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Fossils from northern Yukon trace ancient hyenas

Bryan Nesbit



A pair of fossilized teeth found near Old Crow, Yukon, in the 1970s finally reveal the migratory trajectory of ancient hyena species that found their way into the northern tundra during the last Ice Age.

Yukon government palaeontologist Grant Zazula had suspected for years that teeth belonged to a genus of hyenas. But it was not until Jack Tseng, an evolutionary biologist and early mammal predators from the University of Buffalo, had come to confirm his suspicions.

Grant Zazula and Jack Tseng published the results of their study Tuesday in the journal Open Quaternary.

“During most of the ice age, there was a variety of strange animals that shuttled through the Yukon through the Bering Strait land bridge. They traveled all over North America and Asia, “says Zazula.

They leave little clues of their passage behind them and these fossils are an example.

Grant Zazula, Yukon Government paleontologist

The fossils belong to a genus of hyenas called Chasmaporthetes . They were discovered by Charlie Thomas, a Gwich’in First Nation elder who was working with scientists in the 1970s.

Other Chasmaporthetes fossils have been found in Mexico and Mongolia, but never in between.

The Chasmaporthetes are the only type of hyenas found outside of Europe, Asia or Africa.

Passage of hyenas

“Approximately 6000 kilometers separate the two sites of Mexico and Mongolia,” says Grant Zazula. “So everyone thought that hyenas had to cross the Yukon through the Bering land bridge and enter North America through this passage,” he says.

“We had never been able to prove that this was the case because there was never any physical evidence found in the Yukon. ”

The chasmaporthetes would have been about the same size as modern hyenas, but with longer legs to help them move more efficiently over long distances.

This detail is important because the chasmaporthetes would have been hunters, in addition to being scavengers. Grant Zazula believes that tall grasses found in the tundra at the time would have been an ideal habitat for camels, caribou and mammoths from the Ice Age, ideal prey for hyenas.

Skillful “bone breakers”

“They were probably very good bone breakers,” says Jack Tseng. “Do not get me wrong, they were good hunters all the same, but when they had to eat carrion, they could clean a carcass like no other predator.”

At this stage of the study, scientists can only give an approximation of the time that chasmaporthetes spent in the Yukon.

While the age of fossils found near Old Crow is estimated between 850,000 years and 1.4 million years ago, the first wave of chasmaporthetes fossils found in Mexico and the southern United States dates back to 4, 75 million years.

Teeth prove, however, that the hyenas passed through the Bering Strait to head south of the continent.

“We have found more than 50,000 bones of ice age animals in the Old Crow area, but we have only two hyena teeth,” says Zazula.

“So it’s a rare animal. The discovery of these fossils is very significant, “he says.

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Are We Alone In The Universe?

Nichole Kerr



The premise of film ET and the extraterrestrial is not about to be realized, since the most advanced researches to date have not been able to detect signals associated with the presence of an intelligent life around the neighboring stars of our solar system.

Our Sun is one of the hundreds of billions of stars in the Milky Way, one of the billions of galaxies that make up our ever-expanding Universe.

It is in this perpetual whirlwind that we find Homo sapiens who have been living on the Earth for 300,000 years, a tiny blue planet orbiting a star among many others. Ever since, humans have been wondering about the immensity of the sky.

What if other intelligent creatures existed in this vast cosmos? Our imagination has created representations in both literature and cinema, but the reality is more down to earth.

Not in our system

In recent years, it has become increasingly clear that little green men will not come from Mars. Perhaps not even in our solar system, where astrophysicists focus their research on finding simpler life forms, such as microorganisms.

But Homos sapiens do not give up the idea of ​​finding celestial companions.

To discover an advanced civilization, humans are looking ever further in the universe, thanks to ever more sophisticated tools.

To date, they have found more than 4000 planets around other stars than the Sun. Of this number, about twenty of them are at a distance from their star that could allow the presence of a form of life .

Humans are also probing the cosmos for radio signals that emanate from a technologically developed civilization. They have been doing it since the 1960s thanks, among other things, to the various projects of the SETI Institute, whose objective is to detect the presence of advanced civilizations in our Milky Way.

One of these projects is Breakthrough Initiatives, funded by Russian billionaire Yuri Milner for $ 100 million over a 10-year period.

The researchers associated with it have just published the results of the most advanced analyzes to date. They analyzed no less than 1 petabyte (1 million gigabytes) of data collected in radio and optical wavelengths.

Nothing in our galactic neighborhood either

This first assessment of three years of stalking extraterrestrial technosignatures shows no trace of intelligent life around 1327 stars that are within 160 light years of our solar system. Nothing. Nothingness.

And this, despite the use of ever more powerful instruments, such as the Green Bank telescope in the United States, which is the largest directional radio telescope in the world.

“We have not detected any signals from an advanced civilization that would attempt to contact us with incredibly powerful instruments,” says Danny Price, astronomer at the SETI Research Center at the University of California, Berkeley. .

We analyzed thousands of hours of observations of nearby stars. We did not find any obvious evidence of extraterrestrial artificial signals. However, that does not mean that there is no intelligent life. We may not be looking at the right place or with enough precision!

Danny Price, astronomer at the SETI Research Center

The scientist does not lose hope of a possible communication of the third type. He argues that current research may be conducted at low frequencies, and radio interference from the Earth could also affect signal perception.

In addition, new telescopes will soon join the research effort, such as the MeerKAT Observatory in South Africa, which will help refine the analyzes.

We must also recognize that Homo sapiens are conducting this quest with the technological means they have developed over the scientific breakthroughs they are making. They may not have sophisticated instruments to get there.

One thing is certain, if scientists ever see such an extraterrestrial signal, it will have to be thoroughly analyzed to confirm its authenticity. In the process, humanity will achieve one of its greatest discoveries.

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A link between childhood viral infections and multiple sclerosis?

Nichole Kerr



There is a link between childhood viral infections and the development of multiple sclerosis in adulthood, say Swiss researchers.

Multiple sclerosis is considered an autoimmune disease whose severity and evolution are very different from one person to another. It attacks the central nervous system by targeting myelin, which is in a way the protective envelope of nerve fibers.

The deterioration of this substance causes inflammation, which in turn causes interruptions in the propagation of nerve impulses.

When the myelin is slightly deteriorated, the impulse is transmitted without too many interruptions, but when this deterioration increases, the nerve fibers are altered and become incapable of communicating.

Mysterious causes

So far, the causes of multiple sclerosis remain mysterious, and there is no cure for it.

Researchers associate its triggering with genetic and environmental components, but which exactly?


  • On average, 1 in 1,000 people have multiple sclerosis;
  • the disease is usually diagnosed in people aged 20 to 40 years;
  • northern countries are more affected than countries close to the equator;
  • Canada has the highest rate of multiple sclerosis in the world (about 1 in 400 cases).

The viral track

Prof. Doron Merkler and his colleagues from the Faculty of Medicine at the University of Geneva have studied in mice the potential link between transient cerebral viral infections that occurred in early childhood and the appearance of an autoimmune disease. cerebral immune later in life.

We wondered whether early childhood viral infections were among the possible causes.

Doron Merkler

Transient brain infections can be rapidly controlled by the immune system, even without the child’s noticing.

“But such a transient infection may, under certain circumstances, leave a local imprint in the brain, which could be characterized by inflammatory signature,” says Prof. Merkler.

Swiss scientists are therefore interested in this type of impression in young brains and the appearance of the disease years later.

They caused a transient viral infection in a group of adult mice and a group of mice that cleared the infection within a week, showing a similar antiviral response.

Then they let the two groups of rodents age and then transfer immune cells to brain structures called self-reactive cells that are found in a patient with multiple sclerosis.

Such cells may also be present in humans, without necessarily being associated with a disease, as they are controlled by different mechanisms and do not have access to the brain.

Karin Steinbach, Faculty of Medicine, University of Geneva
Their results show that :

in the group of mice infected with the virus in adulthood, autoreactive cells did not induce brain lesions;

in infected mice when young, self-reactive cells migrated to the brain at the precise location of infection and began to destroy their structures.
According to the researchers, the brain area struck in childhood undergoes a tissue modification that leads, years later, the immune system to turn against itself in this specific place, triggering autoimmune lesions.

T lymphocytes give the signal

When analyzing the tissues of the virus-infected area in the mice group, the researchers observed an accumulation of immune cells, memory-resident T cells in the brain tissue.

Normally, these are distributed throughout the brain, ready to protect it in case of viral attack. But here, these cells accumulate in excess in the precise place of the infant infection, changing the structure of the tissue.

Doron Merkler

They also found that this cellular accumulation produces a molecule that attracts self-reactive cells, opening them access to the brain.

They then start destroying their structures, causing multiple sclerosis.

In order to verify this observation, we blocked the autoreactive cell receptor that perceives the signal produced by the accumulation of memory T cells resident in the brain, and indeed, the mice have been protected from brain damage!

Doron Merkler

In humans

“We then looked at whether, in people with multiple sclerosis, we found this accumulation of memory T-cells residing in the brain tissue that produces the call signal to self-reactive cells, and that’s the case! Adds Karin Steinbach.

Scientists believe that such a mechanism could exist in humans. However, other work is needed to establish it.

We are continuing our research in this direction, particularly to understand why T cells accumulate in a child’s brain as a result of infection and do not occur in an adult.

Karin Steinbach

The details of this work are published in the journal Science Translational Medicine.

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Close-up of the Uranus rings

Bryan Nesbit



New Rare Images of the Uranus Rings have recently published

The image of Saturn comes quickly to mind when it comes to rings, but it is not the only planet in our solar system to have rings. Jupiter, Neptune and Uranus also have some, though they are more difficult to observe from Earth.

The rings around Uranus were only discovered in 1977, since they reflect very little light in the visible spectrum and are hardly observable in near infrared radiation.

However, new thermal images (heat) captured with the help of two observation instruments (the Very Large Telescope and the ALMA network) installed in the Atacama desert in Chile allow today to better identify these 13 rings around of the seventh planet of the solar system.

These thermal images allowed, for the first time, an American-British team of astrophysicists to estimate the average temperature of the rings around Uranus at 77 Kelvin, which corresponds to -196 degrees Celsius.

The data collected also confirm that Uranus’ brightest and densest ring, Epsilon, is very different from other known ring systems in our system.

The rings of Saturn, mainly glossy, are broad, shiny and composed of particles whose sizes vary from dust grains (in ring D) to blocks of tens of meters (in the main rings).

Imke de Pater, University of California at Berkeley

The paper is available to view on pre-publication archive arXiv.

But the rings of Uranus do not seem to have very fine particles. For example, the Epsilon ring is composed of rocks not smaller than a golf ball, but which can also reach larger dimensions.

Jupiter and Neptune both have very dusty rings, consisting mainly of fine particles. In comparison, the rings of Jupiter contain mostly small particles of the order of one micron (one micron is one thousandth of a millimeter). The rings of Neptune are also mainly composed of dust.

There is dust in orbit around Uranus, but it is between its rings.

The composition of the rings of Uranus is different from that of the main ring of Saturn. […]. They are really dark, like charcoal, and extremely narrow compared to the rings of Saturn.

Imke de Pater, University of California at Berkeley

“The widest ring, Epsilon, varies from 20 to 100 kilometers wide, while those of Saturn are 100 km or tens of thousands of kilometers wide,” adds Imke de Pater.

The details of this work are published in the journal The Astrophysical Journal.

During its final descent to Saturn in 2017, the Cassini spacecraft collected data, including hundreds of very high resolution images and various measurements taken using its many instruments. Scientists continue to analyze them today.

NASA’s Jet Propulsion laboratory scientists describe in a series of studies published in Science magazine complex elements sculpted by the gravitational interactions between Saturn’s moons and the particles present in its rings.

Specific textures and patterns are visible in the images, and raise questions about the interactions that shaped them. New maps also reveal how colors, chemistry and temperature move through the rings.

In addition, the results of one of these researches suggest that the rings of Saturn are relatively young, galactically, and would have formed 10 to 100 million years ago.

It has been established for several years that the icy little moon of Saturn, Enceladus, contains an underground ocean.

New research by US researchers at the University of Washington suggests that this ocean probably has a pH closer to that of the Earth than it was estimated today. In addition, the concentrations of carbon dioxide and hydrogen would also be higher than estimated.

It has been established for several years that the icy little moon of Saturn, Enceladus, contains an underground ocean.

New research by US researchers at the University of Washington suggests that this ocean probably has a pH closer to that of the Earth than it was estimated today. In addition, the concentrations of carbon dioxide and hydrogen would also be higher than estimated.

This new knowledge suggests that conditions are more favorable to microbial life than previous estimates.

Recall that in 2017, other work had detected hydrogen in a plume of steam emanating from cracks in the thick layer of ice Enceladus.

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