Sometime between 3.7 and 4.5 billion years ago, life appeared on earth. How exactly it materialized from the primordial goop, however, is still a fundamental mystery about our planet — one that a group of scientists from McMaster University and the Max Planck Institute say they are one step closer to solving. Darwin, they argue in a new study, may have been right all along: It seems that life really did emerge in earth’s “warm little ponds.”
In a paper published Monday in the Proceedings of the National Academy of Sciences, they posit that life on Earth started out in ancient hot tubs — warm pools of water that emerged as the continents rose out of the early global ocean. Using data from a new numerical model that simulates the conditions of the ancient earth, they explain that the building blocks of life could indeed have emerged if the right interstellar ingredients were added to the mix.
“In order to understand the origin of life, we need to understand Earth as it was billions of years ago,” co-author Thomas Henning, Ph.D., explained in a statement. “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.”
Their argument relies on the assumption that the early earth was bombarded with meteorites that carried life-starting essential elements. As the meteorites crashed into these ponds, they leached their contents into the water over numerous wet and dry cycles. In this hot soup, the first RNA polymers — precursors to relatively more complicated DNA — emerged roughly 4.17 billion years ago.
The researchers posit that the world was, at first, inhabited by only RNA-based life. They argue that DNA, which we now consider to be the fundamental building block of life on earth, is “too complex” to have been the first element of life to emerge.
There’s a growing body of evidence showing that meteorites can indeed carry the essential components of nucleotides, the building blocks that make up RNA and DNA. Scientists first realized that there were components of DNA in meteorites in the 1960s, but it wasn’t until 2011 that researchers proved that they were actually created in space and didn’t just represent contamination from terrestrial life. That year, NASA-funded researchers at the Goddard Astrobiology Analytical Laboratory found the nucleobases adenine and guanine, as well as hypoxanthine and xanthine, in samples of comet Wild 2 from NASA’s Stardust mission.
In a competing theory, called panspermia, scientists argue that life didn’t emerge on Earth at all and was instead transported in after developing elsewhere. In panspermia,extraterrestrial life — probably bacterial spores — hitched a ride on bombarding space rocks to our planet.
This theoretical paper is just the first step in gaining a better understanding of how life on Earth began. Next year, the scientists behind it plan on testing their theory in the new Origins of Life laboratory at McMaster University, which will allow them to replicate earth’s pre-life conditions in a sealed environment.