You do know that Sera is basically an alternate form of Earth. There is no evidence of space travel capabilities in the Gears universe.
"In the Gears of War universe, Sera is the first planet where Humans constructed a permanent colony. Life on Sera was generally rich and full, and the colonists experienced an extensive artistic renaissance resulting in a diverse and happy population, proud of their accomplishments."
First planet where Humans constructed a permanent colony. That basically says there were previous planets but no permanent colonies.
There is no space travel in the Gears universe. Whoever wrote that in the wiki obviously worded it wrong.
No longer is the giant list on the page it has now been moved to the GB Gears of War 3 Community Thing in the guides section. If you're not on the chart and would like to be just tell me, I'll still update it.