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Artist's impression of a megalodon compared with a shark underwater.

An artist’s impression of a megalodon — an extinct shark species — alongside a modern shark (right).Victor Habbick Visions/Science Photo Library/Getty

Microfossils reveal mysterious shark die-off

Up to 90% of the global shark population was wiped out in a mass extinction around 19 million years ago. Researchers identified the disappearance by studying microfossils in deep-sea sediment cores collected in the North and South Pacific oceans. After thriving for some 40 million years, shark numbers and diversity suddenly dropped and have not recovered since. “The sharks basically just disappeared overnight,” says palaeobiologist Elizabeth Sibert. The reason why this happened remains a mystery.

ABC News | 7 min read

Reference: Science paper

The human genome: filling in the blanks

Scientists are a step closer to completely sequencing the entire human genome. An international collaboration of researchers has worked out how some stretches of DNA containing many repeating letters (or base pairs) fit together, and discovered about 115 genes that code for proteins in the process. The newly sequenced genome adds nearly 200 million base pairs to the most recent human genome sequence, which researchers have used as a reference since 2013.

Nature | 4 min read

Completing the human genome: Chart showing number of base pairs sequenced since the year 200 up to a total of 3056,899,953.

COVID-19 coronavirus update

WHO approves eighth COVID vaccine

The World Health Organization (WHO) has approved a second Chinese vaccine for emergency use. CoronaVac, an inactivated-virus vaccine produced by Sinovac, based in Beijing, has a lower efficacy than do the other vaccines already listed by the WHO. But trials suggest that CoronaVac is highly effective at preventing severe disease and death. “CoronaVac will significantly contribute to the global fight against COVID-19 as a safe and moderately effective SARS-CoV-2 vaccine,” says clinical researcher Murat Akova.

Nature | 5 min read

Lax social distancing fuelled variant’s rise

The coronavirus variant behind Brazil’s ferocious second wave of COVID-19 emerged, in part, because of relaxed social distancing, according to an analysis of viral sequences from the outbreak’s epicentre. In late 2020, researchers first spotted the P.1 variant — also called Gamma — in people who returned to Japan from Manaus in Brazil’s Amazonas state. Genomic analysis found that P.1 rose with breathtaking swiftness in Amazonas and quickly replaced other circulating lineages. Its rise coincided with increased travel and contact. “You need these mutations combined with epidemiological factors, then you have the perfect storm,” says virologist Gonzalo Bello.

Nature | 4 min read

Reference: Nature Medicine paper

Nasal spray could provide protection

A nasal spritz of a designer antibody offers strong protection against variants of SARS-CoV-2 — at least in mice. Since the pandemic’s early days, scientists have been developing antibody treatments for COVID-19. But those available have not been very popular with doctors, partly because they are delivered through intravenous infusions rather than directly to the respiratory tract, so it takes high doses for them to be effective. Now, researchers have engineered an antibody that can be delivered directly into the nose. They envision the spray being used by people who have been exposed to the virus, and as an extra line of defence for those who might not be fully protected by vaccines.

Nature | 4 min read

Features & opinion

Biden’s new science adviser talks priorities

Geneticist Eric Lander has been sworn in as director of the White House Office of Science and Technology Policy after a months-long confirmation process. In a first for any US president, Joe Biden elevated the position to his cabinet, potentially granting Lander more access and influence than any US science adviser before him. Nature spoke to Lander on his first day in office about some of the goals he has been tasked with — including preparing for future pandemics, protecting research integrity and ensuring all Americans participate in and benefit from science.

Nature | 7 min read

Podcast: On the origin of numbers

Archaeologists, linguists and a host of other researchers worldwide are trying to answer some big questions — when, and how, did humans learn to count? Hear from some of the scientists at the forefront of this effort on this week’s Nature Podcast.

Nature Podcast | 18 min listen

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Image of the week

Researchers at Cornell University broke their own record for the highest-resolution image of atoms. They used a technique called ptychography to capture this close-up of atoms in a praseodymium orthoscandate crystal.Cornell University

Quote of the day

“It would be a very sad Earth if there weren’t elephants striding across it.”

A vast new database, The Elephant Ethogram, catalogues major insights into elephant behaviour and communication. (The New York Times | 9 min read)