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8 | New Scientist | 22 February 2020

CHINA’s Wutai mountains may
contain the earliest fossil evidence
of an evolutionary milestone: the
moment that complex eukaryotic
life appeared on Earth.
Eukaryotes have large cells
with complex internal structures.
While the first eukaryotic
organisms were all single-celled,
they gave rise to all multicellular
life – including fungi, plants
and animals.
Leiming Yin at the Nanjing
Institute of Geology and
Palaeontology in China and his
colleagues found the fossils in
a set of rocks called the Hutuo
Group in the Wutai mountains.
Previous studies have shown
that the rocks were laid down
between 2.15 and 1.95 billion
years ago.
In total, the researchers found
eight kinds of microfossil: four are
bacteria, two couldn’t be identified
and two appear to be eukaryotes.
Of these two, one appears to
belong to a known genus of
eukaryotes called Dictyosphaera.
There were also six specimens
of a new genus that the team

has dubbed Dongyesphaera.
Both types of fossil have roughly
spherical cells with multilayered
outer walls and visible spines –
all features that the team says
suggests they are eukaryotes,
not bacteria (Precambrian
Research, doi.org/dmsf).
Experts contacted by

New Scientist gave the fossils a
cautious welcome.
It is plausible that they are
eukaryotes, says Małgorzata
Moczydłowska-Vidal at Uppsala
University in Sweden.“I could go
for them being eukaryotic,” says
Anette Högström at the Arctic
University of Norway in Tromsø.
However, the identification
is solely based on the shapes of
the fossils, says Yuangao Qu at
the Institute of Deep-sea Science
and Engineering at the Chinese
Academy of Sciences in Sanya.
“If more geochemical data
could be obtained, it would
be more convincing.”
If confirmed to be eukaryotes,
the fossils are arguably the oldest
known. Previously the oldest
confirmed eukaryotes were
around 1.5 billion years old.
Some researchers have claimed
to have found significantly older
eukaryotes: one 2017 study
reported fungi, which are
eukaryotes, in rocks 2.4 billion
years old. However, these older
microfossils are rare and poorly
preserved, and it isn’t clear that

they are really eukaryotes, says
Högström. They could be bacteria
that look superficially like fungi,
for instance.
If eukaryotes really were
present as early as 2 billion years
ago, they emerged in the wake of
tumultuous changes. The first
oxygen built up in the atmosphere
2.4 billion years ago, albeit at low
levels, in the Great Oxidation
Event. This was followed by an
ice age known as Snowball Earth.
These abrupt environmental
variations may have triggered the
evolution of eukaryotes, says Qu.
However, the mechanisms
of this are unclear, says
Moczydłowska-Vidal. She says
that the Great Oxidation Event
“might have triggered the
evolution of the first eukaryotes”,
but adds that this isn’t certain.
Meanwhile, it is even less clear
how the Snowball conditions
could have contributed, she says.
“The only certain thing is that
these microbes originated in
a marine environment with
relatively high oxygen levels
PR in the surface layers,” she says. ❚










Particle physics

Antimatter looks like
matter – which is a
problem for physics

PHYSICISTS have made a key
measurement of anti-atoms, and
found that they look just like atoms.
The result means we are no closer
to solving the mystery of why we live
in a universe made only of matter,
or why there is anything at all.
Antimatter particles are the
same as matter particles, but
have the opposite electrical charge.
If the two meet, they annihilate
in a blitz of light and energy.
The problem is that the standard

model, physicists’ well-tested
theory of particles and their
interactions, predicts that matter
and antimatter were created in
equal quantities in the big bang,
so both should have disappeared in
an orgy of annihilation shortly after.
This has led to the suggestion
that there is a small imbalance
between matter and antimatter
properties, which allowed some
matter to survive and form the
universe of stars and galaxies we
live in. But we have failed to find
much evidence of one.
Now the ALPHA collaboration at
the CERN particle physics lab near
Geneva, Switzerland, has measured

a property known as the Lamb shift,
which is caused by fluctuations
in the quantum vacuum thought
to pervade all of space, in atoms
of antihydrogen.
These consist of a positively
charged electron, or positron,

circling an antiproton. Just as
the standard model predicts, the
Lamb shift was the same in atoms
of hydrogen and antihydrogen.
It is too early to conclude that the

Lamb shift can’t help to explain the
antimatter mystery, however. The
measurements are consistent only
to within one decimal place, so it
is possible that future research
will discover subtle differences
between the Lamb shift of atoms
and anti-atoms (Nature, DOI:
“This measurement is certainly
an important step forward,” says
Chloé Malbrunot, who works on
the rival ASACUSA experiment,
also at CERN. ❚

Read an exclusive feature on the
mysteries of antimatter in next
week’s New Scientist

Richard Webb


Michael Marshall

The oldest complex cells

Two-billion-year-old fossils may be world’s earliest eukaryotes

This Dictyosphaera
fossil may be one of the
earliest complex cells

“An imbalance between
matter and antimatter may
have allowed some matter
to survive the big bang”
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