2021-01-16 New Scientist

16 | New Scientist | 16 January 2021

OUR primate ancestors might

have become “protomusical”

to advertise their ability

to perform death-defying

leaps from tree to tree.

Why humans make and

appreciate music is an

evolutionary mystery. “Music

is a hugely important part of

our lives and often involves

powerful emotions,” says

Edward Hagen at Washington

State University. But he says

we still don’t fully understand

why it has this hold over us.

David Schruth at the

University of Washington

and his colleagues have a new

explanation. They say the roots

of human music can be traced

back to the branches of trees

more than 50 million years

ago, when the first primates

appeared. Fossil evidence

suggests that those early

primates moved around the

forest canopy by leaping from

branch to branch, a perilous way

to travel that relies on extremely

good hand-eye coordination

and muscular control.

Schruth’s team argues that

early primates would have

benefited if they could judge the

acrobatic skills of their peers and

identify suitable mates or avoid

territorial confrontations with

more accomplished leapers.

Singing might have helped.

Put simply, a primate that calls

in an elaborate, musical way

is advertising that it has fine

control over its vocal cord

muscles. Schruth’s team says

this might have convinced other

primates that the caller also had

fine control over its limbs.

To test the idea, the team

assessed the musicality – for

instance, the tone and the

rhythm – of 830 acoustic calls

by more than 50 living primate

species, and examined data

on how often the species leap

and swing from branches.

The species that leap and swing

the most tend to have more

complicated calls, which the

team dubbed as “protomusical”

(bioRxiv, doi.org/ghrd89).

Schruth prefers not to

discuss the work until it has

undergone peer review.

Whether the research adds to

our understanding of the origin

of music depends on how we

define the term, says Hagen,

who wasn’t involved in the

study. “Some people would

exclude what we see in primates

and songbirds as music,” he

says. “Others, and I’m one

of them, do see a continuity

between human music and

primate vocalisations.”

Hagen doesn’t think human

music has a single, simple

explanation. Last year, he

and his colleagues argued that

our human ancestors originally

used music-like vocalisations

in two ways: groups vocalised

together to send a signal

of strength and unity to

intimidate outsiders, and

mothers used solo vocalisations

to communicate with infants.

A different paper published

last year presented yet another

idea: that humans used music

to forge social bonds.

All these ideas might be

compatible, says Hagen.

Protomusic could have evolved

in primates both to attract

mates and for territorial

signalling. Later, as early

humans began cooperating

in larger numbers, protomusic

might have been repurposed

so it could attract rather than

frighten outsiders, while also

strengthening social bonds

within groups. This would help

explain how our music can

stir such a range of emotions

and why it is so much more

sophisticated and complex than

the songs of other species. ❚

BLACK holes may be cosmological

engines. When their magnetic fields

disconnect and reconnect, they can

accelerate plasma particles near the

event horizon – the point beyond

which nothing can escape a black

hole’s gravitational pull.

We expect black holes to spin

because they are formed out of a

collection of matter that is spinning

before it condenses. Around

a spinning black hole, there are

magnetic fields, which are dragged

along and can influence the

direction of matter falling towards

the event horizon. These provide

the power to the engine.

Luca Comisso at Columbia

University in New York and Felipe

Asenjo at Adolfo Ibáñez University

in Chile analysed the effect of those

magnetic fields on plasma particles

near the event horizon. Some

particles are accelerated by

the breaking and rejoining of

magnetic field lines, and others

are decelerated, acquiring “negative

energy”. A black hole can drag

space-time – the fabric of space

itself – along with it, flinging some

particles away while others pass

the event horizon and fall into

the heart of the black hole.

When the black hole swallows

the decelerated plasma particles

and the accelerated particles escape,

the black hole’s energy decreases,

say Comisso and Asenjo (arxiv.org/

abs/2012.00879). “It is because of

this strong rotation of the space-

time very close to the event horizon

of the black hole that particles can

take a negative energy value,” says

Comisso. “It’s similar to a person

eating candies with ‘negative

calories’ and losing weight.”

Roger Blandford at Stanford

University in California says this

finding could help us understand

the full picture of how black holes

lose energy, and how magnetic

fields lead to the jets of matter and

energy seen around black holes. ❚

Do an orangutan’s

calls advertise

its abilities?

Astrophysics Evolution

Robert Lea Colin Barras

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News

“Species that leap

and swing the most

tend to have more

complicated calls”

Origins of music linked

to daredevil behaviour

Black holes leak

energy when they

eat nearby plasma