New Scientist - USA (2022-06-04)

22 | New Scientist | 4 June 2022

Wildlife

THE rarest seal species in the

world started its population decline

millennia ago, possibly due to the

rise of ancient human civilisations.

Mediterranean monk seals

(Monachus monachus) are very

endangered. Once widespread

throughout the Mediterranean

Sea, Black Sea and warmer North

Atlantic coastlines, there are

currently only a few hundred

left in disjointed populations.

Previous research has shown

that these groups have low genetic

variation, leaving them susceptible

to disease and other threats.

But it wasn’t clear precisely how

these seals became so vulnerable.

Jordi Salmona at the Paul

Sabatier University in France and his

colleagues sought to answer this by

delving into the animals’ genetics.

They collected DNA from samples of

the skin, hair, faeces and bones

of 383 monk seals, from both

current and extinct populations.

After analysing the DNA, they used

models to infer the timing of past

drops in the number of seals and

their genetic diversity.

They found many monk seal

populations shrank to a tenth or

less of their original size between

800 BC and AD 600 – a period

that saw the rise of civilisations

and widespread seafaring in the

Mediterranean basin.

The researchers suspect that

hunting by people may have baked

diminished genetic diversity into the

future of the seals. The team points

to the Roman Empire’s exploitation

of wildlife at this time, which we

know led to localised extinctions

of other species (bioRxiv, doi.org/

hwjd). Jake Buehler

Romans may have set rare

seals on the path to peril

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News In brief

A WEATHER satellite may have

solved the mystery of why the star

Betelgeuse briefly lost its shine.

In late 2019, the red supergiant

star, which is about 550 light years

from Earth, suddenly became a

lot fainter, an event known as

the Great Dimming.

Previous research had

suggested a cloud of dust and a

cool spot on the star may have

been the cause. Daisuke Taniguchi

at the University of Tokyo, Japan,

now believes we know for sure

thanks to an unlikely source: a

satellite designed to monitor

weather on our planet.

The satellite – Himawari-8 –

is used to observe weather in

Japan and nearby regions from

a geostationary orbit nearly

36,000 kilometres up. However,

it also occasionally sees stars

appear beyond the edges of Earth –

including Betelgeuse once per day.

Astronomy^

Taniguchi used publicly

available data from the satellite to

get regular infrared observations

of the star from 2017 to 2021. These

allowed him to confirm the cause

of the Great Dimming, which

ended in early 2020. There was

indeed a cloud of dust, picked

up by the satellite’s instruments,

and the temperature of the star

also dropped by 140°C (Nature

Astronomy, DOI: 10.1038/s41550-

022-01680-5).

The cause of the dust isn’t clear.

It may have been a shockwave in

the star that expelled gas that then

condensed into dust. This could

also explain the cooling of the star,

although it isn’t yet certain if the

events were related.

Taniguchi already has plans to

use Himawari-8 to observe more

stars, to examine their evolution

and dust production, and other

weather satellites could be useful

too. “I hope after the publication

of this paper, other satellites will

publicly open their data,” he says.

Jonathan O’Callaghan

Stellar puzzle settled

by an unlikely source

PEOPLE with a high genetic risk for

dementia can reduce their chance

of developing the condition via a

healthier lifestyle, a study suggests.

Adrienne Tin at Johns Hopkins

University in Maryland and her

team used data from more than

11,000 people in the US. They had

an average age of 54 at the start of

the study and were followed, on

average, for 26 years. Of these,

8823 were of primarily European

Health

descent and 2738 primarily African

descent. Each was scored on seven

health factors: smoking, diet,

weight, physical activity, and

control of blood sugar, cholesterol

and blood pressure.

Changes to these factors,

promoted as “Life’s Simple 7”, are

known to maintain good heart

health. Previous studies have

shown this can also cut the risk of

developing dementia, says Tin. In

the study, the team wanted to see

if this was still true for those most

at risk of dementia due to genetics.

The researchers assessed each

person’s genetic risk for dementia

and found that people of primarily

European descent in the highest

genetic risk group could cut their

dementia risk by 8 per cent for

each point they increased their

healthy lifestyle score on a 14-point

scale (Neurology, doi.org/hwjr).

They saw similar results for people

of primarily African descent, but

the smaller sample size means that

conclusion is less certain, says Tin.

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Lifestyle can counter

genetic dementia risk