Recent studies indicate that life on Earth originated 1.5 billion years earlier than had been previously estimated. Here we examine the most prominent theories on the origin of life.
For centuries, humans have pondered the origin of life on Earth and the meaning of existence, seeking answers to fundamental questions about our origins and destination.
It's an inquiry that involves the fundamental sciences of chemistry, biology and physics, as well as philosophy, psychology and aspects of faith. And the earliest scholars were involved in all spheres of investigation. Nevertheless, those core sciences are generally considered more precise and quantifiable than the others, and that's where researchers tend to concentrate their efforts today.
In the 19th century, French scientist Louis Pasteur proved that life originates only from other living things. Living plants, animals, and microorganisms reproduce within their own respective species.
What about the original life form? If it emerged from non-living matter, when and how exactly did this occur?
It appears that life may be much older than we currently think.
A study directed by Cardiff University in Wales, UK, implies that the origin of complex life on Earth may have occurred 1.5 billion years earlier than the previously estimated timeline. Investors in rocky samples in Gabon reveal signs indicating a potential for life about 2.1 billion years ago.
The study implies that the collision of two continental plates over 2 billion years ago created a nutrient-rich environment that facilitated the evolution of complex organisms.
It would have possibly produced phosphorus and marine oxygen, which are crucial for the transformation from single-celled organisms to more complex forms of life.
The existence of this supposedly complex life form was indeed short-lived, appearing to be confined to a body of water surrounded by land, thus unable to spread across the globe.
This study disputes the prevailing scientific view that animal life emerged 635 million years ago, and proposes an initial, unsuccessful effort at developing complex life on Earth.
What are some other proposed explanations for the emergence of life on Earth?
Certain researchers have voiced skepticism about the recent discoveries and are urging additional investigation.
However, the research has revived discussion regarding the origins of complex life on Earth.
Over the past 100 years, researchers have developed a few sophisticated technologies.
Here, we review some of the most widespread ones.
1. The Primordial Ooze Theory
One of the most widely accepted views is the "primordial soup" theory, which proposes that life emerged from carbon-based compounds in a primeval sea.
(1809-1882) was the first to propose that life could have started in "a warm little pond."
However, it wasn't until the 1950s that his theory was put to the test. An American chemist and Nobel laureate, Harold Urey, and chemist Stanley Miller set up a primitive early Earth atmosphere in a laboratory. They combined water, methane, ammonia, and hydrogen in a sealed container and inserted electric sparks to mimic lightning as a catalyst.
After several days, the essential components that are the foundation of living organisms, known as amino acids, had taken shape.
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An alternative theory is that Earth life began in outer space. According to this hypothesis, life forms, or at least the building blocks necessary for life, came from space and originated on Earth.
This theory of where life first arose doesn't provide exact details regarding its origin or the form it took when it arrived on our planet. The most widely accepted notion is that life may have been introduced to Earth after a meteorite containing microorganisms hit our planet.
Two of the key proponents of this theory were British astrophysicists Fred Hoyle and Chandra Wickramasinghe, whose work in the 1970s showed that comets have sufficient organic matter to potentially seed life on planets like Earth.
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It is proposed that Earth's life may have originated around underwater hydrothermal vents, which are submarine openings that discharge hot and mineral-laden water.
British geologist and member of the NASA Astrobiology Institute, Michael Russell, proposed that alkaline hydrothermal vents, emitting hydrogen, hydrogen sulfide, and methane, had the perfect conditions for the formation of simple organic molecules.
Despite the harsh conditions surrounding hydrothermal vents, such as temperatures that can reach as high as 400°C (752°F), microorganisms thrive in these environments through the process of chemosynthesis.
Chemical synthesis is a process that enables microbes to produce their own food by utilizing energy from chemical reactions as opposed to sunlight. This allows them to exist in dimly lit regions, such as the ocean floor.
4. The RNA world
According to the RNA world hypothesis, over a long time before the emergence of DNA and proteins as we know them today, life on Earth was founded on a highly flexible molecule: RNA (ribonucleic acid).
Deoxyribonucleic acid (DNA) enables organisms to evolve, endure, and reproduce, and. DNA sequences are converted into instructions that empower the creation of proteins — intricate molecules accountable for nearly all physical and biological functions that occur within our bodies — and sustains us.
On the other hand, RNA fulfills two vital roles for living things: It preserves genetic information and functions as a catalyst for crucial chemical processes.
In the 1980s, the chemists Thomas Cech and Sidney Altman discovered ribozymes, RNA molecules possessing enzymatic activities, and received a Nobel Prize.
Scientists have suggested that RNA molecules with the ability to replicate themselves and facilitate simple reactions existed before modern living beings. They propose that these RNA molecules, able to catalyze reactions, were later surpassed by proteins, which are more effective as catalysts.
Several theories about the origins of life exist, but these are the most widely known and studied by the scientific community.
All— including the latest from Cardiff University— emphasize the intricacy of the question that remains persistently intriguing and captivating for us today.
Edited by: Zulfikar Abbany
Primary source:
Researchers now believe complex life on Earth started around 3.5 billion years ago, not 2 billion years ago as previously estimated. https://www.cardiff.ac.uk/news/view/2830233-complex-life-on-earth-began-around-1.5-billion-years-earlier-than-previously-thought,-new-study-claims
Author: Fernando Mateos Frühbeck
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