Scientists are one step closer to understanding the origins of complex life on Earth after shedding new light on a mystery about our microbial ancestors. The key, they suspect, may lie in how simple microbes that lived billions of years ago adapted to the presence of oxygen.Humans, like all plants, fungi and animals on Earth, are eukaryotes — organisms with cells that have a clearly defined DNA-containing nucleus and other structures such as mitochondria, organelles that provide cells with power by converting nutrients into energy.Between 2.4 billion and 2.1 billion years ago, oxygen levels dramatically increased in Earth’s atmosphere, known as the Great Oxidation Event. A few hundred thousand years after the event, the first identifiable traces of eukaryotes, preserved as microfossils, appeared on our planet, suggesting that oxygen has long been a crucial ingredient for the evolution of complex life.AdvertisementAdvertisementMany scientists believe that eukaryotes evolved from the combination of two types of microbes.But in a puzzling twist, one of the microbes, known as Asgard archaea, has only been found in oxygen-deprived environments such as hydrothermal vents on the ocean floor — despite appearing to share complex similarities with eukaryotes.Researchers have questioned how Asgards even crossed paths with other microbes that required oxygen for survival to create eukaryotes if they existed in such different environments.But a new investigation of Asgard genomes has revealed previously unknown l …
