Life on earth began more than 3 billion years ago and evolved over time from the simplest of microbes to a dazzling variety of complexity. But how did the primordial soup become the first organisms in the only known habitat of life in the universe?
The theory got off to a “shocking” start. Another idea is completely scary. And a theory is out of this world!
Inside, learn how mysterious it all is as we reveal the various scientific theories about the origins of life on earth.
It started with an electric spark
Lightning could have provided the spark necessary for the beginning of life. Electric sparks can generate amino acids and sugars from an atmosphere charged with water, methane, ammonia and hydrogen, as the famous Miller-Urey experiment of 1953 shows in its early days. Larger and more complex molecules could form over millions of years. Although research since then has shown that Earth’s early atmosphere was indeed hydrogen depleted, scientists have suggested that volcanic clouds in the early atmosphere contained methane, ammonia, and hydrogen, and were also filled with lightning bolts. Read on to find out.
Life molecules found in clay
According to an idea by the organic chemist Alexander Graham CairnsSmith from the University of Glasgow in Scotland, the first life molecules may have been found in clay. Connections together, it also helped organize them into patterns, much like our genes do today.
The main function of DNA is to store information about how other molecules should be organized. Cairns-Smith suspects that the mineral crystals in the clay may have arranged the organic molecules in organized patterns. Organic molecules did this work and organized themselves..
Or maybe life began on the ocean floor. Keep learning how.
Life began in deep-sea vents
Deep-sea vents theory suggests that life may have started in underwater hydrothermal vents that spew out important hydrogen-rich molecules. Its rocky corners may have concentrated these molecules. and they provided mineral catalysts for critical reactions. These chimneys, which are rich in chemical and thermal energy, are already supporting living ecosystems.
The next idea is a terrifying thought. Continue reading!
Life had a cold start
Ice could have covered the oceans 3 billion years ago as the sun was about a third less bright than it is today, scientists say. This ice sheet, possibly hundreds of feet thick, could have protected the fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold may also have helped these molecules survive longer and allow key reactions to occur.
Understanding the origin of life may involve unraveling the mystery of DNA formation, as we explain below.
The answer lies in understanding DNA formation
Nowadays, DNA needs proteins to form, and proteins need DNA to form, so how could that be? The answer can be RNA, which stores information like DNA can, as an enzyme like proteins, help to create both DNA and proteins. DNA and proteins later followed this “RNA world” because they are more efficient.
RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question that remains is how RNA got here in the first place. And while some scientists believe that the molecule could have formed spontaneously on Earth, others consider it highly unlikely. Nucleic acids other than RNA have also been suggested, such as the more esoteric PNA or TNA, suggests a 2015 study; the missing link in this RNA puzzle may have been found.
We have two final ideas for you.
Life Had Simple Beginnings
Instead of developing from complex molecules like RNA, life could have started with smaller molecules that interact with each other in reaction cycles, in simple capsules similar to the cell membrane, and more complex molecules could have evolved over time, who performed these reactions better than smaller, scenarios called “Metabolism First” models, as opposed to the “Gene First” model of the “RNA World” hypothesis.
The final theory is really out of this world. See next slide.
Life was brought here from another part of space
Perhaps life didn’t start on Earth at all, but was brought here from another place in space, a concept known as panspermia. For example, rocks are regularly ejected from Mars by cosmic impacts, and several Mars meteorites have been found on Earth, some of which researchers have controversially proposed to bring here microbes that may originally make us all Martians. Other scientists have even suggested that life might have hitchhiked on comets from other star systems. But even if this concept were true, the question of how life began back then would only change on Earth to how life began in other parts of space.
Oh, and if you thought this was all mysterious, consider this: Scientists admit they don’t even have a good definition of life!
Original article on Science Atom.