Fossils flesh out the tale of the first primates

The shapes of fossilized teeth from 65.9 million-year-old, squirrel-like creatures suggest that the branch of the tree of life that gave rise to us humans and other primates flowered while dinosaurs still walked the earth. That’s the claim coming from a team of 10 researchers across the U.S., including biologists at Seattle’s Burke Museum and the University of Washington.

In a study published by Royal Society Open Science, the team lays out evidence that an ancient group of primates known as plesiadapiforms must have emerged before the mass-extinction event that killed off the dinosaurs. (Technically, modern-day birds are considered the descendants of dinosaurs, but that’s another story.)

The evidence comes from an analysis of tooth fossils that were unearthed in the Hell Creek area of northeastern Montana.


Scientists trace coronavirus’ roundabout route

A transmission electron microscope image shows SARS-CoV-2, the virus that causes COVID-19, isolated from a patient in the U.S. Virus particles are emerging from the surface of cells cultured in the lab. The spikes on the outer edge of the virus particles are key to their ability to infect human cells. (NIAID-RML Photo)

Two newly published studies shed light on the origins and spread of the coronavirus pandemic, starting with bats and pangolins in China and ending up with New York’s dramatically deadly outbreak.

One study, published today in the open-access journal Science Advances, analyzed 43 genome sequences from three strains of coronavirus similar to the one that causes COVID-19 in humans. These strains were identified in bats and in pangolins, anteater-like animals prized for their scales. The two pangolins that yielded samples of coronavirus were smuggled into China and seized by customs officials.

The type of coronavirus that has caused the human pandemic, SARS-CoV-2, is more similar to bat viruses than to pangolin viruses. But a key piece of genetic material, relating to the ability of the SARS-CoV-2 spike protein to bind itself to human cells, was identified in pangolin viruses but not in bat viruses.

None of the viruses that were studied is likely to be in the direct line leading to the virus that made the leap to humans, but their diversity suggests that SARS-CoV-2 went through cross-species evolution before making the leap to humans.

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Scientists debate coronavirus evolution

Coronavirus transmission map
A graphic generated by Nextstrain shows how different variants of the SARS-CoV-2 coronavirus have spread around the world. Purple streaks show where the virus was transmitted from China, green and yellow-green streaks show transmission from Europe, and red streaks show transmission from the United States. ( Graphic)

Is the coronavirus behind COVID-19 turning into a more insidious pathogen? Or are such claims overblown?

A fast-moving debate over virus evolution illustrates how not-yet-vetted reports about the course of the coronavirus outbreak can go, um, viral — and how important social media channels have become in the global discussion of the science behind the pandemic.

The nature of SARS-CoV-2, the virus that causes COVID-19, is of such great interest because the disease is so deadly and disruptive: As of today, Johns Hopkins University reports nearly 3.7 million confirmed cases around the world, with a global death toll of more than 250,000. The United States accounts for 1.2 million cases and 71,000 deaths so far, and that toll could double before the worst is over.

Every day, several hundred new studies about SARS-CoV-2 and COVID-19 — most of which haven’t yet gone through the traditional peer-review process — go online, to face scrutiny by researchers and a wide swath of the general public.

One study got more than the usual traction today: The research project, led by scientists at Los Alamos National Laboratory and the University of Sheffield, looked at the way 14 variants of the virus have spread across the world.

The resulting paper was filed to the BioRxiv preprint server last week but has not yet been peer-reviewed. It concluded that one particular variant known as D614G is “of urgent concern.” That variant, a descendant of a form of the virus that started out in China, began spreading in Europe in early February and eventually made the leap to other parts of the world.

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Proteins are ‘bred’ to bond silicon and carbon

Silicon-based life
An artist’s conception shows a fanciful view of organosilicon-based life. (Lei Chen and Yan Liang / for Caltech)

Using directed evolution, researchers say they’ve “bred” protein molecules from an unusual type of bacteria to create chemical bonds between silicon atoms and carbon atoms efficiently.

Chemists have been able to do that in the lab, but it’s not been done biologically before.

“No living organism is known to put silicon-carbon bonds together, even though silicon is so abundant, all around us, in rocks and all over the beach,” Caltech researcher Jennifer Kan, the lead author of a report on the experiment published in the journal Science, said in a news release.

Silicon is the second most abundant element in Earth’s crust (after oxygen), and the idea of living organisms based on silicon rather than carbon has been a science-fiction standard for decades. The best-known example is the Horta, the rock-eating creature on the planet Janus VI in the original “Star Trek” TV series.

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Supernovae spread radioactive fallout on Earth

Image: Supernova
An artist’s impression shows a supernova explosion in its prime. (Credit: Greg Stewart / SLAC)

Researchers say they’ve found evidence of supernova explosions that spewed radioactive fallout over Earth during the age when humanity’s ancestors were evolving into upright-walking, big-brained creatures.

One of two studies published in the journal Nature identifies deposits of radioactive iron-60 in deep-sea cores extracted from the bottom of the Indian, Pacific and Atlantic oceans. The deposits were traced back to one time frame ranging from 1.5 million to 3.2 million years ago, and another period 6.5 million to 8.7 million years ago.

The researchers behind that study, led by Anton Wallner of Australian National University, say the iron-60 was blasted toward us by “multiple supernova and massive-star events” that occurred within 325 light-years of Earth.

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Scientists take gorilla genome to next level

Image: Susie the gorilla
Researchers sequenced and assembled an updated gorilla genome using a DNA sample from a gorilla named Susie. (Credit: Lincoln Park Zoo)

A team led by University of Washington researchers has taken a second turn at sequencing the gorilla genome, putting together puzzle pieces that didn’t match up the first time around.

The results are likely to bring about revisions in the evolutionary tale of the western lowland gorilla, and where it fits in the primate family tree that includes us humans.

“I believe there is far more genetic variation than we had previously thought. The first step is finding it,” UW geneticist Evan Eichler, the senior author of a research paper on the project published by the journal Science, said in a news release.

One of the co-authors from UW, Christopher Hill, told GeekWire in an email that the new research is part of an effort to create a comprehensive catalog of the genetic differences between humans and other great apes.

“The differences between species may aid researchers in identifying regions of the human genome that are associated with cognition, behavior and neurological diseases,” Hill said. “Having complete and accurate reference genomes to compare allows researchers to uncover these differences.”

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