Did life emerged in the oceans? Understand this theory!

About how life emerged in the oceans has fascinated scientists and philosophers for centuries. 

The most accepted answer, based on chemical and biological evidence, suggests yes: the primitive seas played a crucial role in this process. 

In this text, we will explore how the unique conditions of the early oceans created an ideal environment for the first organic molecules, examine scientific theories, and analyze the impact of this event on the evolution of life. Continue here to follow along!

The primitive oceans and the conditions for life – life emerged in the oceans

Earth about 4 billion years ago was a young and hostile planet. The surface was filled with active volcanoes, and the atmosphere carried toxic gases such as methane, ammonia and water vapor. 

In this chaotic scenario, oceans began to form, creating an aquatic environment rich in essential minerals and nutrients.

Studies by Stanley Miller and Harold Urey in the 1950s showed that simple organic molecules could arise spontaneously under conditions similar to those on the early Earth. 

In this way, these experiments recreated a “primordial soup” that was enriched by compounds that fell with meteorites. 

The table below summarizes the required chemical elements and their possible origins:

Recent research reinforces the hypothesis that underwater hydrothermal vents were crucial places for the emergence of life. 

These sources emit heat and chemicals, creating energy-rich microenvironments. 

The temperature and chemistry in these locations favored reactions that formed complex molecules.

Theories about the emergence of life in the oceans

The theory of abiogenesis is widely accepted to explain how inorganic compounds gave rise to the first cells. 

The “primordial soup” in the early oceans may have allowed molecules such as amino acids and nucleotides to combine into more complex structures. 

These combinations led to the emergence of the first single-celled organisms.

Another fascinating hypothesis is that of “RNA worlds”. RNA, a molecule capable of storing information and carrying out chemical reactions, may have been the first molecule to emerge. 

Studies indicate that RNA may have formed in small salty lakes linked to the oceans, where cycles of drying and hydration catalyze chemical reactions.

Hydrothermal vents are also significant candidates in this debate. Researchers discovered that compounds such as methane and hydrogen sulfide, released by these sources, could have served as an energy base for the first forms of life. 

As scientist Jack Szostak rightly pointed out, “deep aquatic environments provided stability and energy for the first living systems.”

The importance of tides and marine chemistry

In addition to hydrothermal vents, tides may have played an essential role in the origin of life. 

The Moon’s gravitational forces caused periodic variations in sea level, creating cycles of immersion and exposure to the surface. 

These cycles favored the concentration of organic molecules and, potentially, the emergence of more complex structures.

Another crucial factor was the chemistry of the early oceans. Minerals dissolved in water, such as iron and sulfur, acted as catalysts for important chemical reactions.

Modern experiments show that these conditions could generate lipid vesicles, which would function as primitive cell membranes, protecting essential molecules from the external environment.

Did life evolve in the oceans?

The oceans not only provided the ideal environment for the origin of life, but also for its evolution. 

The first single-celled organisms, such as archaea, adapted to the extreme conditions of the deep sea. 

These life forms eventually gave rise to more complex organisms.

Photosynthesis played a transformative role. About 2.5 billion years ago, cyanobacteria began releasing oxygen into the oceans, drastically altering the planet’s chemistry. 

This event allowed the emergence of more advanced life forms, dependent on oxygen.

The life beyond the oceans: the transition to dry land

After billions of years of evolution in the oceans, some life forms began to explore new environments. 

Studies show that the first multicellular organisms, such as algae and primitive jellyfish, appeared on the seabed before colonizing coastal areas.

The transition from water to land was an evolutionary milestone. Plants and animals have developed specialized structures to survive outside the aquatic environment, such as roots and lungs. 

However, even today, around 80% of terrestrial species still depend on the oceans directly or indirectly.

Modern studies and future implications

The search for answers about how life emerged in the oceans continues. Research carried out on Mars and the moons of Jupiter and Saturn, such as Europa and Enceladus, is looking for signs of life in environments similar to Earth’s primitive oceans. 

Scientists believe that studying these celestial bodies can clarify the conditions for the emergence of life.

Additionally, analysis of microscopic fossils and chemical traces in ancient rocks continues to provide valuable insights. 

Recent studies indicate that organic molecules may have formed more quickly than previously thought, challenging traditional theories.

The role of solar radiation in early oceans

Solar radiation played a crucial role in the chemical processes that led to the emergence of life in the early oceans. 

In the absence of an ozone layer, the intense ultraviolet radiation that reaches the Earth catalyzes fundamental chemical reactions. 

These reactions, combined with the rich chemistry of ocean waters, facilitated the formation of complex organic molecules.

Recent research indicates that the interaction between sunlight and compounds such as cyanide and sulfide could have generated nucleotides, essential components of RNA and DNA. 

These processes demonstrate how ultraviolet radiation, often considered destructive, may have been indispensable in the formation of precursor molecules for life.

Furthermore, the cycles of light and dark in the oceans helped create an environment conducive to cyclical chemical reactions, important for molecular organization. 

These cycles were the first steps towards biological complexity. As evolutionary biologist John Desmond Bernal has pointed out, “life is the result of chemistry under control, shaped by the environment.”

The oceans as the cradle of biodiversity

The oceans were not only the starting point for life, but also the environment where biodiversity began to flourish. 

From the first prokaryotic cells to multicellular organisms, the seas have been the main habitat for billions of years. This long marine history shaped the diversity we see today.

During the Cambrian period, about 540 million years ago, an explosion of life occurred in the oceans. 

This event marked the emergence of a wide range of organisms, including the earliest ancestors of many modern animal groups. 

Fossils from this era, found in places like the Burgess Shale in Canada, reveal an impressive mosaic of life forms.

The oceans continue to be one of the most biodiverse environments on the planet. Around 80% of marine species remain unknown, demonstrating how much there is still to learn about this vast and mysterious ecosystem. 

The preservation of the oceans is therefore essential to ensure that we continue to explore and learn from the cradle of life.

Conclusion: the oceans as the cradle of existence

Although there are still debates about the details, it is undeniable that the oceans were the primordial stage where the first molecules of life emerged and evolved. 

They not only provide stability but also the rich chemical diversity necessary for biological complexity.

As Carl Sagan pointed out, “we are stardust shaped by water.” This connection between the oceans and our existence continues to inspire scientific research and expand the boundaries of human knowledge. 

The answer to the question “did life emerge in the oceans?” it is a key piece in understanding not only our past, but also our role in the cosmos.

Roberta 12 de January de 2025