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Chimera Blastocyst

A blastocyst of the monkey–human chimaeras.Credit: Weizhi Ji, Kunming University of Science and Technology

Monkey–human embryos reignite debate

Scientists have successfully grown monkey embryos containing human cells for the first time. Researchers injected cynomolgus monkey (Macaca fascicularis) embryos with human stem cells and observed the human and monkey cells divide and grow together in a dish. At least 3 embryos survived to 19 days after fertilization. Human–animal hybrids — known as chimaeras — might someday provide better models for drug testing, or they could be used to grow human organs for transplants. But the latest work has divided developmental biologists because it uses non-human primates. “There are much more sensible experiments in this area of chimaeras as a source of organs and tissues,” says developmental biologist Alfonso Martinez Arias. Experiments with livestock animals, such as pigs and cows, are “more promising and do not risk challenging ethical boundaries”

Nature | 5 min read

How many T. rex ever existed?

Over the 2 million or so years during which the species existed, 2.5 billion Tyrannosaurus rex roamed Earth. Palaeontologists used a method employed by ecologists studying contemporary creatures to estimate the population density of T. rex during the late Cretaceous period. The figure has allowed researchers to estimate just how exceedingly rare it is for animals to fossilize. “You hold a fossil in your hand and you know it’s rare. The question is, how rare?” says palaeontologist Charles Marshall. “To know that, you need to know how many of them existed.”

Nature | 4 min read

Reference: Science paper

NAS weighs first ejections for harassment

The US National Academy of Sciences (NAS) is considering withdrawing, for the first time, the life membership of two scientists because of sexual harassment. Science reports that the NAS is investigating whether astronomer Geoffrey Marcy and evolutionary biologist Francisco Ayala violated the organization’s code of conduct. To kick off the process, the NAS requires that someone registers a complaint; a French computational chemist did so after reading in Nature that no one had used the complaint system put in place in 2019, even though several academy members are known sexual harassers.

Science | 5 min read

Read more: The US National Academy of Sciences can now kick out harassers. So why hasn’t it? (Nature | 6 min read, from September)

COVID-19 coronavirus update

Curbing vaccine disinformation

In March, Twitter put its foot down: users who repeatedly spread false information about COVID-19 vaccines will have their accounts suspended or shut down. It was a new front in a high-stakes battle over misinformation that could help to determine how many people get vaccinated, and how swiftly the pandemic ends. The battle is also being fought in computer-science and sociology laboratories across the United States, where scientists who track the spread of false information on social media honed their skills during the US presidential election last year. They are now shifting focus from false claims that the election was ‘stolen’ to untruths about COVID-19 vaccines.

Nature | 5 min read

Brazil is losing babies to COVID-19

The heartrending story of one family’s loss begins a BBC story that digs into why so many infants are dying of COVID-19 in Brazil. The disease very rarely kills young children, but 1,300 babies in Brazil have died from the virus. Runaway infections, a lack of political will, a health-care system at its breaking point, a dearth of tests and deep-set socioeconomic inequality are all factors.

BBC | 10 min read

Features & opinion

This is what a cleaner world looks like

Lockdowns dramatically reduced emissions and air pollution — as illustrated in eye-opening before-and-after photographs of cities in India and China. Atmospheric scientists rushed to gather data from satellites and air-monitoring stations to map how cleaner air could benefit human health — including the risk of severe COVID-19. “As air-quality researchers, we are always wondering if we will benefit or not from reducing emissions — nobody really knows,” says atmospheric scientist Fei Liu. “Before the pandemic, we just did simulation. This time, it really happened.”

Chemistry World | 10 min read

‘If I could travel in time’ by Zed 5755

Inspired by the quirks of student essays, author Jessy Randall imagines a young person’s view of our time from the far future in the latest short story for Nature’s Futures series. The result is funny, relatable and a little bit heartbreaking.

Nature | 4 min read

Podcast: The US sanitation crisis

A surprising number of people in the richest country in the world live without access to adequate sanitation. Environmental-health advocate Catherine Coleman Flowers tells the Nature Podcast about her new book, Waste, which looks at the roots and consequences of this crisis. She focuses on Lowndes County, Alabama — an area inhabited largely by poor Black people — where an estimated 90% of households have failing or inadequate wastewater systems.

Nature Podcast | 18 min listen

Read more: Toilets – what will it take to fix them? (Nature | 6 min read)

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Where I work

Phd student Hannah Franklin photographed at the Francis Crick Institute, London.

Hannah Franklin is a PhD student in neuroscience at University College London, and is based at the Francis Crick Institute.Credit: Leonora Saunders for Nature

Hannah Franklin is a PhD student in neuroscience and a volunteer vaccinator at the Francis Crick Institute in London. “Knowing how viruses mutate can make you feel less positive about tackling the COVID-19 situation, but the Crick is doing a fantastic job,” she says. (Nature | 3 min read)

Quote of the day

“There is a long-standing and well-established distinction drawn between fundamental and classified research. Short of pursuing a policy of complete academic decoupling from China, blurring the lines between these two modes of operation risks putting far too many innocent researchers in harm’s way.”

The US Department of Justice’s ‘China Initiative’ is unfairly targeting scientists of Chinese descent for their alleged ties with the Chinese government, argues a Nature Physics editorial.