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Women outside traditional swahili house, Matemwe, Zanzibar, Tanzania.

Women in Lamu Island, Kenya — home to a Swahili coast settlement that dates to the medieval period.Credit: Michael Heffernan/Getty

Ancient DNA illuminates Swahili origins

Genomes point to the diverse origins of Swahili culture, with people carrying a mix of local African, Middle Eastern and South Asian ancestry. Researchers analysed the genomes of 54 individuals buried in Kenya and Tanzania between 1250 and 1800 and found that they were descended from people who began mixing around 1000. Nearly all the East African ancestry seemed to come from women, whereas most of the Asian ancestry was contributed by men from Persia. The results support the oral traditions of Swahili people and dispel the colonial idea that Swahili civilization is “essentially an Arab civilization”, says anthropological archaeologist Chapurukha Kusimba, who co-led the study.

Nature | 5 min read

Reference: Nature paper

Alarm over exercise for long COVID

Advocates say a trial of exercise as a treatment for long COVID, proposed by the US National Institutes of Health (NIH), could harm participants. A large proportion of people with long COVID, which affects up to 23 million people in the United States, experience post-exertional malaise — a worsening of symptoms such as fatigue, difficulty regulating body temperature and cognitive dysfunction — after even light exercise. The NIH said the exercise trial would use “criteria to make sure that people who could be harmed by exercise will not be included”.

Nature | 6 min read

Luque cites ‘envy’ in 13-year suspension

One of the world’s most-cited scientists, chemist Rafael Luque, has been suspended without pay for the next 13 years from the University of Córdoba in Spain. Luque is being punished for working at institutions in Saudi Arabia and Russia while holding a full-time publicly funded contract with Córdoba. Luque says the university has “shot themselves in the foot” because its place in international rankings will plummet without his output (he has published 58 papers so far this year alone). “They have a grudge against me because I am a very prolific scientist and a lot of people adore me,” he says. “They are envious and mediocre people.”

El País | 6 min read

535 times less

An estimation of the mass of minerals, such as lithium, copper and cobalt, that will need to be mined each year by 2040 to support a green-energy economy, compared with the mass of fossil fuels mined each year now. (Distilled | 5 min read)

Features & opinion

Split-site doctorates boost African research

University partnerships in which African PhD students split their time between institutions inside and outside the continent are helping to build Africa’s research base. Africa needs another one million doctoral scholars to catch up with the international average for researchers per capita. Joint programmes that tap into into expertise, mentorship and supervision from elsewhere are beneficial for both sides — but there are not enough of them to meet demand.

Nature | 11 min read

Define marine heatwaves properly now

Marine heatwaves devastate ecosystems and the coastal communities that rely on them, costing billions each year. But the language around them is confusing, argue 16 members of the US National Oceanic and Atmospheric Administration Marine Ecosystem Task Force. One crucial difference must be clarified, they say: extreme conditions compared with historical temperatures, and extreme conditions compared with an evolving ‘new normal’ of rising temperatures owing to climate change. “Duelling definitions mean that headlines such as ‘marine heatwaves are getting more frequent’ and ‘marine heatwaves are not getting more frequent’ can be simultaneously true,” they write.

Nature | 10 min read

Image of the week

A composite of six images of a sleeping doormouse on a black background, showing the fur shining under UV light

Credit: Karmel Ritson and Grete Nummert

Researchers at Tallinn Zoo have found that hibernating garden dormice (Eliomys quercinus) glow under ultraviolet light — their fur transforms from brown (left) to bright purple (middle). If the UV light passes through a yellow filter, the mice appear bright red, with blue-green feet and noses (right). The phenomenon — called photoluminescence — could allow the rodents to signal to each other or to avoid predators by blending in with certain plants. Or it could just be a side effect of something they ate — no one is really sure. (Reference: Zoology paper)

See more of the month’s sharpest science shots, selected by Nature’s photo team.

Quote of the day

“I’m calling you on a cell phone, but a real cell phone, a personal, handheld, portable cell phone.”

Motorola engineer Martin Cooper made the first public call from a mobile 50 years ago today — and chose to phone up his rival, Bell Labs chief Joel Engel. (CNN | 5 min read)