Life on Earth could have originated in cold conditions near the surface, before spreading to warmer environments, according to research that analyzes the possible gene sequences belonging to the earliest life.
All life on Earth today originates from two distinct developments in our planet’s biological history. These are the emergence of the first life forms billions of years ago, and the subsequent evolution of the last universal common ancestor (LUCA) of all extant organisms.
Whatever they were at the time, these two extinct species – the first life and LUCA – likely occupied radically different environments, suggesting that early life had to undergo a series of evolutionary changes.
The scientists suggested that life first emerged near Earth’s surface under some form of radiation shield, such as water, ice cover, sediment or other barriers, and had access to unshielded environments that could generate key biomolecules. Temperatures on Earth may have also been relatively cold at that time.
In contrast, the last universal common ancestor – the microbial species from which all life that exists today came from – may have lived in moderate temperatures, perhaps at least four billion years ago.
The researchers suggested that since life apparently originated in a very different environment than the one in which LUCA lived, early organisms likely evolved to survive radical changes in their surroundings.
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