 Earth was very hostile to life before 4.2–4.3 Ga and the conclusion is that before the Archean Eon, life as we know it would have been challenged by these environmental conditions.While life could have arisen before the Archean, the conditions necessary to sustain life could not have occurred until the Archean Eon.Life in the Archean was limited to simple single-celled organisms (lacking nuclei), called Prokaryota.