Fan Theories 14

A History of the Pokémon World/"Earth"
(by way of "Watchmen", the "Culture" novels, "2001: A Space Odyssey" and "Warhammer 40,000")

c.12,000,000,000 years BCE
Sublimation of first civilisations and Minds

c.350,000,000-300,000,000 years BCE 
Mew culture/civilisation/society develops on Earth and,later, on Venus also
They possibly colonise Mars
Mew eventually terraform/"Mewform" a variety of planets in other solar systems 
The "starter" Pokémon evolve at some point

It is possible they were bio-engineered by Mew (singular or plural) to re-terraform the Earth in the case of another die-off 

c.4-3,000,000 years BCE
Monoliths visit Earth
They take various proto-Hominid tribes to other planets around the galaxy to observe their evolution in different environments-I'm tempted to use this as an example/explanation for the prevalence of human/humanoid societies in the Culture galaxy. This doesn't really have a lot of relevance to Pokémon. 

c.2,000,000 years BCE
Drowzee evolves from the psychic tapir

c.6000 BCE
Formation of the Culture

Sixteenth century
Nikolai uses "arcane science" to create the world's first artificial Pokémon  
John Dee describes prototype Pokeball

Nineteenth century
For argument's sake, the events in "Watchmen" occur a hundred years before, making the Pokémon World a hundred years more advanced 
The Culture make a brief visit to Earth during the Cold WarRussia invades Afghanistan
Cold war ends
Doctor Manhattan leaves Earth for good stating he may create life elsewhere


Twentieth century:

1920's
First working Pokeball invented
Technologies created by Doctor Manhattan allow for the development and creation of:
Pokeball transfer technology

1930's
Howard Carter discovers a mummified Meowth in an Egyptian tomb
A Magikarp is caught off the east African coast
Garyados photographed at Loch Ness
(note: I am using the "cryptid" theory of Pokemon origins not the one invoking Battlestar Galactica)
Pokeballs first mass produced

And:
The successful teleportation of Pokémon
The revival of extinct Pokémon from DNA
The creation of artificial Pokémon such as Porygon

1950's
Silph meter invented

Confirmation of the existence of Ghost-type Pokémon
Establishment of the first Pokémon reserves

1960's
Oak receives Professorship after identifying all 150 Pokémon in the Kanto region. He is later pressured to remove a number of Pokémon by agents unknown when he helps develop the Pokedex.

1980's
Ash Ketchum is born


1990's
Jessie and James meet at Pokémon Tech
They later join Team Rocket

Mew DNA is discovered in French Guiana;
Mewtwo is then created from this
Oak adds Mewtwo to the Pokedex

Ash Ketchum meets Pikachu

Ash enters a four year Coma :
-The other Pallet trainers receive the required the eight Gym badges
-Sabrina takes over the Saffron City Gym
during this time
-This is why the anime Ash is so far behind Gary Oak and the other Pallet Town trainers, who didn't have to face Sabrina  

Twenty-first century
First official contact with the Culture
Culture Minds consider Psychic and Ghost Pokémon to be entities returning from the Sublimed 
The events of "Detective Pikachu"
Discovery missions explore Jupiter and Saturn

Fifteen millennia later

The War in Heaven occurs among the Sublimed (see previous blogs) and the resulting warp storms cut civilised systems off from each other
New Dark Age

31st millennium Unification of Earth/Terra by a Legendary Pokémon posing as a human
Great Crusade
Horus Heresy
Pokémon considered to be warp entities