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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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