may have been found in 3.48-billion-year-old geyserite and other related mineral deposits (often found around hot springs and geysers) uncovered in the Pilbara Craton of Western Australia. In July 2018, scientists reported that the earliest life on land may have been bacteria living on land 3.22 billion years ago. In May 2019, scientists reported the discovery of a fossilized fungus, named Ourasphaira giraldae, in the Canadian Arctic, that may have grown on land a billion years ago, well before plants were living on land. Evolution of terrestrial antioxidants Oxygen began to accumulate in Earth's atmosphere over 3 Ga, as a by-product of photosynthesis in cyanobacteria (blue-green algae). However, oxygen produces destructive chemical oxydation which was toxic to most previous organisms. Protective endogenous antioxidant enzymes and exogenous dietary antioxidants helped to prevent oxidative damage. For example, brown algae accumulate inorganic mineral antioxidants such as rubidium, vanadium, zinc, iron, copper, molybdenum, selenium and iodine, concentrated more than 30,000 times more than in seawater. Most marine mineral antioxidants act in the cells as essential trace elements in redox and antioxidant metalloenzymes. When plants and animals began to enter rivers and land about 500 Ma, environmental deficiency of these marine mineral antioxidants was a challenge to the evolution of terrestrial life. Terrestrial plants slowly optimized the production of new endogenous antioxidants such as ascorbic acid, polyphenols, flavonoids, tocopherols, etc. A few of these appeared more recently, in last 200–50 Ma, in fruits and flowers of angiosperm plants. In fact, angiosperms (the dominant type of plant today) and most of their antioxidant pigments evolved during the Late Jurassic period. Plants employ antioxidants to defend their structures against reactive oxygen species produced during photosynthesis. Animals are exposed to the same oxidants, and they have evolved endogenous enzymatic antioxidant systems. Iodine in the form of the iodide ion I- is the most primitive and abundant electron-rich essential element in the diet of marine and terrestrial organisms; it acts as an electron donor and has this ancestral antioxidant function in all iodide-concentrating cells, from primitive marine algae to terrestrial vertebrates. Evolution of soil Before the colonization of land there was no soil, a combination of mineral particles and decomposed organic matter. Land surfaces were either bare rock or shifting sand produced by weathering. Water and dissolved nutrients would have drained away very quickly. In the Sub-Cambrian peneplain in Sweden, for example, maximum depth of kaolinitization by Neoproterozoic weathering