Diverse life forms may have evolved earlier than previously thought


Date:
April 13, 2022
Source:
University College London
Summary:
Researchers analyzed a fist-sized rock from Quebec, Canada,
estimated to be between 3.75 and 4.28 billion years old. In an
earlier article, the team found tiny filaments, knobs and tubes in
the rock which appeared to have been made by bacteria. However,
not all scientists agreed that these structures -- dating about
300 million years earlier than what is more commonly accepted as
the first sign of ancient life -- were of biological origin. Now,
after extensive further analysis of the rock, the team have
discovered a much larger and more complex structure -- a stem with
parallel branches on one side that is nearly a centimeter long --
as well as hundreds of distorted spheres, or ellipsoids, alongside
the tubes and filaments. The researchers say that, while some of
the structures could conceivably have been created through chance
chemical reactions, the 'tree-like' stem with parallel branches
was most likely biological in origin, as no structure created via
chemistry alone has been found like it.



FULL STORY ========================================================================== Diverse microbial life existed on Earth at least 3.75 billion years
ago, suggests a new study led by UCL researchers that challenges the conventional view of when life began.


==========================================================================
For the study, published in Science Advances, the research team analysed
a fist-sized rock from Quebec, Canada, estimated to be between 3.75 and
4.28 billion years old. In an earlier Nature paper (see below) the team
found tiny filaments, knobs and tubes in the rock which appeared to have
been made by bacteria.

However, not all scientists agreed that these structures -- dating about
300 million years earlier than what is more commonly accepted as the
first sign of ancient life -- were of biological origin.

Now, after extensive further analysis of the rock, the team have
discovered a much larger and more complex structure -- a stem with
parallel branches on one side that is nearly a centimetre long -- as
well as hundreds of distorted spheres, or ellipsoids, alongside the
tubes and filaments.

The researchers say that, while some of the structures could conceivably
have been created through chance chemical reactions, the "tree-like"
stem with parallel branches was most likely biological in origin, as no structure created via chemistry alone has been found like it.

The team also provide evidence of how the bacteria got their energy in different ways. They found mineralised chemical by-products in the rock
that are consistent with ancient microbes living off iron, sulphur and
possibly also carbon dioxide and light through a form of photosynthesis
not involving oxygen.



========================================================================== These new findings, according to the researchers, suggest that a variety
of microbial life may have existed on primordial Earth, potentially as
little as 300 million years after the planet formed.

Lead author Dr Dominic Papineau (UCL Earth Sciences, UCL London Centre
for Nanotechnology, Centre for Planetary Sciences and China University
of Geosciences) said: "Using many different lines of evidence, our study strongly suggests a number of different types of bacteria existed on Earth between 3.75 and 4.28 billion years ago." "This means life could have
begun as little as 300 million years after Earth formed. In geological
terms, this is quick -- about one spin of the Sun around the galaxy."
"These findings have implications for the possibility of extraterrestrial
life.

If life is relatively quick to emerge, given the right conditions, this increases the chance that life exists on other planets." For the study,
the researchers examined rocks from Quebec's Nuvvuagittuq Supracrustal
Belt (NSB) that Dr Papineau collected in 2008. The NSB, once a chunk of seafloor, contains some of the oldest sedimentary rocks known on Earth,
thought to have been laid down near a system of hydrothermal vents,
where cracks on the seafloor let through iron-rich waters heated by magma.



==========================================================================
The research team sliced the rock into sections about as thick as paper
(100 microns) in order to closely observe the tiny fossil-like structures, which are made of haematite, a form of iron oxide or rust, and encased
in quartz. These slices of rock, cut with a diamond-encrusted saw, were
more than twice as thick as earlier sections the researchers had cut,
allowing the team to see larger haematite structures in them.

They compared the structures and compositions to more recent fossils
as well as to iron-oxidising bacteria located near hydrothermal
vent systems today. They found modern-day equivalents to the twisting filaments, parallel branching structures and distorted spheres (irregular ellipsoids), for instance close to the Loihi undersea volcano near Hawaii,
as well as other vent systems in the Arctic and Indian oceans.

As well as analysing the rock specimens under various optical and Raman microscopes (which measure the scattering of light), the research team
also digitally recreated sections of the rock using a supercomputer
that processed thousands of images from two high resolution imaging
techniques. The first technique was micro-CT, or microtomography, which
uses X-rays to look at the haematite inside the rocks. The second was
focused ion beam, which shaves away miniscule -- 200 nanometre-thick --
slices of rock, with an integrated electron microscope taking an image in-between each slice.

Both techniques produced stacks of images used to create 3D models of
different targets. The 3D models then allowed the researchers to confirm
the haematite filaments were wavy and twisted, and contained organic
carbon, which are characteristics shared with modern-day iron-eating
microbes.

In their analysis, the team concluded that the haematite structures
could not have been created through the squeezing and heating of the rock (metamorphism) over billions of years, pointing out that the structures appeared to be better preserved in finer quartz (less affected by
metamorphism) than in the coarser quartz (which has undergone more metamorphism).

The researchers also looked at the levels of rare earth elements in the
fossil- laden rock, finding that they had the same levels as other ancient
rock specimens. This confirmed that the seafloor deposits were as old as
the surrounding volcanic rocks, and not younger imposter infiltrations
as some have proposed.

Prior to this discovery, the oldest fossils previously reported were
found in Western Australia and dated at 3.46 billion years old, although
some scientists have also contested their status as fossils, arguing
they are non-biological in origin.

The new study involved researchers from UCL Earth Sciences, UCL Chemical Engineering UCL London Centre for Nanotechnology, and the Centre for
Planetary Sciences at UCL and Birkbeck College London, as well as from
the U.S.

Geological Survey, the Memorial University of Newfoundland in Canada,
the Carnegie Institution for Science, the University of Leeds, and the
China University of Geoscience in Wuhan.

The research received support from UCL, Carnegie of Canada, Carnegie Institution for Science, the China University of Geoscience in Wuhan,
the National Science Foundation of China, the Chinese Academy of Sciences,
and the 111 project of China.


========================================================================== Story Source: Materials provided by University_College_London. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* Tubular_and_filamentous_microfossils ========================================================================== Journal References:
1. Dominic Papineau, Zhenbing She, Matthew S. Dodd, Francesco
Iacoviello,
John F. Slack, Erik Hauri, Paul Shearing, Crispin T. S. Little.

Metabolically diverse primordial microbial communities in Earth's
oldest seafloor-hydrothermal jasper. Science Advances, 2022; 8
(15) DOI: 10.1126/sciadv.abm2296
2. Matthew S. Dodd, Dominic Papineau, Tor Grenne, John F. Slack, Martin
Rittner, Franco Pirajno, Jonathan O'Neil, Crispin
T. S. Little. Evidence for early life in Earth's oldest
hydrothermal vent precipitates. Nature, 2017; 543 (7643): 60 DOI:
10.1038/nature21377 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220413141532.htm

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