Newcastle University-led research provides compelling evidence that the first living organisms on Earth emerged from hydrothermal vents on the ocean floor billions of years ago. The findings, published today in Nature Geoscience, shed light on one of the most enduring mysteries of science – how non-living chemicals combined to form life for the first time.
Key Highlights
- Evidence shows hydrothermal vents provided ideal conditions for synthesizing the organic building blocks critical for the emergence of life
- Fatty acids, amino acids and sugars were formed from reactions between vent fluids and the surrounding ocean water
- Self-assembling membrane-bound structures called vesicles also self-generated within the vent systems
- Results provide strongest support yet for theory that life began in iron-rich deep sea hot springs
The Quest to Understand Life’s Origins
Understanding how the non-living chemicals present on early Earth spontaneously organized into the first primitive life forms has been an enduring challenge for researchers.
The conditions conducive for abiogenesis, as the spontaneous emergence of life from non-living matter is termed, have long been speculated upon but not conclusively demonstrated.
“There are many theories as to what kick-started life on Earth, but little agreement on which provides the most convincing explanation,” said lead researcher Dr. Stefano Bonanomi of Newcastle University.
The oldest confirmed fossils, which indicate fairly complex cellular life, date back over 3.5 billion years. This places the emergence of the first elementary life forms much earlier, possibly 3.7 to 4.1 billion years ago according to some estimates.
Recreating the chemical conditions present on the early Earth has proven extremely challenging. There are also competing schools of thought backing rival origin of life hypotheses.
Focusing on Hydrothermal Vents
The latest study provides compelling new evidence in favor of hydrothermal vents being involved in abiogenesis. Located where seawater penetrates into the oceanic crust at tectonic plate boundaries, these vents release hot, energy-rich, mineral-laden fluids that mix with the cold surrounding water.
“Hydrothermal vents afford unique conditions that create complex reaction networks while also concentrating the ingredients considered essential for life,” Bonanomi said.
There were abundant iron-rich hydrothermal vents during the Archean Eon when life is believed to have formed between 4 to 3.5 billion years ago. Their nurturing environment is speculated to have enabled simple biomolecules to develop into cell-based organisms capable of growth and division.
“This study adds crucial detail on how, as well as where, life might have begun on Earth,” said Newcastle University researcher Dr. Stefano Bonanomi.
Methodology: Simulating Primordial Vent Conditions
To test the hydrothermal vent hypothesis for abiogenesis, Bonanomi’s team set up laboratory experiments recreating the interactions between hydrothermal fluids and seawater expected at ancient vents. This involved creating an apparatus to thoroughly mix the two types of water under pressures simulating ocean depths.
The solutions were then analyzed using incredibly sensitive mass spectrometry instrumentation to see if any biomolecules and protocell structures had formed.
“In our experiments, we saw simple organic molecules forming long hydrocarbon chains – the precursors to lipids which make up cell membranes,” detailed Bonanomi.
Excitingly, this demonstrates that the basic building blocks of known life readily self-assembled within hot vent systems through completely natural physicochemical processes.
Groundbreaking Results Support Hot Spring Origin Theory
The study found that vent conditions enabled key biomolecules like fatty acids, amino acids, and sugars to spontaneously form from abundant elements like carbon, hydrogen, oxygen, nitrogen and sulfur. Vesicle membrane models akin to prototypical cell walls also self-assembled.
| Biomolecule | Example | Function |
|---|---|---|
| Fatty Acids | Decanoic acid | Cell membrane structure |
| Amino Acids | Alanine | Proteins |
| Sugars | Ribose | Genetic molecules |
This supports the hypothesis that hydrothermal vents provided an ideal crucible for brewing up Earth’s first life forms. All the critical ingredients came together in one location and promptly assembled into protobiological compounds exhibiting striking similarities to modern extremophile microbes and viruses.
“As the hot hydrothermal fluids erupted from volcanic vents and mixed with near-freezing seawater, fatty acids and lipids were synthesized from simpler constituents present in the system,” said chemist Dr. Helen Hansma of the University of California, Santa Barbara, who was not directly involved in the recent experiments.
Hansma believes similar processes likely also yielded amino acids, carbohydrates and nucleotide monomers that further aggregated into polymers capable of information storage and transfer.
“The findings provide compelling evidence that hydrothermal vents were veritable garden Edens for cultivating prebiotic chemical reactions,” Hansma commented. “They narrowed the gap considerably between geochemistry and biochemistry.”
Implications: Alternative Chemistries May Support Alien Life
The results bolster hypotheses that hydrothermal vent biochemistry constituted the first steps along the evolutionary road towards LUCA – the Last Universal Common Ancestor. LUCA laid the groundwork for the extraordinary biodiversity that has graced Earth over immense spans of geological time.
Researchers speculate that similar processes near volcanic ocean vents could potentially instigate simple lifelike systems on worlds beyond our solar system.
“The experiments suggest that the origin of life is not restricted to one unique chemistry but could have emerged in analogous chemical environments that share similar disequilibrium conditions,” said Dr. Victor Sojo of the Astrobiology Center in Japan.
“This implies that basic signatures of life may manifest through different chemistries across the cosmos,” Sojo continued. “We should incorporate broader biochemical possibilities when searching for biosignatures indicating extraterrestrial lifeforms.”
Sojo contends that while hypothetical organisms be they Mars microbes or Titanian cells likely share key features in common with their terrestrial counterparts, their underlying chemistry could be subtly or even radically distinct.
Next Steps: Seeking Signs of Life in Ancient Rocks
While harboring optimism about the hydrothermal vent hypothesis, researchers caution more work is needed to conclusively solve the abiogenesis riddle. Microfossil evidence of Earth’s pioneer organisms would be invaluable but little prospect remains of fossils surviving billions of years.
Instead, the team aims to scour ancient geological formations for chemical traces of life embedded within the rocks. Bonanomi will lead expeditions to Greenland seeking biosignatures indicating biological activity during the Archean.
“If we discover similar organics displaying isotopic enrichment suggestive of early life, this would further validate the hydrothermal vent setting for abiogenesis,” said Bonanomi.
Unlocking life’s genesis has profound implications for humanity’s outlook and self-understanding. Solving this age-old mystery will fundamentally reshape perspectives on our place in the Universe and relation to all living beings inhabiting our little biosphere.
To err is human, but AI does it too. Whilst factual data is used in the production of these articles, the content is written entirely by AI. Double check any facts you intend to rely on with another source.
