New Delhi: Microscopic fossils discovered in ancient Australian mudstone cores have provided definitive evidence that the earliest known complex organisms
depends entirely on oxygen to survive. The study, published in Nature, analysed more than 12,000 single-celled fossils extracted from geological drill cores stored in Darwin. The samples originate from a 1.7 billion year old inland sea that once covered the Northern Territory in Australia. Globally, these specimens represent the oldest known records of eukaryotes, the cellular lineage encompassing all modern planets, animals and fungi. The scientists dissolved the sedimentary rock cores to isolate the organic fossil residues for microscopic analysis, while simultaneously evaluating the chemical composition of the surrounding mudstones to reconstruct the ancient marine environment.
The investigation revealed that why eukaryote fossils spanned diverse habitats from coastal mudflats to the open ocean, they were strictly confined to oxygenated waters. Conversely, rock samples indicating oxygen-free conditions yielded only simple, single-celled prokaryotes, or simpler unicellular organisms. The distribution demonstrates that even the earliest ancestral eukaryotes required oxygenated environments to thrive. The discovery directly challenges recent theories suggesting that early complex life evolved in anoxic environments, or without oxygen. The research validates the traditional scientific consensus that oxygen availability was the primary catalyst for the evolutionary leap to complex life.
Why did life become multicellular?
Understanding the environmental drivers behind early eukaryotic evolution remains a fundamental pursuit within life sciences. Continued investigation into these ancient microfossils promises to further clarify the primordial origins of complex and terrestrial life. The rise of atmospheric oxygen fundamentally enabled multicellularity by providing a massive energy boost. Simple, single-celled organisms rely on inefficient, low energy processes. Oxygen allowed cells to switch to aerobic respiration, generating up to 18 times more energy per sugar molecule. This surplus of energy fuelled the complex molecular machinery required for cells to stick together, communicate and specialise.
