Life on Earth started between 3.7 and 4.5 billion years ago after meteorites crashed down into warm little ponds and brought along with them the ingredients needed to form life, findings of a new study suggest.
It was in these ponds' nutrient-rich broth that the first self-replicating molecules formed and became the first genetic code for life.
Darwin's Warm Little Ponds
The idea that life on Earth descended from something that emerged in warm little ponds is not new. It was suggested by Charles Darwin in the 19th century but the theory is faced with challenges from another claim that points at hydrothermal vents in the ocean.
The leading rival theory posits that life started in roiling fissures in the ocean floors where the elements of life came together in blasts of hot water.
In a new study published in the journal PNAS, researchers constructed a comprehensive model, which revealed that Darwin's idea was plausible.
Formation Of RNA
The mathematical model, which factored in data of the Earth's formation, biology, geology, and chemistry, supported the theory that ribonucleic acid (RNA) polymers formed in small warm ponds of water.
RNA is believed to be the earliest genetic material given that it is present in living cells and has the ability to store genetic information and catalyze its own replication.
The calculations showed that the required conditions were present in thousands of ponds, and the important combinations needed for the formation of life were far more likely to have formed in these ponds than in hydrothermal vents. Researchers said that the conditions in ocean floors were not likely to generate life because the bonding that is needed to form RNA requires both wet and dry cycles.
"We build a comprehensive numerical model for the evolution of nucleobases in warm little ponds leading to the emergence of the first nucleotides and RNA," the researchers wrote in their study. "We find that RNA polymers must have emerged very quickly after the deposition of meteorites (less than a few years).
Role Of Meteorites
Meteorites contributed to the process by leaching enough organic molecules to the pools ensuring that RNA started self-replicating in at least one of these pools.
"We need to understand Earth as it was billions of years ago. As our study shows, astronomy provides a vital part of the answer. The details of how our solar system formed have direct consequences for the origin of life on Earth," said study co-author Thomas Henning, from the Max Planck Institute for Astronomy.