14 | NewScientist | 3 May 2014

JOIN them or beat it. Hunter-gatherer groups didn’t adopt farming in Europe, but were instead displaced by farmers or joined their groups.

That’s the suggestion from a genetic analysis of the remains of 11 Stone Age individuals who lived between 5000 and 7000 years ago.

One theory of how farming spread globally is that hunter-gatherers were converted to an

agricultural way of life as they encountered farmers. The latest findings tell a different story.

Pontus Skoglund of Uppsala University in Sweden and his colleagues sequenced the DNA of four Stone Age farmers and seven hunter-gatherers – and found deep-rooted genetic differences. “It is quite clear that the two groups were very different,” he says. He thinks the farmers were

so successful that they displaced hunter-gatherers as they spread across the continent.

The data also showed the farmers had a small amount of hunter-gatherer DNA. This suggests that as the farmers swept north, they bred with some hunter-gatherers and assimilated them into their cultures (Science, doi.org/sh3).

The exchange seems to have been unidirectional: there is scant evidence that farmers joined the hunter-gatherer groups.

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Not you again: sweat of male scientists stresses lab mice

UH-OH. Lab rats and mice get more stressed out by male

researchers than by females. The finding could mean that

thousands of behavioural experiments have overlooked

an important factor affecting their results.

Jeffrey Mogil, a neuroscientist at McGill University in

Montreal, Canada, noticed that mice seemed to respond

to pain differently in his experiments than in those of a

female colleague. To investigate, he and his team gave

pain-inducing injections to anaesthetised mice and rats.

When the animals awoke, the team recorded their facial

grimaces, a measure of pain intensity.

When a man sat in the room with the rodents, they

grimaced less than with a woman. This reduced pain

sensitivity is a side effect of stress, as it allows for the

preparation of the fight or flight response.

The animals also showed reduced pain responses

when T-shirts worn by men were near their cages, but

not when those worn by women were. Mice exposed to

the male T-shirts also stayed closer to the walls – a sign

of fear – when placed in a new environment (Nature Methods, DOI: 10.1038/nmeth.2935).

The animals are probably reacting to odours that could

signal a strange male of their own species. Male humans

activate the response because they produce the same

mammalian scent molecules. This may explain why it is

often difficult to replicate biomedical studies, says Mogil.

Farming didn’t interest hunter-gatherers

Smoke ring clue to solar wind origins

WHAT has the sun been smoking? Patterns in the sun’s atmosphere that resemble smoke rings may help unravel what drives the solar wind, the stream of charged particles filling the solar system.

A team led by Miloslav Druckmüller at the Brno University of Technology in the Czech Republic took multiple photographs of several recent solar eclipses, when the sun’s atmosphere, or corona, was visible as a halo around the blacked-out sun. The team superimposed many shots for each eclipse.

Structures in the corona had been spotted before, but the new images allowed the researchers to link the smoke rings, plus other shapes, to eruptions on the sun’s surface called solar prominences.

This connection seems to show that prominences create coronal disturbances big enough to boost the solar wind (The Astrophysical Journal, doi.org/shx).

The anti-appetite molecule in fibre

A LITTLE fibre goes a long way. Gary Frost at Imperial College

London has found that mice on a high-fat diet gained weight less rapidly if fibre was added to their food. They used scanners to track what happens to acetate – a fatty acid produced in the gut – when fibre is broken down.

Rather than just travelling to the liver to be metabolised, the acetate also made its way to the brain, where it settled in the hypothalamus – a region of the brain that helps control hunger. Injecting acetate into the brain also curbed rodents’ appetites (Nature Communications, DOI: 10.1038/ncomms4611).

If acetate does the same in humans, eating more fibre could curb appetites and battle obesity.

IN BRIEF