Here is the timeline, from the first evolution til before first contact.
50 million+ years ago: First rhinoceros specie appear
11.5 million years ago: Genus Ceratotherium evolves
9.2 million years ago: Dominate specie, Ceratotherium sapiens evolves
8.7 million years ago: Specie of bison becomes sentience
Three million B.G: Spread of Bronze Age
500 thousand B.G: Spread of Iron Age
27 thousand B.G: Domestication age began
50 B.G: Rhinam began first permanent settlements
157 A.F: Five tribes began the foundation of the first village
275 A.F: Two villages has a dispute over a nearby orchard; first war, lasting five weeks.
398 A.F: Village on Norner(Germany) develops first true weapons; used to conquer a nearby tribe
997 A.F: Villages are underneath one of three superpowers; Norner, Tuska(Eygpt), or Undata(Current day United States of America) with Aundia(Australia) as a spiritual place.
1000 A.F: Rhimen 'discovers' Bison sapiens referred to as Ushitaur
1206 A.F: First vehicle are developed, soon scraped due to enviromental issues
1489 A.F: Aundia develop first crystal generator to power new cities, other territories bargain for blueprints
1698 A.F: Tuska attempts to invade Southern Norner, Eastern Undata prepares weapon to attack
Seventh Lunar cycle 1699 A.F: Tuska and Norner begin open conflict, Aundia maintains wait and see, Ushitaur began intergrating with their rhimen neighbors
Third Lunar cycle 1705 A.F: Norner allies with Undata to push back Tuska, Aundia begins peace talks
Fifth Lunar cycle 1705 A.F: All three major nations signs the Quahorn accord, which allows Aundia to control any funding to prevent world wars
Eight Lunar cycle 1705 A.F: A physical difference is shown between rhimen. Those that has a lineage as warriors having decorate tattoos, sharper horns and gray skin while those that who are farmers by nature have yellow skin and shorter horns.
1997 A.F: The four Grand Crashes met once more, only this time to plan to travel to Gaia's moon
Twelfth Lunar cycle 2020 A.F: The first manned mission to the moon succeeded, giving rise to the need to build bigger and better ships
2096 A.F: Rhimen geneticist Doctor Damein Wu began studies into extending the rhimen specie's age max from four decades
Ninth Lunar cycle 2116 A.F: Before dying of old age, Dr. Wu places age slowing formula, Pheonix blood, into various water supplies. Lifespan of rhiman and ushi-oni extended from forty something to over nine centuries and fertility increased
2269 A.F: A new caste of rhimen began showing up. They tend to gray skin with blood red faces and are more violent. The red faces come from their practice of drinking blood before going to battle.
2284 A.F: The four Grand Crash unite under one banner, forming the Ungulate Union
2299 A.F: Discovers Prothean's on Mars, they began reverse engineering technology. Most have been identified as unneeded...except for element zero
2389 A.F: Most planets in the solar system have been terraformed. Mars has several universities dedicated to study the Protheans' culturally as well as their technology, Venus became known for its varoius colosseums that hosted gladitorial battles, and Neptune became a nature preserve
2472 A.F: The newly named Foresters, larger than other rhimen, were named. Although narrower the horns are stronger and longer. They tend to have brown skin with moss on their shoulders and humps
3656 A.F/2157 C.E: First Contact War begins