Charles Darwin's theory of evolution remains a controversial subject when related to the idea of intelligent design, but findings of a new study suggest that the English naturalist may have been right about where life on Earth began.
Water World Theory And Darwin's Warm Little Pond
Most scientists today think that the first life-forms evolved in hydrothermal vents of the sea. Otherwise known as the "water world" theory, this concept posits that life may have started inside the warm and gentle springs of the seafloor.
Darwin had a different idea, though. His "warm little pond" theory speculated that life on Earth may have started on land. Now, fossil evidence of early life discovered in old hot spring deposits in Pilbara Craton in Western Australia suggests Darwin may have been correct about the terrestrial origins of life on Earth.
For the new study published in the journal Nature Communications, University of New South Wales scientist Tara Djokic and colleagues analyzed deposits found in the ancient Dresser Formation in the Pilbara Craton of Western Australia that are estimated to be about 3.5 billion years old.
The area from where the fossils were collected is now a barren wilderness, but scientists found evidence suggesting it was once home to a volcanic hot spring system.
The researchers think that the presence of geyserite, a mineral deposit formed at near-boiling temperature and is often found in geysers and hot springs, in these Pilbara deposits indicate that they were formed on land.
The researchers also discovered stromatolites, layered rock structures produced by communities of ancient microbes and well-preserved bubbles. It is not clear how these bubbles formed, but the researchers said that since they have been preserved well after billions of years, it could mean that these bubbles were once trapped within a sticky substance linked to microbial activity.
"Newly discovered terrestrial hot spring facies in the ca. 3.5 Ga Dresser Formation contain a range of highly distinctive and varied textural biosignatures, providing direct evidence that at least some of Earth's earliest life thrived on land, in hot springs," the researchers wrote in their study, which was published on May 9.
Oldest Evidence For Microbial Life On Land
The world's oldest evidence for microbial life on land was previously found in deposits in South Africa, which contain ancient soils rich in organic matter. The South African deposits were estimated to be between 2.7 and 2.9 billion years old, which means that the Pilbara hot spring deposits, at about 3.5 billion years of age, were older.
The findings support Darwin's idea that life may have emerged from a terrestrial pond.
"This may have implications for an origin of life in freshwater hot springs on land, rather than the more widely discussed idea that life developed in the ocean and adapted to land later," Djokic said.
"The discovery of potential biological signatures in these ancient hot springs in Western Australia provides a geological perspective that may lend weight to a land-based origin of life."