top of page

But Life Could Not Wait ...

Writer's picture: Peter StorkPeter Stork

Updated: Nov 29, 2024


A single cell without a nucleus showing strands of DNA
At the foundation of life for billions of years

Our planet was born 4.567 billion years ago when cosmic dust and gas that orbited the young sun coalesced into a molten mass. This scorching sphere, devoid of stable landmasses or oceans, was subject to intense meteoric bombardment and inhospitable to any form of life. Because of the hellish conditions prevailing at the time, the first geological eon after the planet’s birth was the Hadean, named after the Greek god of the underworld. It lasted 500 million years.

As magma oceans solidified, they left behind hot volatiles, resulting in a heavy atmosphere of carbon dioxide, hydrogen and water vapour, with a surface temperature of 230 °C. Short-wave sun radiation most likely split surface water into oxygen and hydrogen; the reducing atmosphere would have removed the former. At the same time, the latter, along with the similarly light helium, would have left like today through atmospheric escape. The interplanetary collision that created the moon would have added to the hellish conditions.

The Earth’s magnetic field was still 700 million years away, and a fully oxygenated atmosphere, which is needed for life as we know it, would be absent for another 2 billion years.

For decades, scientists hypothesised that life on Earth began well past the era of Hades’ reign—around 3.8 billion years ago. This view was supported by the understanding that the planet needed to have cooled enough to support life and by the oldest known fossils from this period.  

However, recent findings published in Nature Ecology & Evolution profoundly challenged this longstanding view.

As the Earth’s surface gradually cooled, it formed the first solid crust, paving the way for the accumulation of water vapour into vast oceans and the rise of proto-continents. By the end of the Hadean, landmasses and large bodies of water began to appear around 4 billion years ago.

According to recent findings, the Last Universal Common Ancestor, or LUCA, existed prior to this time, 4.2 billion years ago, when Earth’s landscape was markedly different from today’s—a world still characterised by flowing lava and a nascent solid crust.

Scientists call the hypothetical common ancestor cell from which the three domains of single-celled microorganisms originated (Bacteria, Archaea, and Eukaryotes -- Eukaryotes are cells with a nucleus) the Last Universal Common Ancestor or LUCA. It is assumed that LUCA, like all single-celled organisms, had an outer membrane, a double layer of lipids, that kept proteins and other molecules where they were needed.

Tracing life back to the Hadean is an arduous task for scientists. What makes it so tricky is that traditional methods of paleontology are no longer applicable. Earth was too tumultuous and hot for fossils of that period to exist. So, how do we know from the dawn of the Earth that LUCA is not a fancy figment of scientific imagination?

To circumvent these limitations, scientists successfully employed advanced genetic and molecular techniques. They were not only able to date LUCA to 4.2 billion years ago, extending the timeline of life on Earth by 400 million years earlier than the previously estimated 3.8 billion years based on older methods, but they also discovered that life emerged rapidly after the formation of the Earth. Recalling that Earth was a molten mass when it first consolidated about 4.5 billion years ago, the emergence of life 300 million years later suggests that life began as soon as the planet's environment became even minimally habitable. This rapid appearance implies that the conditions necessary for life might be less stringent and more common in the universe than previously thought.

The new research findings also indicate that LUCA likely had a genome size of around 2.5 million base pairs encoding about 2,600 proteins, similar to modern prokaryotes (simple, single-celled organisms without a nucleus, such as bacteria). In other words, LUCA must have been a primitive, anaerobic organism capable of producing energy by converting hydrogen and carbon dioxide into energy. More surprisingly, the findings suggest that LUCA used a rudimentary immune system to adapt to these harsh conditions and enter the evolutionary arms race to fend off ancient viruses.

This points to complex biological mechanisms early on, challenging previous notions of primitive life being overly simple. It also highlights the inherent complexity that life has had since its inception and the need to fight pathogens as soon as life itself appeared, a struggle still with us 4.2 billion years later.

The dating of LUCA has special significance for understanding geological and biological interactions. The fact that life could thrive in such volatile conditions indicates a more dynamic interplay between Earth's physical transformations and life's adaptability. This reshapes our understanding of how planetary processes influence life, with important implications for astrobiology.

Knowing that life emerged so quickly on Earth and developed complex mechanisms like an immune system in such a short geological timeframe expands the potential for life on other planets. This could adjust our criteria for habitable conditions and what to look for in the search for extraterrestrial life.

These new findings do not just add a few hundred million years to the age of life on Earth; they profoundly deepen our understanding of life’s resilience and complexity, altering how we think about life on Earth and throughout the cosmos.


Typical Infogram of Single Cell Microorganisms



9 views0 comments

Recent Posts

See All

Comments


 Background

The knowledge and expertise I offer draws on my diverse educational and professional background, experience in international consulting (Geo-science) and theology (PhD 2006), and academic affiliations as a former Research Fellow of the Australian Catholic University, Emeritus Faculty of the Australian National University and Fellow of ISCAST (the Australian Institute for Science and Theology).

Peter_edited_edited.jpg

The Discovery Papers

Sydney, Australia

Email: info@discoverypages.com

bottom of page