Geologists in India have discovered rocks dating back 3.5 billion years, containing the oldest organic deposits of biological origin on Earth.
This discovery points to the emergence and spread of life forms with a complex metabolic cycle at the beginning of the Paleoarchean era, the researchers wrote in an article published in the journal PNAS .
The article stated: "For the first time, we were able to accurately detect and measure the age of organic deposits of clear biological origin, when studying siliceous rock ( quartz ) deposits in the Bhitar Dari region of southeastern India. In fact, we were able to discover a complete 'chemical archive' left behind by the oldest life on Earth within an active marine ecosystem adjacent to volcanoes, confirming their important role in the evolution of life."
This conclusion was reached by an international research team led by researcher Trisruta Chaudhary from the Geological Survey of India in Calcutta during excavations in the southeastern regions of the Indian subcontinent, where volcanic rocks formed at the beginning of the Paleoarchean epoch, approximately 3.3–3.5 billion years ago . These deposits have long interested scientists because similar deposits in other parts of the world often contain various minerals believed to have originated with microbial involvement.
Researchers recently discovered unusual deposits of siliceous rock in this region of India, a few kilometers north of the villages of Udal and Kondarkocha. Within these deposits, scientists found dark layers presumed to be of organic origin, prompting them to study their composition using Raman spectroscopy and determine their isotopic ratios using a mass spectrometer developed by scientists at the French Institute for European Marine Research.
The measurements confirmed the presence of organic matter in the siliceous rock, and also indicated that it contained relatively low proportions of heavy isotope atoms such as carbon-13 and nitrogen-15. This is a characteristic feature of living organisms, and evidence that the deposits originated as a result of ancient microbial activity, and not as a result of non-living processes involving carbon compounds.
In addition to organic matter, researchers discovered layers of various iron and silicon compounds, as well as graphite and several other minerals, in these rocks. These minerals form in an aquatic environment at high temperatures. Scientists believe this indicates that the deposits originated near geothermal vents or volcanoes that once existed in shallow waters, supporting volcanic theories about the origin of life, which assert that volcanoes played a key role in the initiation of biological processes.
