New Scientist - USA (2019-11-09)

16 | New Scientist | 9 November 2019

Zoology

Brainwaves help

take out the trash

AS YOU sleep, slow waves of

electrical activity in your brain

seem to help rinse away waste

products that could harm cells.

This may play a role in preventing

conditions such as Alzheimer’s.

Brainwaves are made by large

networks of brain cells firing

together in rhythm, but much

about their function is unclear.

To see if they play a role in cleaning

the brain, Laura Lewis at Boston

Ötzi’s attempt to flee

his pursuers charted

MOSS buried alongside Ötzi the

Iceman bolsters the theory that

his last journey was through a

gorge, possibly fleeing someone.

The well-preserved 5300-year-

old mummified body was found

in the Alps on the border of Italy

and Austria in 1991. His demise

was gruesome: he probably bled to

death after being hit by an arrow.

Now James Dickson at the

University of Glasgow, UK, and his

colleagues have used thousands of

fragments of moss and liverwort

buried alongside or inside Ötzi to

understand his final days.

The plants were from at least 75

different species, only 23 of which

live in that precise area today. One

of the most intriguing discoveries

was of the bog moss Sphagnum

affine in Ötzi’s colon. This moss

is typically found in wetlands and

probably came from the bottom

of the Vinschgau valley in South

Ancient humans Neuroscience

FEMALE Asian elephants stop

reproducing towards the end of

their lives, putting them among

the few species that experience

something akin to the menopause.

Only humans, orcas, narwhals,

beluga whales and short-finned

pilot whales are known to exhibit

what biologists call extended

post-reproductive lifespan.

The existence of such a stage

is an evolutionary riddle: why

should individuals give up trying

to leave more descendants?

Now Asian elephants have been

added to the list, thanks to Simon

Chapman at the University of Turku,

Finland, and his team. They studied

records of 3802 female elephants

used in timber camps in Myanmar

between 1940 and 2018. Their

mortality and fertility patterns are

like those of wild Asian elephants.

The oldest in this group lived into

their 70s, but most had their last

calf by 55. The team calculates that

the proportion of years lived by

females in a post-reproductive

phase is 16 per cent: some way

short of humans’ 43 per cent but

considerably more than African

elephants’ 4 per cent (BMC

Evolutionary Biology, doi.org/ddhj).

In elephants, halting reproduction

may be behavioural rather than

physiological, says Chapman. Such

behaviour could be a step towards

evolving a true menopause.

One idea to explain menopause is

the grandmother hypothesis. It says

that if older females help care for

grandchildren, they end up with

more descendants than by having

more children of their own. There is

some evidence for this in the Asian

elephants studied. Sam Wong

Elephants found to have

menopause-like stage of life

University, Massachusetts,

and her team used EEG caps to

measure electrical activity in the

brains of 13 people while they

napped inside MRI scanners.

They also monitored blood

oxygen levels (in red, pictured)

in their brains and the flow

of cerebrospinal fluid, a watery

liquid that surrounds the brain

and spinal cord. The team found

that, during sleep, large waves of

cerebrospinal fluid flow into and

out of the brain every 20 seconds,

a process thought to remove

waste. The inward flow was

preceded by patterns of slow

waves of electrical activity.

These brainwaves coincided

with blood flowing out of the

brain, which the team says helps

balance the total volume of fluid

around the brain (Science,

doi.org/ddmr).

People with Alzheimer’s have

fewer slow brainwaves, says Lewis.

However, it isn’t clear whether this

is a cause or a symptom of the

condition. Layal Liverpool

Tyrol, Italy. Some people believe

this was Ötzi’s home as an adult.

The moss had long been used

for staunching wounds because

of its mild antiseptic properties.

It may have been used to treat a

deep wound he received to his

right palm possibly 48 hours or

less before his death, says Dickson.

Dickson was also surprised

to find fragments of the moss

Neckera complanata in his

intestines, a low-altitude moss

of the woodlands. Ötzi was found

at 3200 metres above sea level,

which is way above the treeline.

This suggests Ötzi travelled

from the forests below, possibly at

1200 metres but maybe as low as

600 metres above sea level, and

went north up a gorge (PLoS ONE,

doi.org/ddhp).

“It seems puzzling that he took

the most stressful track through a

gorge, but considering scenarios

that he was on the run, a gorge

provided most opportunities to

hide,” Dickson and his colleagues

write. Ruby Prosser Scully

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