2020-02-22_New_Scientist

16 | New Scientist | 22 February 2020

Animal behaviour

Quantum distance

record smashed

TWO clouds of atoms that store

quantum information, called

quantum memories, have been

connected across a longer distance

than ever before. They could prove

useful for one day building a

quantum version of the internet.

Quantum communication

relies on a phenomenon known

as entanglement. When a pair

of particles or systems are

entangled, measuring one

Signs of mystery

hominin in genes

FOUR West African populations

carry genes from what may be an

undiscovered archaic hominin.

Previous research has shown

that Homo sapiens bred with

Neanderthals and Denisovans

after migrating from Africa, but

little is known about the presence

of genes from ancient hominins

in people whose ancestors never

left Africa, partly because ancient

DNA can degrade in hot climates.

Sriram Sankararaman and Arun

Durvasula at the University of

California, Los Angeles, overcame

this by using a computer model to

compare gene variations in 405

West African genomes with those

in Neanderthal and Denisovan

genomes. They looked at both

modern and ancient segments

within the genomes of Yoruba

people from Ibadan, Nigeria. They

found more instances of genetic

variation in the ancient segments

Ancient humans^ Physics

YOU know not to poke a jellyfish,

but some jellies can sting without

even touching you – by detaching

tiny bits of their body that float

off and move independently.

Upside-down jellyfish jettison

small balls of stinging cells in a

sticky mucus to kill prey such as

shrimp. The jellies then seem to

suck in their dinner by pulsating.

It is as if we could spit out our

teeth and they killed things for

us somehow, says Cheryl Ames

at Tohoku University in Japan.

“It’s a real evolutionary novelty.”

Species of upside-down jellyfish

of the genus Cassiopea, such as

C. xamachana (pictured), live in

warm coastal waters such as those

off Florida, Australia and the Red

Sea. Their sting isn’t generally seen

as dangerous, but there have been

reports from people of “stinging

water” in the vicinity of the animals.

Ames’s group has found that

this happens because the creatures

shed hollow balls of stinging cells

up to half a millimetre wide. Dubbed

cassiosomes, they can move in

circles to boost their chances of

bumping into prey.

The jellies released cassiosomes

and mucus when brine shrimp, their

natural prey, were put in their tank.

The cassiosomes killed the shrimp

in under a minute (Communications

Biology, doi.org/dmnt). In the wild,

the dead shrimp are then sucked

into the jellies’ feeding pores by

their pulsating motions.

These jellies tend to float at the

bottom of coastal lagoons, and

extend their networks of mucus to

float above them. The mucus may

not be easily visible to swimmers,

says Ames. Clare Wilson

Upside-down jellyfish sends

out tiny jelly drones to kill

of them seems to influence

the measured state of the other

instantly, regardless of their

distance. This can be used to

create an encrypted channel.

Individual photons have

been entangled across distances

exceeding 1000 kilometres, but

for larger systems of particles,

which hold more information,

maintaining this entanglement

is harder. The maximum distance

between entangled quantum

memories had been 1.3 kilometres.

Xiao-Hui Bao at the University

of Science and Technology of

China and his team have smashed

that record, entangling quantum

memories over 22 kilometres of

underground fibre-optic cable.

Their quantum memories were

each made of about 100 million

extremely cold rubidium atoms in

a vacuum chamber. The quantum

state of each system of atoms was

entangled with the state of a single

photon, and the photons sent

through the cables (Nature,

doi.org/ggkrvj). Leah Crane

than are seen in Neanderthal and

Denisovan genes, suggesting that

neither of these groups of ancient

humans were the source of the

genomic variance.

Similar patterns were seen in

the genomes of Mende people

in Sierra Leone, Esan people in

Nigeria and those in western areas

of Gambia. The four populations

are estimated to derive between

2 and 19 per cent of their ancestry

from an archaic group of genes.

We don’t know whether this

archaic hominin is a “ghost”, for

which we have no physical record,

or one we have traces of already,

such as Homo heidelbergensis.

The mystery hominin probably

diverged from the ancestors of

Neanderthals, Denisovans and

modern humans before that

lineage split into these groups,

say the researchers. Interbreeding

between this unknown hominin

and ancestors of the modern

populations occurred in the past

124,000 years (Science Advances,

doi.org/dmn6). Bethan Ackerley

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