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About 3 billion years ago, the simplest bacteria began to evolve into a diverse array of living forms that we see today. The actual origin of life, also known as abiogenesis, is still a subject of scientific debate and disagreement. Here are a few more scientific theories on how life on Earth got its start, even though science is still unsure.
Until we find evidence of life outside our planet, these questions remain unanswered. To better understand whether life exists elsewhere in the universe (and if so, under what conditions), we might look at how life began on Earth.
On the subject of the origin of life on Earth, we’ll take a look at many scientific theories. Fossils and radiometric dating support the 5 billion-year-old origin of life. However, it’s less clear how this works. Hypotheses about the beginnings of life are far more hypothetical than either the fundamental dogma or the theory of evolution.
Electric Sparks
In 1953, the Miller-Urey experiment demonstrated that lightning could manufacture amino acids and sugars from an environment rich in water, methane, ammonia, and hydrogen. This suggests that lightning may have had a role in the early days of life on Earth. It was previously thought hydrogen-poor clouds in Earth’s early atmosphere were filled with methane, ammonia, and hydrogen. However, a new study has shown that these clouds may have been packed with lightning.
Life Molecule Colliding with Clay
A theory suggests that the first life’s molecules may have collided on clay. In addition to bringing these chemical components together, these surfaces may have played a role in organising them into patterns, similar to the way our genes do now. The primary function of DNA is to hold instructions for the arrangement of other molecules. Proteins are built from amino acids, and the genetic sequences in DNA serve as a blueprint for this arrangement. Organic molecules may have been formed into organised patterns by mineral crystals in clay, according to Cairns-Smith. Organic molecules eventually took over and arranged themselves over some time.
Vents in the Deep Sea
Beneath the deep-sea vent idea, hydrogen-rich molecules may have spewed out of hydrothermal vents on the ocean floor. If these molecules were concentrated in their rock crevices, they may have been able to offer mineral catalysts for important reactions.
Because the sun was about a third less bright 3 billion years ago, the ice has covered the oceans. Organic chemicals in the water beneath this ice sheet may have been shielded from UV radiation and destroyed by cosmic impacts thanks to its thickness, which is estimated to be hundreds of feet. Perhaps the cold helped molecules survive longer, which allowed for important processes to take place.
Proteins, which form in tandem with DNA, are essential for the formation of both of these structures. An enzyme similar to proteins, RNA may hold the key to this mystery, as it can store information and aid in the production of both DNA and proteins.
This “RNA universe” was overtaken by DNA and proteins, which are more efficient. A gene’s on/off switch is controlled by RNA, which is still present in cells and organisms. It’s still unclear how RNA ended up in this location in the first place. Scientists are divided on whether life as we know it could have spontaneously evolved on Earth. Other nucleic acids, such as the more esoteric PNA or TNA, have been proposed as well.
Effortless Evolution
Life may have started as simple molecules interacting with each other in cycles of reactions, rather than sophisticated molecules like RNA. A “metabolism-first” model instead of the “gene-first” model of the “RNA world” hypothesis contends that these reactions were originally contained in simple capsules similar to cell membranes and that over time more complex molecules that performed these reactions better than smaller ones could have evolved.
Panspermia
Panspermia is the theory that life didn’t begin on Earth at all, but was instead delivered here by aliens. For example, meteorites from Mars have been found on Earth, which some academics contend carried bacteria here, perhaps making us all Martians originally. Rocks are periodically blasted from Mars by cosmic impacts. The topic of how life began on Earth would only shift to the origins of life elsewhere in the universe if this theory is right.
Conclusion
Non-living organic substances like proteins and RNA may have given rise to life. It was therefore proposed that atmospheric conditions on Earth were responsible for the synthesis of organic molecules from inorganic ones, which was followed by the hypothesis of chemical evolution.
