Miri
History
According to the history of the inhabitants which has taken extensive research and investigation to confirm, the original settlers were a mix of genetically enhanced and normal humans. No documentation remains with information on the numbers of settlers or the transport ships used.
Much of the colonies early records were destroyed or allowed to deteriorate to the point that they were almost useless over the 300 years dureing which only children survived.
This
These colonists were isolationists who violently repulsed the first attempt to contact them by a later expedition from Earth, and so no further contact was attempted. As it turned out, the Ophiucus system was in a "backwater" part of the galaxy that subsequent years of Earth-based space exploration passed by, and so the belligerent colony was easily ignored and almost forgotten. Around 300 years before the events shown in Miri, scientists on Ophiucus IV developed the experimental life-prolongation project that resulted in the deaths of every adult on the planet.
Settlers
Religion
Environment
Animals
Economy
Communities
Population
Federation Intelligence Files
Extensive search of Earth records from the Eugenics War period, plus the following recovery years has resulted in the recovery of a few documents that support the belief that the colony on Ophiucus IV was founded by colonists from earth during the first wave of space colonization. (1990 to 2030)
This is further supported by the isolationist attitude taken by the governing body during early contact with space explorers from Earth. As a result no further contact was established until Captain James T. Kirk of the USS Enteprise answered a distress call in 2266.
See Starfleet records File 2266-28473, Miri for a complete record of the USS Enteprise actions on the surface of the planet.
To understand why Ophiucus IV looks so much like Earth see Hodgkin's Law of Parallel Planetary Development.