculate that the universe was a dark place for the first few hundred million years, before the first stars and galaxies formed.

"Witnessing the moment when the universe was first bathed in starlight is a major quest in astronomy.

"Our observations indicate that cosmic dawn occurred between 250 and 350 million years after the beginning of the universe, and, at the time of their formation, galaxies such as the ones we studied would have been sufficiently luminous to be seen with the James Webb Space Telescope."

The researchers analysed starlight from the galaxies as recorded by the Hubble and Spitzer Space Telescopes, examining a marker in their energy distribution indicative of the presence of atomic hydrogen* in their stellar atmospheres. This provides an estimate of the age of the stars they contain.

This hydrogen signature increases in strength as the stellar population ages but diminishes when the galaxy is older than a billion years. The age-dependence arises because the more massive stars that contribute to this signal burn their nuclear fuel more rapidly and therefore die first.

Co-author Dr Romain Meyer (UCL Physics & Astronomy and the Max Planck Institute for Astronomy in Heidelberg, Germany) said: "This age indicator is used to date stars in our own neighbourhood in the Milky Way but it can also be used to date extremely remote galaxies, seen at a very early period of the universe.

"Using this indicator we can infer that, even at these early times, our galaxies are between 200 and 300 million years old."

In analysing the data from Hubble and Spitzer, the researchers needed to estimate the "redshift" of each galaxy which indicates their cosmological distance and hence the look-back time at which they are being observed. To achieve this, they undertook spectroscopic measurements using the full armoury of powerful ground-based telescopes - the Chilean Atacama Large Millimetre Array (ALMA), the European Very Large Telescope, the twin Keck telescopes in Hawaii, and Gemini-South telescope.

These measurements enabled the team to confirm that looking at these galaxies corresponded to looking back to a time when the universe was 550 million years old.

Co-author Professor Richard Ellis (UCL Physics & Astronomy), who has tracked ever more distant galaxies over his career, said: "Over the last decade, astronomers have pushed back the frontiers of what we can observe to a time when the universe was only 4% of its present age. However, due to the limited transparency of Earth's atmosphere and the capabilities of the Hubble and Spitzer Space Telescopes, we have reached our limit.

"We now eagerly await the launch of the James Webb Space Telescope, which we believe has the capability to directly witness cosmic dawn.

"The quest to see this important moment in the universe's history has been a holy grail in astronomy for decades. Since we are made of material processed in stars, this is in some sense the search for our own origins."**

The new study involved astronomers at the University of California-Santa Cruz, the University of California, and the University of Texas.

The researchers received support from the Kavli Foundation, the European Research Council, the National Aeronautics and Space Administration (NASA), and the National Science Foundation (NSF) in the United States.

The NASA-led James Webb Space Telescope, the successor to the Hubble observatory, is scheduled to be launched into space in November. It will be the premier observatory over the next decade, serving thousands of astronomers worldwide. It consists of an infrared observatory, an immense mirror 6.5 metres wide, and a diamond-shaped sunshield. UCL scientists at the Mullard Space Science Laboratory have built and tested key hardware components for the NIRSpec (Near-Infrared Spectrograph), one of the telescope's four instruments.

*Atomic hydrogen is hydrogen that has not been split into protons and electrons.

**All the heavier elements in the universe - everything except for hydrogen, helium and lithium - are synthesised in stars and then seeded across the universe when the stars explode at the end of their lives. This includes the elements that make up humans - the calcium in our bones, the iron in our blood.

CAPTION

Colour image of the galaxy cluster used to detect one of the six galaxies, MACS0416-JD, examined in a study led by researchers at University College London and the University of Cambridge. This galaxy has an estimated age of 351 million years, which means that this galaxy was formed 178 million years after the Big Bang. The stellar mass of this galaxy is one billion times the mass of the Sun. This object is currently the most distant galaxy detected with ALMA.

CREDIT

Credit: ESA/Hubble, NASA, HST Frontier Fields

Cosmic hand hitting a wall

HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS

Research News

 

IMAGE: ASTRONOMERS ESTIMATE THAT LIGHT FROM THE SUPERNOVA EXPLOSION REACHED EARTH ABOUT 1,700 YEARS AGO, OR WHEN THE MAYAN EMPIRE WAS FLOURISHING AND THE JIN DYNASTY RULED CHINA. HOWEVER, BY COSMIC... view more 

CREDIT: NASA/SAO/NCSU/BORKOWSKI ET AL.

Motions of a remarkable cosmic structure have been measured for the first time, using NASA's Chandra X-ray Observatory. The blast wave and debris from an exploded star are seen moving away from the explosion site and colliding with a wall of surrounding gas.

Astronomers estimate that light from the supernova explosion reached Earth about 1,700 years ago, or when the Mayan empire was flourishing and the Jin dynasty ruled China. However, by cosmic standards the supernova remnant formed by the explosion, called MSH 15-52, is one of the youngest in the Milky Way galaxy. The explosion also created an ultra-dense, magnetized star called a pulsar, which then blew a bubble of energetic particles, an X-ray-emitting nebula.

Since the explosion the supernova remnant - made of debris from the shattered star, plus the explosion's blast wave - and the X-ray nebula have been changing as they expand outward into space. Notably, the supernova remnant and X-ray nebula now resemble the shape of fingers and a palm.

Previously, astronomers had released a full Chandra view of the "hand," as shown in the main graphic. A new study is now reporting how quickly the supernova remnant associated with the hand is moving, as it strikes a cloud of gas called RCW 89. The inner edge of this cloud forms a gas wall located about 35 light-years from the center of the explosion.

To track the motion the team used Chandra data from 2004, 2008, and then a combined image from observations taken in late 2017 and early 2018. These three epochs are shown in the inset of the main graphic.

The rectangle (fixed in space) highlights the motion of the explosion's blast wave, which is located near one of the fingertips. This feature is moving at almost 9 million miles per hour. The fixed squares enclose clumps of magnesium and neon that likely formed in the star before it exploded and shot into space once the star blew up. Some of this explosion debris is moving at even faster speeds of more than 11 million miles per hour. A color version of the 2018 image shows the fingers in blue and green and the clumps of magnesium and neon in red and yellow.

While these are startling high speeds, they actually represent a slowing down of the remnant. Researchers estimate that to reach the farthest edge of RCW 89, material would have to travel on average at almost 30 million miles per hour. This estimate is based on the age of the supernova remnant and the distance between the center of the explosion and RCW 89. This difference in speed implies that the material has passed through a low-density cavity of gas and then been significantly decelerated by running into RCW 89.

The exploded star likely lost part or all of its outer layer of hydrogen gas in a wind, forming such a cavity, before exploding, as did the star that exploded to form the well-known supernova remnant Cassiopeia A (Cas A), which is much younger at an age of about 350 years. About 30% of massive stars that collapse to form supernovas are of this type. The clumps of debris seen in the 1,700-year-old supernova remnant could be older versions of those seen in Cas A at optical wavelengths in terms of their initial speeds and densities. This means that these two objects may have the same underlying source for their explosions, which is likely related to how stars with stripped hydrogen layers explode. However, astronomers do not understand the details of this yet and will continue to study this possibility.

A paper describing these results appeared in the June 1, 2020, issue of The Astrophysical Journal Letters, and a preprint is available online. The authors of the study are Kazimierz Borkowski, Stephen Reynolds, and William Miltich, all of North Carolina State University in Raleigh.

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NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science from Cambridge Massachusetts and flight operations from Burlington, Massachusetts.

Recycling next-generation solar panels fosters green planet

CORNELL UNIVERSITY

Research News

ITHACA, N.Y. - Tossing worn-out solar panels into landfills may soon become electronics waste history.

Designing a recycling strategy for a new, forthcoming generation of photovoltaic solar cells - made from metal halide perovskites, a family of crystalline materials with structures like the natural mineral calcium titanate - will add a stronger dose of environmental friendliness to a green industry, according to Cornell University-led research published June 24 in Nature Sustainability.

The paper shows substantial benefits to recycling perovskite solar panels, though they are still in the commercial development stage, said Fengqi You, the Roxanne E. and Michael J. Zak Professor in Energy Systems Engineering in the College of Engineering.

"When perovskite solar panels reach the end of their useful life, how do we deal with this kind of electronic waste?" said You, also a faculty fellow at the Cornell Atkinson Center for Sustainability. "It is a new class of materials. By properly recycling it, we could potentially reduce its already low carbon footprint.

"As scientists design solar cells, they look at performance," You said. "They seek to know energy conversion efficiency and stability, and often neglect designing for recycling."

Last year, You and his laboratory found that photovoltaic wafers in solar panels containing all-perovskite structures outperform photovoltaic cells made from state-of-the-art crystalline silicon, and the perovskite-silicon tandem - with cells stacked like pancakes to better absorb light - perform exceptionally well.

Perovskite photovoltaic wafers offer a faster return on the initial energy investment than silicon-based solar panels because all-perovskite solar cells consume less energy in the manufacturing process.

Recycling them enhances their sustainability, as the recycled perovskite solar cells could bring 72.6% lower primary energy consumption and a 71.2% reduction in carbon footprint, according to the paper, "Life Cycle Assessment of Recycling Strategies for Perovskite Photovoltaic Modules," co-authored by Xueyu Tian, a doctoral student at Cornell Systems Engineering, and Samuel D. Stranks of the University of Cambridge.

"Lowering the energy needed to produce the cells indicates a significant reduction of energy payback and greenhouse gas emissions," said Tian.

The best recycled perovskite cell architecture could see an energy payback time of about one month, with a carbon footprint as low as 13.4 grams of carbon dioxide equivalent output per kilowatt hour of electricity produced. Without recycling, the energy payback time and carbon footprint of new perovskite solar cells show a range of 70 days to 13 months, and 27.5 to 158.0 grams of carbon dioxide equivalent throughout their life cycles.

Today's market-leading silicon photovoltaic cells can expect an energy payback period of 1.3 to 2.4 years, with an initial carbon footprint between 22.1 and 38.1 grams of carbon dioxide equivalent emissions per kilowatt hour output.

"Recycling makes perovskites outcompete all other rivals," Tian said.

Informed state and federal policies, along with recycling infrastructure development strategies, can further mitigate the environmental impacts in making photovoltaic solar cells.

Said You: "The real value of an effective green perovskite solar panel industry may rely on a recycling program."

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The National Science Foundation supported this research.

 

Artificial intelligence breakthrough gives longer advance warning of ozone issues

University of Houston research team finds 'holy grail' of air quality forecasting

UNIVERSITY OF HOUSTON

Research News

 

IMAGE: UNIVERSITY OF HOUSTON PROFESSOR YUNSOO CHOI AND DOCTORAL STUDENT ALQAMAH SAYEED STUDY ATMOSPHERIC DATA. view more 

CREDIT: UNIVERSITY OF HOUSTON

Ozone levels in the earth's troposphere (the lowest level of our atmosphere) can now be forecasted with accuracy up to two weeks in advance, a remarkable improvement over current systems that can accurately predict ozone levels only three days ahead. The new artificial intelligence system developed in the University of Houston's Air Quality Forecasting and Modeling Lab could lead to improved ways to control high ozone problems and even contribute to solutions for climate change issues.

"This was very challenging. Nobody had done this previously. I believe we are the first to try to forecast surface ozone levels two weeks in advance," said Yunsoo Choi, professor of atmospheric chemistry and AI deep learning at UH's College of Natural Sciences and Mathematics. The findings are published online in the scientific journal, Scientific Reports-Nature.

Ozone, a colorless gas, is helpful in the right place and amount. As a part of the earth's stratosphere ("the ozone layer"), it protects by filtering out UV radiation from the sun. But when there are high concentrations of ozone near earth's surface, it is toxic to lungs and hearts.

"Ozone is a secondary pollutant, and it can affect humans in a bad way," explained doctoral student Alqamah Sayeed, a researcher in Choi's lab and the first author of the research paper. Exposure can lead to throat irritation, trouble breathing, asthma, even respiratory damage. Some people are especially susceptible, including the very young, the elderly and the chronically ill.

Ozone levels have become a frequent part of daily weather reports. But unlike weather forecasts, which can be reasonably accurate up to 14 days ahead, ozone levels have been predicted only two or three days in advance - until this breakthrough.

The vast improvement in forecasting is only one part of the story of this new research. The other is how the team made it happen. Conventional forecasting uses a numerical model, which means the research is based on equations for the movement of gasses and fluids in the atmosphere.

The limitations were obvious to Choi and his team. The numerical process is slow, making results expensive to obtain, and accuracy is limited. "Accuracy with the numerical model starts to drop after the first three days," Choi said.

The research team used a unique loss function in developing the machine learning algorithm. A loss function helps in optimization of the AI model by mapping decision to their associated costs. In this project, researchers used index of agreement, known as IOA, as the loss function for the AI model over conventional loss functions. IOA is a mathematical comparison of gaps between what is expected and how things actually turn out.

In other words, team members added historical ozone data to the trials as they gradually refined the program's reactions. The combination of the numerical model and the IOA as the loss function eventually enabled the AI algorithm to accurately predict outcomes of real-life ozone conditions by recognizing what happened before in similar situations. It is much like how human memory is built.

"Think about a young boy who sees a cup of hot tea on a table and tries to touch it out of curiosity. The moment the child touches the cup, he realizes it is hot and shouldn't be touched directly. Through that experience, the child has trained his mind," Sayeed said. "In a very basic sense, it is the same with AI. You provide input, the computer gives you output. Over many repetitions and corrections, the process is refined over time, and the AI program comes to 'know' how to react to conditions that have been presented before. On a basic level, artificial intelligence develops in the same way that the child learned not to be in such a hurry to grab the next cup of hot tea."

In the lab, the team used four to five years of ozone data in what Sayeed described as "an evolving process" of teaching the AI system to recognize ozone conditions and estimate the forecasts, getting better over time.

"Applying deep learning to air quality and weather forecasting is like searching for the holy grail, just like in the movies," said Choi, who is a big fan of action plots. "In the lab, we went through some difficult times for a few years. There is a process. Finally, we've grasped the holy grail. This system works. The AI model 'understands' how to forecast. Despite the years of work, it somehow still feels like a surprise to me, even today."

Before success in the laboratory can lead to real-world service, many commercial steps are ahead in before the world can benefit from the discovery.

"If you know the future - air quality in this case - you can do a lot of things for the community. This can be very critical for this planet. Who knows? Perhaps we can figure out how to resolve the climate change issue. The future may go beyond weather forecasting and ozone forecasting. This could help make the planet secure," said Choi.

Sounds like a happy ending for any good action story.

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Making citizen science inclusive will require more than rebranding

NORTH CAROLINA STATE UNIVERSITY

Research News

 

Scientists need to focus on tangible efforts to boost equity, diversity and inclusion in citizen science, researchers from North Carolina State University argued in a new perspective.

Published in the journal Science, the perspective is a response to a debate about rebranding "citizen science," the movement to use crowdsourced data collection, analysis or design in research. Researchers said that while the motivation for rebranding is in response to a real concern, there will be a cost to it, and efforts to make projects more inclusive should go deeper than that. Their recommendations speak to a broader discussion about how to ensure science is responsive to the needs of a diverse audience.

"At its heart, citizen science is a system of knowledge production that doesn't block entry based on credentials," said first author Caren Cooper, associate professor of forestry and environmental resources at NC State. "Those of us in citizen science have been saying 'science is for everyone, you don't need a degree or special training.' But, the sad irony is that it hasn't been for everyone. The overwhelming majority of participants resemble their academic counterparts, who are often white, affluent and have advanced degrees. We want to take the good intentions that are driving rebranding, and commit to long-term, sustained efforts to reimagine an inclusive citizen science."

The term "citizen science" was coined in the 1990s, researchers said, to describe science led by institutions that use volunteers to collect data. It has evolved to encompass many types of projects with public involvement in design, leadership or data collection and analysis. As a "citizen science campus," there are projects underway at NC State in which undergraduates, faculty, staff and the general public can help collect data. Examples include projects that rely on volunteers to help figure out the microbial content of sourdough bread or detect the presence of lead pipes in homes around the state.

In an effort to resolve concerns that the term is exclusionary to people who do not have citizenship status in a given nation, some organizations have moved toward using the term "community science," among other names. But researchers said community science is a distinct and existing research movement led and designed by communities, rather than institutions, to address environmental or social justice problems.

"It's a huge dis to community science to flippantly change the name like it isn't already being utilized, and could be considered disrespectful to people who are doing this work and have been for many years," said co-author Zakiya Leggett, assistant professor of forestry and environmental resources. "If you have a citizen science project, but you advertise it as 'community science,' it does a disservice to both practices."

In addition, there is a cost to losing the term "citizen science," they said, since the term has gained momentum globally. In the United States, the term is used in a federal law authorizing the government to include volunteers in scientific research irrespective of their credentials and citizenship status.

"There is a lot of work that has gone toward incorporating 'citizen science' as a part of policy, as well as being accepted into mainstream science," said co-author Madhusudan Katti, associate professor of forestry and environmental resources at NC State. "The name has been caught up in politicization of citizenship and nationalist politics, and rebranding is a little bit reactive. The concern is genuine, but the fix is not deep enough. Renaming something doesn't make it different from what it's been all along."

The researchers argued for strategic planning to advance accessibility, justice, equity, diversity and inclusion in citizen science.

"One approach that could work for citizen science is 'centering in the margins.' That can include centering research agendas based on the areas that are underserved by science," Cooper said.

Other tactics could involve ensuring there are diverse perspectives in project leadership, or overcoming economic barriers to participation. They also said there is a need for funding to support science that addresses interests, concerns and needs of people who have historically or are currently underserved by science.

They said rebranding, if needed, should only happen if it is called for as part of a broader strategic plan. They also said rebranding efforts should refrain from co-opting existing terminology, avoid exporting issues in the United States to the rest of the world, and identify terminology to help further clarify distinctions for different types of projects.

"We wanted the fact that diversity and inclusion in citizen science remains elusive to serve as a canary in the coal mine to the rest of the scientific community - it takes far more than words and good intentions to be inclusive," Cooper said. "We can learn from community science without co-opting it. We need to figure this out without expecting quick-fix solutions, because those can do more harm than good."

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The perspective, "Inclusion in citizen science: The conundrum of rebranding," was published online in Science. In addition to Cooper, Katti and Leggett, other authors included Chris L. Hawn, Lincoln R. Larson, Julia K. Parrish, Gillian Bowser, Darlene Cavalier, Robert R. Dunn, Mordechai (Muki) Haklay, Kaberia Kar Gupta, Na'Taki Osborne Jelks, Valerie A. Johnson, Omega R. Wilson and Sacoby Wilson. Researchers reported funding from the National Science Foundation, through grant No. 1713562, to Cooper and Larson.

Research shows Alaska infrastructure at risk of earlier failure

UNIVERSITY OF ALASKA FAIRBANKS

Research News

 

IMAGE: THIS ILLUSTRATION FROM THE ARTICLE SHOWS THE LOCATION OF TEMPERATURE SENSORS AT THE DALTON HIGHWAY RESEARCH SITE. view more 

CREDIT: DRONE PHOTO BY SORAYA KAISER; ILLUSTRATION DISTRIBUTED UNDER CREATIVE COMMONS 4.0 INTERNATIONAL

Roads, bridges, pipelines and other types of infrastructure in Alaska and elsewhere in the Arctic will deteriorate faster than expected due to a failure by planners to account for the structures' impact on adjacent permafrost, according to research by a University of Alaska Fairbanks Geophysical Institute permafrost expert and others.

The researchers say planners must account for the sideward repercussions of their projects in addition to the usual projection of the direct top-down effects.

The finding was presented in a May 31 paper in The Cryosphere, a publication of the European Geosciences Union.

UAF Geophysical Institute geophysics professor Vladimir Romanovsky is among the 13 authors of the paper. Principal researcher for the project is Thomas Schneider von Deimling of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Potsdam, Germany.

The research focused on a portion of the Dalton Highway on Alaska's North Slope about 10 miles south of the Prudhoe Bay oil fields. Sensors monitored the temperature at seven locations, three to the west of the highway and four on the east.

The researchers found that top-down thawing isn't confined to the area beneath the road surface. They found instead that thawing spreads outward, leading to destabilization of the embankment and subgrade and that it is caused by the formation of taliks -- areas of ground that have thawed and remains unfrozen year-round -- under a roadway's toe, the prepared zone at the base of the embankment and abutting the natural terrain.

The result, the authors write, is an accelerating thaw rate and earlier than anticipated road failure -- and a warning that other types of Arctic infrastructure such as pipelines, fuel storage tanks and airports will fail sooner than projected.

The fieldwork and subsequent computer modeling of a gravel road built on continuous permafrost found that a slow and gradual thaw will lead to an accelerated "and likely irreversible permafrost degradation" and that "road failure is inevitable once a critical level of ground warming has been reached" absent extensive ground-cooling measures, the authors write.

The authors write that their findings show a shortcoming in other infrastructure risk assessment methods, which fail to adequately capture changes in permafrost and don't analyze the interaction between the infrastructure and the adjacent ground.

Those shortcomings make current estimates of infrastructure failure dates inaccurate.

"You cannot make blank decisions when you're dealing with permafrost," said Romanovsky, a longtime permafrost researcher. "You always have to be more specific about the region, about the amount of ice in permafrost and about the infrastructure itself. And when you take all of this into consideration -- and climate change -- you can make a much more educated decision."

The research will prove more beneficial in the planning of new roads than in the maintenance of existing roads, for which little can be done to change their initial construction. The research will, however, give transportation managers a better idea of when existing roads are likely to fail, Romanovsky said.

"The Department of Transportation can, using these results, understand how much they have to plan to spend to keep roads in good condition," he said. "They have a good idea in the near term, but they don't know what to expect, say, 10 years from now when the permafrost will be even more vulnerable than it is right now and how this thawing process will continue."

The authors conclude by saying it is "crucial to consider climate change effects when planning and constructing infrastructure on permafrost as a transition from a stable to a highly unstable state can well occur within the infrastructure's service lifetime (about 30 years)."

They add that their focus on the Dalton Highway illustrates that "such a transition can even occur in the coming decade for infrastructure built on continuous permafrost that displays cold and relatively stable conditions today."

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ADDITIONAL CONTACT: Vladimir Romanovsky, University of Alaska Geophysical Institute, veromanovsky@alaska.edu.

NOTE TO EDITORS: Images from the research paper are available with this press release online at http://www.gi.alaska.edu. The research paper is available at https://tc.copernicus.org/articles/15/2451/2021/#abstract

CAPTION

This diagram models half a road in cross-section from the road center to the adjacent tundra. The graphic illustrates the subdivision into four structural units (road center, shoulder, toe and tundra). The grayish area with black dots represents the road embankment. The light blue shading indicates potential maximum snow height. The dark blue area illustrates ponding next to the road.

CREDIT

Image distributed under Creative Commons 4.0 International

 

The quiet of pandemic-era lockdowns allowed some pumas to venture closer to urban areas

Tracking data show how pumas in California's Santa Cruz Mountains responded to regional shelter-in-place orders

UNIVERSITY OF CALIFORNIA - SANTA CRUZ

Research News

 

IMAGE: A TRAIL CAMERA SHOWS A PUMA RESTING IN THE SANTA CRUZ MOUNTAINS OF CALIFORNIA. MOUNTAIN LIONS IN THIS REGION NORMALLY AVOID URBAN AREAS OUT OF FEAR OF HUMANS. view more 

CREDIT: SANTA CRUZ PUMA PROJECT

New research from the University of California, Santa Cruz shows how regional shelter-in-place orders during the coronavirus pandemic emboldened local pumas to use habitats they would normally avoid out of fear of humans. This study, published in the journal Current Biology, is part of a growing wave of research working to formally document the types of unusual changes to wildlife movements and behaviors that people around the world reported during pandemic lockdowns.

Golden jackals, for example, were spotted foraging in broad daylight in urban Tel Aviv, Israel, and mountain lions were seen strolling through downtown Santiago, Chile. Urban environments had suddenly become quiet and empty as shelter-in-place orders brought human movement to a grinding halt--an effect some researchers have called the "anthropause." Wildlife seemed to be taking advantage. The new study shows this was certainly true for pumas in the Santa Cruz Mountains. Researchers were able to clearly connect changes in the cats' habitat use with reduced human mobility during shelter-in-place orders.

Chris Wilmers, an environmental studies professor at UC Santa Cruz, led this research. Wilmers is the principal investigator for the Santa Cruz Puma Project, and he has been studying local mountain lion populations for over a decade. In particular, his research uses data from GPS tracking collars placed on wild pumas to show how fear of humans affects mountain lion behavior and ecology. When the pandemic hit, his team was already tracking data from several collared cats, and he recognized a unique research opportunity.

"When the shelter-in-place orders started, it was immediately clear that things were very different," Wilmers said. "You'd go outside and there were very few cars. Entire neighborhoods were completely quiet. So we wondered how this might affect the mountain lion population. Would they respond this quickly to reduced human presence?"

To answer that question, the team analyzed about two years worth of mountain lion tracking data for a set of six collared cats to see where the pumas roamed and what types of habitats they used. Researchers compared these tracks with the distribution of housing density and the geographic boundaries of the "urban edge," which indicates where vehicle and pedestrian traffic is heightened. During regional shelter-in-place orders, they found that cats were significantly more likely to move into or closer to the urban edge. And these changes happened rapidly: within days or weeks of the beginning of COVID-19 lockdowns.

In an effort to hone in on the cause of this change, the team ruled out any influence of natural factors--like topography, vegetation cover, or distance to the nearest water source--that might affect the cats' choice of habitats. They also compared year-over-year tracking data to show that seasonal variability wasn't affecting the results. Pumas do have a strong preference for habitats with lower housing density, but this factor did not change significantly during the study period. The key difference that appeared to be driving the trend of mountain lions moving into urban areas was reduced human mobility during the pandemic.

After regional shelter-in-place orders went into effect on March 17, 2020, local human mobility declined more than 50 percent, according to Apple mobility data, which show the number of navigation requests for driving and walking trips received through Apple Maps. During this time period, when people confined themselves in their homes, the data showed a strong relationship between declining levels of human mobility and pumas' increased willingness to venture closer to or into urban areas.

"We found that they totally relaxed their fear of the urban edge," Wilmers said. "It's not that they weren't scared of cities; they were still scared, but only of high housing density, not the extra impact of human mobility. If you take all the car trips and pedestrian trips and human mobility out of it, then, all of a sudden, mountain lions don't fear the city as much."

Wilmers says this finding helps to build understanding of the unique impacts of human mobility on wildlife. Conservation efforts often focus on the ways that humans are destroying habitats--through development and pollution, for example--but the mere presence of people moving across a landscape also takes a toll on animals that fear humans. And this too is a conservation challenge.

"It's important because our mobility just keeps increasing," Wilmers explained. "In the early part of the 20th century, we got cars, and that really increased our mobility. Now we have things like ride-sharing apps, mountain bikes, and electric bikes, and these are all ways that we're becoming more and more mobile across more types of landscapes. It's an important thing to think about as we try to conserve and manage ecosystems."

Another key point this research illustrates is that fear, or the removal of a source of fear, can bring about rapid changes in animal behavior that ripple out through ecosystems. Ecologists call this concept the "landscape of fear." And the pandemic showed just how integrated into this landscape humans really are. People are usually the ones exerting the influence of fear upon other animals, but there are some things that even we fear.

"Humans have always been the top dog in landscapes of fear, but this study shows that those influences of humans can be reversed relatively quickly by a pathogen, particularly a pandemic-causing pathogen," Wilmers said. "It's interesting from a theoretical perspective, and it's also important in a practical sense because it shows that, not only are pandemics going to have major health consequences for people, but there are also going to be important ecological impacts."

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