This early era in the history of the Earth was appropriately named, from the Greek word for "dawn" eos and "ancient" archios. Solid land began making its appearance in this era (around 3.3 billion years ago) in the form of Vaalbara, the first supercontinent.
The Eoarchean is an era in the geologic timescale lasting from 3800 Ma to 3600 Ma (million years ago). It is the first part of the Archaean Eon, preceded by the Hadean eon. In chronostratigraphy, its zone rank is an erathem.
The International Commission on Stratigraphy does not recognize the lower boundary of the era nor the preceding Hadean Eon.
Examination of lunar samples has lead to a belief in an event called the Late Heavy Bombardment (LHB) which is understood to be a characteristic of the beginning of the Eoarchean era. Evidence of this event exists from a number of large craters on our moon. The LHB is believed to have victimised the inner solar system which would mean that Earth itself would have been subjected to this bombardment. The cause of the LHB is still contested.
It is widely speculated that events transpired within this period where inorganic matter underwent a process that lead to the origin of life. This debated process is referred to as abiogenesis. There are very many scientific theories revolving around the origins of DNA during this period which is believed to have lead to the first forms of discovered life which were primitive forms of bacteria known to have existed as early as the Paleoarchean era.
The Eoarchean was followed by the Paleoarchean era.
The Fermi Paradox
Scientists have proposed that there are hundreds of billions of planets capable of supporting life in our galaxy. And that's just our galaxy. So where are they? A proposal called the Gaian Bottleneck says that early life on most planets is very fragile and that sudden cooling or heating of the planet wipes out this life causing it to go extinct. Earth has a very stable and unique atmosphere that moderates the changes in temperature to the point where life does not go completely extinct during these changes. The survivors of these climate changes have evolved over time to become the creatures (including us) that we now know on Earth.
Everybody has parents. Their parents also had parents. Then their parents also had parents. All homo sapiens in the world today are suggested to have common ancestral parents. Those parents are Y-chromosomal Adam, who is the paternal ancestor believed to have lived around 140,000BCE, and Mitochondrial Eve, who is the maternal ancestor believed to have lived around 200,000BCE. But even these individuals had to have parents, and based on that theory you can go back through evolution, right to the very beginning of life on Earth.
And so this is the basis of the theory of L.U.C.A., very much a suggestion first hinted at by naturist Charles Darwin when he suggested that all lifeforms have a common ancestor. The fact that DNA is present in all forms of life whether they be animal, plant, fungus or bacteria points to everything having a common ancestor. This ancestor is L.U.C.A. or the Last Universal Common Ancestor, and this individual is believed to have existed around 3.8-3.5 billion years ago.
Fossils found in stromalites date to about 3.7 billion years ago. The fossils were part of an outcrop of ancient rock that had lost its usual snow cover. The rock layer forming the outcrop, known to geologists as the Isua supracrustal belt, lies on the southwest coast of Greenland and is some 3.9 to 3.7 billion years old.