New Clues to the Origin of Life on Earth From Microbial Remains in Ancient Rocks

Pyritized Stromatolites

Photomicrograph of pyritized stromatolites from the 3.5 billion-year-old Dresser Formation. The stromatolites are delineated by pyrite, also known as fool’s gold. Credit: UNSW Sydney

Western Australia’s famous 3.5-billion-year-old stromatolites contain microbial remains of some of the earliest life on Earth, UNSW scientists have found.

Scientists have found exceptionally preserved microbial remains in some of Earth’s oldest rocks in Western Australia – a major advance in the field, offering clues for how life on Earth originated.

The UNSW researchers found the organic matter in stromatolites – fossilized microbial structures – from the ancient Dresser Formation in the Pilbara region of Western Australia.

The stromatolites have been thought to be of biogenic origin ever since they were discovered in the 1980s. However, despite strong textural evidence, that theory was unproven for nearly four decades, because scientists hadn’t been able to show the definitive presence of preserved organic matter remains – until today’s publication in the prestigious journal Geology.

“This is an exciting discovery – for the first time, we’re able to show the world that these stromatolites are definitive evidence for the earliest life on Earth,” says lead researcher Dr. Raphael Baumgartner, a research associate of the Australian Center for Astrobiology in Professor Martin Van Kranendonk’s team at UNSW. 

Professor Van Kranendonk says the discovery is the closest the team has come to a “smoking gun” to prove the existence of such ancient life.

“This represents a major advance in our knowledge of these rocks, in the science of early life investigations generally, and – more specifically – in the search for life on Mars. We now have a new target and new methodology to search for ancient life traces,” Professor Van Kranendonk says.

Drilling deep, looking closely

Ever since the Dresser Formation was discovered in the 1980s, scientists have wondered whether the structures were truly microbial and therefore the earliest signs of life.

“Unfortunately, there is a climate of mistrust of textural biosignatures in the research community. Hence, the origin of the stromatolites in the Dresser Formation has been a hotly debated topic,” Dr. Baumgartner says.

“In this study, I spent a lot of time in the lab, using micro-analytical techniques to look very closely at the rock samples, to prove our theory once and for all.”

Stromatolites in the Dresser Formation are usually sourced from the rock surface, and are therefore highly weathered. For this study, the scientists worked with samples that were taken from further down into the rock, below the weathering profile, where the stromatolites are exceptionally well preserved.

“Looking at drill core samples allowed us to look at a perfect snapshot of ancient microbial life,” Dr. Baumgartner says.

Using a variety of cutting-edge micro-analytical tools and techniques – including high-powered electron microscopy, spectroscopy, and isotope analysis – Dr. Baumgartner analyzed the rocks.

He found that the stromatolites are essentially composed of pyrite – a mineral also known as ‘fool’s gold’ – that contains organic matter.

“The organic matter that we found preserved within pyrite of the stromatolites is exciting – we’re looking at exceptionally preserved coherent filaments and strands that are typical remains of microbial biofilms,” Dr. Baumgartner says.

The researchers say that such remains have never been observed before in the Dresser Formation, and that actually seeing the evidence down the microscope was incredibly exciting.

“I was pretty surprised – we never expected to find this level of evidence before I started this project. I remember the night at the electron microscope where I finally figured out that I was looking at biofilm remains. I think it was around 11 p.m. when I had this ‘eureka’ moment, and I stayed until three or four o’clock in the morning, just imaging and imaging because I was so excited. I totally lost track of time,” Dr. Baumgartner says.

Clues for search for life on Mars

Just over two years ago, Dr. Baumgartner’s colleague Tara Djokic, a UNSW Ph.D. candidate, found stromatolites in hot spring deposits in the same region in WA, pushing back the earliest known existence of microbial life on land by 580 million years.

“Tara’s main findings were these exceptional geyserite deposits that indicate that there have been geysers in this area, and therefore fluid expulsions on the exposed land surface,” Dr. Baumgartner says.

“Her study was focused on the broader geological setting of the paleo-environment – lending support to the theory that life originated on land, rather than in the ocean – whereas my study really went deeper on the finer details of the stromatolite structures from the area.”

The scientists say that both studies are helping us answer a central question: where did humanity come from?

“Understanding where life could have emerged is really important in order to understand our ancestry. And from there, it could help us understand where else life could have occurred – for example, where it was kick-started on other planets,” Dr. Baumgartner says.

Just last month, NASA and European Space Agency (ESA) scientists spent a week in the Pilbara with Martin Van Kranendonk for specialist training in identifying signs of life in these same ancient rocks. It was the first time that Van Kranendonk shared the region’s insights with a dedicated team of Mars specialists – a group including the Heads of NASA and ESA Mars 2020 missions.

“It is deeply satisfying that Australia’s ancient rocks and our scientific know-how are making such a significant contribution to our search for extraterrestrial life and unlocking the secrets of Mars,” says Professor Van Kranendonk.

Reference: “Nano−porous pyrite and organic matter in 3.5-billion-year-old stromatolites record primordial life” by Raphael J. Baumgartner, Martin J. Van Kranendonk, David Wacey, Marco L Fiorentini, Martin Saunders, Stefano Caruso, Anais Pages, Martin Homann and Paul Guagliardo, 25 September 2019, Geology.
DOI: 10.1130/G46365.1

4 Comments on "New Clues to the Origin of Life on Earth From Microbial Remains in Ancient Rocks"

  1. Where does this leave the evidence published in NATURE in 2017 by Dodd et al.?

    “Although it is not known when or where life on Earth began, some of the earliest habitable environments may have been submarine-hydrothermal vents. Here we describe putative fossilized microorganisms that are at least 3,770 million and possibly 4,290 million years old in ferruginous sedimentary rocks, interpreted as seafloor-hydrothermal vent-related precipitates, from the Nuvvuagittuq belt in Canada. These structures occur as micrometre-scale haematite tubes and filaments with morphologies and mineral assemblages similar to those of filamentous microorganisms from modern hydrothermal vent precipitates and analogous microfossils in younger rocks. The Nuvvuagittuq rocks contain isotopically light carbon in carbonate and carbonaceous material, which occurs as graphitic inclusions in diagenetic carbonate rosettes, apatite blades intergrown among carbonate rosettes and magnetite–haematite granules, and is associated with carbonate in direct contact with the putative microfossils. Collectively, these observations are consistent with an oxidized biomass and provide evidence for biological activity in submarine-hydrothermal environments more than 3,770 million years ago.”

    • I dont think you can direcvtly compare these articles. They are describing two slightly different things.

      This article described the (definitive) biogenic origin of stromatolites. The other paper describes (putative) evidence for the earliest forms of life.

      I guess the sentence: “For the first time, we’re able to show the world that these stromatolites are definitive evidence for the earliest life on Earth (…)” led to some confusion.

  2. The problem is that we have the inquiry too complex, overly-methodological and underly-conceptual.
    As ever, Occam’s razor prevails: https://youtu.be/ImWZZ7sOa40.

  3. They still teach we came from monkeys and lie about giants. So who cares what they say. It’s all lies anyway

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